ISL85415EVAL1Z

USERS MANUAL ISL85415EVAL1Z AN1859 Rev 4.00 Wide VIN 500mA Synchronous Buck Regulator May 16, 2014 Description Quick Setup Guide The ISL85415EVAL1Z kit is intended for use for point-of-load 1. Ensure that the circuit is correctly connected to the supply applications sourcing from 3V to 36V. The kit is used to and loads prior to applying any power. demonstrate the performance of the ISL85415 Wide V Low IN 2. Connect the bias supply to VIN, the plus terminal to VIN (P4) Quiescent Current High Efficiency Sync Buck Regulator with and the negative return to GND (P5). 500mA output current. 3. Verify that the position is ON for S1. The ISL85415 is offered in a 4mmx3mm 12 Ld DFN package 4. Turn on the power supply. with 1mm maximum height. The converter occupies 1.516 2 5. Verify the output voltage is 3.3V for V cm area. OUT. Evaluating the Other Output Voltage Key Features The ISL85415VAL1Z kit output is preset to 3.3V however, Wide input voltage range 3V to 36V output voltages can be adjusted from 0.6V to 15V. The output Synchronous operation for high efficiency voltage programming resistor, R , will depend on the desired 2 output voltage of the regulator and the value of the feedback No compensation required resistor R , as shown in Equation 1. 1 Integrated high-side and low-side NMOS devices 0.6 (EQ. 1) --------------------------- R = R Selectable PFM or forced PWM mode at light loads 2 1 V 0.6 OUT Internal fixed (500kHz) or adjustable switching frequency If the output voltage desired is 0.6V, then R is shorted. Please 1 300kHz to 2MHz note that if V is less than 1.8V, the switching frequency and OUT Continuous output current up to 500mA compensation must be changed for 300kHz operation due to minimum on-time limitation. Please refer to datasheet Internal or external soft-start ISL85415 for further information. Minimal external components required Table 1 on page 2 shows the component selection that should Power-good and enable functions available be used for the respective V . OUTs Recommended Equipment The following materials are recommended to perform testing: 0V to 50V Power Supply with at least 2A source current capability Electronic loads capable of sinking current up to 1.5A Digital multimeters (DMMs) 100MHz quad-trace oscilloscope Signal generator FIGURE 1. FRONT OF EVALUATION BOARD ISL85415EVAL1Z FIGURE 2. BACK OF EVALUATION BOARD ISL85415EVAL1Z AN1859 Rev 4.00 Page 1 of 13 May 16, 2014ISL85415EVAL1Z TABLE 1. EXTERNAL COMPONENT SELECTION V L C R R C R R C OUT 1 OUT 1 2 FB FS COMP COMP (V) (H) (F) (k ) (k ) (pF) (k ) (k ) (pF) 12 45 10 90.9 4.75 22 115 100 470 5 22 2x22 90.9 12.4 100 120 100 470 3.3 22 2x22 90.9 20 100 120 100 470 2.5 22 2x22 90.9 28.7 100 120 100 470 1.8 22 22 100 50 22 120 50 470 Frequency Control The ISL85415 has a FS pin that controls the frequency of operation. Programmable frequency allows for optimization between efficiency and external component size. It also allows low frequency operation for low V when minimum on time would limit the operation otherwise. OUTs Default switching frequency is 500kHz when FS is tied to V (R = 0). CC 10 By removing R the switching frequency could be changed from 10 300kHz (R = 340k) to 2MHz (R = 32.4k). Please refer to datasheet 12 12 ISL85415 for calculating the value of R . Do not leave this pin floating. 10 Disabling/Enabling Function The ISL85415 evaluation board contains S1 switch that enables or disables the part, thus allowing low quiescent current state. Table 2 details this function. TABLE 2. SWITCH SETTINGS S1 ON/OFF CONTROL ON Enable V OUT OFF Disable V OUT SYNC Control The ISL85415 evaluation board has a SYNC pin that allows external synchronization frequency to be applied. Default board configuration has R = 200k to V , which defaults to PWM 6 CC operation mode and also to the pre-selected switching frequency (see ISL85415 datasheet and previous section set by R 12 Frequency Control for details). If this pin is tied to GND the IC will operate in PFM mode. S2 switch allows to force the PFM or PWM modes. Soft-Start /COMP Control R selects between internal (R = 0) and external soft-start. 15 15 R selects between internal (R = 0) and external 11 11 compensation. Please refer to Pin Description Table of the datasheet. ISL85415 AN1859 Rev 4.00 Page 2 of 13 May 16, 2014