USERS MANUAL ISL8016CIR1EVAL1Z AN1630 Rev 1.00 6A Low Quiescent Current High Efficiency Synchronous Buck Regulator May 17, 2011 Description Quick Setup Guide The ISL8016CIR1EVAL1Z kit is intended for use by individuals 1. Ensure that the circuit is correctly connected to the supply with requirements for Point-of-Load applications sourcing from and loads prior to applying any power. 2.7V to 5.8V. The ISL8016CIR1EVAL1Z simple smallest factor 2. Connect the bias supply to VIN, the plus terminal to VIN, J1, evaluation board is used for a quick and easy demonstration of and the negative return to PGND, J2. the performance of the ISL8016 low quiescent high efficiency 3. Connect the output load to VOUT, the plus terminal to synchronous buck regulator. VOUT1, J3 and the negative return to PGND, J4. The ISL8016 is offered in a 3mmx4mm 20 Ld QFN package 4. Verify that the position is PWM for S1. with 1mm maximum height. The complete converter occupies 2 5. Verify the position is OPEN for S2 and S3. can be as small as 0.15in area. 6. Verify that the position is ON for S4 and S5. Key Features 7. Turn on the power supply. High Efficiency Synchronous Buck Regulator with up to 97% 8. Verify the output voltage is 1.8V for VOUT1. Efficiency Evaluating the Other Output Voltage 0.8% Reference Accuracy Over-Temperature/Load/Line The ISL8016CIR1EVAL1Z kit output is preset to 1.8V for Fixed Output Voltage Option VOUT1, however, output voltages can be adjusted from 0.6V to 10% Output Voltage Margining 5V. The output voltage programming resistor, R1, will depend on the desired output voltage of the regulator. The value for the Adjustable Current Limit feedback resistor is typically between 0 and 200k as Current Sharing Capable shown in Equation 1. Start-up with Pre-Biased Output VFB (EQ. 1) ------------------------ R2 = R1 VO VFB Internal Soft-Start - 1ms or Adjustable If the output voltage desired is 0.6V, then R2 is left Soft-Stop Output Discharge During Disabled unpopulated and R1 is shorted. For faster response Adjustable Frequency from 500kHz to 4MHz - Default at 1MHz performance, add 10pF to 47pF in parallel to R1. Check bode plot to insure optimum performance. External Synchronization up to 4MHz - Master to Slave Phase Shifting Capability Frequency Control ISL8016 has an FS pin that controls the frequency of operation. Recommended Equipment Programmable frequency allows for optimization between The following materials are recommended to perform testing: efficiency and external component size. Default switching 0V to 10V Power Supply with at least 10A source current frequency is 1MHz when FS is tied to VIN (R6 = 0 and R5 is capability or 5V battery open). By connecting R5 to GND, the switching frequency could be changed from 500kHz (R5 = 390k) to 4MHz (R5 = 40k) Electronic Loads capable of sinking current up to 7A according to Equation 2: Digital Multimeters (DMMs) 3 200 10 Rk = ------------------------------ 10 (EQ. 2) 100MHz quad-trace oscilloscope T kHz f OSC Signal generator When using R5 to adjust the operational frequency, this also sets external compensation mode. Please refer to the ISL8016 datasheet (FN7616) for more details. AN1630 Rev 1.00 Page 1 of 12 May 17, 2011ISL8016CIR1EVAL1Z Soft-Start Control Swtiches Control Short CSS1 to SGND for internal soft-start (approximately 1ms). The ISL8016 evaluation board contains S1 thru S5 for various Populate CSS1 to adjust the soft-start time. This capacitor, along controls of the ISL8016 circuitries. Table 1 details this function. with an internal 1.6mA current source, sets the soft-start interval TABLE 1. SWITCH SETTINGS of the converter, t . SS S1 MODE FUNCTION CSS1F = 3.33 t s (EQ. 3) SS 1 PWM Fixed PWM frequency at light load CSS must be less than 33nF to insure proper soft-start reset after 3 PFM Force continuous mode fault condition. Synchronization Control S2 ISET PROGRAM OUTUT CURRENT The ISL8016 can be synchronized from 700kHz to 4MHz by an 1 LOW SET OUTPUT LOAD TO 2A. external signal applied to the SYNCIN pin. The rising edge on the SYNCIN triggers the rising edge of the PHASE pulse. Make sure that - OPEN SET OUTPUT LOAD TO 6A. the minimum on-time of the PHASE node is greater than 140ns. 3 HIGH SET OUTPUT LOAD TO 4A. SYNCOUT is a 250A current pulse signal output triggered by the rising edge of the clock or the SYNCIN signal (whichever is S3 VSET SET OUTPUT MARGIN greater in frequency) to drive the other ISL8016 and avoid the systems beat frequencies effects. To implement time shifting 1 LOW SET OUTPUT VOLTAGE -10%. between the master circuit to the slave, it is recommended to - OPEN NO OUTPUT VOLTAGE MARGIN add a capacitor, C13 as shown in the schematic. The time delay from SYNCOUT Master to SYNCIN Slave is calculated in pF using 3 HIGH SET OUTPUT VOLTAGE +10%. the following: CpF = 0.357 tns (EQ. 4) 6 S4 ENABLE FUNCTION Where, t is the desired time shift between the master and the 1OFF DISABLE VOUT1 slave circuits in ns. Care must be taken to include PCB parasitic 3PFM ENABLE VOUT1 capacitance of ~3pF to 10pF. The maximum should be limited to 1/Fs-100ns to insure that S5 ENABLE FUNCTION SYNCOUT has enough time to discharge before the next cycle starts. 1OFF DISABLE VOUT2 3PFM ENABLE VOUT2 AN1630 Rev 1.00 Page 2 of 12 May 17, 2011