PRELIMINARY Evaluates: MAXM17544 in 3.3V MAXM17544 3.3V Output Output-Voltage Application Evaluation Kit General Description Features The MAXM17544 evaluation kit (EV kit) is a demonstration Highly Integrated Solution with Integrated Shield circuit of the MAXM17544 high-voltage, high-efficiency, Inductor current-mode scheme, synchronous step-down, DC-DC Wide 4.5V to 42V Input Range switching power module. The EV kit is designed for a 3.3V Preset 3.3V Output with a Fixed Resistor-Divider on output and delivers up to 3.5A load current from a wide FB (Feedback Pin) input-voltage range of 4.5V to 42V. The EV kit switches at an optimal 500kHz switching frequency to allow the use of Programmable Output-Voltage Feature (0.9V to 12V) small component-sizes, helping to minimize solution-size Up to 3.5A Output Current while maintaining high-performance. The EV kit provides High 91.2% Efficiency (V = 12V, V = 3.3V at 0.74A) IN OUT a precision-enable input, an open-drain RESET output 500kHz Switching Frequency signal, and external frequency synchronization to provide a simple and reliable startup sequence and eliminate beat Enable/UVLO Input, Resistor-Programmable UVLO frequency between regulators. The EV kit also includes Threshold optional component footprints to program different output Adjustable Soft-Start Time voltages, an adjustable input undervoltage-lockout, and Selectable PWM, PFM, or DCM Mode a soft-start time to control inrush current during startup. The MAXM17544 IC data sheet provides a complete Open-Drain RESET Output description of the part that should be read in conjunction External Frequency Synchronization with this evaluation kit data sheet prior to modifying the Overcurrent and Overtemperature Protection demo circuit. Low-Profile, Surface-Mount Components Lead(Pb)-Free and RoHS Compliant Ordering Information appears at end of data sheet. Fully Assembled and Tested 19-7625 Rev 0 5/15PRELIMINARY Evaluates: MAXM17544 in 3.3V MAXM17544 3.3V Output Evaluation Kit Output-Voltage Application On the bottom layer, additional footprints of optional Quick Start components are included to ease board modification for Recommended Equipment different input/output configurations. MAXM17544 EV kit Soft-Start Input (SS) 4.5V to 42V DC power supply (V ) IN The device utilizes an adjustable soft-start function to Dummy load capable of sinking 3.5A limit inrush current during startup. The soft-start time is Digital voltmeter (DVM) programmed by the value of the external capacitor from SS to GND (C1). The selected output capacitance (C ) SEL 100MHz dual-trace oscilloscope and the output voltage (V ) determine the minimum OUT Procedure value of C1, as shown by the following equation: The EV kit is fully assembled and tested. Follow the steps 3 C128 10 C V below to verify board operation. Caution: Do not turn on SEL OUT the power supply until all connections are completed. where C1 is in nF and C is in F SEL 1) Set the power supply at a voltage between 4.5V and The soft-start time (t ) is calculated by the equation SS 42V. Disable the power supply. below: 2) Connect the positive and negative terminals of the power supply to IN and PGND PCB pads, respectively. t = C1/ 5.55 SS 3) Connect the positive and negative terminals of the 3.5A load to OUT and PGND2 PCB pads, respectively, where t is in ms and C1 is in nF. SS and set the load to 0A. Programmable Undervoltage Lockout (UVLO) 4) Connect the DVM across the OUT PCB pad and the PGND2 PCB pad. The EV kit offers an adjustable-input undervoltage- 5) Verify that no shunts are installed across pin 1-2 on lockout level by resistor-dividers connected between jumper JU1 to enable UVLO (see Table 1 for details). IN, EN/UVLO, and GND pins. For normal operation, a 6) Verify that a shunt is installed across JU3 to disable shunt should not be installed across pins 1-2 on JU1 the external synchronization (see Table 3 for details). to enable the output through an internal pullup 3.3M 7) Verify that a shunt is installed across JU2 to enable resistor from the EN/UVLO pin to IN pin. To disable the PWM mode (see Table 2 for details). output, install the shunt across pins 1-2 on JU1 to 8) Enable the input power supply. pull EN/UVLO pin to GND. See Table 1 for JU1 9) Verify the DVM displays 3.3V. jumper settings. The EV kit also provides an optional 10) Increase the load up to 3.5A to verify the DVM continues R3 PCB footprint to program a UVLO threshold voltage displaying 3.3V. at which an input-voltage level device turns on. The R3 resistor can be calculated by the following equation: Detailed Description of Hardware The EV kit is a proven circuit to demonstrate the high- 4009.5 R3 = voltage, high-efficiency, and compact solution- (V 1.215) INU size of the synchronous step-down, DC-DC power where V is the input voltage at which the device is module. The output voltage is preset for 3.3V to operate INU from 4.5V to 42V and provides up to 3.5A load current. required to turn on, and R3 unit is in k. The optimal frequency is set at 500kHz to maximize efficiency and minimize component size. The EV kit includes Table 1. UVLO Enable/Disable jumpers JU1 to enable/disable UVLO of the device, JU2 to congfi ure in PWM, PFM, or DCM mode in advantage Configuration (JU1) of light-load efficiency, and JU3 to enable/disable external SHUNT clock synchronize (SYNC). The RESET PCB pad is also EN PIN MAXM17544 OUTPUT POSITION available for monitoring output voltage regulation to enable/disable the application circuit of the load. The elec- Installed Connected to GND Disable trolytic capacitor (C8) is required only when the V power Not installed* Connected to VIN Enable IN supply is situated far from device circuit. When R4 is *Default position. open, the device switches at 500kHz switching frequency. Maxim Integrated 2 www.maximintegrated.com