The ISL85403 is a 40V, 2. 5A synchronous buck or boost-buck controller with an integrated high-side MOSFET and low-side driver. In Buck mode, the ISL85403 supports a wide input range of 3V to 40V. In Boost-Buck mode, the input range can be extended down to 2. 5V and output regulation can be maintained when VIN drops below VOUT, enabling sensitive electronics to remain on in low input voltage conditions. The ISL85403 has a flexible selection of Forced PWM mode and PFM mode. In PFM mode, the quiescent input current is as low as 180µA (AUXVCC connected to VOUT). The load boundary between PFM and PWM can be programmed to cover wide applications. The low-side driver can either be used to drive an external low-side MOSFET for a synchronous buck or left unused for a standard non-synchronous buck. The low-side driver can also be used to drive a boost converter as a preregulator followed by a buck controlled by the same IC, which greatly expands the operating input voltage range down to 2. 5V or lower. ISL85403 offers robust current protection. It uses peak current mode control with cycle-by-cycle current limiting. It is implemented with frequency foldback under current limit condition; also, the hiccup overcurrent mode ensures reliable operations under harsh short conditions. The ISL85403 has comprehensive protections against various faults including overvoltage and over-temperature protection.


  • Buck mode: input voltage range 3V to 40V
  • Boost mode expands operating input voltage lower than 2.5V
  • Selectable Forced PWM mode or PFM mode
  • 300µA IC quiescent current (PFM, no load); 180µA input quiescent current (PFM, no load, VOUT tied to AUXVCC)
  • Less than 5µA (MAX) shutdown input current (IC disabled)
  • Operational topologies
    • Synchronous buck
    • Non-synchronous buck
    • Two-stage boost buck
    • Non-inverting single inductor buck boost
  • Programmable frequency from 200kHz to 2.2MHz and frequency synchronization capability
  • ±1% tight voltage regulation accuracy
  • Reliable overcurrent protection
    • Temperature compensated current sense
    • Cycle-by-cycle current limiting with frequency foldback
    • Hiccup mode for worst case short condition
  • 20 Ld 4x4 QFN package
  • Pb-free (RoHS compliant)


  • General purpose
  • 24V bus power
  • Battery power
  • Point of load
  • Embedded processor and I/O supplies


Title language Type Format File Size Date
star ISL85403 Datasheet Datasheet PDF 2.53 MB
ISL85403EVAL1Z User Guide Manual - Development Tools PDF 1.29 MB
R16AN0005: Achieving a Regulated Supply (5V or 12V) from an Input Range of 3V to 40V using the ISL85403 Rev.1.00 Application Note PDF 485 KB
AN9208: High Frequency Power Converters Application Note PDF 592 KB
AN1965: Effectively Using the Intersil Small Form Factor Power Management Evaluation Boards Application Note PDF 2.35 MB
AN1681: Grounding Techniques Application Note PDF 509 KB
AN1684: Nonideality of Ground Application Note PDF 397 KB
AN9210: A New Pspice Subcircuit For The Power MOSFET Featuring Global Temperature Options Application Note PDF 650 KB
AN9209: A Spice-2 Subcircuit Representation For Power MOSFETs Using Empirical Methods Application Note PDF 387 KB
AN7244: Understanding Power MOSFETs Application Note PDF 349 KB
Five Easy Steps to Create a Multi-Load Power Solution White Paper PDF 846 KB
R16ZZ0001: Tips for Using the ISL85403 in Boost-Buck Mode Other PDF 1.02 MB
ISL85403 Boost-Buck Regulator iSim:PE Model Schematic SXSCH 285 KB
ISL85403 Buck Regulator iSim:PE Model Schematic SXSCH 261 KB
ISL85403 Buck-Boost Regulator iSim:PE Model Schematic SXSCH 276 KB

select_allSoftware & 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

memoryBoards & Kits

Part Number Title Type Company
ISL85403DEMO1Z 2.5A Regulator with Integrated High-Side MOSFET Demonstration Board Demonstration Renesas
ISL85403EVAL2Z 2.5A Regulator with Integrated High-Side MOSFET Evaluation Board Evaluation Renesas