Click here for production status of specific part numbers. Evaluates: MAX17686 for Isolated MAX17686 Evaluation Kit +24V Output Configuration General Description Quick Start The MAX17686EVKITA is a fully assembled and tested Recommended Equipment circuit board that demonstrates the performance of the One 15V60V DC, 0.5A power supply MAX17686 high-efficiency, iso-buck DC-DC Converter. One resistive load 100mA sink capacity The EV kit operates over a wide input-voltage range of 17V to 60V and uses primary-side feedback to regulate Two digital multimeters (DMM) the output voltage. The EV kit output is programmed to Caution: Do not turn on the power supply until all +24V at 100mA, with 8% output voltage regulation. connections are completed. The EV kit comes installed with the MAX17686 in a 10-pin Test Procedure (3mm x 2mm) TDFN package. The EV kit comes with the default output configuration Features programmed to +24V. 17V to 60V Input Voltage Range 1) Verify that J1 is open. +24V, 100mA Continuous Current 2) Set the power supply output to 24V. Disable the power supply. EN/UVLO Input 3) Connect the positive terminal of the power supply 200kHz Switching Frequency to the V PCB pad and the negative terminal to the IN Overcurrent Protection nearest PGND PCB pad. Connect a 100mA resistive No Optocoupler load across the +24V PCB pad and the GND0 PCB pad. Delivers up to 2.4W Output Power 4) Connect a DMM configured in voltmeter mode across the +24V 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. Provides robust primary and secondary output 6) Enable the input power supply. short-circuit protection 7) Verify that primary voltage is at +10.3V with respect to Complies with CISPR22(EN55022) Class B PGND. Conducted and Radiated Emissions 8) Verify that output voltage is at +24V (with allowable tolerance of 8%) with respect to GND0. 9) If required, vary the input voltage from 17V to 60V, Ordering Information appears at end of data sheet. and the load current from 0mA to 100mA and verify that output voltage is at +24V (with allowable tolerance of 8%). 319-100301 Rev 0 1/19Evaluates: MAX17686 for Isolated MAX17686 Evaluation Kit +24V Output Configuration Hot-Plug-In and Long Input Cables Detailed Description The MAX17686 EV kit PCB provides an electrolytic The MAX17686EVKITA evaluation kit (EV kit) is a fully capacitor (C2, 22F/100V) to dampen input voltage assembled and tested circuit board that demonstrates the peaks and oscillations that can arise during hot-plug-in performance of the MAX17686 high efficiency, iso-buck and/or due to long input cables. This capacitor limits the DC-DC converter designed to provide an isolated power peak voltage at the input of the MAX17686 IC, when the up to 2.4W. The EV kit generates +24V, 100mA from a EV kit is powered directly from a precharged capacitive 17V to 60V input supply. The EV kit features a forced source or an industrial backplane PCB. Long input cables PWM control scheme that provides constant switching- between input power source and the EV kit circuit can frequency of 200kHz operation at all load and line conditions. cause input-voltage oscillations due to the inductance The EV kit includes an EN/UVLO PCB pad to monitor and of the cables. The equivalent series resistance (ESR) program the EN/UVLO pin of the MAX17686. The V PRI of the electrolytic capacitor helps damp out the oscilla- PCB pad helps measure the regulated primary output tions caused by long input cables. Further, capacitor C1 voltage (V ). An additional RESET PCB pad is available PRI (0.1F/100V), placed near the input of the board, helps in for monitoring the health of primary output voltage (V ). PRI attenuating high frequency noise. RESET is pulled low if FB voltage drops below 92.5% of its set value. RESET goes high impedance 1024 clock Enable Control (J1) cycles after FB voltage rises above 95.5% of its set The EN/UVLO pin on the device serves as an on/off value. The programmable soft-start feature allows users control while also allowing the user to program the input to reduce the input inrush current. undervoltage-lockout (UVLO) threshold. J1 configures The iso-buck is a synchronous-buck-converter-based the EV kit output for turn-on/turn-off control. Install a topology, useful for generating isolated outputs at low shunt across J1 pins 2-3 to disable V . See Table 1 for OUT power level without using an optocoupler. The detailed proper J1 configurations. procedure for setting the soft-start time, ENABLE/UVLO NOTE 1: The secondary output diodes D1 is rated to divider, primary output voltage (V ) selection, adjusting PRI carry short-circuit current only for few 100s of ms and is the primary output voltage, primary inductance selection, not rated to carry the continuous short-circuit current. turns-ratio selection, output capacitor selection, output NOTE 2: The iso-buck converter typically needs 10% minimum diode selection and external loop compensation are given load to regulate the output voltage. In this design when in MAX17686 IC data sheet. the +24V rail is healthy, the U2 sinks the minimum load Electro-Magnetic Interference (EMI) current required to regulate the output voltages within 8% regulation. Compliance to conducted emissions (CE) standards requires an EMI filter at the input of a switching power converter. The EMI filter attenuates high-frequency cur- L f rents drawn by the switching power converter and limits 120H the noise injected back into the input power source. C FROM f TO EVKIT Ci 2.2F 2.2F LISN INPUT Use of EMI filter components as shown in Figure 1 results in lower conducted emissions, below CISPR22 Class B Lf = COILCRAFT LPS6235-124D limits. The MAX17686 EV kit PCB layout is also designed C AND C = GRM32ER72A225KA35 (2.2F/1210/100V/X7R) i f to limit radiated emissions from the switching nodes of the power converter resulting in radiated emissions below Figure 1. EMI Filter Components CISPR22 Class B limits. Table 1. Enable Control (EN/UVLO) (J1) Jumper Settings SHUNT POSITION EN/UVLO PIN V OUT 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 16V IN *Default position. Maxim Integrated 2 www.maximintegrated.com