MAX8625AEVKIT+

19-4153; Rev 2; 4/09 MAX8625A Evaluation Kit The MAX8625A evaluation kit (EV kit) is a fully assembled and tested PCB demonstrating the MAX8625A step-up/step-down switching regulator. The MAX8625A utilizes Maxim’s proprietary H-bridge topology that provides seamless transitions through all converter operating modes without the glitches commonly seen with other similar devices. The MAX8625A EV kit converts a 2.5V to 5.5V DC input to a preprogrammed 3.3V output capable of providing up to 800mA. The output voltage is also programmable from 1.25V to 4.2V by use of a resistor-divider. The MAX8625A EV kit provides onboard jumper settings that allow programming one of two switching modes: fixed-frequency PWM (FPWM) or high-efficiency skip. Additional on-board jumpers allow enable or shutdown of the MAX8625A IC. Features ♦ 2.5V to 5.5V Input-Voltage Range ♦ 3.3V Preset Output Voltage ♦ Programmable Output Voltage from 1.25V to 4.2V ♦ Glitch-Free Step-Up/Step-Down Transitions ♦ Selectable Switching Modes FPWM Mode High-Efficiency Skip Mode ♦ Soft-Start ♦ Output Overload Protection ♦ Thermal Protection ♦ Small 3mm x 3mm, 14-Pin TDFN IC Package ♦ Lead(Pb)-Free and RoHS Compliant ♦ Fully Assembled and Tested Ordering Information Component List DESIGNATION QTY DESCRIPTION C1–C4 4 22µF ±20%, 10V X5R ceramic capacitors (1206) Taiyo Yuden LMK316BJ226ML C5 1 0.1µF ±10%, 16V X5R ceramic capacitor (0402) Taiyo Yuden EMK105BJ104KV 2 1µF ±10%, 10V X5R ceramic capacitors (0402) Taiyo Yuden LMK105BJ105KV C6, C7 JU1, JU2 L1 2 1 PART TYPE MAX8625AEVKIT+ EV Kit +Denotes lead(Pb)-free and RoHS compliant. Component Suppliers SUPPLIER PHONE WEBSITE Digi-Key Corp. 800-344-4539 www.digikey.com 3-pin headers Sullins PEC36SAAN Digi-Key S1012E-36-ND Sullins Electronics Corp. 760-744-0125 www.sullinselectronics.com Taiyo Yuden 408-573-4150 www.t-yuden.com 3.3µH inductor TOKO 1101AS-3R3M (DEA4012CK series) TOKO America, Inc. 408-432-8281 www.tokoam.com R1, R2 0 Not installed, resistors (0402) R1 is open; R2 is short (PCB trace) U1 1 Step-up/down regulator (14 TDFN) Maxim MAX8625AETD+ — 1 PCB: MAX8625A EVALUATION KIT+ Note: Indicate that you are using the MAX8625A when contacting these component suppliers. ________________________________________________________________ Maxim Integrated Products For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com. 1 Evaluates: MAX8625A General Description Evaluates: MAX8625A MAX8625A Evaluation Kit Quick Start Required Equipment • • • • • MAX8625A EV kit One variable DC power supply capable of supplying 2.5V to 5.5V at 2.5A One digital multimeter (DMM) One ammeter One electronic load capable of sinking 800mA Procedure The MAX8625A EV kit is fully assembled and tested. Follow these steps to verify board operation: 1) Preset the variable DC power supply to 3.3V. Turn off the power supply. Caution: Do not turn on the power supply until all connections are completed. 2) Connect the positive lead of the power supply to the VIN pad on the EV kit, and the negative lead of the power supply to the GND pad on the EV kit. 3) Connect the positive input of the DMM to the VOUT pad on the EV kit, and the negative input of the DMM to the GND pad on the EV kit to measure the output voltage at VOUT. 4) Connect an 800mA electronic load and ammeter between the VOUT and GND pads on the EV kit. 5) Ensure that shunts are placed on pins 2-3 of jumpers JU1 and JU2 to enable the IC in FPWM mode, as shown in Table 1. 6) Turn on the power supply. 7) Verify that the voltage at VOUT is approximately 3.3V. 8) Sweep the voltage of the power supply between 2.5V to 5.5V and verify that the voltage at VOUT is approximately 3.3V over the entire input range. When evaluation of the MAX8625A EV kit is completed, use the following steps to power down the EV kit: 1) Turn off the power supply. 2) Disconnect power supply, cables, and test leads from the EV kit. Table 1. Jumper Settings 2 JUMPER FUNCTION JU1 Install a shunt across pins 2-3 to connect SKIP to IN for FPWM mode. Install a shunt across pins 1-2 to connect SKIP to GND for skip mode. Do not switch the converter from FPWM (position 2-3) to SKIP (position 1-2) or vice versa on the fly. The MAX8625A is not designed for dynamic transitions between skip and FPWM modes. JU2 Install a shunt across pins 2-3 to enable the IC. Install a shunt across pins 1-2 to disable the IC. Enable the MAX8625A after the supply voltage is above UVLO. Tying the ON pin to the supply and then ramping up the supply voltage is not recommended. _______________________________________________________________________________________ MAX8625A Evaluation Kit Evaluates: MAX8625A L1 3.3μH VIN 2.5V TO 5.5V 13 C6 1μF C1, C2 22μF 14 1 2 3 4 LX1 LX1 LX2 LX2 9 OUT 10 OUT IN IN U1 6 JU1 SKIP C7 1μF C3, C4 22μF R1 OPEN MAX8625A 3 2 1 VOUT 3.3V FB 7 R2 SHORT 3 2 1 5 JU2 8 ON GND REF GND 11 GND 12 C5 0.1μF Figure 1. MAX8625A EV Kit Schematic Detailed Description of Hardware Setting the Output Voltage The MAX8625A EV kit output voltage is preset at 3.3V, but can be adjusted from 1.25V to 4.2V by the selection of R1 and R2 resistance values (Figure 1). To program the output voltage, follow the procedure below: 1) Select a 100kΩ resistance value for R2. 2) Determine the value of R1 from the following equation: ⎛V ⎞ R1 = 100kΩ × ⎜ OUT − 1⎟ ⎝ VFB ⎠ where VFB = 1.25V and VOUT is the desired output regulation voltage. VOUT must be between 1.25V and 4.2V. 3) Cut the trace shorting the pads of resistor R2. 4) Install resistors R1 and R2 on the MAX8625A EV kit. Note: Adjusting the output voltage affects the maximum output current available from the MAX8625A EV kit and may require changing the value of inductance of L1. Refer to the Applications Information section in the MAX8625A IC data sheet for more information. Selecting the Switching Mode The MAX8625A EV kit has two selectable switching modes: 1) Fixed-frequency PWM (FPWM) mode 2) High-efficiency skip mode Fixed-Frequency PWM Mode (FPWM) In FPWM mode, the MAX8625A operates at a constant 1MHz switching frequency with no pulse skipping. This scheme is desirable in noise-sensitive applications because the output ripple frequency spectrum is minimized and predictable. FPWM mode consumes higher supply current at light loads due to constant switching. High-Efficiency Skip Mode In skip mode, the IC switches only as necessary to maintain the output in regulation at light loads, but still operates with fixed-frequency PWM at medium and heavy loads. This operation maximizes light-load efficiency and reduces the input quiescent current. To select the switching mode, shunt jumper JU1 on the MAX8625A EV kit as indicated in Table 1. Selecting Shutdown Mode To place the MAX8625A in shutdown mode, shunt pins 1-2 of jumper JU2 on the MAX8625A EV kit. To enable the MAX8625A, shunt pins 2-3 of jumper JU2 on the MAX8625A EV kit. _______________________________________________________________________________________ 3 Evaluates: MAX8625A MAX8625A Evaluation Kit Figure 2. MAX8625A EV Kit Component Placement Guide—Top Silkscreen 4 _______________________________________________________________________________________ MAX8625A Evaluation Kit Evaluates: MAX8625A Figure 3. MAX8625A EV Kit PCB Layout—Component Side _______________________________________________________________________________________ 5 Evaluates: MAX8625A MAX8625A Evaluation Kit Figure 4. MAX8625A EV Kit PCB Layout—Solder Side 6 _______________________________________________________________________________________ MAX8625A Evaluation Kit REVISION NUMBER REVISION DATE 0 5/08 Initial release — 1 11/08 Modified the jumper settings in Table 1 2 DESCRIPTION PAGES CHANGED 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 _____________________ 7 © 2009 Maxim Integrated Products Maxim is a registered trademark of Maxim Integrated Products, Inc. Evaluates: MAX8625A Revision History