View RT9204CS_417011.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

Preliminary
RT9204
Dual Regulator - Standard Buck PWM DC-DC and Linear Power Controller
General Description
The RT9204 is a dual power controllers designed for high performance graphics cards and computer applications. The IC integrates a standard buck controller, a linear regulator driver and protection functions into a small 8-pin package. The RT9204 uses a internal compensated voltage mode PWM control for simple application design. An internal 0.8V reference allows the output voltage to be precisely regulated to low voltage requirement. A fixed 600kHz oscillator reduce the component size for saving board area. The RT9204 protects the converter and regulator by monitoring the output under voltage.
Features
Operate from 5V 0.8V Internal Reference Voltage Mode PWM Control Fast Transient Response Fixed 600kHz Oscillator Frequency Full 0~100% Duty Cycle Internal Soft Start Internal PWM Loop Compensation
Pin Configurations
Part Number RT9204CS (Plastic SOP-8) Pin Configurations
TOP VIEW
GND 1 VCC 2 DRV 3 FBL 4 8 UGATE 7 BOOT 6 SD 5 FB
Applications
Motherboard Power Regulation for Computers Subsystems Power Supplies Cable Modems, Set Top Box, and DSL Modems DSP and Core Communications processor Supplies Memory Power Supplies Personal Computer Peripherals Industrial Power Supplies 5V-Input DC-DC Regulators Low Voltage Distributed Power Supplies
Ordering Information
RT9204 Package type S : SOP-8 Operating temperature range C : Commercial standard
DS9204-00 February 2002
www.richtek-ic.com.tw
1
RT9204
Typical Application Circuit
R1 10 VAUX 3.3V Q1 2D1802 R4 100 R5 100 1 2 3 4 C5 1F GND VCC DRV FBL
Preliminary
5V UGATE BOOT SD FB 8 7 6 5 VOUT1 2.5V C3 MU 0.1F L1 5H + C4 1000F R2 120 R3 250 C7 10nF D1 C2 1F + C1 470F
RT9204
VOUT2 1.6V
C6 220F
+
Fig.1 RT9204 powered from 5V only
R1 C5 1F VAUX 3.3V 1 2 Q1 R4 100 R5 100 3 4 C7 1F 8 7 6 5 VOUT1 2.5V L1 5H + C4 1000F R2 120 R3 250 C3 10nF D1 10 12V
5V GND VCC DRV FBL UGATE BOOT
MU C2 1F
RT9204
SD FB
VOUT2 1.6V C6 220F +
+ C1 470F
Fig.2 RT9204 powered from 12V
www.richtek-ic.com.tw
DS9204-00 February 2002
2
Preliminary
MU
+C OUT 1000F
RT9204
D
L 5H
G
S
C1 1F + C2 470F
CVCC 1F
GND VCC BOOT
CBOOT 0.1F
Diode
RT9204
GND Return
Layout Placement
Layout Notes 1. Put C1 & C2 to be near the MU drain and ML source nodes. 2. Put RT9204 to be near the COUT 3. Put CBOOT as close as to BOOT pin 4. Put CVCC as close as to VCC pin
Function Block Diagram
6.0V Regulator Power on Reset DRV FBL 0.8V Reference _
UVP
LDO
VCC
BOOT
++ _
Soft Start + 1V _ _
OVP
+
0.5V 0.8V FB +
35dB
UVP
Control Logic ++ UGATE
+
SS
PWM
Error Amp
GND
600kHz Oscillator
DS9204-00 February 2002
_
_
www.richtek-ic.com.tw
3
RT9204
Absolute Maximum Ratings
Supply Voltage VCC BOOT & UGATE to GND Input, Output or I/O Voltage Power Dissipation, PD @ TA = 25C SOP-8 Package Thermal Resistance SOP-8, JA Ambient Temperature Range Junction Temperature Range Storage Temperature Range Lead Temperature (Soldering, 10 sec.) CAUTION:
Preliminary
7V 15V GND-0.3V ~ 7V 0.625W 160C/W 0C ~ +70C -40C ~ +125C -65C ~ +150C 260C
Stresses beyond the ratings specified in "Absolute Maximum Ratings" may cause permanent damage to the device. This is a stress only rating and operation of the device at these or any other conditions above those indicated in the operational sections of this specification is not implied.
Electrical Characteristics
(VCC = 5V, TA = 25C, Unless otherwise specified.) Parameter Symbol VCC Supply Current Nominal Supply Current VCC Regulated Voltage Power-On Reset Rising VCC Threshold VCC Threshold Hysteresis Reference Reference Voltage Oscillator Free Running Frequency Ramp Amplitude PWM Error Amplifier DC Gain PWM Controller Gate Driver Upper Drive Source Upper Drive Sink Linear Regulator DRV Driver Source Protection FB Over-Voltage Trip FB & FBL Under-Voltage Trip Soft-Start Interval SD Pin Threshold SD pin Sink Current
www.richtek-ic.com.tw
Test Conditions
Min --3.75 --
Typ 3 6 4.1 0.5 0.8 600 1.75 35 7 5 -1 0.5 1 1.5 40
Max --4.35 -0.816 650 -----------
Units mA V V V V KHz VP-P dB mA V V mS V A
ICC VCC
UGATE, LGATE open VBOOT=12V
Both FB & FBL
0.784 550
VOSC
---
RUGATE RUGATE
VBOOT = 12V; VBOOT - VUGATE = 1V VUGATE = 1V VDRV = 2V FB Rising FB & FBL Falling VCC = 5V VCC = 5V
--100 ------
DS9204-00 February 2002
4
Preliminary Typical Operating Charateristics
Power On
VCC = 5V VOUT = 2.2V VCC VCC
RT9204
Power Off
VCC = 5V VOUT = 2.2V
VOUT1 VOUT2
VOUT1 VOUT2
Time
Time
Load Transient
UGATE
Load Transient
UGATE
VOUT VOUT VCC = 5V VOUT = 2.2V COUT = 3000F VCC = 5V VOUT = 2.2V COUT = 3000F
Time
Time
Short Hiccup
VCC = 5V VOUT = 2.2V Reference (V)
Reference vs. Temperature
0.803 0.802 0.801 0.800 0.799 0.798 0.797 0.796
VOUT
UGATE
Time
-50
0
50
100
150
Temperature ( C)
DS9204-00 February 2002
www.richtek-ic.com.tw
5
RT9204
Preliminary
4.3 4.2 4.1
POR (Rising/Falling) vs. Temperature
315 630
Oscillator Frequency vs. Temperature
310 620 305 610
Rising
Frequency (kHz)
300 600 295 590 290 580 285 570 280 560 275 550
POR (V)
4.0 3.9 3.8
Falling
3.7 3.6 -50 0 50 100 150
Temperature ( C)
540 270 -50
0
50
100
150
Temperature ( C)
www.richtek-ic.com.tw
DS9204-00 February 2002
6
Preliminary Functional Pin Description
GND (Pin 1) Signal and power ground for the IC. All voltage levels are measured with respect to this pin. VCC (Pin 2) This is the main bias supply for the RT9204. This pin also provides the gate bias charge for the lower MOSFETs gate. The voltage at this pin monitored for power-on reset (POR) purpose. This pin is also the internal 6.0V regulator output powered from BOOT pin when BOOT pin is directly powered from ATX 12V. DRV (Pin 3) This pin is linear regulator output driver. Connect to external bypass NPN transistor base or NMOSFET gate terminal. FBL (Pin 4) This pin is connected to the linear regulator output divider. This pin also connects to internal linear regulator error amplifier inverting input and protection monitor. FB (Pin 5) This pin is connected to the PWM converter's output divider. This pin also connects to internal PWM error amplifier inverting input and protection monitor. SD (Pin 6) Active low design with a 40A pull low current source. Pull this pin to VCC to shutdown both PWM and linear regulator. BOOT (Pin 7) This pin provides ground referenced bias voltage to the upper MOSFET driver. A bootstrap circuit is used to create a voltage suitable to drive a logic-level Nchannel MOSFET when operating at a single 5V power supply. This pin also could be powered from ATX 12V, in this situation, an internal 6.0V regulator will supply to VCC pin for internal voltage bias. UGATE (Pin 8) Connect UGATE pin to the PWM converter's upper MOSFET gate. This pin provides the gate drive for the upper MOSFET.
RT9204
DS9204-00 February 2002
www.richtek-ic.com.tw
7
RT9204
Functional Description
Preliminary
The RT9204 operates at either single 5V power supply with a bootstrap UGATE driver or 5V/12V dual-power supply form the ATX SMPS. The dualpower supply is recommended for high current application, the RT9204 can deliver higher gate driving current while operating with ATX SMPS based on dual-power supply. The Bootstrap Operation In a single power supply system, the UGATE driver of RT9204 is powered by an external bootstrap circuit, as the Fig.1. The boot capacitor, CBOOT, generates a floating reference at the PHASE node. Typically a 0.1F CBOOT is enough for most of MOSFETs used with the RT9204. The voltage drop between BOOT and PHASE node is refreshed to a voltage of VCC - diode drop (VD) while the low side MOSFET turning on.
R1
VCC
6.0V Regulator
BOOT C1 1F
R1 10
12V 5V +
UGATE
C2 1F
RT9204
Fig.2 Dual Power Supply Operation
Power On Reset The Power-On Reset (POR) monitors the supply voltage (normal +5V) at the VCC pin and the input voltage at the OCSET pin. The VCC POR level is 4.1V with 0.5V hysteresis and the normal level at OCSET pin is 1.5V (see over-current protection). The POR function initiates soft-start operation after all supply voltages exceed their POR thresholds.
C2 1F
VCC
BOOT UGATE
D1 0.1F +
5V
Soft Start A built-in soft-start is used to prevent surge current from power supply input during power on. The softstart voltage is controlled by an internal digital counter. It clamps the ramping of reference voltage at the input of error amplifier and the pulse-width of the output driver slowly. The typical soft-start duration is 2mS.
PHASE
RT9204
Fig.1 Single 5V power Supply Operation Dual Power Operation The RT9204 was designed to regulate a 6.0V at VCC pin automatically when BOOT pin is powered by 12V. In a system with ATX 5V/12V power supply, the RT9204 is ideal for higher current application due to the higher gate driving capability, VUGATE = 7V. A RC (10/1F) filter is also recommended at BOOT pin to prevent the ringing induced from fast power on, as shown in Fig.2.
Under Voltage and Over Voltage Protection The voltage at FB pin is monitored and protected against OC (over current), UV (under voltage), and OV (over voltage). The UV threshold is 0.5V and OVthreshold is 1.0V. Both UV/OV detection have 30S triggered delay. When OC or UV trigged, a hiccup restart sequence will be initialized, as shown in Fig.3. Only 3 times of trigger are allowed to latch off. Hiccup is disabled during soft-start interval.
www.richtek-ic.com.tw
DS9204-00 February 2002
8
Preliminary
COUNT = 1 COUNT = 2 Internal SS 4V 2V 0V FB or FBL Voltage OVERLOAD APPLIED COUNT = 3
RT9204
Shutdown Pulling high the SD pin by a small single transistor can shutdown the RT9204 PWM controller as shown in typical application circuit. Normally SD pin can be floating because an internal 40A current source will pull low the SD shutdown pin voltage.
T0T1
T2 TIME
T3
L VL VI D C R VO
Fig. 3
Q
Applications Information
Inductor Selection The RT9204 was designed for VIN = 5V, step-down application mainly. Fig.4 shows the typical topology and waveforms of step-down converter. The ripple current of inductor can be calculated as follows: ILRIPPLE = (5V - VOUT)/L x TON Because operation frequency is fixed at 600kHz, TON = 3.33 x VOUT/5V The VOUT ripple is VOUT RIPPLE = ILRIPPLE x ESR ESR is COUT capacitor equivalent series resistor Table 1 shows the ripple voltage of VOUT: VIN = 5V
C.C.M.
TS
Table 1
TON VI VL TOFF
- VO - VO
iL IL
Q IL = I O
iQ
*Refer to Sanyo low ESR series (CE, DX, PX...) The suggested L and C are as follows: 2H with 1500F COUT 5H with 1000F COUT Fig.4 VOUT Inductor 1000F (ESR = 53m) 1500F (ESR = 33m) 3000F (ESR = 21m) 2H 100mV 62mV 40mV 3.3V 5H 40mV 25mV 16mV 2H 110mV 68mV 43mV 2.5V 5H 44mV 28mV 18mV 2H 93mV 58mV 37mV 1.5V 5H 37mV 23mV 15mV
iD
IQ
ID
DS9204-00 February 2002
www.richtek-ic.com.tw
9
RT9204
Input / Output Capacitor
Preliminary
High frequency/long life decoupling capacitors should be placed as close to the power pins of the load as physically possible. Be careful not to add inductance to the PCB trace, as it could eliminate the performance from utilizing these low inductance components. Consult with the manufacturer of the load on specific decoupling requirements. The output capacitors are necessary for filtering output and stabilizing the close loop (see the PWM loop stability). For powering advanced, high-speed processors, capacitors it with is required low to meet with the are requirement of fast load transient, high frequency ESR/ESL capacitors recommended. Another concern is high ESR induced ripple may trigger UV or OV protections. Linear Regulator Driver The linear regulator of RT9204 was designed to drive bipolar NPN or MOSFET pass transistor. For MOSFET pass transistor, normally DRV need to provide minimum VOUT2+VT+gate-drive voltage to keep VOUT2 as setting voltage. When driving MOSFET operating at 5V power supply system, the gate-drive will be limited at 5V. In this situation shown in Fig. 5, low VT threshold MOSFET (VT = 1V) and Vout2 setting below 2.5V were suggested. In VBOOT = 12V operation condition as Fig. 6, VCC is regulated as higher to 6V providing more gate-drive for pass MOSFET transistor, VOUT2 can be set as 3.3V.
30 40 VOUT = 3.3V COUT = 1500F(33m) L=2H VOUT = 1.5V VOUT = 2.5V VOUT = 3.3V PO = 2.9kHz ZO = 3.2kHz
VOUT2 3.3V VBOOT = 12V 6V DRV BOOT FBL VCC RT9204 R4 R4 < 1K R3 +
Fig. 6 PWM Loop Stability The RT9204 is a voltage mode buck controller designed for 5V step-down applications. The gain of error amplifier is fixed at 35dB for simplified design. The output amplitude of ramp oscillator is 1.6V, the loop gain and loop pole/zero are calculated as follows: DC loop gain GA = 35dB x
5 0.8 x 1.6 VOUT 1 LC filter pole PO = x x LC 2
Error Amp pole PA = 300kHz ESR zero ZO =
1 x x ESR x C 2
The RT9204 Bode plot as shown Fig.7 is stable in most of application conditions.
VOUT2 2.5V DRV BOOT FBL VCC = 5V VCC RT9204 R4 R4 < 1K R3 +
20 Loop Gain
10
100
1k
10k
100k
1M
Fig. 7
Fig. 5
www.richtek-ic.com.tw
DS9204-00 February 2002
10
Preliminary
Reference Voltage Because RT9204 use a low 35dB gain error amplifier, shown in Fig. 8. The voltage regulation is dependent on VIN & VOUT setting. The FB reference voltage of 0.8V were trimmed at VIN = 5V & VOUT = 2.5V condition. In a fixed VIN = 5V application, the FB reference voltage vs. VOUT voltage can be calculated as Fig. 9.
I3 56K 1K REP 0.8V _ FB I2 EA + _ +
PWM
RT9204
VIN L VOUT1 + C OUT R1 C1 DRV RT9204 FB FBL R2 R2 < 1K R4 R4 < 1K R3 + VOUT2
R1 ) R2 R3 VOUT2 = 0.8 V x (1 + ) R4 VOUT1 = 0.8 V x (1 +
+ _
Fig. 10 PWM Layout Considerations MOSFETs switch very fast and efficiently. The speed with which the current transitions from one device to another causes voltage spikes across the interconnecting impedances and parasitic circuit
RAMP 1.75V
Fig. 8
0.82 0.81 FB (V) 0.8 0.79 0.88 0.5 VIN = 5V
elements. The voltage spikes can degrade efficiency and radiate noise, that results in ocer-voltage stress on devices. Careful component placement layout and printed circuit design can minimize the voltage spikes induced in the converter. Consider, as an example, the turn-off transition of the upper MOSFET prior to
1
1.5
2
2.5 VOUT (V)
3
3.5
4
4.5
turn-off, the upper MOSFET was carrying the full load current. During turn-off, current stops flowing in the upper MOSFET and is picked up by the low side MOSFET or Schottky diode. Any inductance in the switched current path generates a large voltage spike during the switching interval. Careful component selections, layout of the critical components, and use shorter and wider PCB traces help in minimizing the magnitude of voltage spikes. There are two sets of critical components in a DC-DC converter using the RT9204. The switching power components are most critical because they switch large amounts of energy, and as such, they tend to generate equally large amounts of noise. The critical small signal components are those connected to sensitive nodes or those supplying critical bypass current.
Fig. 9 Feedback Divider The reference of RT9204 is 0.8V. Both the PWm and LDO output voltages can be set using a resistor based divider as shown in Fig.9. Put the R1&R2 and R3&R4 as close as possible to FB pin and R2&R4 should be less than 1 k to avoid noise coupling. The C1 capacitor is a speed-up capacitor for reducing output ripple to meet with the requirement of fast transient load. Typically a 1nF ~ 0.1F is enough for C1.
DS9204-00 February 2002
www.richtek-ic.com.tw
11
RT9204
Preliminary
IQ1 5V + Q1 IQ2 PHASE + IL VOUT +
The power components and the PWM controller should be placed firstly. Place the input capacitors, especially the high-frequency ceramic decoupling capacitors, close to the power switches. Place the output inductor and output capacitors between the MOSFETs and the load. Also locate the PWM controller near by MOSFETs. A multi-layer printed circuit board is recommended. Fig.11 shows the connections of the critical components in the converter. Note that the capacitors CIN and COUT each of them represents numerous physical capacitors. Use a dedicated grounding plane and use vias to ground all critical components to this layer. Apply another solid layer as a power plane and cut this plane into smaller islands of common voltage levels. The power plane should support the input power and output power nodes. Use copper filled polygons on the top and bottom circuit layers for the PHASE node, but it is not necessary to oversize this particular island. Since the PHASE node is subjected to very high dV/dt voltages, the stray capacitance formed between these island and the surrounding circuitry will tend to couple switching noise. Use the remaining printed circuit layers for small signal routing. The PCB traces between the PWM controller and the gate of MOSFET and also the traces connecting source of MOSFETs should be sized to carry 2A peak currents. Fig. 11
UGATE VCC GND RT9204 FB GND
LOAD
www.richtek-ic.com.tw
DS9204-00 February 2002
12
Preliminary Package Information
H A M
RT9204
JB
F
C D I
Symbol A B C D F H I J M
Dimensions In Millimeters Min 4.801 3.810 1.346 0.330 1.194 0.178 0.102 5.791 0.406 Max 5.004 3.988 1.753 0.508 1.346 0.254 0.254 6.198 1.270
Dimensions In Inches Min 0.189 0.150 0.053 0.013 0.047 0.007 0.004 0.228 0.016 Max 0.197 0.157 0.069 0.020 0.053 0.010 0.010 0.244 0.050
DS9204-00 February 2002
www.richtek-ic.com.tw
13
RT9204
Preliminary
RICHTEK TECHNOLOGY CORP.
Headquarter
6F, No. 35, Hsintai Road, Chupei City Hsinchu, Taiwan, R.O.C. Tel: (8863)5510047 Fax: (8863)5537749
RICHTEK TECHNOLOGY CORP.
Taipei Office (Marketing)
8F-1, No. 137, Lane 235, Paochiao Road, Hsintien City Taipei County, Taiwan, R.O.C. Tel: (8862)89191466 Fax: (8862)89191465 Email: marketing@richtek-ic.com.tw
www.richtek-ic.com.tw
DS9204-00 February 2002
14

▲Up To Search▲

Price & Availability of RT9204CS

	To Download RT9204CS Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .