Application Note 1492 Author: Huong Doan ISL8088EVAL1Z REVA Dual 800mA Low Quiescent Current 2.25MHz High Efficiency Synchronous Buck Regulator Description Quick Setup Guide The ISL8088EVAL1Z kit is intended for use by individuals with requirements for Point-of-Load applications sourcing from 2.75V to 5.5V. The ISL8088EVAL1Z evaluation board is used to demonstrate the performance of the ISL8088 low quiescent current mode converter. 1. Ensure that the circuit is correctly connected to the supply and loads prior to applying any power. The ISL8088 is offered in a 3mmx3mm 10 Ld DFN package with 1mm maximum height. The complete converter occupies less than 1.8cm2 area. 4. Turn on the power supply. 2. Connect the bias supply to VIN. Plus terminal to VIN and negative return to PGND. 3. Verify that position is ON for SW2 and SW3. 5. Verify the output voltage is 2.5V for VOUT1 and 1.8V for VOUT2. Evaluating the Other Output Voltage Key Features: • Dual 800mA High Efficiency Synchronous Buck Regulator with up to 97% Efficiency • 800mA Guaranteed Output Current per channel • Power-Good (PG) output with 1ms Delay • 2.75V to 5.5V Supply Voltage • 3% Output Accuracy Over-Temperature/Load/Line • Start-up with Pre-biased Output • Internal Digital Soft-Start - 2ms The ISL8088EVAL1Z kit output is preset to 2.5V for VOUT1 and 1.8V for VOUT2; however, output voltages can be adjusted from 0.6V to 3.3V. The output voltage programming resistor, R2 (or R5 in Channel 2), will depend on the desired output voltage of the regulator. The value for the feedback resistor is typically between 0Ω and 750kΩ as shown in Equation 1. Let’s set R3 = 100kΩ, then R2 will be: (EQ. 1) VOUT R2 = R3 ⎛ ------------------ – 1⎞ ⎝ VFB ⎠ If the output voltage desired is 0.6V, then R3 is left unpopulated and short R2. For faster response performance, add 10pF in parallel to R2. • Soft-Stop Output Discharge During Disabled • 30µA Quiescent Supply Current in PFM Mode • Selectable Forced PWM Mode and PFM Mode Mode Control • External Synchronization up to 4MHz • Typical 6.5µA Logic Controlled Shutdown Current • 100% Maximum Duty Cycle for Lowest Dropout • Internal Current Mode Compensation • Peak Current Limiting. The ISL8088 has a SYNC pin that controls the operation mode. SYNC pin connect to logic high or input voltage VIN for PFM mode; connect to logic low or ground for forced PWM mode. Connect to an external function generator for Synchronization. Negative edge trigger. Do not leave this pin floating. TABLE 1. SWITCH SETTINGS • Over-Temperature Protection • Independent Enable Recommended Equipment SW2&3 ENABLE ON/OFF CONTROL 1 OFF Disable VOUT 3 ON Enable VOUT SW1 SKIP 1 PWM Fixed PWM frequency at light load 3 PFM Force continuous mode The following materials are recommended to perform testing: • 0V to 10V Power Supply with at least 3A source current capability or 5V battery • Electronic Loads capable of sinking current up to 3A FUNCTION • Digital Multimeters (DMMs) • 100MHz quad-trace oscilloscope • Signal generator February 14, 2014 AN1492.2 1 CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures. 1-888-INTERSIL or 1-888-468-3774 | Copyright Intersil Americas LLC 2009, 2010, 2014. All Rights Reserved Intersil (and design) is a trademark owned by Intersil Corporation or one of its subsidiaries. All other trademarks mentioned are the property of their respective owners. ISL8088EVAL1ZREVA Schematic LX1_S 1 2 1 2 3 4 LX1 C8 OPEN C1 10UF 4 3 VIN VIN A LX2 A PGND U1 A VIN 2 1 VOUT1 R1 100K 1 2 SYNC 0 SYNC 2 3 S1 1 C9 OPEN A 11 R14 20 A FB2 10 EN2 9 8 LX2 7 6 1 2.2UH L2 2 SYNC ISL8088IRZ VOUT2 VOUT2 C4 10UF R13 20 C6 OPEN VOUT2 VOUT2_S 1 2 4 A A C3 10PF R2 316K R5 200K C5 10PF PGND2 PGND A PGND1 A 4 5 C2 10UF PGND A 2 VOUT2_S A PFM PWM LX1 2 FB2 EN2 PG LX2 SYNCH FB1 EN1 VIN LX1 NC PGND EP Application Note 1492 SYNC R11 3 VOUT1_S 4 C7 OPEN 1 3 VOUT1 VOUT1 VOUT1_S 2.2UH L1 FB1 EN1 3 PGND R3 100K A VIN VIN R6 100K PG VIN A R7 100K R10 2K 2 R4 100K SGND 2 3 S2 1 ON/EX OFF EN1 SGND EN2 2 3 S3 1 R9 OPEN ON/EX OFF EN2 PG EN2 1 PG 2N7002 Q2 2 EN1 D2 31 EN1 A NOTE: PLEASE KEEP FB1, FB2 PINS TRACES SHORT A A A DRAWN BY: RELEASED HUONG DOAN BY: TU BUI / HUONG DOAN UPDATED BY: DATE: 03/20/2008 DATE: DATE: ENGINEER: HUONG DOAN TITLE: DATE: ISL8088 3/20/08 DUAL 800MA LOW IQ BUCK SCHEMATIC AN1492.2 February 14, 2014 Application Note 1492 TABLE 2. BILL OF MATERIALS PART NUMBER QTY UNIT ISL8088EVAL1ZREVAPCB 1 ea H1045-00100-50V5-T 2 ea REFERENCE DESIGNATOR C3, C5 DESCRIPTION MANUFACTURER PART MANUFACTURER PWB-PCB, ISL8088EVAL1Z, REVA, ROHS TITAN ISL8088EVAL1ZREVAPCB CAP, SMD, 0603, 10pF, 50V, 5%, COG, ROHS YAGEO CC0603JRNP09BN100 VENKEL C0603COG500-100JNE KEMET C0603C100J5GACTU MURATA GRM1885C1H100JA01D AVX 06035A100JAT2A VENKEL C0805X5R6R3-106KNE KEMET C0805C106K9PACTU AVX 08056D106KAT2A MURATA GRM21BR60J106KE19L TAIYO YUDEN JMK212BJ106KG TOKO MDT2520-CR2R2M H1045-DNP 0 ea C9 CAP, SMD, 0603, DNPPLACE HOLDER, ROHS H1046-00106-6R3V10-T 3 ea C1, C2, C4 CAP, SMD, 0805, 10µF, 6.3V, 10%, X5R, ROHS H1046-DNP 0 ea C6 to C8 CAP, SMD, 0805, DNPPLACE HOLDER, ROHS MDT2520-CR2R2M 2 ea L1, L2 COIL-PWR INDUCTOR, SMD, 2520, 2.2µH, 20%, 1.35A, ROHS 1514-2 6 ea PGND, PGND1, PGND2, VIN, VOUT1,VOUT2 CONN-TURRET, TERMINAL KEYSTONE POST, TH, ROHS 1514-2 5000 4 ea EN1, EN2, PG, SYNC CONN-MINI TEST PT, VERTICAL, RED, ROHS KEYSTONE 5000 5001 1 ea SGND CONN-MINI TEST PT, VERTICAL, BLK, ROHS KEYSTONE 5001 LTST-C170CKT 1 ea D2 LED-GaAs RED, SMD, 2mmx1.25mm, 100mW, 40mA, 10mcd, ROHS LITEON/VISHAY LTST-C170CKT ROHM SML-210LTT86 STANLEY ELEC. BR112H-TR INTERSIL ISL8088IRZ ISL8088IRZ 1 ea U1 IC-DUAL SYNC. BUCK REGULATOR, 10P, DFN, 3X3, ROHS 2N7002-T 1 ea Q2 NAT’L SEMICNDTR TRANSISTOR, N-CHANNEL, 3LD, SOT-23, MOTOROLA 60V, 115mA H2511-00200-1/10W1-T 2 ea R13, R14 RES, SMD, 0603, 20Ω, 1/10W, 1%, TF, ROHS H2511-00R00-1/10W-T 1 ea R11 H2511-01003-1/10W1-T 5 ea R1, R3, R4, R6, R7 RES, SMD, 0603, 100k, 1/10W, 1%, TF, ROHS H2511-02001-1/10W1-T 1 ea R10 3 2N7002 2N7002LT1 PANASONIC ERJ-3EKF20R0V YAGEO RC0603FR-0720RL VENKEL CR0603-10W-20R0FT KOA RK73H1JTTD2001F VENKEL CR0603-10W-2001FT RESISTOR, SMD, 0603, 0Ω, 1/10W, TF, ROHS RES, SMD, 0603, 2k, 1/10W, 1%, TF, ROHS AN1492.2 February 14, 2014 Application Note 1492 TABLE 2. BILL OF MATERIALS (Continued) PART NUMBER H2511-02003-1/10W1-T H2511-03163-1/10W1-T QTY UNIT 1 ea 1 ea REFERENCE DESIGNATOR R5 R2 DESCRIPTION RES, SMD, 0603, 200k, 1/10W, 1%, TF, ROHS RES, SMD, 0603, 316k, 1/10W, 1%, TF, ROHS MANUFACTURER VENKEL CR0603-10W-2003FT YAGEO RC0603FR-07200KL VISHAY/DALE CRCW0603200KFKEA PANASONIC ERJ-3EKF2003V ROHM MCR03EZPFX2003 PANASONIC ERJ-3EKF3163V VENKEL CR0603-10W-3163FT ROHM MCR03EZPFX3163 YAGEO RC0603FR-07316KL VISHAY/DALE CRCW0603316KFKEA H2511-DNP 0 ea R9 RES, SMD, 0603, DNPPLACE HOLDER, ROHS GT11MSCBE-T 3 ea S1 to S3 SWITCH-TOGGLE, SMD, C&K COMPONENTS ULTRAMINI, 1P, SPST MINI 4 MANUFACTURER PART GT11MSCKE AN1492.2 February 14, 2014 Application Note 1492 ISL8088EVAL1Z Board Layout FIGURE 1. TOP COMPONENTS FIGURE 2. TOP LAYER ETCH 5 AN1492.2 February 14, 2014 Application Note 1492 ISL8088EVAL1Z Board Layout (Continued) FIGURE 3. 2ND LAYER ETCH FIGURE 4. 3RD LAYER ETCH 6 AN1492.2 February 14, 2014 Application Note 1492 ISL8088EVAL1Z Board Layout (Continued) FIGURE 5. BOTTOM LAYER COMPONENTS (MIRRORS) Intersil Corporation reserves the right to make changes in circuit design, software and/or specifications at any time without notice. Accordingly, the reader is cautioned to verify that the Application Note or Technical Brief is current before proceeding. For information regarding Intersil Corporation and its products, see www.intersil.com 7 AN1492.2 February 14, 2014