ISL88550AEVAL1Z Kit: Synchronous Step Down Controller with Sourcing and Sinking LDO Regulator

Transcription

1 ISL88AEVALZ Kit: Synchronous Step Down Controller with Sourcing and Sinking LDO Regulator Application Note July, 8 AN. General Description ISL88A integrates a synchronous buck PWM controller to generate VDDQ, a sourcing and sinking LDO linear regulator to generate VTT, and a ma reference output buffer to generate VTTR. The buck controller drives two external N-Channel MOSFETs to generate output voltages down to.v from a V to V input with output currents up to A. The LDO can sink or source up to.a continuous and.a peak current with fast response. Both the LDO output and the ma reference buffer output can be made to track the IN voltage via a built-in resistive divider. These features make the ISL88A ideally suited for DDR memory applications in desktops, notebooks and graphic cards. The PWM controller in the ISL88A uses constant-on-time PWM architecture with a programmable switching frequency of up to khz. This control scheme handles wide input/output voltage ratios with ease and provides ns instant-on response to load transients while maintaining high efficiency and a relatively constant switching frequency. The ISL88A 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 % of /. The high bandwidth of this LDO regulator allows excellent transient response without the need for bulk capacitors, thus reducing the cost and size. Pinout TPO SHDNA# ISL88A (8 LD TQFN) TOP VIEW SKIP# GND Features Buck Controller Constant-On PWM with ns Load-Step Response Up to 9% Efficiency V to V Input Voltage Range.8V/.V fixed or.v to.v Adjustable Output khz, khz, khz, khz Switching Frequencies Programmable Current Limit with Foldback Capability.ms Digital Soft-Start and Independent Shutdown Overvoltage/Undervoltage Protection Option Power-Good Window Comparator LDO Section Fully Integrated VTT and VTTR Capability VTT has ±.A Sourcing/Sinking Capability VTT and VTTR Outputs Track / VTT and VTTR within % of / All Ceramic Output Capacitor Designs.V to.8v Input IN Range Analog Soft-Start Option and Independent Shutdown Power-Good Window Comparator Applications DDR I and DDR II Memory Power Supplies Desktop Computers Notebooks and Desknotes Graphics Cards Game Consoles Networking and RAID SS VTTS VTTR PGND VTT VTTI IN PGND VDD 8 LGATE BOOT Ordering Information 9 PHASE PART PACKAGE ILIM 8 UGATE ISL88AEVALZ Evaluation Board POK POK OUT STBY# 8 9 CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures INTERSIL or Intersil (and design) is a registered trademark of Intersil Americas Inc. Copyright Intersil Americas Inc., 8. All Rights Reserved All other trademarks mentioned are the property of their respective owners.

2 Application Note What s Inside The Evaluation Board Kit contains the following materials: The ISL88AEVALZ REVA board The ISL88A data sheet ISL88AEVALZ Kit (this document) Recommended Equipment The following materials are recommended to perform testing: V to V power supply with at least A source current capability, battery, notebook AC-adapter V Bias supply for VDD Two electronic loads capable of sinking current up to A Dummy loads for the LDO s Digital multimeters (DMMs) MHz quad-trace oscilloscope Signal generator Quick Setup Guide. Ensure that the circuit is correctly connected to the supply and loads prior to applying any power.. Connect the bias supply to VDD, the + terminal to P (VDD) and - return to TP (AGND).. Verify that position s are ON for SW, SW, SW, and SW. Verify that position is ON for SW. Make sure that no other switch position is ON at the same time.. Turn on the power supply.. Turn on V bias supply.. Verify the outputs voltages are.8v for VDDQ and.9v for VTT. Evaluating the Other Output Voltage Descriptor The ISL88EVALZ kit outputs are preset to.8v and.9v; however, VDDQ output voltage can be adjusted from.8v to.v by using Equation : R = ( R 8 [( VOUT/V) ] ) (EQ. ) Set R8 to kω; and V to.v VDDQ output can also be set to.v by shorting pin to GND with R. 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 R is removed. TABLE. SWITCH SETTINGS SW SKIP OPERATING MODE Connect to GND Normal operation mode, allow automatic PWM/PFM switchover for pulse-skipping at light load. Connect to Low noise, fixed-frequency PWM mode. No Connection NA TABLE. SWITCH SETTINGS SW SHDNA# SHUTDOWN CONTROL Connect to GND Shutdown mode. VDDQ, VTTR, and VTT output. Connect to Enable ISL88. Rising edge clear the fault protection. Connect to for normal operation. No Connection NA TABLE. SWITCH SETTINGS SW t ON t ON ON-TIME SELECTION Connect to GND. t ON set to khz frequency Connect to. t ON set to khz frequency Connect to. t ON set to khz frequency - t ON set to khz frequency TABLE. SWITCH SETTINGS SW FAULT PROTECTION CONTROL Connect to GND Disable OVP and UVP Connect to Enable OVP and UVP Connect to Disable OVP and enable UVP - Enable OVP and disable UVP TABLE. SWITCH SETTINGS SW STBY# FAULT PROTECTION CONTROL Connect to GND Shutdown VTT in high impedance state. VTTR is still active. Connect to V CC Enable VTT No Connection AN. July, 8

3 AN. July, 8 ISL88AEVALZ Schematic DDR II C.UF 8K R.K TP VDDQ SHDNA# VDDQ R IRF8 C TP UF ISL88CR P VTT POK STBY#.UF C POK PF C C.8K TP P C UF R8 R R S R Q DNP Q K SKIP# C C UF SHDNA# 8 P P8 C UF C UF.UF C UF C UF C9 UF C R DNP IRF8 L UH R TP 8 R D C P VTTI R POK TP K R K R POK TP R K STBY# VDD P TP R UF C SKIP# 8 P D 9 8 C8.UF UF C C U 8 9 C8 PF 9 UF S UF C9 UF C S S R9.K R P C.UF S EP POK ILIM VTTR PGND VTT VTTI IN PHASE LGATE BOOT UGATE OUT SKIP PGND VDD NC SHDNA GND VTTS SS STBY POK Application Note

4 Application Note TABLE. COMPONENT LIST DES QTY VALUE TOL. VOLTAGE PACKAGE PART NUMBER MANUFACTURER DESCRIPTION C, C.µF % V SM8 - AVX, Samsung, TDK, Murata Multilayer Capacitor C, C, C9 µf % >.V SMD8 - AVX, Samsung, TDK, Murata Multilayer Capacitor C, C µf % V SMD8 - AVX, Samsung, TDK, Murata XR Capacitor C, C µf % V SM8 - AVX, Samsung, TDK, Murata Multilayer Capacitor C.µF % V SM8 - AVX, Samsung, TDK, Murata Multilayer Capacitor C % V SMD - AVX, Samsung, TDK, Murata C Series Capacitor (EIA:CC) C9, C9 µf %.V EIA_CASE_D EEFUEGR Panasonic AL POLYMER C pf % V SM8 - AVX, Samsung, TDK, Murata Multilayer Capacitor C.µF % V SM8 - AVX, Samsung, TDK, Murata Multilayer Capacitor C, C, C8, C, C, C, C8, C Open % V SM8/ SM - AVX, Samsung, TDK, Murata Multilayer Capacitor D Open - V SOT BATWT On-Semi V Schottky Barrier Diode D - A V SMA BLA Diodes-Inc A Low VF Schottky Barrier L.µH % mω _x_ SDL HM-HR C-R FDA-RM Falco BI Sumida Toko Shielded SMD Inductor Q - A V SOIC8 IRF8V IR V 8.A N-Power MOSFET Q - A V SOIC8 IRF8AV IR V.8A N-Power MOSFET R, R, R, R, R, R 8 % V 8 - Generic Thick Film Chip R k % V 8 - Generic Thick Film Chip R9.k % V 8 - Generic Thick Film Chip R, R k % V 8 - Generic Thick Film Chip R 8k % V 8 - Generic Thick Film Chip R k % V 8 - Generic Thick Film Chip R, R Open % V 8/ - Generic Thick Film Chip R8.8k % V 8 - Generic Thick Film Chip R k V 8 - Generic Thick Film Chip SW-SW DIP DIP-SW Grayhill Dip Switch SPST U TQFN ISL88A Intersil High Efficiency Output Rectifier Controller AN. July, 8

5 Application Note ISL88AEVALZ Board Layout FIGURE. TOP COMPONENTS FIGURE. TOP LAYER ETCH AN. July, 8

6 Application Note ISL88AEVALZ Board Layout (Continued) FIGURE. ND LAYER ETCH FIGURE. RD LAYER ETCH AN. July, 8

7 Application Note ISL88AEVALZ Board Layout (Continued) FIGURE. BOTTOM LAYER COMPONENTS (MIRRORED) FIGURE. 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 AN. July, 8