Click here for production status of specific part numbers. Evaluates: MAX17687 for Isolated +12V MAX17687 Evaluation Kit Output Configuration General Description Quick Start The MAX17687EVKITA evaluation kit (EV kit) is a fully Recommended Equipment assembled and tested circuit board that demonstrates the One 15V - 60V DC, 1A Power Supply performance of the MAX17687 high-efficiency, iso-buck One resistive load 750mA sink capacity DC-DC Converter. The EV kit operates over a wide input- voltage range of 16V to 60V and uses primary-side feedback to Two Digital Multimeters (DMM) regulate the output voltage. The EV kit has isolated output, Caution: Do not turn on the power supply until all programmed to +12V at 750mA, with 10% output voltage connections are completed. regulation. Procedure The EV kit comes installed with the MAX17687 in a 20-pin The EV kit comes with the default secondary output (4mm x 4mm) TQFN package. programmed to +12V. Features 1) Verify that JU2 is open 16V to 60V Input Voltage Range 2) Set the power supply output to 24V. Disable the +12V, 750mA Continuous Current power supply EN/UVLO Input 3) Connect the positive terminal of the power supply to the VIN PCB pad and the negative termi- 200kHz Switching Frequency nal to the nearest PGND PCB pad. Connect a 750mA Overcurrent Protection resistive load across the VOUT PCB pad and the No Optocoupler GND0 PCB pad. Delivers up to 10W Output Power 4) Connect a DMM configured in voltmeter mode across the VOUT PCB pad and the nearest GND0 PCB pad. Overtemperature Protection 5) Connect a DMM configured in voltmeter mode across Proven PCB layout the VPRI PCB pad and the nearest PGND PCB pad. Complies with CISPR22(EN55022) Class B 6) Enable the input power supply. Conducted and Radiated Emissions 7) Verify that the primary voltage is at +8V with respect to PGND. 8) Verify that output voltage is at +12V (with allowable Ordering Information appears at end of data sheet. tolerance of 10%) with respect to GND0. 9) If required, vary the input voltage from 16V to 60V, and the load current from 0mA to 750mA and verify that output voltage is at +12V (with allowable tolerance of 10%). 319-100287 Rev 0 12/18Evaluates: MAX17687 for Isolated +12V MAX17687 Evaluation Kit Output Configuration Use of EMI filter components as shown in Figure 1 results Detailed Description in lower conducted emissions, below CISPR22 Class B The MAX17687EVKITA evaluation kit (EV kit) is a fully limits. The MAX17687 EV kit PCB layout is also designed assembled and tested circuit board that demonstrates to limit radiated emissions from switching nodes of the the performance of the MAX17687 high-efficiency, iso- power converter, resulting in radiated emissions below buck, DC-DC converter designed to provide an isolated CISPR22 Class B limits. power up to 10W. The EV kit generates +12V, 750mA voltages from a 16V to 60V input supply. The EV kit Hot-Plug-In and Long Input Cables features a forced-PWM control scheme that provides The MAX17687 EV kit PCB provides an electrolytic constant switching-frequency of 200 kHz operation at all capacitor (C8, 47F/100V) to dampen input voltage load and line conditions. peaks and oscillations that can arise during hot-plug-in The EV Kit includes an EN/UVLO PCB pad to monitor and/or due to long input cables. This capacitor limits the and program the EN/UVLO pin of the MAX17687. The peak voltage at the input of the MAX17687 IC, when the VPRI PCB pad helps measure the regulated primary EV kit is powered directly from a precharged capacitive output voltage (V ). An additional RESET PCB pad source or an industrial backplane PCB. Long input cables, PRI is available for monitoring the health of primary output between input power source and the EV kit circuit can voltage (V ). RESET pulls low if FB voltage drops cause input-voltage oscillations due to the inductance PRI below 92%(typ) of its set value and RESET goes high of the cables. The equivalent series resistance (ESR) impedance 1024 clock cycles after FB voltage rises of the electrolytic capacitor helps damp out the oscilla- above 95% of its set value. The programmable soft-start tions caused by long input cables. Further, capacitor C9 feature allows users to reduce the input inrush current. (0.1F/100V), placed near the input of the board, helps in attenuating high frequency noise. The iso-buck is a synchronous-buck-converter-based topology, useful for generating isolated outputs at low Enable Control (JU2) power level without using an opto-coupler. The detailed The EN/UVLO pin on the device serves as an on/off procedure for setting the soft-start time, EN/UVLO divider, control while also allowing the user to program the input primary output voltage (V ) selection, adjusting the PRI undervoltage lockout (UVLO) threshold. Jumper JU2 primary output voltage, primary inductance selection, configures the EV kits output for turn-on/turn-off control. turns-ratio selection, output capacitor selection, output Install a shunt across jumper JU2 pins 2-3 to disable diode selection and external loop compensation are given VOUT. See Table 1 for proper JU2 jumper configurations. in MAX17687 IC data sheet. Electro-Magnetic Interference (EMI) Lf Compliance to conducted emissions (CE) standards 220H FROM TO EV KIT Ci Cf requires an EMI filter at the input of a switching power 4.7F LISN INPUT 4.7F x 2 converter. The EMI filter attenuates high-frequency cur- L = WURTH 7447714221 f rents drawn by the switching power converter, and limits C AND C = GRM32ER71K475KE14 (4.7F/1210/80V/X7R) i f the noise injected back into the input power source. Figure 1. Conducted Emissions Filter Table 1. Enable Control (EN/UVLO) (JU2) Jumper Settings SHUNT POSITION EN/UVLO PIN V OUTPUT OUT JU2 1-2 Connected to V Always Enabled IN 2-3 Connected to GND Always Disabled Open* Connected to midpoint of R2, R3 resistor-divider Enabled at V 15V IN *Default position. Note 1: The secondary output diodes D1 is rated to carry short-circuit current only for few hundredths of a millisecond and is not rated to carry the continuous short-circuit current. Note 2: The iso-buck converter typically needs 10% minimum load to regulate the output voltage. In this design when the +12V rail is healthy, D2 sinks the minimum load current required to regulate the output voltages within 10% regulation. Maxim Integrated 2 www.maximintegrated.com