Evaluates: MAX17681 for Isolated MAX17681 Evaluation Kit +15V or +12V Output Configuration General Description Quick Start The MAX17681EVKITC 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 to connections are completed. +15V at 200mA, with 8% output voltage regulation. The second configuration uses a post regulator (MAX17651) to Procedure produce +12V at 100mA with better than 3% regulation. The EV kit comes with the default output configuration programmed to +15V. 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 +15V Output Thin-SOT (TSOT) package. 1) Verify that the J1 is open Features 2) Verify that the R7 and R14 is not installed 17V to 36V Input Voltage Range 3) Set the power supply output to 24V. Disable the power supply +15V, 200mA or +12V, 100mA Continuous Current 4) Connect the positive terminal of the power supply to EN/UVLO Input the VIN PCB pad and the negative terminal to the 200kHz Switching Frequency nearest PGND PCB pad. Connect a 200mA resistive 89.5% Peak Efficiency load across the +15V PCB pad and the GND0 PCB pad. Overcurrent Protection 5) Connect a DMM configured in voltmeter mode No Optocoupler across the +15V PCB pad and the nearest GND0 Delivers up to 3W Output Power PCB pad. Overtemperature Protection 6) Enable the input power supply. Proven PCB layout 7) Verify that output voltage is at +15V (with allowable tolerance of 8%) with respect to GND0. 8) If required, vary the input voltage from 17V to 36V, and the load current from 0mA to 200mA and verify Ordering Information appears at end of data sheet. that output voltage is at +15V (with allowable tolerance of 8%). 19-8241 Rev 2 8/17Evaluates: MAX17681 for Isolated MAX17681 Evaluation Kit +15V or +12V Output Configuration V PCB pad helps measure the regulated primary output Test Procedure for +12V Output PRI voltage (V ). An additional RESET PCB pad is available PRI 1) Verify that the J1 is open for monitoring the health of primary output voltage (V ). PRI 2) Place 0 resistors in R7, Place a 681k pack-out RESET is pulled low if FB voltage drops below 92.5% of resistor (comes with EV kit package) in R14. its set value. RESET goes high 1024 clock cycles after FB 3) Set the input power supply output to 24V. Disable the voltage rises above 95.5% of its set value. The programmable power supply soft-start feature allows users to reduce the input inrush current. 4) Connect the positive terminal of the power supply to the VIN PCB pad and the negative terminal to the The iso-buck is a synchronous-buck-converter-based nearest PGND PCB pad. Connect a 100mA resistive topology, useful for generating isolated outputs at low load across the +12V PCB pad and the GND0 power level without using an optocoupler. The detailed PCB pad. procedure for setting the soft-start time, ENABLE/UVLO divider, primary output voltage (V ) selection, adjusting 5) Connect a DMM configured in voltmeter mode PRI the primary output voltage, primary inductance selection, across the +12V PCB pad and the nearest GND0 turns-ratio selection, output capacitor selection, output PCB pad. diode selection and external loop compensation are given 6) Enable the input power supply. in MAX17651 IC data sheet. The MAX17651s output 7) Verify that output voltage is at +12V (with allowable voltage setting, and related additional information, are tolerance of 3%) with respect to GND0. detailed in MAX17651 IC data sheet. 8) If required, vary the input voltage from 17V to 36V, Enable Control (J1) and the load current from 0mA to 100mA and verify The EN/UVLO pin on the device serves as an on/off that output voltage is at +12V (with allowable tolerance control while also allowing the user to program the input 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 VOUT. See Table 1 for The MAX17681EVKITC 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 diode (D1) is rated to DC-DC converter designed to provide an isolated power carry the short-circuit current only for few 100s of ms and up to 3W. The EV kit generates either +15V, 200mA or is not rated to carry the continuous short-circuit current. +12V, 100mA from a 17V to 36V input supply. The EV NOTE 2: The iso-buck converter typically needs 10% kit features a forced PWM control scheme that provides minimum load to regulate the output voltage. In this constant switching-frequency of 200kHz operation at all design, when the +15V rail is healthy, the U3 sinks the load and line conditions. minimum load current required to regulate the output The EV Kit includes an EN/UVLO PCB pad to monitor voltages within 8% regulation. and program the EN/UVLO pin of the MAX17681. The 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 VIN 15.5V *Default position. Maxim Integrated 2 www.maximintegrated.com