ISL88550AEVAL1Z Kit: Synchronous Step Down Controller with Sourcing and Sinking LDO Regulator ® Application Note July 23, 2008 General Description Features ISL88550A integrates a synchronous buck PWM controller to generate VDDQ, a sourcing and sinking LDO linear regulator to generate VTT, and a 10mA reference output buffer to generate VTTR. The buck controller drives two external N-Channel MOSFETs to generate output voltages down to 0.7V from a 2V to 25V input with output currents up to 15A. The LDO can sink or source up to1.5A continuous and 2.5A peak current with fast response. Both the LDO output and the 10mA reference buffer output can be made to track the REFIN voltage via a built-in resistive divider. These features make the ISL88550A ideally suited for DDR memory applications in desktops, notebooks and graphic cards. Buck Controller The PWM controller in the ISL88550A uses constant-on-time PWM architecture with a programmable switching frequency of up to 600kHz. This control scheme handles wide input/output voltage ratios with ease and provides 100ns “instant-on” response to load transients while maintaining high efficiency and a relatively constant switching frequency. The ISL88550A offers full programmable UVP/OVP and skip mode options ideal in portable applications. Skip mode allows for improved efficiency at lighter loads. The VTT and VTTR outputs track to within 1% of VREFIN/2. The high bandwidth of this LDO regulator allows excellent transient response without the need for bulk capacitors, thus reducing the cost and size. AN1200.3 • Constant-On PWM with 100ns Load-Step Response • Up to 95% Efficiency • 2V to 25V Input Voltage Range • 1.8V/2.5V fixed or 0.7V to 3.5V Adjustable Output • 200kHz, 300kHz, 450kHz, 600kHz Switching Frequencies • Programmable Current Limit with Foldback Capability • 1.7ms Digital Soft-Start and Independent Shutdown • Overvoltage/Undervoltage Protection Option • Power-Good Window Comparator LDO Section • Fully Integrated VTT and VTTR Capability • VTT has ±2.5A Sourcing/Sinking Capability • VTT and VTTR Outputs Track VREFIN/2 • VTT and VTTR within 1% of VREFIN/2 • All Ceramic Output Capacitor Designs • 1.0V to 2.8V Input REFIN Range • Analog Soft-Start Option and Independent Shutdown • Power-Good Window Comparator Applications Pinout • DDR I and DDR II Memory Power Supplies ISL88550A (28 LD TQFN) TOP VIEW • Desktop Computers TPO SHDNA# AVDD SKIP# GND PGND1 VDD • Notebooks and Desknotes 28 27 26 25 24 23 22 • Graphics Cards • Game Consoles BOOT REF 3 19 PHASE ILIM 4 18 UGATE POK1 5 17 VIN POK2 6 16 OUT STBY# 7 15 FB 8 9 10 11 12 13 14 REFIN 20 VTTI 2 VTT OVP/UVP PGND2 LGATE VTTR 21 VTTS 1 SS TON 1 • Networking and RAID Ordering Information PART PACKAGE ISL88550AEVAL1Z Evaluation Board CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures. 1-888-INTERSIL or 1-888-468-3774 | Intersil (and design) is a registered trademark of Intersil Americas Inc. Copyright Intersil Americas Inc. 2006, 2008. All Rights Reserved All other trademarks mentioned are the property of their respective owners. Application Note 1200 What’s Inside TABLE 1. SWITCH 1 SETTINGS The Evaluation Board Kit contains the following materials: SW1 SKIP OPERATING MODE 1 Connect to GND Normal operation mode, allow automatic PWM/PFM switchover for pulse-skipping at light load. • ISL88550AEVAL1Z Kit (this document) 2 Connect to AVDD Low noise, fixed-frequency PWM mode. Recommended Equipment 3 No Connection NA • The ISL88550AEVAL1Z REVA board • The ISL88550A data sheet The following materials are recommended to perform testing: NOTE: Only toggle one position at a time • 0V to 22V power supply with at least 15A source current capability, battery, notebook AC-adapter TABLE 2. SWITCH 2 SETTINGS SW2 • 5V Bias supply for VDD • Two electronic loads capable of sinking current up to 15A • Dummy loads for the LDO’s SHDNA# 1 Connect to GND Shutdown mode. VDDQ, VTTR, and VTT output. 2 Connect to AVDD Enable ISL88550. Rising edge clear the fault protection. Connect to AVDD for normal operation. 3 No Connection NA • Digital multimeters (DMMs) • 100MHz quad-trace oscilloscope • Signal generator SHUTDOWN CONTROL NOTE: Only toggle one position at a time Quick Setup Guide 1. Ensure that the circuit is correctly connected to the supply and loads prior to applying any power. 2. Connect the bias supply to VDD, the + terminal to P3 (VDD) and - return to TP5 (AGND). 3. Verify that position 2’s are ON for SW1, SW2, SW3, and SW5. Verify that position 1 is ON for SW4. Make sure that no other switch position is ON at the same time. 4. Turn on the VIN power supply. TABLE 3. SWITCH 3 SETTINGS SW3 tON tON ON-TIME SELECTION 1 Connect to GND. tON set to 600kHz frequency 2 Connect to AVDD. tON set to 200kHz frequency 3 Connect to REF. tON set to 450kHz frequency - OPEN tON set to 300kHz frequency NOTE: Only toggle one position at a time 5. Turn on 5V bias supply. 6. Verify the outputs voltages are 1.8V for VDDQ and 0.9V for VTT. Evaluating the Other Output Voltage TABLE 4. SWITCH 4 SETTINGS SW4 The ISL88550EVAL1Z kit outputs are preset to 1.8V and 0.9V; however, VDDQ output voltage can be adjusted from 0.8V to 3.5V by using Equation 1: OVP/UVP FAULT PROTECTION CONTROL Descriptor R 10 = ( R 8 ⁄ [ ( VOUT/VFB ) – 1 ] ) (EQ. 1) Set R8 to 25kΩ; and VFB to 0.7V 1 Connect to GND Disable OVP and UVP 2 Connect to AVDD Enable OVP and UVP 3 Connect to REF Disable OVP and enable UVP - OPEN Enable OVP and disable UVP NOTE: Only toggle one position at a time VDDQ output can also be set to 2.5V by shorting FB pin to GND with R10. VTT output voltage is half on VDDQ in DDR application. VTTI can be powered directly from VDDQ. For better efficiency, VTTI can be powered from an external power supply. Make sure that R13 is removed. TABLE 5. SWITCH 5 SETTINGS SW5 STBY# FAULT PROTECTION CONTROL 1 Connect to GND Shutdown VTT in high impedance state. VTTR is still active. 2 Connect to VCC Enable VTT 3 No Connection NOTE: Only toggle one position at a time 2 AN1200.3 July 23, 2008 ISL88550AEVAL1Z Schematic DDR II P3 R5 10 TP5 1 2 1 R1 0 ILIM UGATE 18 POK1 VIN 17 OUT 16 EP C16 10UF IRF7821 1 2 TP1 4 L1 1UH Q2 VIN 1 8 2 7 3 6 4 5 15 FB STBY R6 0 C14 10UF FB C18 OPEN IRF7832 VDDQ 1 D4 R25 OPEN TP2 4 C27 C29 C22 22UF 220UF 220UF C15 OPEN DNP C24 0.1UF 1 R14 0 TP4 VTTI 1 C9 10UF TP3 P15 1 4 R13 0 P14 1 VTT P16 2 C3 10UF C7 OPEN R2 0 FB R10 1 C12 10UF C23 0.1UF C13 10UF AVDD REF 6 5 4 6 5 4 6 5 4 6 5 4 6 5 4 R12 20K REF R4 100K TP11 1 1 2 3 1 2 3 1 2 3 S4 SKIP# SHDNA# TON S5 OVP/UVP POK1 1 2 3 S3 S2 1 2 3 S1 STBY# 15.8K C6 1UF C5 10UF R11 100K TP10 1 POK2 10.0K C2 10UF 3 C8 3300PF R8 1 P7 1 2 3 ISL88550CR 5 1 POK2 4 VIN 3 PHASE 19 0 U1 C10 0.22UF R3 8 9 10 11 12 13 14 29 20 6 2 R9 56.2K POK1 5 POK2 6 STBY# 7 21 BOOT 7 3 P8 Application Note 1200 C1 0.22UF C17 470PF LGATE 8 2 1 R15 200K OVP/UVP REF Q1 1 1 4 TON SS VTTS VTTR PGND2 VTT VTTI REFIN TON 1 OVP/UVP 2 REF 3 DNP 2 3 R16 182K VDDQ D3 NC SHDNA AVDD SKIP GND PGND1 VDD 1 P2 C11 4.7UF 2 C4 1UF 3 VIN 28 27 SHDNA# 26 25 SKIP# 24 23 22 1 P1 VDD 1 AVDD AN1200.3 July 23, 2008 Application Note 1200 TABLE 6. COMPONENT LIST REF DES QTY VALUE TOL. VOLTAGE PACKAGE PART NUMBER MANUFACTURER DESCRIPTION C1, C10 2 0.22µF 10% 50V SM0805 - AVX, Samsung, TDK, Murata Multilayer Capacitor C2, C3, C9 3 10µF 10% >6.3V SMD0805 - AVX, Samsung, TDK, Murata Multilayer Capacitor C14, C16 2 10µF 10% 25V SMD1812 - AVX, Samsung, TDK, Murata X5R Capacitor C4, C6 2 1µF 10% 10V SM0805 - AVX, Samsung, TDK, Murata Multilayer Capacitor C11 1 4.7µF 10% 10V SM0805 - AVX, Samsung, TDK, Murata Multilayer Capacitor C27 0 OPEN 20% 10V SMD1210 - AVX, Samsung, TDK, Murata C Series Capacitor (EIA:CC1210) C29, C29 2 220µF 20% 4.0V EIA_CASE_D EEFUE0G221R C17 1 470pF 10% 50V SM0805 - AVX, Samsung, TDK, Murata Multilayer Capacitor C24 1 0.1µF 10% 50V SM0805 - AVX, Samsung, TDK, Murata Multilayer Capacitor C5, C7, C8, C12, C13, C15, C18, C23 0 Open 10% 50V SM0805/ SM1206 - AVX, Samsung, TDK, Murata Multilayer Capacitor D3 0 Open - 30V SOT23 BAT54WT1 D4 1 - 3A 40V SMA B340LA L1 1 1.0µH 20% 2mΩ 13_5x13_5 SD10L1 HM65-H1R0 C6125-1R0 FDA1254-1R0M Q1 1 - 11A 30V SOIC8 Q2 1 - 16A 30V R1, R2, R3, R6, R13, R14 8 0 1% R12 1 20k R9 1 R4, R11 Panasonic AL POLYMER On-Semi 30V Schottky Barrier Diode Diodes-Inc 3A Low VF Schottky Barrier Falco BI Sumida Toko Shielded SMD Inductor IRF7821V IR 30V 8.3A N-Power MOSFET SOIC8 IRF7811AV IR 30V 10.8A N-Power MOSFET 150V 0805 - Generic Thick Film Chip Resistor 1% 150V 0805 - Generic Thick Film Chip Resistor 56.2k 1% 150V 0805 - Generic Thick Film Chip Resistor 2 100k 1% 150V 0805 - Generic Thick Film Chip Resistor R16 1 182k 1% 150V 0805 - Generic Thick Film Chip Resistor R15 1 200k 1% 150V 0805 - Generic Thick Film Chip Resistor R5, R25 0 Open 1% 150V 0805/1206 - Generic Thick Film Chip Resistor R8 1 15.8k 1% 150V 0805 - Generic Thick Film Chip Resistor R10 1 10k 150V 0805 - Generic Thick Film Chip Resistor SW1-SW5 5 - - - DIP06 DIP06-SW03 Grayhill Dip Switch SPST U1 1 - - - TQFN ISL88550A Intersil High Efficiency Output Rectifier Controller 4 AN1200.3 July 23, 2008 Application Note 1200 ISL88550AEVAL1Z Board Layout FIGURE 1. TOP COMPONENTS FIGURE 2. TOP LAYER ETCH 5 AN1200.3 July 23, 2008 Application Note 1200 ISL88550AEVAL1Z Board Layout (Continued) FIGURE 3. 2ND LAYER ETCH FIGURE 4. 3RD LAYER ETCH 6 AN1200.3 July 23, 2008 Application Note 1200 ISL88550AEVAL1Z Board Layout (Continued) FIGURE 5. BOTTOM LAYER COMPONENTS (MIRRORED) FIGURE 6. BOTTOM LAYER ETCH (MIRRORED) 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 AN1200.3 July 23, 2008