USERS MANUAL ISL91108IIA-EVZ/ISL91108IIN-EVZ AN1903 Rev 1.00 Evaluation Board March 11, 2014 TABLE 3. DESCRIPTION OF JUMPERS Evaluation Board Features JUMPER DESCRIPTION ISL91108 high efficiency buck-boost regulator J3 Jumper to select EN input logic state. Set EN = V to Input voltage rating from 1.8V to 5.5V IN enable device, or set EN = GND to disable device. Resistor programmable output voltage on the J4 Jumper to select MODE input logic state. Set ISL91108IIA-EVZ evaluation board MODE = V to enable auto-PFM mode, or set IN Fixed 3.3V output voltage on the ISL91108IIN-EVZ MODE = GND to select forced PWM mode. evaluation board To use external sync feature, remove this jumper and Up to 1.5A output current (PVIN = 3.0V, V = 3.3V) OUT apply an external clock between 2.75MHz and 2.5MHz switching frequency 3.25MHz on the center pin on the J4 header. Jumper selectable EN (enabled/disabled) Quick Setup Guide Jumper selectable MODE (auto-PFM/forced-PWM) 1. Install jumper on J3, shorting EN to VIN. Connectors, testpoints, and jumpers for easy evaluation 2. Install jumper on J4, shorting MODE to VIN. Required Equipment 3. Connect power supply to J1, with voltage setting between 1.8V and 5.5V. Power supply capable of delivering up to 5.5V and 4A 4. Connect electronic load to J2. Electronic load 5. Place scope probes on VOUT testpoint, and other testpoints Multimeter to measure voltages and currents of interest. Oscilloscope 6. Turn on the power supply. 7. Monitor the output voltage startup sequence on the Testpoints, Connectors, and scope. The waveforms will look similar to that shown in Jumpers Figures 1 and 2. TABLE 1. DESCRIPTION OF TEST POINTS 8. Turn on the electronic load. 9. Measure the output voltage with the voltmeter. The voltage TEST POINT(S) DESCRIPTION should regulate within data sheet spec limits. TP1 LX1 (Input side of power inductor) 10. To determine efficiency, measure input and output voltages TP2 LX2 (Output side of power inductor) at the Kelvin sense testpoints (S+ and S-) which are part of J1 and J2 headers. The bench power supply can be TP3 V OUT connected to the PVIN and GND headers on J1. The electronic load can be connected to the VOUT and GND headers on J2. Measure the input and output currents. TABLE 2. DESCRIPTION OF CONNECTORS Calculate efficiency based on these measurements. CONNECTOR DESCRIPTION 11. To test external sync, remove the jumper at J4, then apply J1 Header for connecting input power. Includes S+ and S- an external clock between 2.75MHz and 3.25MHz on the sense lines. MODE input (the center pin of header J4). J2 Header for connecting external load. Includes S+ and S- sense lines. AN1903 Rev 1.00 Page 1 of 8 March 11, 2014ISL91108IIA-EVZ/ISL91108IIN-EVZ Typical Start-up Waveforms Output Voltage Programming The ISL91108IIA-EVZ evaluation board uses resistors to program the output voltage. To change the output voltage, resistor R1 should be removed and replaced with a resistor value LX1 corresponding to the desired output voltage, as shown in Table 4. 2V/DIV A precision resistor with 1% tolerance should be used. LX2 2V/DIV TABLE 4. OUTPUT VOLTAGE PROGRAMMING DESIRED OUTPUT VOLTAGE R1 RESISTOR VALUE V OUT (V) (k ) 2V/DIV 2.0 90.9 EN 2.5 127 2V/DIV 3.0 165 400s/DIV V = 2V IN V = 3.3V 3.3 187 OUT = 200mA I OUT 3.6 210 FIGURE 1. ISL91108 START-UP WITH V = 2V and V = 3.3V IN OUT 4.0 243 4.5 280 5.0 316 LX1 2V/DIV LX2 2V/DIV V OUT 2V/DIV EN 2V/DIV 400s/DIV V = 4V IN V = 3.3V OUT I = 200mA OUT FIGURE 2. ISL91108 START-UP WITH V = 4V and V = 3.3V IN OUT AN1903 Rev 1.00 Page 2 of 8 March 11, 2014