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ZL2005
Data Sheet February 18, 2009 FN6848.0
Digital-DCTM Integrated Power Management and Conversion IC
Description
The ZL2005 is an innovative mixed-signal power management and conversion IC that combines a compact, efficient, synchronous DC/DC buck controller, adaptive drivers and key power and thermal management functions in one IC, providing flexibility and scalability while decreasing board space requirements and design complexity. Zilker Labs' Digital-DC technology enables a unique blend of performance and features not available in either traditional analog or newer digital approaches, resolving the issues associated with providing multiple, low-voltage power domains on a single PCB. The ZL2005 is designed to be a flexible building block for DC power and can be easily adapted to designs ranging from a single-phase power supply operating from a 3.3 V input to a multi-phase supply operating from a 12 V input. The ZL2005 eliminates the need for complicated power supply managers as well as numerous external discrete components. All operating features can be configured by simple pin-strap selection, resistor selection or through the on-board serial port. The PMBusTM-compliant ZL2005 uses the SMBusTM serial interface for communication with other Digital-DC products or a host controller.
DLY FC ILIM EN PG (0,1) (0,1) (0,1) CFG UVLO V25 VR VDD
Features
Power Management * Digital soft start/stop * Precision delay and ramp-up * Power good/enable * Voltage tracking, sequencing and margining * Voltage/current/temperature monitoring * I2C/SMBus communication * Output overvoltage and overcurrent protection * PMBus compliant Power Conversion * Efficient synchronous buck controller * 3 V to 14 V input range * 0.6 V to 5.5 V output range * 1% output accuracy * Internal 3 A drivers support >30 A power stage * Fast load transient response * Phase interleaving * RoHS compliant (6 x 6 mm) QFN package
Applications
* * * * Servers/storage equipment Telecom/datacom equipment Power supplies (memory, DSP, ASIC, FPGA) Point of load converters
V (0,1) SS (0,1) VTRK MGN SYNC
POWER MANAGEMENT
LDO BST GH SW GL ISENA ISENB
DRIVER NONVOLATILE MEMORY SCL SDA SALRT PWM CONTROLLER
CURRENT SENSE TEMP SENSOR
I2 C
MONITOR ADC
SA (0,1)
VTRK VSEN TACH XTEMP PGND SGND DGND
Figure 1. Block Diagram
1
Figure 2. Efficiency vs. Load Current
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures. 1-888-INTERSIL or 1-888-468-3774 | Intersil (and design) is a registered trademark of Intersil Americas Inc. Copyright Intersil Americas Inc. 2009. All Rights Reserved All other trademarks mentioned are the property of their respective owners.
ZL2005
Table of Contents
1 2 3 4 Electrical Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pin Descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Typical Application Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ZL2005 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.1 Digital-DC Architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2 Power Conversion Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3 Power Management Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.4 Multi-mode Pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Power Conversion Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.1 Internal Bias Regulators and Input Supply Connections. . . . . . . . . . . . . . . . . . . . . . 5.2 High-side Driver Boost Circuit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.3 Output Voltage Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.4 Start-up Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.5 Soft Start Delay and Ramp Times . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.6 Power Good . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.7 Switching Frequency and PLL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.8 Selecting Power Train Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.9 Current Limit Threshold Selection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.10 Loop Compensation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.11 Non-Linear Response Settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.12 Efficiency Optimized Driver Dead-time Control. . . . . . . . . . . . . . . . . . . . . . . . . . . . . Power Management Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.1 Input Undervoltage Lockout (UVLO). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.2 Output Overvoltage Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.3 Output Pre-Bias Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.4 Output Overcurrent Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.5 Thermal Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.6 Voltage Tracking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.7 Voltage Margining . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.8 I2C/SMBus Communications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.9 I2C/SMBus Device Address Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.10 Phase Spreading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.11 Output Sequencing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.12 Monitoring via I2C/SMBus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.13 Temperature Monitoring Using the XTEMP Pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.14 Fan Monitoring using the TACH Pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.15 Device Security Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Package Dimensions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ordering Information. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 8 10 11 11 12 13 13 15 15 15 15 16 17 18 18 20 23 26 27 28 29 29 29 30 30 31 31 33 33 33 34 34 35 35 36 36 37 38
5
6
7 8
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Electrical Characteristics
Table 1. Absolute Maximum Ratings
Operating beyond these limits may cause permanent damage to the device. Functional operation beyond the recommended operating conditions is not implied. Unless otherwise specified, all voltages are measured with respect to SGND. Parameter Pin(s) Value Unit
DC supply voltage Logic I/O voltage
Analog input voltages
VDD DLY(0,1), EN, ILIM(0,1), MGN, PG, SA(0,1), SALRT, SCL, SDA, SS(0,1), SYNC, TACH, UVLO, V(0,1) ISENB, VSEN, VTRK, XTEMP, ISENA VR V25 BST GH GL BST, SW SW SW DGND, SGND, PGND - - - All
-0.3 to 17 -0.3 to 6.5
V V
-0.3 to 6.5 -1.5 to +30 -0.3 to 6.5 120 -0.3 to 3 120 -0.3 to +30 (VSW - 0.3) to (VBST+0.3) (PGND-0.3) to (VR+0.3+PGND) -0.3 to 8 (PGND-0.3) to 30 (PGND-5) to 30 -0.3 to +0.3 -55 to 150 -55 to 150 300 2
V V V mA V mA V V V V V V V
oC o o
MOSFET drive reference Logic reference High-side supply voltage High-side drive voltage Low-side drive voltage Boost to switch differential voltage (VBST - VSW) Switch node continuous Switch node transient (<100 ns) Ground voltage differential (VDGND-VSGND), (VPGND-VSGND) Junction temperature Storage temperature range Lead temperature (soldering, 10 s) ESD HBM tolerance (100 pF, 1.5 k)
C C
kV
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Table 2. Recommended Operating Conditions and Thermal Information
Parameter Symbol Min Typ Max Unit
Input Supply Voltage Range, VDD Output Voltage Range Operating Junction Temperature Range Junction to Ambient Thermal Impedance1 Junction to Case Thermal Impedance2
NOTES:
VR tied to VDD (Figure 9) VR floating (Figure 9) VOUT TJ
3.0 4.5 0.6 -40 - -
- - - 35 5
5.5 14 5.5 125 - -
V V V C C/W C/W
JA JC
1. JA is measured in free air with the device mounted on a multi-layer FR4 test board and the exposed metal pad soldered to a low impedance ground plane using multiple vias. 2. For JC, the "case" temperature is measured at the center of the exposed metal pad
Table 3. Electrical Specifications
Unless otherwise specified VDD = 12 V, TA = -40oC to +85oC. Typical values are at TA = 25oC. Parameter Condition Min Input and Supply Characteristics Typ Max Unit
Supply current (IDD) (No load on GH and GL) Standby supply current (IDD) VR reference voltage (VR) V25 reference voltage (V25)
Output Characteristics
fSW = 200 kHz fSW = 2,000 kHz EN = Low 2C/SMBus activity no I VDD 6 V IVR < 50 mA VR 3 V IV25 < 50 mA
- - - 4.5 2.25 0.6 - - -1 - -100 -100 -100
16 25 2 5.2 2.5 - 10 0.025 - 110 - - -
30 50 5 5.5 2.75 5.5 - - 1 200 100 100 100
mA mA mA V V V mV % of F.S.1 % A mV mV A
Output voltage adjustment range Set using resistors Output voltage setpoint resolution Output voltage accuracy VSEN input bias current Current sense differential input voltage (ground referenced) Current sense differential input voltage ( VOUT referenced) Current sense input bias current
NOTE:
1. Percentage of Full Scale (F.S.) with temperature compensation applied
Set using I2C/SMBus Over line, load and temperature VSEN = 5.5 V VISENA - VISENB VISENA - VISENB Ground referenced
Current sense input bias current (VOUT referenced, VOUT <= 3.6V) Soft start delay duration range Soft start delay duration accuracy
4
ISENA ISENB Set using DLY pin or resistor Configurable via I2C/SMBus
-1 -100 7 0.007 -
- - - - 6
1 100 200 500 -
A A ms s ms
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Table 3. Electrical Specifications
Unless otherwise specified VDD = 12 V, TA = -40oC to +85oC. Typical values are at TA = 25oC. (Continued) Parameter Condition Min Typ Max Unit
Soft start ramp duration range Soft start ramp duration accuracy
Logic Input/Output Characteristics
Set using SS pin or resistor Configurable via I2C/SMBus
0 0 -
- - 100
200 200 -
ms ms s A mA mA V V V V V kHz % % ns % ns Hz %
Logic input bias current MGN input bias current Logic input low threshold (VIL) Logic input OPEN (N/C) Logic input high threshold (VIH) Logic output low (VOL) Logic output high (VOH)
EN, PG, SCL, SDA, SALRT, TACH During configuration restore
-10 -1 -1 - - 2 - 2.25 200
- - - - 1.4 - - - - - - - - - - -
10 1 1 0.8 - - 0.4 - 2000 5 - - 13 - 500 10
Multi-mode logic pins IOL <= 4 mA IOH >= - 2 mA
Oscillator and Switching Characteristics
Switching frequency range Switching frequency setpoint accuracy Maximum PWM duty cycle Minimum SYNC pulse width Input clock frequency drift tolerance
Tachometer Characteristics
Predefined settings (See table 14) Factory default External clock signal
-5 95 150 -13 150 1 -10
TACH pulse width TACH frequency range TACH accuracy
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Table 3. Electrical Specifications
Unless otherwise specified VDD = 12 V, TA = -40oC to +85oC. Typical values are at TA = 25oC. (Continued) Parameter Condition Min Typ Max Gate Drivers Unit
High-side driver voltage (VBST - VSW) High-side driver peak gate drive current (pull down) High-side driver pull-up resistance High-side driver pull-down resistance Low-side driver peak gate drive current (pull-up) Low-side driver peak gate drive current (pull-down) Low-side driver pull-up resistance Low-side driver pull-down resistance Switching timing GH rise and fall time GL rise and fall time
Tracking
- (VBST - VSW) = 4.5 V (VBST - VSW) = 4.5 V, (VBST - VGH) = 50 mV (VBST - VSW) = 4.5 V, (VGH - VSW) = 50 mV VR = 5 V VR = 5 V VR = 5 V, (VR - VGL) = 50 mV VR = 5 V, (VGL - PGND) = 50 mV (VBST - VSW) = 4.5 V, CLOAD = 2.2 nF VR = 5 V, CLOAD = 2.2 nF VTRK = 5.5 V VTRK >= 0.3 V 2 - - - - - -
4.5 3 0.8 0.5 2.5 1.8 1.2 0.5
- - 2 2 - - 2 2
V A A A
- - - - 100
5 5 110
20 20 200 + 100
ns ns A mV
VTRK input bias current VTRK tracking threshold
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Table 3. Electrical Specifications
Unless otherwise specified VDD = 12 V, TA = -40oC to +85oC. Typical values are at TA = 25oC. (Continued) Parameter Condition Min Typ Max Fault Protection Characteristics Unit
UVLO threshold range UVLO setpoint accuracy UVLO hysteresis UVLO delay Power good VOUT low threshold Power good VOUT high threshold Power good VOUT hysteresis Power good delay
Factory default Configurable via I2C/SMBus
2.85 -100 - 0 - - - - 0 0
- - 3 - - 90 115 5 - - 85
16 100 - 100 2.5 - - - 200 500 - 110 - 115 - 60 - - - 32 - 12700 - 125 -
Factory default Factory default Factory default Set using pin-strap or resistor4 Configurable via I2C/SMBus Factory default
VSEN undervoltage threshold Configurable via I2C/SMBus Factory default VSEN overvoltage threshold Configurable via I2C/SMBus VSEN undervoltage/overvoltage fault response time Current limit setpoint accuracy (VOUT referenced) Current limit setpoint accuracy2 (Ground referenced) Current limit protection delay Temperature compensation of current limit protection threshold Thermal protection threshold Thermal protection hysteresis
NOTES:
1. Percentage of Full Scale (F.S.) with temperature compensation applied 2. TA = 0oC to +85oC 3. SW = 1/fSW, fSW switching frequency 4. Automatically set to same value as soft start ramp time
0
- 115
0 - 5 -
- 16 - 10 10 5 - 4400 - 125 - 15
Factory default Configurable via I2C/SMBus
V mV % % s % VOUT % VOUT % ms s % VOUT % VOUT % VOUT % VOUT s s % F.S.1 % F.S. SW3 ppm/ C C C C
|VISENA - VISENB|> 12 mV Factory default Configurable via I2C/SMBus Factory default Configurable via I2C/SMBus Factory default Configurable via I2C/SMBus
- - 1 - 100 - - 40 -
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Pin Descriptions
PG DLY1 DLY0 EN CFG MGN TACH XTEMP V25
34 33 32 36 35 31 30 29
DGND SYNC SA0 SA1 ILIM0 ILIM1 SCL SDA SALRT
28
1 2 3 4 5 6 7 8 9 12 13 14 10 11 15 16 17 18
27 26
36-Pin MLF 6 x 6 mm
Exposed Paddle
Connect to SGND
25 24 23 22 21 20 19
VDD BST GH SW PGND GL VR ISENA ISENB
Figure 3. Pin Assignments (top view)
Table 4. Pin Descriptions
Pin Label Type1 Description
1 2 3 4 5 6 7 8 9 10 11 12 13 14
NOTES:
DGND SYNC SA0 SA1 ILIM0 ILIM1 SCL SDA SALRT FC0 FC1 V0 V1 UVLO
PWR I/O, M2 I, M I, M I/O I/O O I I I, M I, M
Digital ground. Connect to low impedance ground plane. Clock synchronization input. Used to set the frequency of the internal switch clock, to sync to an external clock or to output internal clock. Serial address select pins. Used to assign unique address for each individual device or to enable certain management features. Current limit select. Sets the overcurrent threshold voltage for ISENA, ISENB. Serial clock. Connect to external host and/or to other ZL2005s. Serial data. Connect to external host and/or to other ZL2005s. Serial alert. Connect to external host if desired. Loop compensation selection pins. Output voltage selection pins. Used to set VOUT setpoint and VOUT max. Undervoltage lockout selection. Sets the minimum value for VDD voltage to enable VOUT.
1. I = Input, O = Output, PWR = Power or Ground, M = Multi-mode pin (refer to Section 4.4, "Multi-mode Pins," ) 2. The SYNC pin can be used as a logic pin, a clock input or a clock output. 3. VDD is measured internally and the value is used to modify the PWM loop gain.
8
FC0 FC1 V0 V1 UVLO SS0 SS1 VTRK VSEN
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Table 4. Pin Descriptions (Continued)
Pin Label Type1 Description
15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 ePad
NOTES:
SS0 SS1 VTRK VSEN ISENB ISENA VR GL PGND SW GH BST VDD3 V25 XTEMP TACH MGN CFG EN DLY0 DLY1 PG SGND
I, M I I I I PWR O PWR PWR O PWR PWR PWR I I I I I I, M O PWR
Soft start pins. Set the output voltage ramp time during turn-on and turn-off. Tracking sense input. Used to track an external voltage source. Output voltage feedback. Connect to output regulation point. Differential voltage input for current limit. Differential voltage input for current limit. High voltage tolerant. Internal 5V reference used to power internal drivers. Low side FET gate drive. Power ground. Connect to low impedance ground plane. Drive train switch node. High-side FET gate drive. High-side drive boost voltage. Supply voltage. Internal 2.5 V reference used to power internal circuitry. External temperature sensor input. Connect to external 2N3904 diode connected transistor. Tachometer input used to measure fan speed. Connect to TACH output of external fan. Digital VOUT margin control Configuration pin. Used to control the switching phase offset, sequencing and other management features. Enable. Active signal enables PWM switching. Softstart delay select. Sets the delay from when EN is asserted until the output voltage starts to ramp. Power good output. Exposed thermal pad. Connect to low impedance ground plane. Internal connection to SGND.
1. I = Input, O = Output, PWR = Power or Ground, M = Multi-mode pin (refer to Section 4.4, "Multi-mode Pins," ) 2. The SYNC pin can be used as a logic pin, a clock input or a clock output. 3. VDD is measured internally and the value is used to modify the PWM loop gain.
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Typical Application Example
VIN 12V VR POWER GOOD OUTPUT
PG 36 DLY1 35 DLY0 34 EN 33 CFG 32 MGN 31 TACH 30 XTEMP 29
CV25
V25 28
10 F 4V DB BAT54 1 F 16 V CB LOUT 2.2 H QH Si7344
CIN 3 x 10 F 25 V
1 DGND
VIN 27 BST 26 GH 25 SW 24
VR
2 SYNC 3 SA0 4 SA1 5 ILIM0 6 ILIM1
VOUT
ZL2005
PGND 23 GL 22 VR 21 ISENA 20 ISENB 19
I2C/SMBusTM
7 SCL 8 SDA 9 SALRT 14 UVLO 17 VRTK 10 FC0 11 FC1 15 SS0 16 SS1 12 V0 13 V1
18 VSEN
EPAD
CVR 4.7 F 6.3 V
QL NTMSF4108
COUT 47 F 6.3 V
470 F 2.5 V
POS-CAP
2*220 F 6.3 V 100 m RTN
Notes: 1. Conditions: VIN = 12 V, VOUT = 1.8 V, Freq = 400 kHz, IOUT = 20 A 2. The I2C/SMBus requires pullup resistors. Please refer to the I2C/SMBus specifications for more details.
Figure 4. Typical Application Circuit
10
SGND
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4.1
ZL2005 Overview
Digital-DC Architecture
The ZL2005 is an innovative mixed-signal power conversion and power management IC based on Zilker Labs' patented Digital-DC technology that provides an integrated, high performance step-down converter for a wide variety of power supply applications. Its unique digital PWM loop utilizes an innovative mixed-signal topology to enable precise control of the power conversion process with no software required, resulting in a very flexible device that is also easy to use. An extensive set of power management functions is fully integrated and can be configured using simple pin connections or via the I2C/SMBus hardware interface using standard PMBus commands. The user configuration can be saved in an on-chip non-volatile memory (NVM), allowing ultimate flexibility. Once enabled, the ZL2005 is immediately ready to regulate power and perform power management tasks with no programming required. The ZL2005 can be configured by simply connecting its pins according to the tables provided in this document. Advanced configuration options and real-time configuration changes are available via the I2C/SMBus interface if desired, and continuous monitoring of multiple operating parameters is possible with minimal interaction from a host controller. Integrated sub-regulation circuitry enables single supply operation from any supply between 3V and 14V with no secondary bias supplies needed. Zilker Labs provides a comprehensive set of on-line tools and application notes to assist with power supply design and simulation. An evaluation board is also available to help the user become familiar with the device. This board can be evaluated as a stand-alone platform using pin configuration settings. Additionally, a WindowsTM-based GUI is provided to enable full configuration and monitoring capability via the I2C/SMBus interface using an available computer and the included USB cable. Please refer to www.zilkerlabs.com for access to the most up-to-date documentation and the PowerPilotTM simulation tool, or call your local Zilker Labs' sales office to order an evaluation kit.
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ZL2005 4.2 Power Conversion Overview
INPUT VOLTAGE BUS PG EN MGN ILIM(0,1) SS(0,1) DLY(0,1) V(0,1) FC(0,1) VDD
TACH VTRK SYNC GEN POWER MANAGEMENT
VR LDO
VR BST
DIGITAL COMPENSATOR PLL
D-PWM NLR ADC
MOSFET DRIVERS
GH SW GL
VOUT
SYNC
+
- VSEN
REFCN
DAC ADC VDD
ISENB ISENA VSEN XTEMP
SMBUS
{
SALRT SDA SCL SA(0,1)
COMMUNICATION
ADC
MUX TEMP SENSOR
Figure 5. ZL2005 Detailed Block Diagram
The ZL2005 operates as a voltage-mode, synchronous buck converter with a selectable, constant frequency Pulse Width Modulator (PWM) control scheme that uses external MOSFETs, inductor and capacitors to perform power conversion. Figure 6 illustrates the basic synchronous buck converter topology showing the primary power train components. This converter is also called a step-down converter, as the output voltage must always be lower than the input voltage.
VIN
DB VR BST GH QH CB QL L1 CIN
In its most simple configuration, the ZL2005 requires two external N-channel power MOSFETs, one for the top control MOSFET (QH) and one for the bottom synchronous MOSFET (QL). The amount of time that QH is on as a fraction of the total switching period is known as the duty cycle D, which is described by the following equation:
VOUT D --------------VIN
ZL2005
SW GL
VOUT
COUT
Figure 6. Synchronous Buck Converter
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During time D, QH is on and VIN - VOUT is applied across the inductor. The current ramps up as shown in Figure 7. output regulation point. The VSEN signal is then compared to a reference voltage that has been set to the desired output voltage level by the user. The error signal derived from this comparison is converted to a digital value with a low-resolution, analog to digital (A/ D) converter. The digital signal is applied to an adjustable digital compensation filter, and the compensated signal is used to derive the appropriate PWM duty cycle for driving the external MOSFETs in a way that produces the desired output. The ZL2005 also incorporates a non-linear response (NLR) loop to reduce the response time and output deviation in response to a load transient. The ZL2005 has an efficiency optimization circuit that continuously monitors the power converter's operating conditions and adjusts the turn-on and turn-off timing of the high-side and low-side MOSFETs to optimize the overall efficiency of the power supply.
VIN - VOUT VOLTAGE (V)
ILpk CURRENT (A) Io ILv
0
-VOUT D Time 1-D
Figure 7. Inductor Waveform When QH turns off (time 1-D), the current flowing in the inductor must continue to flow from the ground up through QL, during which the current ramps down. Since the output capacitor COUT exhibits a low impedance at the switching frequency, the AC component of the inductor current is filtered from the output voltage so the load sees nearly a DC voltage. Typically, buck converters specify a maximum duty cycle that effectively limits the maximum output voltage that can be realized for a given input voltage. This duty cycle limit ensures that the low-side MOSFET is allowed to turn on for a minimum amount of time during each switching cycle, which enables the bootstrap capacitor (CB in Figure 6) to be charged up and provide adequate gate drive voltage for the high-side MOSFET. See Section 5.2, "High-side Driver Boost Circuit," for more details. In general, the size of components L1 and COUT as well as the overall efficiency of the circuit are inversely proportional to the switching frequency, fSW. Therefore, the highest efficiency circuit may be realized by switching the MOSFETs at the lowest possible frequency; however, this will result in the largest component size. Conversely, the smallest possible footprint may be realized by switching at the fastest possible frequency but this gives a somewhat lower efficiency. Each user should determine the optimal combination of size and efficiency when determining the switching frequency for each application. The block diagram for the ZL2005 is illustrated in Figure 5. In this circuit, the target output voltage is regulated by connecting the VSEN pin directly to the
13
4.3
Power Management Overview
The ZL2005 incorporates a wide range of configurable power management features that are simple to implement with no external components. Additionally, the ZL2005 includes circuit protection features that continuously safeguard the load from damage due to unexpected system faults. The ZL2005 can continuously monitor input voltage, output voltage/current, internal temperature, and the temperature of an external thermal diode. A Power Good output signal is provided to enable power-on reset functionality for an external processor. All power management functions can be configured using either simple pin configuration techniques (Figure 8) or via the I2C/SMBus interface. Monitoring parameters can be pre-configured to provide alerts for specific conditions. See Application Note AN13 for more details on SMBus monitoring.
4.4
Multi-mode Pins
In order to simplify circuit design, the ZL2005 incorporates patented multi-mode pins that allow the user to easily configure many aspects of the device without requiring the user to program the IC. Most power management features can be configured using these pins. The multi-mode pins can respond to four different connections as shown in Table 5. Any combination of connections is allowed among the multi-mode pins.
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These pins are sampled when power is applied or by issuing a PMBus Restore command (See Application Note AN13). Table 5. Multi-mode Pin Configuration
Pin Tied To Value
GND (Logic low) OPEN (N/C) HIGH (Logic high) Resistor to GND
< 0.8 VDC No connection > 2.0 VDC Set by resistor value
Pin-strap Settings: This is the simplest implementation method, as no external components are required. Using this method, each pin can take on one of three possible states: GND, OPEN, or HIGH. These pins can be connected to the VR or V25 pins for logic HIGH settings, as either pin provides a regulated voltage greater than 2V. Using a single pin, the user can select one of three settings, and using two pins, the user can select one of nine settings. Resistor Settings: This method allows a greater range of adjustability when connecting a finite valued resistor (in a specified range) between the multi-mode pin and SGND. Standard 1% resistor values are used, and only every fourth E96 resistor value is used so that the device can reliably recognize the value of resistance connected to the pin while eliminating the errors associated with the resistor accuracy. A total of 25 unique selections are available using a single resistor. I2C/SMBus Settings: Almost any ZL2005 function can be configured via the I2C/SMBus interface using standard PMBus commands. Additionally, any value that has been configured using the pin-strap or resistor setting methods can also be re-configured and/or verified via the I2C/SMBus. See Application Note AN13 for details.
Figure 8. Pin-strap and Resistor Setting Examples
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5
5.1
Power Conversion Functional Description
Internal Bias Regulators and Input Supply Connections 5.2 High-side Driver Boost Circuit
The ZL2005 employs two internal low dropout (LDO) regulators to supply bias voltages for internal circuitry, allowing it to operate from a single input supply. The internal bias regulators are as follows: VR: The VR LDO provides a regulated 5V bias supply for the MOSFET driver circuits. It is powered from the VDD pin and can supply up to 100mA output current. A 4.7 F filter capacitor is required at the VR pin. V25: The V25 LDO provides a regulated 2.5V bias supply for the main controller circuitry. It is powered from an internal 5V node and can supply up to 50 mA output current. A 10 F filter capacitor is required at the V25 pin. Note: The internal bias regulators are designed for powering internal circuitry only. Do not attach external loads to any of these pins. The multi-mode pins may be connected to the VR or V25 pins for logic HIGH settings. When the input supply (VDD) is higher than 5.5V, the VR pin should not be connected to any other pin. It should only have a filter capacitor attached as shown in Figure 9. Due to the dropout voltage associated with the VR bias regulator, the VDD pin must be connected to the VR pin for designs operating from a VDD supply from 3.0V to 5.5V. Figure 9 illustrates the required connections for both cases. For input supplies between 4.5V and 5.5V, either method can be used.
The gate drive voltage for the upper MOSFET driver is generated by a floating bootstrap capacitor, CB (see Figure 4). When the lower MOSFET (QL) is turned on, the SW node is pulled to ground and the capacitor is charged from the internal VR bias regulator through diode DB. When QL turns off and the upper MOSFET (QH) turns on, the SW node is pulled up to VDD and the voltage on the BST pin is boosted approximately 5V above VIN to provide the necessary voltage for the high-side driver. A Schottky diode should be used for DB to maximize the high-side drive voltage.
5.3
Output Voltage Selection
The output voltage may be set to any voltage between 0.6V and 5.5V provided that the input voltage is higher than the desired output voltage by an amount sufficient to prevent the device from exceeding its maximum duty cycle specification. By connecting the V0 and V1 pins to logic high, logic low, or leaving them floating, VOUT can be set to any of nine standard voltages as shown in Table 6. Table 6. Pin-strap Output Voltage Settings
LOW 0.6V 1.2V 2.5V V0 OPEN 0.8V 1.5V 3.3V HIGH 1.0V 1.8V 5.0V
V1
LOW OPEN HIGH
If an output voltage other than those in Table 6 is desired, the resistor setting method can be used. Using this method, resistors R0 and R1 are selected to produce a specific voltage between 0.6V and 5.5V in 10 mV steps. Resistor R1 provides a coarse setting and R0 a fine adjustment, thus eliminating the additional errors associated with using two 1% resistors in a standard analog implementation (this typically adds 1.4% error using two 1% resistors).
Figure 9. Input Supply Connections
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To set VOUT using resistors, follow the steps below to calculate an index value and then use Table 7 to select the resistor that corresponds to the calculated index value as follows: 1. Calculate Index1: Index1 = 4 x VOUT 2. Round the result down to the nearest whole number. 3. Select the value for R1 from Table 7 using the Index1 rounded value from step 2. 4. Calculate Index0 using equation Index0 = 100 x VOUT - 25 x Index1... 5. Select the value for R0 from Table 7 using Index0 from step 4. Table 7. Resistors for Setting Output Voltage
Index R0 or R1 Index R0 or R1
Figure 10. Output Voltage Resistor Setting Example The output voltage may also be set to any value between 0.6V and 5.5V using the I2C/SMBus interface. See Application Note AN13 for details.
5.4
Start-up Procedure
0 1 2 3 4 5 6 7 8 9 10 11 12 Example:
10 k 11 k 12.1 k 13.3 k 14.7 k 16.2 k 17.8 k 19.6 k 21.5 k 23.7 k 26.1 k 28.7 k 31.6 k
13 14 15 16 17 18 19 20 21 22 23 24
34.8 k 38.3 k 42.2 k 46.4 k 51.1 k 56.2 k 61.9 k 68.1 k 75 k 82.5 k 90.9 k 100 k
The ZL2005 follows a specific internal start-up procedure after power is applied to the VDD pin. Table 8 describes the start-up sequence. If the device is to be synchronized to an external clock source, the clock must be stable prior to asserting the EN pin. The device requires approximately 10-20 ms to check for specific values stored in its internal memory. If the user has stored values in memory, those values will be loaded. The device will then check the status of all multi-mode pins and load the values associated with the pin settings. Once this process is completed, the device is ready to accept commands via the I2C/SMBus interface and the device is ready to be enabled. Once enabled, the device requires approximately 6 ms before its output voltage may be allowed to start its ramp-up process. If a soft start delay period less than 6 ms has been configured (using the DLY (0,1) pins), the device will default to a 6 ms delay period. If a delay period of 6 ms or higher is configured, the device will wait for the configured delay period before starting to ramp its output. After the delay period has expired, the output will begin to ramp towards its target voltage according to the pre-configured soft-start ramp time (using the SS (0,1) pins).
For VOUT = 1.33V: Index1 = 4 x 1.33V = 5.32 (5); From Table 7, using Index = 5 R1 = 16.2 k Index0 = (100 x 1.33V) - (25 x 5) = 8; From Table 7; R0 = 21.5 k
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Table 8. ZL2005 Start-up Sequence
Step # Step Name Description Time Duration
1 2 3 4 5
Power Applied Input voltage is applied to the ZL2005's VDD pin Internal Memory Check Multi-mode Pin Check Device Ready Pre-ramp Delay
Depends on input supply ramp time
The device will check for values stored in its internal memory. Approx 10-20 ms (device This step is also performed after a Restore command. will ignore an enable signal or PMBus traffic during The device loads values configured by multi-mode pins. this period) The device is ready to accept an enable signal. -- The device requires approximately 6 ms following an enable signal and prior to ramping its output. Additional pre-ramp Approx. 6 ms delay may be configured using the Delay pins. Table 9. Soft Start Delay Settings
LOW LOW DLY1 OPEN HIGH 0 ms
1
5.5
Soft Start Delay and Ramp Times
In some system applications, it may be necessary to set a delay from when an enable signal is received until the output voltage starts to ramp to its nominal value. In addition, the designer may wish to precisely set the time required for VOUT to ramp to its nominal value after the delay period has expired. The ZL2005 gives the system designer several options for precisely and independently controlling both the delay and ramp time periods for VOUT. These features may be used as part of an overall in-rush current management strategy or to precisely control how fast a load IC is turned on. The soft start delay period begins when the Enable pin is asserted and ends when the delay time expires. The soft-start delay period is set using the DLY (0,1) pins. The soft start ramp enables a controlled ramp to the nominal VOUT value that begins once the delay period has timed out. The ramp-up is guaranteed monotonic and its slope may be precisely set by setting the softstart ramp time using the SS (0,1) pins. The soft start delay and ramp times can be set to standard values according to Table 9 and Table 10 respectively.
DLY0 OPEN
HIGH
5 ms1 50 ms
Reserved 10 ms 20 ms 100 ms 200 ms
NOTE: 1. When the device is set to 0 ms or 5 ms delay, it will begin its ramp up after the internal circuitry has initialized (approx. 6 ms).
Table 10. Soft Start Ramp Settings LOW LOW SS1 OPEN HIGH 0 ms 5 ms 50 ms
1
SS0 OPEN 1 ms 10 ms 100 ms
HIGH 2 ms 20 ms 200 ms
NOTE: 1. When the soft start ramp is set to zero, the device will ramp up as quickly as the internal circuitry and output load capacitance will allow.
If the desired soft start delay and ramp times are not one of the values listed in Table 8 and Table 9, the times can be set to a custom value by connecting a resistor from the DLY0 or SS0 pin to SGND using the appropriate resistor value from Table 11. The value of this resistor is measured upon start-up or Restore and will not change if this resistor is varied after power has been applied to the ZL2005. See Figure 11 for typical connections using resistors. Note: Do not connect a resistor to the DLY1 or SS1 pin. These pins are not utilized for setting soft-start delay and ramp times. Connecting an external resistor to these pins may cause conflicts with other device settings.
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N/C RDLY
Power Good
ZL2005
SS0 SS1
The ZL2005 provides a Power Good (PG) signal that indicates the output voltage is within a specified tolerance of its target level and no fault condition exists. By default, the PG pin will assert if the output is within 10%/+15% of the target voltage These limits may be changed via the I2C/SMBus interface. See Application Note AN13 for details. A PG delay period is defined as the time from when all conditions within the ZL2005 for asserting PG are met to when the PG pin is actually asserted. This feature is commonly used instead of using an external reset controller to control external digital logic. By default, the ZL2005 PG delay is set equal to the soft-start ramp time setting. Therefore, if the soft-start ramp time is set to 10 ms, the PG delay will be set to 10 ms. The PG delay may be set independently of the soft-start ramp using the I2C/SMBus as described in Application Note AN13.
DLY1
DLY0
RSS N/C
Figure 11. DLY and SS Pin Resistor Connections Table 11. DLY and SS Resistor Values
DLY or SS RDLY or RSS DLY or SS RDLY or RSS
0 ms 10 ms 20 ms 30 ms 40 ms 50 ms 60 ms 70 ms 80 ms 90 ms 100 ms
10 k 11 k 12.1 k 13.3 k 14.7 k 16.2 k 17.8 k 19.6 k 21.5 k 23.7 k 26.1 k
110 ms 120 ms 130 ms 140 ms 150 ms 160 ms 170 ms 180 ms 190 ms 200 ms
28.7 k 31.6 k 34.8 k 38.3 k 42.2 k 46.4 k 51.1 k 56.2 k 61.9 k 68.1 k
5.7
Switching Frequency and PLL
The soft start delay and ramp period can be set to custom values via the I2C/SMBus interface. When the soft start delay is set to 0 ms, the device will begin its ramp up after the internal circuitry has initialized (approx. 6ms).
The ZL2005 incorporates an internal phase locked loop (PLL) to clock the internal circuitry. The PLL can be driven by an internal oscillator or driven from an external clock source connected to the SYNC pin. When using the internal oscillator, the SYNC pin can be configured as a clock output for use by other devices. The SYNC pin is a unique pin that can perform multiple functions depending on how it is configured. The CFG pin is used to select the operating mode of the SYNC pin as shown in Table 12. Figure 12 illustrates the typical connections for each mode. Table 12. SYNC Pin Function Selection
CFG Pin SYNC Pin Function
LOW OPEN HIGH
SYNC is configured as an input Auto Detect mode SYNC is configured as an output fSW = 400 kHz (default)
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Logic high
CFG
SYNC
200 kHz - 2 MHz
SYNC
200 kHz - 2 MHz
ZL2005
ZL2005
A) SYNC = output
N/C Logic high N/C
B) SYNC = input
N/C
CFG
CFG
CFG
SYNC
200 kHz - 2 MHz
Open
SYNC
SYNC
ZL2005
OR
Logic low
ZL2005
OR
RSYNC
ZL2005
C) SYNC = Auto Detect
Figure 12. SYNC Pin Configurations
Configuration A: SYNC OUTPUT When the SYNC pin is configured as an output (CFG pin is tied HIGH), the device will operate from its internal oscillator and will drive the resulting internal oscillator signal (preset to 400 kHz) onto the SYNC pin so other devices can be synchronized to it. The SYNC pin will not be checked for an incoming clock signal while in this configuration. Configuration B: SYNC INPUT When the SYNC pin is configured as an input (CFG pin is tied LOW), the device will automatically check for a clock signal on the SYNC pin each time EN is asserted. The ZL2005's oscillator will then synchronize with the rising edge of external clock. The incoming clock signal must be in the range of 200 kHz to 2 MHz and must be stable when the enable pin is asserted. The clock signal must also exhibit the necessary performance requirements (see Table 3). In the event of a loss of the external clock signal, the output voltage may show transient over/undershoot. If this happens, the ZL2005 will turn off the power FETs (QH and QL in Figure 4) typically within 10 S. Users are discouraged from removing an external SYNC clock while the ZL2005 is operating with Enable asserted.
Configuration C: SYNC AUTO DETECT When the SYNC pin is configured in auto detect mode (CFG pin is left OPEN), the device will automatically check for a clock signal on the SYNC pin after enable is asserted. If a clock signal is present, The ZL2005's oscillator will then synchronize the rising edge of the external clock. Refer to SYNC INPUT description. If no incoming clock signal is present, the ZL2005 will configure the switching frequency according to the state of the SYNC pin as listed in Table 13. In this mode, the ZL2005 will only read the SYNC pin connection during the start-up sequence. Changes to SYNC pin connections will not affect fSW until the power (VDD) is cycled off and on. Table 13. Switching Frequency Selection
SYNC Pin Setting LOW OPEN HIGH Resistor Frequency 200 kHz 400 kHz 1 MHz See Table 14
If the user wishes to run the ZL2005 at a frequency other than those listed in Table 13, the switching frequency can be set using an external resistor, RSYNC, connected between SYNC and SGND using Table 14.
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Table 14. RSYNC Resistor Values fSW 200 kHz 222 kHz 242 kHz 267 kHz 296 kHz 320 kHz 364 kHz 400 kHz 421 kHz 471 kHz 533 kHz
RSYNC
fSW 571 kHz 615 kHz 667 kHz 727 kHz 889 kHz 1000 kHz 1143 kHz 1333 kHz 1600 kHz 2000 kHz
RSYNC
To select the appropriate power stage components for a set of desired performance goals, the power supply requirements listed in Table 15 must be known. Table 15. Power Supply Requirements Example
Parameter Range Example Value
10 k 11 k 12.1 k 13.3 k 14.7 k 16.2 k 17.8 k 19.6 k 21.5 k 23.7 k 26.1 k
28.7 k 31.6 k 34.8 k 38.3 k 46.4 k 51.1 k 56.2 k 68.1 k 82.5 k 100 k
The switching frequency can also be set to any value between 200 kHz and 2 MHz using the I2C/SMBus interface. The available frequencies are bounded by the relation fsw = 8 MHz/N, ( with 4<= N <= 40). See Application Note AN13 for details on configuring the switching frequency using the I2C/SMBus interface. If multiple ZL2005s are used together, connecting the SYNC pins together will force all devices to synchronize to one another. The CFG pin of one device must have its SYNC pin set as an output and the remaining devices must have their SYNC pins set as an input or all devices must be driven by the same external clock source. Note: The switching frequency read back using the appropriate PMBus command will differ slightly from the selected value in Table 14. The difference is due to hardware quantization.
Input voltage (VIN) 3.0 - 14.0 V Output voltage (VOUT) 0.6 - 5.0 V 0 to ~25 A Output current (IOUT) Output voltage ripple < 3% of (Vorip) VOUT Output load step (Iostep) < Io Output load step rate -- Allowable output -- deviation due to load step Maximum PCB temp. 120C Desired efficiency -- Other considerations Various
12 V 1.2 V 20 A 1% of VOUT 50% of Io 10 A/S 50 mV 85C 85% Optimize for small size
Design Trade-offs The design of a switching regulator power stage requires the user to consider trade-offs between cost, size and performance. For example, size can be optimized at the expense of efficiency. Additionally, cost can be optimized at the expense of size. For a detailed description of circuit trade-offs, refer to Application Note AN11. To start a design, select a switching frequency (fSW) based on Table 16. This frequency is a starting point and may be adjusted as the design progresses. Table 16. Circuit Design Considerations
Frequency Range Efficiency Circuit Size
5.8
Selecting Power Train Components
The ZL2005 is a synchronous buck controller that uses external MOSFETs, inductor and capacitors to perform the power conversion process. The proper selection of the external components is critical for optimized performance. Zilker Labs offers an online circuit design and simulation tool, PowerPilot, to assist designers in this task. Please visit http://www.zilkerlabs.com to access PowerPilot. For more detailed guidelines regarding component selection, please refer to Application Note AN11.
200 - 400 kHz 400 - 800 kHz 800 kHz - 2 MHz
Highest Moderate Lower
Larger Smaller Smallest
Inductor Selection The output inductor selection process will include several trade-offs. A high inductance value will result in a low ripple current (Iopp), which will reduce the output capacitance requirement and produce a low output ripple voltage, but may also compromise output transient load performance. Therefore, a balance must be
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struck between output ripple and optimal load transient performance. A good starting point is to select the output inductor ripple current (Iopp) equal to the expected load transient step magnitude (Iostep): core loss and the DCR loss and compare the total loss to the maximum power dissipation recommendation in the inductor datasheet. Output Capacitor Selection Several trade-offs also must be considered when selecting an output capacitor. Low ESR values are needed to have a small output deviation during transient load steps (Vosag) and low output voltage ripple (Vorip). However, capacitors with low ESR, such as semi-stable (X5R and X7R) dielectric ceramic capacitors, also have relatively low capacitance values. Many designs can use a combination of high capacitance devices and low ESR devices in parallel. For high ripple currents, a low capacitance value can cause a significant amount of output voltage ripple. Likewise, in high transient load steps, a relatively large amount of capacitance is needed to minimize the output voltage deviation while the inductor current ramps up to the new steady state output current value. As a starting point, allocate one-half of the output voltage ripple to the capacitor ESR and the other half to its capacitance, as shown in the following equations:
I opp = I ostep
(3)
Now the output inductance can be calculated using the following equation:
LOUT =
VOUT x 1 - VOUT VINM f sw x I opp
(
)
(4)
where VINM is the maximum input voltage. The average inductor current is equal to the maximum output current. The peak inductor current (ILpk) is calculated using the following equation where IOUT is the maximum output current:
IL pk = I OUT +
I opp 2
(5)
Select an inductor rated for the average DC current with a peak current rating above the peak current computed above. In over-current or short-circuit conditions, the inductor may have currents greater than 2X the normal maximum rated output current. It is desirable to use an inductor that is not saturated at these conditions to protect the load and the power supply MOSFETs from damaging currents. Once an inductor is selected, the DCR and core losses in the inductor are calculated. Use the DCR specified in the inductor manufacturer's datasheet.
COUT =
I opp 8 x f sw x Vorip
Vorip 2
(8)
ESR =
(9)
2 x I opp
Use these values to make an initial capacitor selection, using a single capacitor or several capacitors in parallel. After a capacitor has been selected, the resulting output voltage ripple can be calculated using the following equation:
PLDCR = DCR x I Lrms
ILrms is given by:
2
(6)
Vorip = I opp x ESR +
2 I opp 2 12
I opp 8 x f sw x COUT
(10)
I Lrms = I OUT +
(7)
where IOUT is the maximum output current. Next, calculate the core loss of the selected inductor. Since this calculation is specific to each inductor and manufacturer, refer to the chosen inductor's datasheet. Add the
21
Because each part of this equation was made to be less than or equal to half of the allowed output ripple voltage, the Vorip should be less than the desired maximum output ripple.
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For more information on the performance of the power supply in response to a transient load, refer to Application Note AN11. Input Capacitor It is highly recommended that dedicated input capacitors be used in any point-of-load design, even when the supply is powered from a heavily filtered 5 or 12 V "bulk" supply. This is because of the high RMS ripple current that is drawn by the buck converter topology. This input ripple (ICINrms) can be determined from the following equation: Calculate the desired maximum RDS(ON) as follows: 2 (14) = P /I R
DS(ON) QL botrms
Note that the RDS(ON) given in the manufacturer's datasheet is measured at 25C. The actual RDS(ON) in the end-use application will be much higher. For example, a Vishay Si7114 MOSFET with a junction temperature of 125C has an RDS(ON) 1.4 times higher than the value at 25C. Select a candidate MOSFET, and calculate the required gate drive current as follows:
I CINrms = I OUT x D x (1 - D )
(11)
I g = f sw x Qg
(15)
Please refer to Application Note AN11 for detailed derivation including efficiency and ripple current. Without capacitive filtering near the power supply input circuit, this current would flow through the supply bus and return planes, coupling noise into other system circuitry. The input capacitors should be rated at 1.2X the ripple current calculated above to avoid overheating of the capacitors due to the high ripple current, which can cause premature failure. Ceramic capacitors with X7R or X5R dielectric with low ESR and 1.1X the maximum expected input voltage are recommended. Bootstrap Circuit Component Selection The high-side driver boost circuit utilizes an external Schottky diode (DB) and an external bootstrap capacitor (CB) to supply sufficient gate drive for the highside MOSFET driver. DB should be a 20 mA, 30 V Schottky diode or equivalent device and CB should be a 1 F ceramic type rated for at least 6.3V. QL Selection The bottom MOSFET should be selected primarily based on the device's RDS(ON) and secondarily based on its gate charge. To choose QL, use the following equation and allow 2-5% of the output power to be dissipated in the RDS(ON) of QL (lower output voltages and higher step-down ratios will be closer to 5%):
Keep in mind that the total allowed gate drive current for both QH and QL is 80 mA. MOSFETs with lower RDS(ON) tend to have higher gate charge requirements, which increases the current and resulting power required to turn them on and off. Since the MOSFET gate drive circuits are integrated in the ZL2005, this power is dissipated in the ZL2005 according to the following equation:
PQL = f sw x Qg x VINM
(16)
QH Selection In addition to the RDS(ON) loss and gate charge loss, QH also has switching loss. The procedure to select QH is similar to the procedure for QL. First, assign 2- 5% of the output power to be dissipated in the RDS(ON) of QH using the equation for QL above. As was done with QL, calculate the RMS current as follows:
I toprms = I Lrms x D
(17)
Calculate a starting RDS(ON) as follows, in this example using 5%:
PQH
= 0 . 05 x V OUT x I OUT
(18)
PQL
= 0 . 05 x V OUT x I OUT
(12)
RDS(ON) = PQH / Itoprms2
(19)
Calculate the RMS current in QL as follows:
I botrms = I Lrms x 1 - D
22
(13)
Select a MOSFET and calculate the resulting gate drive current. Verify that the combined gate drive current from QL and QH does not exceed 80 mA.
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Next, calculate the switching time using
tsw = Qg I gdr
VIN GH SW VOUT R1 R2 CL
(20)
ZL2005
where Qg is the gate charge of the selected QH and Igdr is the peak gate drive current available from the ZL2005. Although the ZL2005 has a typical gate drive current of 3 A, use the minimum guaranteed current of 2 A for a conservative design. Using the calculated switching time, calculate the switching power loss in QH using
GL ISENA ISENB
Figure 13. DCR Current Sensing These components should be selected according to the following equation: RC = L / DCR-------------------------- (24) R1 should be in the range of 500 to 5 k in order to minimize the power dissipation through it. The user should make sure the resistor package size is appropriate for the power dissipated. Once R1 has been calculated, the value of R2 should be selected based on the following equation: R2 = 5 x R1 -----------------------------(25) If RDS(ON) is being used the external low side MOSFET will act as the sensing element as indicated in Figure 14.
Pswtop = VINM x t sw x I OUT x f sw
(21)
The total power dissipated by QH is given by the following equation:
P QHtot
= P QH + P swtop
(22)
MOSFET Thermal Check Once the power dissipations for QH and QL have been calculated, the MOSFETs junction temperature can be estimated. Using the junction-to-case thermal resistance (Rth) given in the MOSFET manufacturer's datasheet and the expected maximum printed circuit board temperature, calculate the junction temperature as follows:
5.9
Current Limit Threshold Selection
Tj max = Tpcb + PQ x Rth
(23)
For further details of thermal analysis and design see Application Note AN10. Current Sensing Components Once the current sense method has been selected (Refer to Section 5.9, "Current Limit Threshold Selection," ), the procedure to select the component is the following: When using the inductor DCR sensing method, the user must also select an R/C network comprised of R1 and CL (see Figure 13).
It is recommended that the user include a current limiting mechanism in their design to protect the power supply from damage and prevent excessive current from being drawn from the input supply in the event that the output is shorted to ground or an overload condition is imposed on the output. Current limiting is accomplished by sensing the current flowing through the circuit during a portion of the duty cycle. Output current sensing can be accomplished by measuring the voltage across a series resistive sensing element according to equation 26. VLIM = ILIM x RSENSE ---------- -------(26) Where: ILIM is the desired maximum current that should flow in the circuit RSENSE is the resistance of the sensing element VLIM is the voltage across the sensing element at the point the circuit should start limiting the output current.
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The ZL2005 supports "lossless" current sensing, by measuring the voltage across a resistive element that is already present in the circuit. This eliminates additional efficiency losses incurred by devices that must use an additional series resistance in the circuit. To set the current limit threshold, the user must first select a current sensing method. The ZL2005 incorporates two methods for current sensing, synchronous MOSFET RDS(ON) sensing and inductor DC resistance (DCR) sensing; Figure 14 shows a simplified schematic for each method. VIN
GH
The current sensing method can be selected using the ILIM1 pin using Table 17. The ILIM0 pin must have a finite resistor connected to ground in order for Table 17 to be valid. If no resistor is connected between ILIM0 and ground, the default method is MOSFET RDS(ON) sensing. The current sensing method can be modified via the I2C/SMBus interface. Please refer to Application Note AN13 for details. In addition to selecting the current sensing method, the ZL2005 gives the power supply designer several choices for the fault response during over or under current condition. The user can select the number of violations allowed before declaring fault, a blanking time and the action taken when a fault is detected. The blanking time represents the time when no current measurement is taken. This is to avoid taking a reading just after a current load step (Less accurate due to potential ringing).It is a configurable parameter. Table 17 includes default parameters for the number of violations and the blanking time using pin-strap.
ZL2005
SW ISENA GL ISENB
VOUT
MOSFET RDS,ON Sensing
VIN
GH SW
ZL2005
GL ISENA ISENB
VOUT
Inductor DCR Sensing
Figure 14. Current Sensing Methods Table 17. Current Sensing Method Selection
ILIM0 Pin
1
ILIM1 Pin
Current Limiting Configuration
Number of Violations Allowed2
Comments
RILIM0 RILIM0
LOW OPEN
RILIM0
HIGH Resistor
Ground-referenced (RDS,ON) sensing Blanking time: 672 ns Output-referenced, down-slope sensing (Inductor DCR sensing) Blanking time: 352 ns Output-referenced, up-slope sensing (Inductor DCR sensing) Blanking time: 352 ns
4 4
Best for low duty cycle and low fSW Best for low duty cycle and high fSW Best for high duty cycle
4
Depends on resistor value used; see Table 18
NOTES:
1. 10 k < RILIM0 < 100 k 2. The number of violations allowed prior to issuing a fault response.
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Table 18. Resistor Configured Current Sensing Method Selection
RILIM1 Current Sensing Method Number of Violations Allowed1
10 k 11 k 12.1 k 13.3 k 14.7 k 16.2 k 17.8 k 19.6 k 21.5 k 23.7 k 26.1 k 28.7 k 31.6 k 34.8 k 38.3 k 42.2 k 46.4 k 51.1 k 56.2 k 61.9 k 68.1 k 75 k 82.5 k 90.9 k
NOTES:
Ground-referenced (RDS,ON) sensing Best for low duty cycle and low fSW Blanking time: 672 ns
Output-referenced, down-slope sensing (Inductor DCR sensing) Best for low duty cycle and high fSW Blanking time: 352 ns
Output-referenced, up-slope sensing (Inductor DCR sensing) Best for high duty cycle Blanking time: 352 ns
1 3 5 7 9 11 13 15 1 3 5 7 9 11 13 15 1 3 5 7 9 11 13 15
1. The number of violations allowed prior to issuing a fault response.
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Once the sensing method has been selected, the user must select the voltage threshold (VLIM) based on equation 26, the desired current limit threshold, and the resistance of the sensing element. The current limit threshold can be selected by simply connecting the ILIM0 and ILIM1 pins as shown in Table 19. The ground-referenced sensing method is being used in this mode.
Table 19. Current Limit Threshold Voltage Settings LOW 20 mV 50 mV 80 mV ILIM0 OPEN 30 mV 60 mV 90 mV HIGH 40 mV 70 mV 100 mV
5.10 Loop Compensation
The ZL2005 operates as a voltage-mode synchronous buck controller with a fixed frequency PWM scheme. Although the ZL2005 uses a digital control loop, it operates much like a traditional analog PWM controller. See Figure 15 for a simplified block diagram of the ZL2005 control loop, which differs from an analog control loop by the constants in the PWM and compensation blocks. As in the analog controller case, the compensation block compares the output voltage to the desired voltage reference and compensation zeros are added to keep the loop stable. The resulting integrated error signal is used to drive the PWM logic, converting the error signal into a duty cycle value to drive the external MOSFETs.
VIN
D DPWM 1-D C RC RO L
ILIM1
LOW OPEN HIGH
The threshold voltage can also be selected in 5 mV increments by connecting a resistor, RLIM0, between the ILIM0 pin and ground according to Table 20. This method is preferred if the user does not desire to use or does not have access to the I2C/SMBus interface and the desired threshold value is contained in Table 20.
Table 20. Current Limit Threshold Voltage Settings VLIM RLIM0 VLIM RLIM0
VOUT
0 mV 5 mV 10 mV 15 mV 20 mV 25 mV 30 mV 35 mV 40 mV 45 mV 50 mV
10 k 11 k 12.1 k 13.3 k 14.7 k 16.2 k 17.8 k 19.6 k 21.5 k 23.7 k 26.1 k
55 mV 60 mV 65 mV 70 mV 75 mV 80 mV 85 mV 90 mV 95 mV 100 mV
28.7 k 31.6 k 34.8 k 38.3 k 42.2 k 46.4 k 51.1 k 56.2 k 61.9 k 68.1 k
Compensation
Figure 15. Control Loop Block Diagram In the ZL2005, the compensation zeros are set by configuring the FC0 and FC1 pins or via the I2C/SMBus interface once the user has calculated the required settings. This method eliminates the inaccuracies due to the component tolerances associated with using external resistors and capacitors. Most applications can be served by using the pin-strap compensation settings listed in Table 21. These settings will yield a conservative crossover frequency at a fixed fraction of the switching frequency (fSw/20) and 60 of phase margin.
The current limit threshold can be set via the I2C/ SMBus interface. Please refer to Application Note AN13 for further details on setting current limit parameters.
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ZL2005
Table 21. Pin-Strap Setting for Loop Compensation
FC0 Range FC0 Pin FC1 Range FC1 Pin
fsw/60 < fn < fsw/30
HIGH
fsw/120 < fn < fsw/60
OPEN
fsw/240 < fn < fsw/120
LOW
fzesr > fsw/10 fsw/10 > fzesr > fsw/30 TBD fzesr > fsw/10 fsw/10 > fzesr > fsw/30 TBD fzesr > fsw/10 fsw/10 > fzesr > fsw/30 TBD
HIGH OPEN LOW HIGH OPEN LOW HIGH OPEN LOW
Step 1: Using the following equation, calculate the resonant frequency of the LC filter, fn.
5.11 Non-Linear Response Settings
The ZL2005 incorporates a non-linear response (NLR) loop that decreases the response time and the output voltage deviation in the event of a sudden output load current step. The NLR loop incorporates a secondary error signal processing path that bypasses the primary error loop when the output begins to transition outside of the standard regulation limits. This scheme results in a higher equivalent loop bandwidth than is possible using a traditional linear loop. When a load current step function imposed on the output causes the output voltage to drop below the lower regulation limit, the NLR circuitry will force a positive correction signal that will turn on the upper MOSFET and quickly force the output to increase. Conversely, a negative load step (i.e., removing a large load current) will cause the NLR circuitry to force a negative correction signal that will turn on the lower MOSFET and quickly force the output to decrease. The ZL2005 has been pre-configured with appropriate NLR settings that correspond to the loop compensation settings in Table 21.
1 f n = -----------------------2 L x C
(27)
Step 2: Based on Table 21, determine the FC0 setting. Step 3: Calculate the ESR zero frequency (fZESR).
1f zesr = ----------------2CRc
(28)
Step 4: Based on Table 21, determine the FC1 setting. The parameters of the feedback compensation can also be set using the I2C/SMBus interface. Refer to Application Note AN13 for details. Refer to Application Note AN16 for details on setting FC0 and FC1. The Zilker Labs web site (www.zilkerlabs.com) provides an on-line tool (PowerPilot) which computes compensation coefficients, and provides a parameterdriven design tool, schematic and BOM generation, and circuit simulation including control loop simulation.
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ZL2005 5.12 Efficiency Optimized Driver Deadtime Control
The ZL2005 utilizes a closed loop algorithm to optimize the dead-time applied between the gate drive signals for the top and bottom FETs. In a synchronous buck converter, the MOSFET drive circuitry must be designed such that the top and bottom MOSFETs are never in the conducting state at the same time. (Potentially damaging currents flow in the circuit if both top and bottom MOSFETs are simultaneously on for periods of time exceeding a few nanoseconds.) Conversely, long periods of time in which both MOSFETs are off reduce overall circuit efficiency by allowing current to flow in their parasitic body diodes. It is therefore advantageous to minimize this deadtime to provide optimum circuit efficiency. In the first order model of a buck converter, the duty cycle is determined by the equation: D = VOUT /VIN -------------------- (29) However, non-idealities exist that cause the real duty cycle to extend beyond the ideal. Deadtime is one of those non-idealities that can be manipulated to improve efficiency. The ZL2005 has an internal algorithm that constantly adjusts deadtime non-overlap to minimize duty cycle, thus maximizing efficiency. This circuit will null out deadtime differences due to component variation, temperature and loading effects. This algorithm is independent of application circuit parameters such as MOSFET type, gate driver delays, rise and fall times and circuit layout. In addition, it does not require drive or MOSFET voltage or current waveform measurements.
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6
6.1
Power Management Functional Description
Input Undervoltage Lockout (UVLO)
end of the delay period. The device will remain in shutdown until permitted to restart. 3. Initiate an immediate shutdown until the fault has been cleared. The user can select a specific number of retry attempts. The default response from a UVLO fault is an immediate shutdown of the device. The device will continuously check for the presence of the fault condition. If the fault condition is no longer present, the ZL2005 will be re-enabled. Please refer to Application Note AN13 for details on how to configure the UVLO threshold or to select specific UVLO fault response options via the I2C/SMBus interface.
The input undervoltage lockout (UVLO) prevents the ZL2005 from operating when the input falls below a preset threshold, indicating the input supply is out of its specified range. The UVLO threshold (VUVLO) can be set between 2.85 V and 16 V using the UVLO pin. The simplest implementation is to connect the UVLO pin as shown in Table 22. If the UVLO pin is left unconnected, the UVLO threshold will default to 4.5 V. Table 22. UVLO Threshold Settings
Pin Setting UVLO Threshold
LOW OPEN HIGH
3V 4.5 V 10.8 V
6.2
Output Overvoltage Protection
If the desired UVLO threshold is not one of the listed choices, the user can configure a threshold between 2.85 V and 16 V by connecting a resistor between the UVLO pin and GND by selecting the appropriate resistor from Table 23.
Table 23. UVLO Resistor Values UVLO RUVLO UVLO RUVLO
The ZL2005 offers an internal output overvoltage protection circuit that can be used to protect sensitive load circuitry from being subjected to a voltage higher than its prescribed limits. This feature is especially useful in protecting expensive processors, FPGAs, and ASICs from excessive voltages. A hardware comparator is used to compare the actual output voltage (seen at the VSEN pin) to a threshold set to 15 % higher than the target output voltage by default. If the voltage at the VSEN pin exceeds this upper threshold level, the PG pin will de-assert. The device can then respond in a number of ways as follows: 1. Initiate an immediate shutdown until the fault has been cleared. The user can select a specific number of retry attempts. 2. Turn off the high-side MOSFET and turn on the low-side MOSFET. The low-side MOSFET remains ON until the device attempts a restart. The default response from an overvoltage fault is an immediate shutdown of the device. The device will continuously check for the presence of the fault condition. If the fault condition is no longer present, the ZL2005 will be re-enabled. Please refer to Application Note AN13 for details on how to select specific overvoltage fault response options via the I2C/SMBus interface.
FN6848.0 February 18, 2009
2.85 V 3.14 V 3.44 V 3.79 V 4.18 V 4.59 V 5.06 V 5.57 V 6.13 V 6.75 V
17.8 k 19.6 k 21.5 k 23.7 k 26.1 k 28.7 k 31.6 k 34.8 k 38.3 k 42.2 k
7.42 V 8.18 V 8.99 V 9.9 V 10.9 V 12 V 13.2 V 14.54 V 16 V
46.4 k 51.1 k 56.2 k 61.9 k 68.1 k 75 k 82.5 k 90.9 k 100 k
VUVLO can also be set to any value between 2.85 V and 16 V via I2C/SMBus. Once an input undervoltage fault condition occurs, the device can respond in a number of ways as follows: 1. Continue operating without interruption. 2. Continue operating for a given delay time, followed by shutdown if the fault still persists at the
29
ZL2005 6.3 Output Pre-Bias Protection
If the pre-bias voltage is higher than the target voltage exists after the pre-configured delay period has expired, the target voltage is set to match the existing pre-bias voltage and both drivers are enabled with a PWM duty cycle that would ideally create the pre-bias voltage. Once the pre-configured soft-start ramp period has expired, the Power Good pin will be asserted (assuming the pre-bias voltage is not higher than the overvoltage limit). The PWM will then adjust its duty cycle to match the original target voltage and the output will ramp down to the pre-configured output voltage. If a pre-bias voltage higher than the overvoltage limit, the device will not initiate a turn-on sequence and will declare an overvoltage fault condition to exist. In this case, the device will respond based on the output overvoltage fault response method that has been selected. See Section 6.2, "Output Overvoltage Protection," for response options due to an overvoltage condition.
An output pre-bias condition exists when an externally applied voltage is present on a power supply's output before the power supply's control IC is enabled. Certain applications require that the converter not be allowed to sink current during start up if a pre-bias condition exists at the output. The ZL2005 provides pre-bias protection by sampling the output voltage prior to initiating an output ramp. If a pre-bias voltage lower than the target voltage exists after the pre-configured delay period has expired, the target voltage is set to match the existing pre-bias voltage and both drivers are enabled. The output voltage is then ramped to the final regulation value at the ramp rate set by the SS (0,1) pins. The actual time the output will take to ramp from the pre-bias voltage to the target voltage will vary depending on the pre-bias voltage but the total time elapsed from when the delay period expires and when the output reaches its target value will match the pre-configured ramp time. See Figure 16.
I
6.4
Output Overcurrent Protection
VOUT
Target voltage Pre-bias voltage
The ZL2005 can protect the power supply from damage if the output is shorted to ground or if an overload condition is imposed on the output. Once the current limit threshold has been selected (see Section 5.9, "Current Limit Threshold Selection," ), the user may determine the desired course of action to be taken when an overload condition exists. The following overcurrent protection response options are available: 1. Initiate a shutdown and attempt to restart an infinite number of times with a preset delay time. 2. Initiate a shutdown and attempt to restart the power supply a preset number of times with a preset delay between attempts. 3. Continue operating throughout a specific delay time, followed by shutdown. 4. Continue operating throughout the fault (this could result in permanent damage to the power supply).
SS Delay SS Ramp
SS Delay
SS Ramp
Time
VPREBIAS < VTARGET
VOUT
Pre-bias voltage Target voltage
Time
PG Delay
5. Initiate an immediate shutdown. The default response from an overcurrent fault is an immediate shutdown of the device. The device will continuously check for the presence of the fault condition. If the fault condition is no longer present, the ZL2005 will be re-enabled.
VPREBIAS > VTARGET
Figure 16. Output Response to Pre-Bias Voltages
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Please refer to Application Note AN15 for details on how to select specific overcurrent fault response options via the I2C/SMBus interface.
6.6
Voltage Tracking
6.5
Thermal Protection
The ZL2005 includes an on-chip thermal sensor that continuously measures the internal temperature of the die and will shut down the device when the temperature exceeds the preset limit. The default temperature limit is set to 125C in the factory, but the user may set the limit to a different value if desired. See Application Note AN13 for details. Note that setting a higher thermal limit via the I2C/SMBus interface may result in permanent damage to the device. Once the device has been disabled due to an internal temperature fault, the user may select one of several fault response options as follows: 1. Initiate a shutdown and attempt to restart an infinite number of times with a preset delay time. 2. Initiate a shutdown and attempt to restart the power supply a preset number of times with a preset delay between attempts. 3. Continue operating throughout a specific delay time, followed by shutdown. 4. Continue operating throughout the fault (this could result in permanent damage to the power supply). 5. Initiate an immediate shutdown. If the user has configured the device to restart, the device will wait the preset delay period (if configured to do so) and will then check the temperature. If the temperature has dropped below a value that is approximately 15C lower than the selected temperature limit (the over-temperature warning threshold), the device will attempt to re-start. If the temperature is still above the over-temperature warning threshold, the device will wait the preset delay period and retry again. The default response from a temperature fault is an immediate shutdown of the device. The device will continuously check for the presence of the fault condition. If the fault condition is no longer present, the ZL2005 will be re-enabled. Please refer to Application Note AN13 for details on how to select specific temperature fault response options via the I2C/SMBus interface.
Numerous high performance systems place stringent demands on the order in which the power supply voltages are turned on. This is particularly true when powering FPGAs, ASICs, and other advanced processor devices that require multiple supply voltages to power a single die. In most cases, the I/O operates at a higher voltage than the Core and therefore the Core supply voltage, must not exceed the I/O supply voltage by some amount (typically 300 mV). Voltage tracking protects these sensitive ICs by limiting the differential voltage between multiple power supplies during the power-up and power down sequence. The ZL2005 integrates a lossless tracking scheme that allows its output to track a voltage that is applied to the VTRK pin with no external components required. The VTRK pin is an analog input that, when tracking mode is enabled, configures the voltage applied to the VTRK pin to act as a reference for the device's output regulation. The ZL2005 offers two modes of tracking: 1. Coincident. This mode configures the ZL2005 to ramp its output voltage at the same rate as the voltage applied to the VTRK pin. 2. Ratiometric. This mode configures the ZL2005 to ramp its output voltage at a rate that is a percentage of the voltage applied to the VTRK pin. The default setting is 50%, but an external resistor string may be used to configure a different tracking ratio. Figure 17 illustrates the typical connection and the two tracking modes.
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ZL2005
VIN
GH Q1 L1 Q2
ZL2005
VTRK
SW GL
VOUT
C1
VTRK
VOUT
VTRK
VOUT
Time
Coincident
VOUT
VTRK
The master ZL2005 device in a tracking group is defined as the device that has the highest target output voltage within the group. This master device will control the ramp rate of all tracking devices and is not configured for tracking mode. A delay of at least 10 ms must be configured into the master device using the DLY0/1 pins, and the user may also configure a specific ramp rate using the SS0/1 pins. Any device that is configured for tracking mode will ignore its soft-start delay and ramp time settings (SS0/1 and DLY0/1 pins) and its output will take on the turn-on/ turn-off characteristics of the reference voltage present at the VTRK pin. The tracking mode for all other devices can be set by connecting a resistor from the SS1 pin to ground according to Table 24. All of the ENABLE pins in the tracking group must be connected together and driven by a single logic source.
VOUT
Time
Ratiometric
Figure 17. Tracking Modes Table 24. Tracking Mode Configuration
RSS1 No resistor Tracking Ratio Upper Track Limit Ramp-up/Ramp-down Behavior
.
10 k 11 k 12.1 k 13.3 k 14.7 k 16.2 k 17.8 k 19.6 k
100%
Tracking mode is disabled Limited by target voltage and 110% of Output not allowed to decrease before PG V(0,1) pin-strap setting Output will always follow VTRK Limited by VTRK pin voltage 110% of V(0,1) pin-strap setting Limited by target voltage and 110% of V(0,1) pin-strap setting Output not allowed to decrease before PG Output will always follow VTRK Output not allowed to decrease before PG Output will always follow VTRK Output not allowed to decrease before PG Output will always follow VTRK
50%
Limited by VTRK pin voltage 110% of V(0,1) pin-strap setting
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ZL2005 6.7 Voltage Margining 6.9 I2C/SMBus Device Address Selection
The ZL2005 offers a simple means to vary its output higher or lower than its nominal voltage setting in order to determine whether the load device is capable of operating over its specified supply voltage range. The MGN pin is a TTL-compatible input that is continuously monitored and can be driven directly by a processor I/O pin or other logic-level output. The ZL2005's output will be forced higher than its nominal setpoint when the MGN pin is driven HIGH, and the output will be forced lower than its nominal setpoint when the MGN pin is driven LOW. When the MGN pin is left floating (high impedance), the ZL2005's output voltage will be set to its nominal voltage setpoint determined by the V0 and V1 pins and/or the I2C/SMBus settings that configure the nominal output voltage. Default margin limits of VNOM 5% are pre-loaded in the factory, but the margin limits can be modified through the I2C/SMBus interface to as high as VNOM + 10% or as low as 0V, where VNOM is the nominal output voltage setpoint determined by the V0 and V1 pins. The margin limits and the MGN command can both be set individually through the I2C/SMBus interface. Additionally, the transition rate between the nominal output voltage and either margin limit can be configured through the I2C/SMBus interface. Please refer to Application Note AN13 for detailed instructions on modifying the margining configurations.
When communicating with multiple ZL2005s using the I2C/SMBus serial interface, each device must have its own unique address so the host can distinguish between the devices. The device address can be set according to the pin-strap options listed in Table 25 to provide up to eight unique device addresses. Address values are right-justified. Table 25. Serial Bus Device Address Selection
SA1 LOW SA0 LOW OPEN HIGH 0x20 0x21 0x22 OPEN 0x23 0x24 0x25 HIGH 0x26 0x27 Reserved
If additional device addresses are required, a resistor can be connected to the SA0 pin according to Table 26 to provide up to 25 unique device addresses. In this case the SA1 pin should be tied to SGND. Table 26. SMBus Address Values
SMBus Address RSA0 SMBus Address RSA0
6.8
I2C/SMBus Communications
The ZL2005 provides an I2C/SMBus digital interface that enables the user to configure all aspects of the device operation as well as monitor the input and output parameters. The ZL2005 can be used with any standard 2-wire I2C host device. In addition, the device is compatible with SMBus version 2.0 and includes an SALRT line to help mitigate bandwidth limitations related to continuous fault monitoring. The ZL2005 accepts most standard PMBus commands.
0x00 0x01 0x02 0x03 0x04 0x05 0x06 0x07 0x08 0x09 0x0A 0x0B 0x0C
10 k 11 k 12.1 k 13.3 k 14.7 k 16.2 k 17.8 k 19.6 k 21.5 k 23.7 k 26.1 k 28.7 k 31.6 k
0x0D 0x0E 0x0F 0x10 0x11 0x12 0x13 0x14 0x15 0x16 0x17 0x18
34.8 k 38.3k 42.2 k 46.4 k 51.1 k 56.2 k 61.9 k 68.1 k 75 k 82.5 k 90.9 k 100 k
If more than 25 unique device addresses are required or if other SMBus address values are desired, both the SA0 and SA1 pins can be configured with a resistor to SGND according to the equation (30) and Table 27. SMBus address = 25 x (SA1 index) + (SA0 index) (30)
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ZL2005
Using this method, the user can theoretically configure up to 625 unique SMBus addresses, however the SMBus is inherently limited to 128 devices so attempting to configure an address higher than 128 will cause the device address to repeat (i.e, attempting to configure a device address of 129 would result in a device address of 1). Therefore, the user should use index values 0-4 on the SA1 pin and the full range of index values on the SA0 pin, which will provide 125 device address combinations. Table 27. SMBus Address Index Values
SA0 or SA1 Index RSA SA0 or SA1 Index RSA
Selecting the phase offset for the device is accomplished by selecting a device address according to the following equation: Phase offset = device address x 45 For example: A device address of 0x00 or 0x20 would configure no phase offset A device address of 0x01 or 0x21 would configure 45 of phase offset A device address of 0x02 or 0x22 would configure 90 of phase offset. The phase offset of each device may also be set to any value between 0 and 337.5 in 22.5 increments via the I2C/SMBus interface. Please refer to Application Note AN13 for details.
0 1 2 3 4 5 6 7 8 9 10 11 12
10 k 11 k 12.1 k 13.3 k 14.7 k 16.2 k 17.8 k 19.6 k 21.5 k 23.7 k 26.1 k 28.7 k 31.6 k
13 14 15 16 17 18 19 20 21 22 23 24
34.8 k 38.3 k 42.2 k 46.4 k 51.1 k 56.2 k 61.9 k 68.1 k 75 k 82.5 k 90.9 k 100 k
6.11 Output Sequencing
A group of ZL2005 devices may be configured to power up in a predetermined sequence. This feature is especially useful when powering advanced processors, FPGAs, and ASICs that require one supply to reach its operating voltage prior to another supply reaching its operating voltage. Multi-device sequencing can be achieved by configuring each device through the I2C/ SMBus interface or by using Zilker Labs' patented autonomous sequencing mode. Autonomous sequencing mode configures sequencing using status information broadcast by ZL2005 onto the I2C/SMBus pins SCL and SDA. No I2C or SMBus host device is involved in this method, but the SCL and SDA pins must be interconnected between all devices that the user wishes to sequence using this method. Note: Pull-up resistors on SCL and SDA are required and should be selected using the criteria in the SMBus 2.0 specification. The sequence order is determined using each device's I2C/SMBus device address. Using autonomous sequencing mode (configured using the CFG pin), the devices must exhibit sequential device addresses with no missing addresses in the chain. This mode will also constrain each device to have a phase offset according to its device address as described in Section 6.10, "Phase Spreading" on this page.
6.10 Phase Spreading
When multiple point of load converters share a common DC input supply, it is desirable to adjust the clock phase offset of each device such that not all devices start to switch simultaneously. Setting each converter to start its switching cycle at a different point in time can dramatically reduce input capacitance requirements and efficiency losses. Since the peak current drawn from the input supply is effectively spread out over a period of time, the peak current drawn at any given moment is reduced and the power losses proportional to the IRMS2 are reduced dramatically. In order to enable phase spreading, all converters must be synchronized to the same switching clock. The CFG pin is used to set the configuration of the SYNC pin for each device as described in Section 5.7, "Switching Frequency and PLL," .
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ZL2005
The group will turn on in order starting with the device with the lowest address and will continue to turn on each device in the address chain until all devices connected have been turned on. When turning off, the device with the highest address will turn off first followed in reverse order by the other devices in the group. Sequencing is configured by connecting a resistor from the CFG pin to ground as described in Table 28. The CFG pin is used to set the configuration of the SYNC pin as well as to determine the sequencing method and order. Please refer to Switching Frequency and PLL for more details on the operating parameters of the SYNC pin. Table 28. CFG Pin Configurations for Sequencing
RCFG SYNC Pin Config Sequencing Configuration
.
addresses differ in only the three least significant bits of the address. For example, addresses 20, 25 and 27 are all within the same group. Addresses 1F, 20 and 28 are all in different groups. Devices in the same address group can broadcast power on and power off sequencing and fault spreading events with each other. Devices in different groups cannot. The Enable pins of all devices in a sequencing group must be tied together and driven high to initiate a sequenced turn-on of the group. Enable must be driven low to initiate a sequenced turnoff of the group. Please refer to Application Note AN13 for details on sequencing via the I2C/SMBus interface.
6.12 Monitoring via I2C/SMBus
A system controller can monitor a wide variety of different ZL2005 system parameters through the I2C/ SMBus interface. The controller can monitor for fault conditions by monitoring the SALRT pin, which will be asserted when any number of pre-configured fault or warning conditions occur. The system controller can also continuously monitor for any number of power conversion parameters including but not limited to the following: 1. Input voltage 2. Output voltage 3. Output current 4. Internal junction temperature 5. Temperature of an external device 6. Switching frequency 7. Duty cycle Please refer to Application Note AN13 for details on how to monitor specific parameters via the I2C/ SMBus interface.
10 k 11 k 12.1 k 14.7 k 16.2 k
Input Auto detect Output Input Auto detect
Sequencing is disabled The ZL2005 is configured as the first device in a nested sequencing group. Turn-on order is based on the device SMBus address. The ZL2005 is configured as a last device in a nested sequencing group. Turn-on order is based on the device SMBus address. The ZL2005 is configured as the middle device in a nested sequencing group. Turn-on order is based on the device SMBus address
17.8 k Output 21.5 k Input 23.7 k Auto detect 26.1 k Output 31.6 k Input 34.8 k Auto detect 38.3 k Output
Multiple device sequencing may also be achieved by issuing PMBus commands to assign the preceding device in the sequencing chain as well as the device that will follow in the sequencing chain. This method places less restrictions on device address (no need of sequential address) and also allows the user to assign any phase offset to any device irrespective of its device address. Event based sequencing and fault spreading are broadcast in address groups of up to eight ZL2005 devices. An address group consists of all devices whose
35
6.13 Temperature Monitoring Using the XTEMP Pin
The ZL2005 supports measurement of an external device temperature using either a thermal diode integrated in a processor, FPGA or ASIC, or using a discrete diode-connected NPN transistor such as a
FN6848.0 February 18, 2009
ZL2005
2N3904 or equivalent. Figure 18 illustrates the typical connections required.
XTEMP
6.15 Device Security Features
Note that the ZL2005 integrates several security measures to ensure that the user can only restore the device to a level that has been made available to them. During the initialization process, the ZL2005 checks for stored values contained in its internal memory. The ZL2005 offers two internal memory storage units that are accessible by the user as follows: 1. Default Store: A power supply module manufacturer may want to protect the module from damage by preventing the user from being able to modify certain values that are related to the physical construction of the module. In this case, the module manufacturer would use the Default Store and would allow the user to restore the device to its default setting but would restrict the user from restoring the device to the factory setting. 2. User Store: The manufacturer of a piece of equipment may want to provide the ability to modify certain power supply settings while still protecting the equipment from modifying values that can lead to a system level fault. The equipment manufacturer would use the User Store to achieve this goal. Please refer to Application Note AN13 for details on how to set specific security measures via the I2C/ SMBus interface.
ZL2005
SGND
2N3904
Discrete NPN
XTEMP
ZL2005
SGND
P FPGA DSP ASIC
Embedded Thermal Diode
Figure 18. External Temperature Monitoring
6.14 Fan Monitoring using the TACH Pin
The ZL2005 can monitor the tachometer pulse of an external 3-wire fan connected to the TACH pin. The device will report a revolutions per minute (RPM) value assuming one pulse per revolution. The TACH pin is only monitored when the device is enabled or when it is configured to always be in monitoring mode. Refer to Application Note AN13 for more details on configuring specific operating modes.
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ZL2005
7
Package Dimensions
NOTES:
1. 2. 3. 4. DIMENSIONING AND TOLERANCING CONFORM TO ASME Y14.5M. - 1994. ALL DIMENSIONS ARE IN MILLIMETERS (mm), O IS IN DEGREES. N IS THE TOTAL NUMBER OF TERMINALS. DIMENSION b APPLIES TO METALLIZED TERMINAL AND IS MEASURED BETWEEN 0.15 AND 0.30 mm FROM TERMINAL TIP. IF THE TERMINAL HAS THE OPTIONAL RADIUS ON THE OTHER END OF THE TERMINAL, THE DIMENSION b SHOULD NOT BE MEASURED IN THAT RADIUS AREA. ND AND NE REFER TO THE NUMBER OF TERMINALS ON EACH D AND E SIDE, RESPECTIVELY. MAXIMUM PACKAGE WARPAGE IS 0.05 mm. MAXIMUM ALLOWABLE BURRS IS 0.076 mm IN ALL DIRECTIONS. PIN #1 ID ON TOP WILL BE LASER MARKED. BILATERAL COPLANARITY ZONE APPLIES TO THE EXPOSED HEAT SINK SLUG AS WELL AS THE TERMINALS.
5. 6. 7. 8. 9.
10. THIS DRAWING CONFORMS TO JEDEC REGISTERED OUTLINE MO-220.
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ZL2005
8
Ordering Information
ZL2005ALNFT
Product Designator Shipping Option T = Tape & Reel 100 pcs T1 = Tape & Reel 1000 pcs Contact factory for other options Lead Finish F = Lead-free Matte Tin Firmware Revision Alpha character Operating Temperature Range L = -40 to +85C Package Designator A = QFN package
Related Documentation
The following application support documents and tools are available to help simplify your design.
Item Description
ZL2005EVK1 AN10 AN11 AN13 AN15 AN16 AN21 AN22 AN23
Evaluation Kit: 12V to 3.3V, 20A DC/DC Converter with Power Management Application Note: ZL2005 and ZL2105 Thermal and Layout Guidelines Application Note: ZL2005 Component Selection Guide Application Note: PMBus Command Set Application Note: ZL2005 Current Protection and Measurement Application Note: ZL2005 Digital Control Loop Compensation Application Note: Protecting Configuration During Manufacturing Application Note: Autonomous Sequencing Technology Application Note: Voltage Tracking with the ZL2005
Revision History
Revision Number Description Date
1.0 1.1 1.2 FN6848.0
Initial release Table 3 update Table 3, 28 update Assigned file number FN6848 to datasheet as this will be the first release with an Intersil file number. Replaced header and footer with Intersil header and footer. Updated disclaimer information to read "Intersil and it's subsidiaries including Zilker Labs, Inc." No changes to datasheet content
2/16/06 4/25/06 9/07/06 2/18/09
38
FN6848.0 February 18, 2009
ZL2005
Zilker Labs, Inc. 4301 Westbank Drive Building A-100 Austin, TX 78746 Tel: 512-382-8300 Fax: 512-382-8329
(c) 2006, Zilker Labs, Inc. All rights reserved. Zilker Labs, Digital-DC, Autonomous Sequencing and the Zilker Labs logo are trademarks of Zilker Labs, Inc. All other products or brand names mentioned herein are trademarks of their respective holders. This document contains information on a product under development. Specifications are subject to change without notice. Pricing, specifications and availability are subject to change without notice. Please see www.zilkerlabs.com for updated information. This product is not intended for use in connection with any high-risk activity, including without limitation, air travel, life critical medical operations, nuclear facilities or equipment, or the like. The reference designs contained in this document are for reference and example purposes only. THE REFERENCE DESIGNS ARE PROVIDED "AS IS" AND "WITH ALL FAULTS" AND INTERSIL CORPORATION AND IT'S SUBSIDIARIES INCLUDING ZILKER LABS, INC. DISCLAIMS ALL WARRANTIES, WHETHER EXPRESS OR IMPLIED. ZILKER LABS SHALL NOT BE LIABLE FOR ANY DAMAGES, WHETHER DIRECT, INDIRECT, CONSEQUENTIAL (INCLUDING LOSS OF PROFITS), OR OTHERWISE, RESULTING FROM THE REFERENCE DESIGNS OR ANY USE THEREOF. Any use of such reference designs is at your own risk and you agree to indemnify Intersil Corporation and it's subsidiaries including Zilker Labs, Inc. for any damages resulting from such use.
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FN6848.0 February 18, 2009

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