Evaluates: MAX17690 No-Opto Flyback MAX17690 No-Opto Flyback with Secondary-Side Synchronous Evaluation Kit Rectification General Description Quick Start The MAX17690A evaluation kit (EV kit) is a fully assembled Recommended Equipment and tested circuit board that demonstrates the operation One 18V36V DC, 1A power supply of an isolated 5W no-opto flyback DC-DC converter with 5W resistive load with 1A sink capacity secondary-side synchronous rectification. This circuit is implemented using the MAX17690, a no-opto, flyback Four digital multimeters (DMM) controller in a 16-pin TQFN package with an exposed MAX17690EVKITA pad. The synchronous rectification on the secondary- side is enabled by replacing the secondary diode with a Warning MOSFET to achieve 89.5% efficiency. The circuit uses the Do not turn on the power supply until all connections MAX17606, a secondary-side synchronous rectifier driver are completed. in a 6-pin SOT23 package for driving the secondary-side Wear protective eye gear at all times. MOSFET. Do not touch any part of the circuit with bare hands/ The EV kit output is configured for an isolated +5V conductive materials when powered up. and provides up to 1A of output current. The EV kit is Make sure all high-voltage capacitors are fully programmed to operate at a 150kHz switching frequency. discharged before handling. Allow 5 minutes after The transformer provides the galvanic isolation between disconnecting input power source before touching input and output, up to 1875V . The EV kit regulates RMS circuit parts. the output voltage within 5% over the line, load, and temperature without using the auxiliary winding/optocoupler Equipment Setup and Test Procedure for output voltage feedback. 1) Set the power supply to +24VDC. Disable the power supply output. Features 2) Connect the positive terminal of the power supply to 18V to 36V Input Range the VIN PCB pad and the negative terminal to the Isolated Output: 5V/1A DC nearest PGND PCB pad. Connect the positive terminal Compact Design with High Frequency (150kHz) Switching of the electronic load to the VOUT PCB pad and the negative terminal to the nearest GND0 PCB pad. No Optocoupler/Third Winding Required to Derive Feedback Signal 3) Connect the resistive load across the output terminals. 90% Peak Efficiency 4) Connect a DMM configured in voltmeter mode across the VOUT PCB pad and the nearest GND0 PCB pad. Galvanic Isolation up to 1875V RMS 5) Enable the power supply. Proven PCB Layout 6) Verify that the output voltmeter displays 5V and, if Fully Assembled and Tested required, measure the output current using a DMM Minimum Load for 5% Regulation: 1% of Full-Load programmed in ammeter mode. 7) If required, vary the input voltage from 18V to 36V, and the load current from 10mA to 1A. Verify that the Ordering Information appears at end of data sheet. output voltage is 5V 5%. 19-8394 Rev 2 11/17Evaluates: MAX17690 No-Opto Flyback MAX17690 No-Opto Flyback Evaluation Kit with Secondary-Side Synchronous Rectification The MAX17606 has provision to program the turn-off trip Detailed Description point of the secondary synchronous rectifier. An external The MAX17690 EV kit provides a proven design to evaluate resistor (R18) connects the drain of the external MOSFET the MAX17690, a high-efficiency no-opto DC-DC flyback to ICs DRN pin. This resistor sets the turn-off trip point controller. The device uses a novel sampling technique to using the precise internal current source. After the eliminate the optocoupler/third winding in sensing the output synchronous rectifier is turned-off to avoid the false voltage across the isolation boundary. The MAX17606, a tripping due to DCM ringing, the MAX17606 programs secondary-side synchronous driver, is used, along with the the minimum turn-off time. The MAX17606 uses the MAX17690, to improve the converter efficiency. resistor (R20) connected between TOFF pin to GND0 to This EV kit provides the programmable soft-start feature program the minimum turn-off time. For selecting R18, to limit the inrush current. The EN/UVLO is used to start R20 and other components related to MAX17606, refer the converter at the desired input voltage. The OVI is used the MAX17606 IC data sheet. to turn-off the converter at the desired input overvoltage level. The MAX17690 provides overcurrent and thermal protection. The details of soft-start time programming, programming the output voltage, peak-current-limit setting, switching frequency setting, and the EN/UVLO, OVI settings are described in the MAX17690 IC data sheet. EV Kit Performance Report OUTPUT VOLTAGE vs. LOAD CURRENT EFFICIENCY vs. LOAD CURRENT toc01 toc02 100 5.20 90 80 5.14 V = 18V IN 70 V = 24V IN V = 18V IN 60 5.08 V = 24V IN 50 V = 36V IN 40 5.02 V = 36V IN 30 20 4.96 10 0 4.90 0 100 200 300 400 500 600 700 800 900 1000 0 100 200 300 400 500 600 700 800 900 1000 LOAD CURRENT (mA) LOAD CURRENT (mA) LOAD TRANSIENT RESPONSE (LOAD CURRENT STEPPED FROM 500mA TO 1A) SOFT-START (FULL LOAD) toc04 toc03 5V/div 2V/div V EN/UVLO 100mV/div V (AC) OUT V OUT 500mA/div I OUT I PRI 500mA/div 1.0ms/div 2ms/div Maxim Integrated 2 www.maximintegrated.com EFFICIENCY (%) OUTPUT VOLTAGE (V)