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19-3436; Rev 1; 11/04
MAX8550 Evaluation Kit
General Description
The MAX8550 evaluation kit (EV kit) is designed to evaluate the MAX8550 DDR power-supply solution for notebooks, desktops, and graphics cards. The EV kit board produces VDDQ at the output of the synchronous PWM buck, VTT at the output of the sourcing/sinking LDO linear regulator, and VTTR at the output of the reference buffer. The VDDQ output is preset to 2.5V and sources up to 12A. The VTT output is always VDDQ/2 and can source/sink up to 3A of peak current and 1.5A of continuous current. The VTTR output is also always VDDQ/2 and can source/sink up to 10mA. The MAX8550 EV kit was conveniently designed with jumpers to select the OVP/UVP, TON, SKIP, STBY, and SHDN_ modes. The board's default settings enable OVP (overvoltage protection), 600kHz switching frequency, low-noise PWM mode, VDDQ, VTT, and VTTR. The VIN input accepts voltages from 9V to 20V and VDD requires a 5V bias supply. The EV kit comes with the MAX8550 installed. Contact the factory for free samples of the MAX8550A or MAX8551 to evaluate these parts. VDDQ Preset to 2.5V/12A VTT 1.25V Source/Sink 1.5A Continuous/3A Peak VTTR 1.25V Source/Sink 10mA VIN Range: 9V to 20V Optimized Switching Frequency: 600kHz Overvoltage/Undervoltage Protection Standby Independent Shutdown Power OK
Features
Evaluates: MAX8550/MAX8550A/MAX8551
Ordering Information
PART MAX8550EVKIT TEMP RANGE 0C to +70C IC PACKAGE 28 Thin QFN 5mm x 5mm
Note: To evaluate the MAX8550A, request a free sample of the MAX8550AETI when ordering the MAX8550 EV kit. To evaluate the MAX8551, request a free sample of the MAX8551ETI when ordering the MAX8550 EV kit.
Component List
DESIGNATION QTY C1 1 DESCRIPTION 0.1F 10%, 50V X7R ceramic capacitor (0603) TDK C1608X7R1H104K 10F 10%, 6.3V X5R ceramic capacitors (1206) TDK C3216X5R0J106K or TDK C3216X5R0J106M 1F 10%, 10V X5R ceramic capacitors (0603) TDK C1608X5R1A105K 4.7F 20%, 6.3V X5R ceramic capacitor (0805) TDK C2012X5R0J475M 0.22F 20%, 16V X7R ceramic capacitors (0603) TDK C1608X7R1C224M 10F 20%, 25V X5R ceramic capacitors (1210) Taiyo Yuden TMK325BJ106MM TDK C3225X5R1E106M DESIGNATION QTY DESCRIPTION Not installed 470F 20%, 25V aluminum electrolytic capacitor (10mm x 16mm) Sanyo 25MV470WX 3900pF, 50V X7R ceramic capacitor (0603) Kemet C0603C392K5RAC 150F, 4V, 25m low-ESR POS capacitors (D2E) Sanyo 4TPE150M 470pF 5%, 50V COG ceramic capacitor (0603) TDK C1608COG1H471J Not installed (0603) Schottky diode, 30V, 100mA (SOD-323) Central CMDSH-3 4-pin headers 3-pin headers
C8D
0
C2, C4A, C4B, C4C, C4D, C4E, C4F
7
C9
1
C3, C6, C13
3
C11, C12
2
C5
1
C14 C15, C16 D1 JU1, JU2 JU3-JU6
1 2 1 2 4
C7, C10
2
C8A, C8B, C8C
3
________________________________________________________________ Maxim Integrated Products
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For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at 1-888-629-4642, or visit Maxim's website at www.maxim-ic.com.
MAX8550 Evaluation Kit Evaluates: MAX8550/MAX8550A/MAX8551
Component List (continued)
DESIGNATION QTY L1 1 DESCRIPTION 1.0H, 20A, 1.6m power inductor (12.6mm x 12.6mm x 5.2mm) TOKO FDA1254-1R0M n-channel MOSFET 30V, 9m (SO-8) International Rectifier IRF7821 n-channel MOSFET 30V, 5m (SO-8) International Rectifier IRF7832 10 5% resistor (0603) 100k 5% resistors (0603) 75k 1% resistor (0603) 124k 1% resistor (0603) Not installed (0603) 0 resistors (0603) Not installed (1812) 20 5% resistor (0603) MAX8550ETI (28-pin 5mm x 5mm Thin QFN) Shunts MAX8550 EV kit PC board
Quick Start
The MAX8550 EV kit is fully assembled and tested. Follow these steps to verify board operation. Do not turn on the power supplies until all connections are completed. 1) Ensure a shunt is placed across pins 1-4 of jumper JU1 to enable OVP and UVP. 2) Ensure a shunt is placed across pins 1-2 of jumper JU2 to set the switching frequency to approximately 600kHz. 3) Ensure a shunt is placed across pins 1-2 of jumper JU3 to enable low-noise PWM mode. 4) Ensure a shunt is placed across pins 2-3 of jumper JU4 to disable the VDDQ buck output. 5) Ensure a shunt is placed across pins 1-2 of jumper JU5 to enable the VTT and VTTR outputs. 6) Ensure a shunt is placed across pins 2-3 of jumper JU6 to set the board in normal operation mode. 7) Connect the 5VDC power supply across the VDD pad and the PGND pad nearest VIN. 8) Connect the 12VDC power supply across the VIN pad and the corresponding PGND pad. 9) Turn on both of the power supplies. 10)Set JU4 (1-2). This turns VDDQ on. 11)Using one of the DVMs, verify that the VDDQ voltage between the VDDQ and PGND pads is 2.5V (2%). 12)Using the other DVM, verify that the VTT voltage between the VTT and PGND pads is 1.25V (2%).
Q1 Q2 R1 R2, R3 R4 R5 R6, R7, R8 R9, R10, R11 R12 R13 U1 None None
1 1 1 2 1 1 2 3 1 1 1 6 1
Component Suppliers
SUPPLIER Central Semiconductor International Rectifier Kemet Sanyo USA TDK TOKO America PHONE WEBSITE 631-435-1110 www.centralsemi.com 310-322-3331 www.irf.com 864-963-6300 www.kemet.com 619-661-6835 www.sanyo.com 847-803-6100 www.component.tdk.com 847-297-0070 www.tokoam.com
Detailed Description
Jumper Selection
Table 1. Overvoltage/Undervoltage Control Input (OVP/UVP)
JUMPER JU1 JU1 JU1 JU1 SHUNT POSITION 1-2 1-3 1-4* Open DESCRIPTION Disable OVP and UVP. Enable UVP. Disable OVP. Enable OVP and UVP. Enable OVP. Disable UVP.
Note: Indicate that you are using the MAX8550 when contacting these component suppliers.
Recommended Equipment
* 5VDC power supply (500mA rated) * 9VDC to 20VDC power supply (5A rated) * Two digital voltmeters (DVM)
*Default position. Note: Refer to the MAX8550/MAX8551 or MAX8550A data sheet for additional information on OVP/UVP. This mode does not directly apply to the MAX8551.
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MAX8550 Evaluation Kit Evaluates: MAX8550/MAX8550A/MAX8551
Table 2. On-Time Selection Input (TON)
JUMPER JU2 JU2 JU2 JU2 SHUNT POSITION 1-2* 1-3 1-4 Open DESCRIPTION JUMPER 600kHz switching frequency 450kHz switching frequency 200kHz switching frequency 300kHz switching frequency JU5 2-3 JU5
Table 5. Shutdown Control Input B (SHDNB)
SHUNT POSITION 1-2* DESCRIPTION The VTT and VTTR outputs are enabled. The VTT and VTTR outputs are shut down.
*Default position. Note: Refer to the MAX8550/MAX8551 or MAX8550A data sheet for additional information on TON. *Default position.
Table 3. Pulse-Skipping Control Input (SKIP)
JUMPER JU3 JU3 SHUNT POSITION 1-2* 2-3 DESCRIPTION Low-noise PWM mode. Pulse-skipping mode. Use only this position when evaluating the MAX8551.
Note: Refer to the MAX8550/MAX8551 or MAX8550A data sheet for additional information on SHDNB. SHDNB is TP0 on the MAX8550A.
Caution: Do not connect an external controller to the SHDNB pad while a shunt is on jumper JU5.
Table 6. Standby Control Input (STBY)
JUMPER JU6 JU6 SHUNT POSITION 1-2 2-3* DESCRIPTION The VTT output is shut down. Normal operation.
*Default position. Note: Refer to the MAX8550/MAX8551 or MAX8550A data sheet for additional information on SKIP.
*Default position. Note: Refer to the MAX8550/MAX8551 or MAX8550A data sheet for additional information on STBY. STBY is STBY on the MAX8550A.
Caution: Do not connect an external controller to the SKIP pad while a shunt is on jumper JU3.
Caution: Do not connect an external controller to the STBY pad while a shunt is on jumper JU6.
Table 4. Shutdown Control Input A (SHDNA)
JUMPER JU4 JU4 SHUNT POSITION 1-2 2-3* DESCRIPTION The VDDQ buck output is enabled. The VDDQ buck output is shut down.
Setting the Buck Regulator Output Voltage (VDDQ)
The output voltage of the buck regulator is preset to 2.5V on the MAX8550 EV kit for DDR memory applications. To pin-strap the output voltage to 1.8V follow the steps below: 1) Remove R9. 2) Solder the 0 resistor from step 1 in the R7 location. Refer to the MAX8550/MAX8551 data sheet to change the external components for optimum performance.
*Default position. Note: Refer to the MAX8550/MAX8551 or MAX8550A data sheet for additional information on SHDNA. SHDNA is SHDN on the MAX8550A.
Low-Side MOSFET Snubber Circuit (Buck)
Fast switching transitions cause ringing because of the resonating circuit formed by the parasitic inductance and capacitance at the switching LX node. This highfrequency ringing occurs at the LX node's rising and
Caution: Do not connect an external controller to the SHDNA pad while a shunt is on jumper JU4.
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MAX8550 Evaluation Kit Evaluates: MAX8550/MAX8550A/MAX8551
falling transitions and may interfere with circuit performance and generate EMI. To dampen this ringing, an optional series RC snubber circuit is added across the low-side switch. Below is a simple procedure for selecting the value of the series RC for the snubber circuit: 1) Connect a scope probe to the LX node labeled on the MAX8550 EV kit schematic and observe the ringing frequency, fR. 2) Estimate the circuit parasitic capacitance (CPAR) at LX by first finding a capacitor value, which, when connected from LX to PGND1, reduces the ringing frequency by half. CPAR can then be approximated as 1/3 the value of the capacitor value found. 3) Estimate the circuit parasitic inductance (LPAR) from the equation: LPAR = 1 (2 x fR )2 x CPAR 4) Calculate R12 for critical dampening from the equation: R12 = 2 x fR x LPAR Adjust the resistor value up or down to tailor the desired damping and the peak voltage excursion. 5) Capacitor C15 should be at least 2 to 4 times the value of CPAR to be effective. The power loss of the snubber circuit (PWR_SNUB) is dissipated in the resistor and can be calculated as: PWR_SNUB = C15 x VIN2 x fSW where VIN is the input voltage and fSW is the switching frequency. Choose the power rating of R12 according to the specific application's derating rule for the power dissipation calculated in the equation above. Recommended snubber values for this EV kit are 3 (R12) and 2.2nF (C15).
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VDDQ VDDQ R13 20 C1 0.1F 13 14 AVDD AVDD R1 10 VDD 11 PGND2 VTTR BST 20 C7 0.22F LX VIN VIN 1 TON DH 5 POK1 LX AVDD DL R3 100k 6 POK2 PGND1 8 SS 24 GND 3 REF C10 0.22F R4 75k 1% 4 ILIM SHDNB AVDD R7 OPEN 15 R9 0 FB STBY 7 SHDNA 27 JU4 23 AVDD 1 2 AVDD 28 JU5 1 2 3 AVDD JU6 1 2 3 STBY 3 SHDNB SHDNA C9 3900pF REF 21 R2 100k 3 18 4 1 2 6 5 Q1 7 IRF7821 8 6 5 17 C8A 10F C8B 10F C8C 10F VIN (9V TO 20V) R10 0 D1 CMDSH-3 C5 4.7F 10 AVDD 22 VDD (5V BIAS SUPPLY) C3 1F 26 REFIN SKIP 25 VTTI 1 JU3 2 3 C2 10F
SKIP
VTT 12 C4C 10F C4D 10F C4F 10F C16 OPEN C4E 10F VTT 9 VTTS
C4A 10F
C4B 10F
Figure 1. MAX8550 EV Kit Schematic
MAX8550
REF 4 3 OVP/UVP AVDD JU1 2 REF 4 3 JU2 2 1 1 2 LX 19 C6 1F C8D OPEN VDDQ L1 1H C11 R12 150F OPEN R11 0 3 1 2 C15 OPEN C12 150F PGND VDDQ 2.5 AT 12A C13 1F PGND 7 Q2 IRF7832 8 4 ON/OFF CONTROL LOGIC STBY SHDNA SHDNB VDDQ ON 1 0 1 0 0 1 ON ON 1 1 1 1 OFF 0 0 0 OFF 0 0 VTT ON OFF OFF ON OFF VTTR ON OFF ON ON OFF C14 470pF R5 124k 1% R8 OPEN 16 OUT VDDQ R6 OPEN
PGND
VTTR
GND
POK1
Evaluates: MAX8550/MAX8550A/MAX8551
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POK2
MAX8550 Evaluation Kit
5
MAX8550 Evaluation Kit Evaluates: MAX8550/MAX8550A/MAX8551
Figure 2. MAX8550 EV Kit Component Placement Guide--Component Side
Figure 3. MAX8550 EV Kit PC Board Layout--Component Side 6 _______________________________________________________________________________________
MAX8550 Evaluation Kit Evaluates: MAX8550/MAX8550A/MAX8551
Figure 4. MAX8550 EV Kit PC Board Layout--Inner Layer 2 (GND, PGND1 and PGND2)
Figure 5. MAX8550 EV Kit PC Board Layout--Inner Layer 3 (GND, PGND1 and PGND2) _______________________________________________________________________________________ 7
MAX8550 Evaluation Kit Evaluates: MAX8550/MAX8550A/MAX8551
Figure 6. MAX8550 EV Kit PC Board Layout--Solder Side
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 _____________________ 8 (c) 2004 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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