19-3436; Rev 1; 11/04 MAX8550 Evaluation Kit 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. Features ♦ 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 Ordering Information PART TEMP RANGE IC PACKAGE MAX8550EVKIT 0°C to +70°C 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 DESCRIPTION 1 0.1µF ±10%, 50V X7R ceramic capacitor (0603) TDK C1608X7R1H104K C2, C4A, C4B, C4C, C4D, C4E, C4F 7 10µF ±10%, 6.3V X5R ceramic capacitors (1206) TDK C3216X5R0J106K or TDK C3216X5R0J106M C3, C6, C13 3 1µF ±10%, 10V X5R ceramic capacitors (0603) TDK C1608X5R1A105K C5 1 4.7µF ±20%, 6.3V X5R ceramic capacitor (0805) TDK C2012X5R0J475M C1 C7, C10 C8A, C8B, C8C DESIGNATION QTY DESCRIPTION C8D 0 Not installed 470µF ±20%, 25V aluminum electrolytic capacitor (10mm x 16mm) Sanyo 25MV470WX C9 1 3900pF, 50V X7R ceramic capacitor (0603) Kemet C0603C392K5RAC C11, C12 2 150µF, 4V, 25mΩ low-ESR POS capacitors (D2E) Sanyo 4TPE150M C14 1 470pF ±5%, 50V COG ceramic capacitor (0603) TDK C1608COG1H471J C15, C16 2 Not installed (0603) 2 0.22µF ±20%, 16V X7R ceramic capacitors (0603) TDK C1608X7R1C224M D1 1 Schottky diode, 30V, 100mA (SOD-323) Central CMDSH-3 JU1, JU2 2 4-pin headers 3 10µF ±20%, 25V X5R ceramic capacitors (1210) Taiyo Yuden TMK325BJ106MM TDK C3225X5R1E106M JU3–JU6 4 3-pin headers ________________________________________________________________ Maxim Integrated Products 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. 1 Evaluates: MAX8550/MAX8550A/MAX8551 General Description Evaluates: MAX8550/MAX8550A/MAX8551 MAX8550 Evaluation Kit Component List (continued) DESIGNATION QTY DESCRIPTION L1 1 1.0µH, 20A, 1.6mΩ power inductor (12.6mm x 12.6mm x 5.2mm) TOKO FDA1254-1R0M Q1 1 n-channel MOSFET 30V, 9mΩ (SO-8) International Rectifier IRF7821 Q2 1 n-channel MOSFET 30V, 5mΩ (SO-8) International Rectifier IRF7832 R1 1 10Ω ±5% resistor (0603) R2, R3 2 100kΩ ±5% resistors (0603) R4 1 75kΩ ±1% resistor (0603) R5 1 124kΩ ±1% resistor (0603) R6, R7, R8 2 Not installed (0603) R9, R10, R11 3 0Ω resistors (0603) R12 1 Not installed (1812) R13 1 20Ω ±5% resistor (0603) U1 1 MAX8550ETI (28-pin 5mm x 5mm Thin QFN) None 6 Shunts None 1 MAX8550 EV kit PC board Component Suppliers SUPPLIER PHONE WEBSITE Central Semiconductor 631-435-1110 www.centralsemi.com International Rectifier 310-322-3331 www.irf.com Kemet 864-963-6300 www.kemet.com Sanyo USA 619-661-6835 www.sanyo.com TDK 847-803-6100 www.component.tdk.com TOKO America 847-297-0070 www.tokoam.com 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) 2 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%). Detailed Description Jumper Selection Table 1. Overvoltage/Undervoltage Control Input (OVP/UVP) JUMPER SHUNT POSITION JU1 1-2 Disable OVP and UVP. JU1 1-3 Enable UVP. Disable OVP. JU1 1-4* Enable OVP and UVP. JU1 Open DESCRIPTION Enable OVP. Disable UVP. *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. _______________________________________________________________________________________ MAX8550 Evaluation Kit SHUNT POSITION DESCRIPTION JU2 1-2* 600kHz switching frequency JU2 1-3 450kHz switching frequency JU2 1-4 200kHz switching frequency JU2 Open 300kHz switching frequency JUMPER Table 5. Shutdown Control Input B (SHDNB) JUMPER SHUNT POSITION JU5 1-2* The VTT and VTTR outputs are enabled. JU5 2-3 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. Table 3. Pulse-Skipping Control Input (SKIP) JUMPER SHUNT POSITION JU3 1-2* Low-noise PWM mode. 2-3 Pulse-skipping mode. Use only this position when evaluating the MAX8551. JU3 DESCRIPTION DESCRIPTION *Default position. 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 SHUNT POSITION DESCRIPTION JU6 1-2 The VTT output is shut down. JU6 2-3* Normal operation. *Default position. *Default position. Note: Refer to the MAX8550/MAX8551 or MAX8550A data sheet for additional information on SKIP. 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. Table 4. Shutdown Control Input A (SHDNA) JUMPER SHUNT POSITION DESCRIPTION JU4 1-2 The VDDQ buck output is enabled. JU4 2-3* The VDDQ buck output is shut down. *Default position. Note: Refer to the MAX8550/MAX8551 or MAX8550A data sheet for additional information on SHDNA. SHDNA is SHDN on the MAX8550A. Caution: Do not connect an external controller to the SHDNA pad while a shunt is on jumper JU4. Caution: Do not connect an external controller to the STBY pad while a shunt is on jumper JU6. 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 0Ω resistor from step 1 in the R7 location. Refer to the MAX8550/MAX8551 data sheet to change the external components for optimum performance. 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 _______________________________________________________________________________________ 3 Evaluates: MAX8550/MAX8550A/MAX8551 Table 2. On-Time Selection Input (TON) Evaluates: MAX8550/MAX8550A/MAX8551 MAX8550 Evaluation Kit 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 = 4 1 4) Calculate R12 for critical dampening from the equation: R12 = 2π × 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 3Ω (R12) and 2.2nF (C15). (2π × fR )2 × CPAR _______________________________________________________________________________________ _______________________________________________________________________________________ PGND C4A 10µF POK2 POK1 4 REF R9 0Ω R6 OPEN 2 4 1 POK2 POK1 TON FB ILIM VDDQ R8 OPEN 16 OUT 15 R7 OPEN 4 REF 24 GND 3 REFIN VTTI MAX8550 14 13 OVP/UVP VTTR PGND2 8 SS 6 5 1 2 10 11 R4 75kΩ 1% AVDD C9 3900pF JU1 3 C4F 10µF C16 OPEN AVDD R5 124kΩ 1% REF C4E 10µF C10 0.22µF R3 100kΩ R2 100kΩ 1 AVDD C6 1µF C4D 10µF JU2 2 3 C14 470pF REF C4C 10µF AVDD GND VTTR C4B 10µF VTT 9 VTTS 12 C1 0.1µF R13 20Ω VDDQ SKIP 25 DL DH VIN LX BST VDD AVDD STBY SHDNB SHDNA PGND1 1 JU3 2 3 SKIP 7 3 3 1 2 AVDD 1 2 6 5 1 2 3 1 2 VIN L1 1µH C8A 10µF LX C15 OPEN STBY C12 150µF C8C 10µF VDDQ C13 1µF 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 PGND VDDQ 2.5 AT 12A PGND VIN (9V TO 20V) C8D OPEN ON/OFF CONTROL LOGIC C8B 10µF C5 4.7µF VDD (5V BIAS SUPPLY) C11 R12 150µF OPEN SHDNB SHDNA 3 AVDD JU6 3 1 2 AVDD JU4 R11 0Ω 7 Q2 IRF7832 8 4 4 6 5 C7 0.22µF D1 CMDSH-3 C3 1µF Q1 7 IRF7821 8 R10 0Ω R1 10Ω LX 28 JU5 27 23 21 18 17 19 20 22 26 AVDD Evaluates: MAX8550/MAX8550A/MAX8551 VTT C2 10µF VDDQ MAX8550 Evaluation Kit Figure 1. MAX8550 EV Kit Schematic 5 Evaluates: MAX8550/MAX8550A/MAX8551 MAX8550 Evaluation Kit 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 Evaluates: MAX8550/MAX8550A/MAX8551 MAX8550 Evaluation Kit 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. 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