Evaluates: MAX17681 for Isolated MAX17681 Evaluation Kit +7V or +5V Output Configuration General Description Quick Start The MAX17681EVKITD is a fully assembled and tested Recommended Equipment circuit board that demonstrates the performance of the One 15V60V DC, 0.5A power supply MAX17681 high-efficiency, iso-buck DC-DC converter. Two resistive loads of 200mA sink capacity The EV kit operates over a wide input-voltage range of 17V to 36V and uses primary-side feedback to regulate Four digital multimeters (DMM) the output voltage. The EV kit has two output configura - Caution: Do not turn on the power supply until all tions. In the first configuration, the output is programmed connections are completed. to +7V at 200mA, with 8% output voltage regulation. The second configuration uses a post regulator (MAX17651) Procedure to produce +5V at 100mA with at least 3% regulation. The EV kit comes with the default output configuration programmed to +7V. The EV kit comes installed with the MAX17681 in a 10-pin (3mm x 2mm) TDFN package and MAX17651 in a 6-lead Test Procedure for +7V Output TSOT package. 1) Verify that J1 is open. Features 2) Verify that the R7 and R14 are not installed. 17V to 36V Input Voltage Range 3) Set the power supply output to 24V. Disable the power supply. +7V, 200mA or +5V, 100mA Continuous Current 4) Connect the positive terminal of the power supply EN/UVLO Input to the V PCB pad and the negative terminal to the IN 200kHz Switching Frequency nearest PGND PCB pad. Connect a 200mA resistive Overcurrent Protection load across the +7V PCB pad and the GND0 PCB pad. No Optocoupler 5) Connect a DMM configured in voltmeter mode Delivers up to 1.4W Output Power across the +7V PCB pad and the nearest GND0 Overtemperature Protection PCB pad. Proven PCB Layout 6) Enable the input power supply. 7) Verify that output voltage is at +7V (with allowable tolerance of 8%) with respect to GND0. Ordering Information appears at end of data sheet. 8) If required, vary the input voltage from 17V to 36V, and the load current from 0mA to 200mA and verify that output voltage is at +7V (with allowable tolerance of 8%). 19-8425 Rev 1 4/16Evaluates: MAX17681 for Isolated MAX17681 Evaluation Kit +7V or +5V Output Configuration available for monitoring the health of primary output volt- Test Procedure for +5V Output age (V ). RESET pulls low if FB voltage drops below PRI 1) Verify that J1 is open. 92.5% of its set value. RESET goes high impedance 1024 2) Place 0 resistors in R7. Place a 681k pack-out resistor clock cycles after FB voltage rises above 95.5% of its set (comes with EV kit package) in R14. value. The programmable soft-start feature allows users 3) Set the input power supply output to 24V. Disable the to reduce the input inrush current. power supply. The iso-buck is a synchronous-buck-converter-based 4) Connect the positive terminal of the power supply topology, useful for generating isolated outputs at low to the V PCB pad and the negative terminal to the IN power level without using an optocoupler. The detailed nearest PGND PCB pad. Connect a 100mA resistive procedure for setting the soft-start time, ENABLE/UVLO load across the +5V PCB pad and the GND0 PCB pad. divider, primary output voltage (V ) selection, adjusting PRI the primary output voltage, primary inductance selection, 5) Connect a DMM configured in voltmeter mode across turns-ratio selection, output capacitor selection, output the +5V PCB pad and the nearest GND0 PCB pad. diode selection and external loop compensation are given 6) Enable the input power supply. in the MAX17681 IC data sheet. The post regulator, 7) Verify that output voltage is at +5V (with allowable MAX17651 output voltage setting and the related additional tolerance of 3%) with respect to GND0. information are detailed in MAX17651 IC data sheet. 8) If required, vary the input voltage from 17V to Enable Control (J1) 36V, and the load current from 0mA to 100mA and The EN/UVLO pin on the device serves as an on/off verify that output voltage is at +5V (with allowable control while also allowing the user to program the input tolerance of 3%). undervoltage-lockout (UVLO) threshold. J1 configures the EV kits output for turn-on/turn-off control. Install a Detailed Description shunt across J1 pins 2-3 to disable V . See Table 1 for OUT The MAX17681EVKITD evaluation kit (EV kit) is a fully proper J1 configurations. assembled and tested circuit board that demonstrates the performance of the MAX17681 high efficiency, iso-buck NOTE 1: The secondary output diodes D1 is rated to DC-DC converter designed to provide an isolated power carry short-circuit current only for few 100s of ms and is up to 1.4W. The EV kit generates either +7V, 200mA or not rated to carry the continuous short-circuit current. +5V, 100mA output from a 17V to 36V input supply. The NOTE 2: The iso-buck converter typically needs 10% EV kit features a forced PWM control scheme that pro- minimum load to regulate the output voltage. In this vides constant switching-frequency of 200kHz operation design, when the +7V rail is healthy, U3 sinks the minimum at all load and line conditions. load current required to regulate the output voltages The EV Kit includes an EN/UVLO PCB pad to monitor within 8% regulation. and program the EN/UVLO pin of the MAX17681. The V PCB pad helps measure the regulated primary PRI output voltage (V ). An additional RESET PCB pad is PRI Table 1. Enable Control (EN/UVLO) (J1) Jumper Settings SHUNT POSITION EN/UVLO PIN VOUT J1 1-2 Connected to V Always Enabled IN 2-3 Connected to GND Always Disabled Open* Connected to midpoint of R1, R2 resistor-divider Enabled at V 15.5V IN *Default position. Maxim Integrated 2 www.maximintegrated.com