Power Electronics
 2.5 A Regulator For Synchronous Buck Or Boost Buck Converter

2.5 A Regulator For Synchronous Buck Or Boost Buck Converter

Intersil's ISL85403 is a 36 V, 2.5 A synchronous buck or boost buck controller with a high-side MOSFET and low-side driver integrated. In buckmode, the ISL85403 supports a wide input range of 3 V to 36 V. In boost-buck mode, the input range can be extended down to 2.5 V 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 operation modes 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 be either 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 pre-regulator followed by a buck controlled by the same IC, which greatly expands the operating input voltage range down to 2.5 V. The ISL85403 offers the most robust current protections. It uses peak current mode control with cycle-by-cycle current limiting. It is implemented with frequency foldback under current limit condition; besides that, the hiccup overcurrent mode is also implemented to guarantee reliable operations under harsh short conditions.

The ISL85403 has comprehensive protections against various faultsincluding overvoltage and over-temperature protections, etc. Key Features

·     Buck mode: input voltage range 3 V to 36 V

·     Boost mode expands operating input voltage lower than 2.5 V

·     Selectable forced PWM mode or PFM mode

·     300 µA IC quiescent current (PFM, no load); 180 µA input quiescent current (PFM, no load, VOUT tied to AUXVCC)

·     Less than 5µA (MAX) shutdown input current (IC disabled)

·     Programmable frequency from 200 kHz to 2.2 MHz and frequency synchronization capability

·     Operational topologies

·     Synchronous buck

·     Non-synchronous buck

·     Two-stage boost buck

·     Non-inverting single inductor buck boost

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