Overview

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.

ISL85403 Functional Diagram
ISL85403 Functional Diagram
  • 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)

Applications

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

Documentation

Design & Development

Software & Tools
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Downloads
ISL85403 Buck Regulator iSim:PE ModelISL85403 Boost-Buck Regulator iSim:PE ModelISL85403 Buck-Boost Regulator iSim:PE Model
 Simulator Renesas
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ISL85403DEMO1Z Regulator with Integrated MOSFET Demo Board

ISL85403DEMO1Z

Demonstration
Learn More

Synchronous Buck Demo Board with 7V to 40V Input Range, 5V 2.5A Output

The ISL85403DEMO1Z demonstration board allows for quick evaluation of the ISL85403 synchronous buck or boost-buck controller in the synchronous buck configuration. It...

Featured Documents:
ISL85403DEMO1Z User Guide
ISL85403EVAL2Z Regulator with Integrated MOSFET Eval Board

ISL85403EVAL2Z

Evaluation
Learn More

Buck-Boost EVB with 8V to 40V Input Range, 12V 1A Output

The ISL85403EVAL2Z board allows for quick evaluation of the ISL85403 synchronous buck or boost-buck controller in the non-inverting buck-boost configuration. It is a...

Featured Documents:
ISL85403EVAL2Z User Guide
Buck-Boost Last Gasp Power Supply for Energy Meters Reference Design Board

CN274-BBGASPPOCZ

Reference Designs
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Buck-Boost Last Gasp Power Supply for Energy Meter Reference Design

In this Reference Design, a supercapacitor is used as a backup power supply. The board allows for quick evaluation of the ISL85403 buck/boost controller in the...

Featured Documents:
Buck-Boost Last Gasp Power Supply for Energy Meter Design Files
CN274-BBGASPPOCZ Power Supply with Supercapacitor User's Manual
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ECAD Models

Schematic symbols, PCB footprints, and 3D CAD models from SamacSys can be found by clicking on products in the Product Options table. If a symbol or model isn't available, it can be requested directly from the website.

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Product Options

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    Part Number
    ISL85403FRZ
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    		 2033 Dec QFN Tray 3 Get Samples,
    ISL85403FRZ-T
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    ISL85403FRZ-TK
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