Application Note 1585 Author: Paul Orfanu ISL85033EVAL2Z (Small Form) Wide VIN Dual Standard Buck Regulator With 3A/3A Output Current - Short Form Description The ISL85033EVAL2Z kit demonstrates performance of the ISL85033 switching regulator IC. An input range of 4.5V to 28V and 3A output per channel (connect in parallel to 6A) allows the ISL85033 to meet a wide variety of POL requirements. The ISL85033 is offered in a 4mmx4mm 28 Ld TQFN package with 1mm maximum height. The complete converter occupies 6.25cm2 area. 100 EFFICIENCY (%) 90 80 12VOUT 1MHz 9VOUT 1MHz 70 5VOUT 500kHz 60 3.3VOUT 500kHz 1.8VOUT 300kHz 0.5 • Wide Input Voltage Range from 4.5V to 28V • Adjustable Output Voltage with Continuous Output Current up to 3A per channel • Current Mode Control • Adjustable Switching Frequency from 300kHz to 2MHz • Independent Power-Good Detection • Selectable In-Phase or Out-of-Phase PWMs Switching Operation • Independent, Sequential, Ratiometric or Absolute Tracking Between Outputs • Internal 2ms Soft-start Time • Overcurrent and Hiccup Mode Short Circuit Protection, Thermal Overload Protection, UVLO • Boot Undervoltage Detection • Channels are Out-of-phase, Reducing Voltage Ripple and Component Size Quick Setup Guide 50 40 0.0 Key Features 1.0 1.5 2.0 OUTPUT LOAD (A) 2.5 3.0 FIGURE 1. EFFICIENCY vs LOAD, TA = +25°C, VIN = 28V 1. Ensure correct board connection to the supply (“+” to VIN1 and “-” to GND2) and loads prior to applying power, then turn on the power supply. 2. Verify the output voltage is 5V for VOUT1 and 3.3V for VOUT2. Frequency Control ISL85033 has an FS pin that controls the frequency of operation. Programmable frequency allows for optimization between efficiency and external component size. ISL85033EVAL2Z has the switching frequency set to 500kHz (FS is tied to VCC). 1.629’ SYNC Control 0.595’ The ISL85033 has a SI pin for external synchronization. Default board configuration has R8 = 0 to GND, which defaults to the internally selected switching frequency. Removing R8 allows the synchronization to be external between 600kHz to 4MHz. Do not leave this pin floating. Output Voltage Selection FIGURE 2. ISL85033EVAL2Z TOP LAYER COMPONENTS ISL85033EVAL2Z board has VOUT1 set to 5V and VOUT2 set to 3.3V. The output voltage programming resistor, R3 (R10 respectively), will depend on the value chosen for the feedback resistor, R2 (R12 respectively), and the desired output voltage, VOUT, see Equation 1. The value for R2 (R12 respectively) is typically between 1k and 10k. R 3 = ( V OUT1 – V FB ) • R 2 ⁄ 0.8 R 10 = ( V OUT2 – V FB ) • R 12 ⁄ 0.8 (EQ. 1) Please note that if VOUT is less than 2.5V, switching frequency and compensation must be changed for 300kHz operation due to minimum on-time limitation. Please refer to data sheet FN6676 for further information. November 29, 2010 AN1585.1 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 Inc. 2010. 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. VCC PGOOD2 SYNCOUT SYNCIN PGOOD1 VCC Application Note 1585 R13 DNP NC1 A VOUT1 A R2 8.06K 1 4 C2 OPEN BOOT1 5 C5 A A 6 0.01UF 7 GND1 29 A ISL85033IRTZ SS1 PGND1 BOOT1 U1 SS2 PGND2 BOOT2 PHASE2 PHASE2 PHASE1 PHASE1 EP A A VIN1 A A GND4 FB1 L2 7UH D2 B340B C14 47UF COMP1 C7 10UF C8 10UF VIN2 SS1 R18 SS2 DNP C10 10UF A GND2 COMP2 A VIN2 C9 4.7UF R17 DNP A VIN1 FB2 VO2 2 SQL004 R16 DNP VOUT2 VOUT2=3.3V 2 1 1 A VIN1 VIN2 R12 8.06K C12 0.01UF 15 R15 0 C15 OPEN BOOT2 16 2 A FB2 18 17 A R11 0 A VCC D1 B340B SQL004 C13 C16 68PF SS2 19 8 9 10 11 12 13 14 2 7UH C3 47UF R10 25.5K 20 69.8K 470PF 1 1 21 COMP2 FB2 A L1 VOUT1 VOUT1=5V COMP1 FB1 COMP2 28 27 26 25 24 23 22 C4 FB1 470PF 69.8K 2 SS1 3 C11 12PF R9 VIN1 VIN1 EN1 VCC EN2 VIN2 VIN2 A 12PF R4 PGOOD1 FS NC SGND SYNCIN SYNCOUT PGOOD2 C6 R3 42.2K R1 0 COMP1 C1 68PF VO1 R14 DNP VOUT2 GND3 SGND A A A A A IF VOUT1=5V (4.5V-5.5V) PLS POPULATE R26 IF VOUT2=5V (4.5V-5.5V) PLS POPULATE R27 OTHERWISE PLS LEAVE R26, R27 DNP! R5 0 ONLY ONLY R7 DNP R6 0 SYNCIN SS1 DRAWN BY: SS2 R8 0 RELEASED UPDATED PAUL ORFANU BY: BY: TIM KLEMANN A DATE: 06/21/2010 DATE: ENGINEER: PAUL ORFANU TITLE: ISL85033 DATE: 06/23/2010 WIDE VIN DUAL S 1.500’ FIGURE 3. ISL85033EVAL2Z SCHEMATIC 1.875’ FIGURE 4. ISL85033EVAL2Z TOP LAYER ETCH FIGURE 5. ISL85033EVAL2Z BOTTOM LAYER COMPONENTS 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 2 AN1585.1 November 29, 2010