19-2611; Rev 0; 10/02 MAX1875 Evaluation Kit The MAX1875 EV kit provides dual 1.8V and 3.3V output voltages from an 8V to 18V input voltage range. It delivers up to 3.5A output current for the 1.8V output and the 3.3V output, with greater than 90% efficiency. Both converters operate 180 degrees out-of-phase to reduce input ripple current. The EV kit operates at 100kHz switching frequency. This EV kit is a fully assembled and tested circuit board. It also allows evaluation of other output voltages in the 0.75V to 15V range. Features ♦ 8V to 18V Input Voltage Range ♦ 1.8V and 3.3V Adjustable Output Voltages ♦ 3.5A Output Current (1.8V Output) ♦ 3.5A Output Current (3.3V Output) ♦ Lossless Foldback Current Limit ♦ 100kHz Switching Frequency ♦ RST Output with 140ms Delay (MAX1876/MAX1858 only) ♦ 180 Degree Out-of-Phase Operation ♦ 24-Pin QSOP Package ♦ Low-Cost Components ♦ Fully Assembled and Tested The MAX1875 EV kit can also be used to evaluate the MAX1876 and MAX1858. Ordering Information PART TEMP RANGE MAX1875EVKIT 0°C to +70°C IC PACKAGE 24 QSOP Component List DESIGNATION QTY DESCRIPTION DESIGNATION QTY L2 1 DESCRIPTION 27µH 5A power inductor C1, C4 2 390µF, 25V aluminum electrolytic capacitors Sanyo 25MV390AX C5, C6, C12 3 0.1µF ceramic capacitors (0805) N1A, N1B, N2A, N2B 2 Dual N-channel MOSFETs 8-pin SO Fairchild FDS6990A C7 1 0.39µF ceramic capacitor (0805) D2–D5 0 Not installed (open) C8 1 0.33µF ceramic capacitor (0805) R1 1 8.06kΩ ±1% resistor (0805) C9, C10, C11, C13, C14 5 470µF, 10V aluminum electrolytic capacitors Sanyo 10MV470AX R2, R4 R3 2 1 10kΩ ±1% resistors (0805) 23.2kΩ ±1% resistor (0805) C17 1 2200pF ceramic capacitor (0805) R5 1 60.4kΩ ±1% resistor (0805) 1 2.7kΩ ±5% resistor (0805) C18 1 1500pF ceramic capacitor (0805) R6 C19 1 0.22µF, 16V X5R ceramic capacitor (0805) Taiyo Yuden EMK212BJ224KG R7 R8 1 1 2kΩ ±5% resistor (0805) 49.9kΩ ±1% resistor (0805) 1 1 4.7µF, 10V X5R ceramic capacitor (1206) Taiyo Yuden LMK316BJ475ML R9 C20 69.8kΩ ±1% resistor (0805) R10 1 100kΩ ±5% resistor (0805) R11 R12, R13 1 2 20Ω ±5% resistor (0805) 3.9Ω ±5% resistors (0805) R14 1 154kΩ ±1% resistor (0805) R15 1 84.5kΩ ±1% resistor (0805) JU1, JU2 U1 2 1 3-pin headers MAX1875EEG 24-pin QSOP None 2 Shunts None 1 MAX1875 PC board C21 1 0.22µF, 50V X7R ceramic capacitor (0805) Taiyo Yuden UMK212BJ224MG or TDK C2012X7R1H224M C22, C23 2 0.01µF ceramic capacitors (0805) C2, C3, C15 0 Not installed (open) D1 1 100mA, 30V dual Schottky diode 23-pin SOT Central Semiconductor CMPSH-3A L1 1 15µH 5A power inductor ________________________________________________________________ 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: MAX1875/MAX1876/MAX1858 General Description The MAX1875 evaluation kit (EV kit) demonstrates a lowcost application circuit. This dual-PWM synchronous DCto-DC converter operates from unregulated AC adapters and generates precision, low-voltage rails for broadband gateways, digital TVs, cable modems, and settop boxes. Evaluates: MAX1875/MAX1876/MAX1858 MAX1875 Evaluation Kit Component Suppliers PHONE FAX Central Semiconductor SUPPLIER 516-435-1110 516-435-1824 WEBSITE Fairchild 408-721-2181 408-721-1635 www.fairchildsemi.com Nihon 847-843-7500 847-843-2798 www.niec.co.jp Sanyo 619-661-6835 619-661-1055 www.sanyovideo.com Taiyo Yuden 408-573-4150 408-573-4159 www.t-yuden.com TDK 847-390-4373 847-390-4428 www.component.tdk.com Tyco Electronics (Transpower) 888-978-2638 605-886-8995 www.trans-power.com www.centralsemi.com Note: Please indicate that you are using the MAX1875 when contacting these component suppliers. Quick Start Before beginning, the following equipment is required: • 8V to 18V power supply • Electronic loads capable of sinking 3.5A each • Digital multimeters (DMMs) • 100MHz dual-trace oscilloscope Follow these steps to verify board operation. Do not turn on the power supply until all connections are completed: 1) Ensure that the circuit is connected correctly to the supply and electronic loads before applying any power. Set electronic loads in resistive mode. 2) Verify that the shunts are across JU1 pins 1 and 2 as well as JU2 pins 2 and 3. 3) Turn on power supply. 4) Verify that the output voltages are 1.8V and 3.3V. Jumper Settings Table 1. Jumper JU1 Functions (EN Mode Selection) JU1 EN PIN MAX1875 OUTPUT 1 and 2 Connected to VL MAX1875 enabled, VOUT1 = 1.8V, VOUT2 = 3.3V 2 and 3 Connected to GND Shutdown mode, VOUT1 = 0V, VOUT2 = 0V Not Installed Connected to EN pad MAX1875 must be enabled by an external signal Table 2. Jumper JU2 Functions (SYNC Mode Selection) JU2 SYNC PIN 1 and 2 Connected to VL Used to sync up an additional MAX1875. CKO is 2x DH1 and phase shifted by 90 degrees. 2 and 3 Connected to GND Used to sync up an additional single buck. CKO is the same frequency and phase as DH1. Not Installed Connected to SYNC pad External clock is applied to SYNC input (200kHz typ) Evaluating Other Output Voltages The EV kit outputs are programmed for 1.8V and 3.3V. However, the output voltages can also be adjusted between 1V and 15V by selecting R1/R2 and R3/R4 values. Select the feedback resistors R2 and R4. R1 and R3 are then given by: R1 (or R3) = R2 (or R4) x [(VOUT / VFB) - 1] where VFB = 1V. Refer to the MAX1875 data sheet for selection of output capacitors, inductors, and compensation networks. EFFECT Evaluating the MAX1876 and MAX1858 Replace U1 with the MAX1876/MAX1858. 2 _______________________________________________________________________________________ _______________________________________________________________________________________ GND VOUT1 1.8V CKO SYNC EN RST R2 10kΩ 1% R1 8.06kΩ 1% C10 C11 C9 470µF 470µF 470µF 10V 10V 10V GND C7 0.39µF (MAX1876 ONLY) R10 100kΩ VL 3 1 2 D2 OPEN C22 0.01µF L1 15µH N1-B R7 2kΩ 1 7 3 1 2 16 14 C17 2200pF R5 60.4kΩ 1% 4 8 9 24 13 12 11 18 7 17 5 V+ OSC CKO SYNC EN RST COMP1 FB1 PGND GND DL1 LXI BST1 DH1 C21 0.22µF 50V R12 3.9Ω 15 JU1 VL N1-A 2 C5 0.1µF BST1 4 D4 OPEN 8 5 JU2 VL 3 C1 C2 390µF OPEN 6 25V R11 20Ω MAX1875 U1 L FB2 DL2 LX2 BST2 DH2 19 VL 3 ILIM2 ILIM1 REF COMP2 C12 0.1µF 1 3 10 6 1 2 20 D5 OPEN R8 49.9kΩ 1% R14 154kΩ 1% VOUT2 5 7 R6 2.7kΩ 4 C6 0.1µF BST2 N2-A 2 VL 5V N2-B BST2 C19 0.22µF C18 1500pF R13 22 3.9Ω 21 23 VL D1 C20 4.7µF 10V R 2 C4 390µF 25V C8 0.33µF C23 0.01µF D3 OPEN L2 27µH C3 OPEN R9 69.8kΩ 1% R15 84.5kΩ 1% VOUT1 3 6 1 8 R4 10kΩ 1% R3 23.2kΩ 1% VIN C15 C13 C14 470µF 470µF OPEN 10V 10V GND VOUT2 3.3V Evaluates: MAX1875/MAX1876/MAX1858 VIN 8V TO 18V BST1 MAX1875 Evaluation Kit Figure 1. MAX1875 EV Kit Schematic 3 Evaluates: MAX1875/MAX1876/MAX1858 MAX1875 Evaluation Kit Figure 2. MAX1875 EV Kit Component Placement Guide— Top Silkscreen Figure 3. MAX1875 EV Kit PC Board Layout—Component Side Figure 4. MAX1875 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. 4 _____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 © 2002 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.