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 source up to 2. 5A and sink up to -2. 0A continuously. 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 graphics cards. 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 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. The buck controller and LDO regulators are provided with independent current limits. Adjustable loss-less fold-back current limit for the buck regulator is achieved by monitoring the drain-to-source voltage drop of the low side synchronous MOSFET. Once overcurrent is removed, the regulator is allowed to enter soft-start again. This helps minimize power dissipation during short-circuit condition. Additionally, overvoltage and undervoltage protection mechanisms are built in. The ISL88550A allow flexible sequencing and standby power management using SHDNA#, and STBY# inputs.


  • Pb-Free (RoHS Compliant) Buck Controller
  • Constant-On PWM with 100ns Load-Step Response
  • Start-up with Pre-biased Output Voltage
  • Up to 95% Efficiency
  • 2V to 25V Input Voltage Range
  • 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/-2.0A Sourcing/Sinking Capability
  • Start-Up with Pre-Biased Output Voltage
  • VTT and VTTR Outputs Track VREFIN/2
  • VTT and VTTR 1% of VREFIN/2
  • Low All-Ceramic Output Capacitor Designs
  • 1.0V to 2.8V Input REFIN Range
  • Analog Soft-Start Option and Independent Shutdown
  • Power-Good Window Comparator


  • DDR, DDR II and DDR III Memory Power Supplies
  • Desktop Computers
  • Notebooks and Desknotes
  • Graphics Cards
  • Game Consoles
  • Networking and RAID

Product Options

Part Number Part Status Pkg. Type Carrier Type MOQ Buy Sample
Active TQFN Tube 60
Active TQFN Reel 6000
Active TQFN Reel 1000

Documentation & Downloads

Title language Type Format File Size Date
Datasheets & Errata
ISL88550A Datasheet Datasheet PDF 1.45 MB
User Guides & Manuals
ISL88550AEVAL1Z User Guide Manual PDF 699 KB
Application Notes & White Papers
Five Easy Steps to Create a Multi-Load Power Solution White Paper PDF 846 KB
How Green is Your Cloud? White Paper PDF 295 KB
AN1684: Nonideality of Ground Application Note PDF 397 KB
AN1681: Grounding Techniques Application Note PDF 509 KB
PCN14036 - Wafer fabrication Site Change for Listed Intersil Products - Palm Bay, Florida Product Change Notice PDF 294 KB
PCN13060 - Test Site Change for the Listed Intersil Products Product Change Notice PDF 223 KB
PCN13025 - Alternate Bond Wire Material and Manufacturing Facilities for Assembly of the Listed Intersil DFN/QFN Packaged Products - Advanced Semiconductor Engineering (ASECL) - Chung-Li , Taiwan and STATS ChipPAC (SCM) - Kuala Lumpur, Mal Product Change Notice PDF 106 KB
PCN13009 - Alternate Bond Wire Material and Manufacturing Facilities for Assembly of the Listed Intersil DFN/QFN Packaged Products - Advanced Semiconductor Engineering (ASECL) - Chung-Li (ASECL), Taiwan and STATS ChipPAC (SCM) - Kuala Lump Product Change Notice PDF 173 KB
PCN10055 - Alternate Bond Wire Material for Assembly of the Listed Intersil DFN/QFN Packaged Products - STATS ChipPAC Malaysia Product Change Notice PDF 248 KB
ISL88550A iSim:PE Model Schematic SXSCH 291 KB

Software & Tool Pages

Title Type Description Company
iSim:PE Offline Simulation Tool Simulator iSim Personal Edition (iSim:PE) speeds the design cycle and reduces risk early in any project, identifying parts that can be used in current as well as next-generation designs. Renesas

Boards & Kits

Part Number Title Type Company
ISL88550AEVAL1Z Synchronous Step-Down Controller with Sourcing/Sinking LDO Regulator Evaluation Board Evaluation Renesas