First 6-Phase Bidirectional DC/DC Controller for Automotive 12V-48V Power Supply Systems


ISL78226 delivers up to 3.75kW at greater than 95% conversion efficiency, and is able to interleave in a modular master/slave architecture to deliver higher power. This innovative design allows engineers to support the rapid adoption of 48V hybrid powertrains that provide improved emissions and better fuel economy for internal combustion engine/electric mild hybrids.

The ISL78226 controller also integrates a digital PMBus interface for system control, telemetry and diagnostics that support ISO 26262 functional safety requirements. Safety is a top concern, and power conversion technology along with the controller’s limp-home mode ensures that drivers will always be able to pull over safely!

Key Features

  • 6-phase bidirectional synchronous 12V to 48V controller
  • Master/slave architecture supports up to 4 ICs in parallel
  • Voltage and current regulation
  • Phase dropping facilitated with companion FET driver
  • Average phase-to-phase current balancing
  • Average current output with ±1.5% accuracy
  • Supply and clock redundancy for functional safety
  • Cycle-by-cycle peak current limiting
  • Cycle-by-cycle negative current limiting
  • Digitally programmable average current limit
  • Analog/digital control of output voltage
  • PMBus for status monitoring and fault response control
  • Selectable phase dropping and diode emulation for light-load efficiency improvement
  • Comprehensive protection with selectable hiccup or latch-off fault responses
  • Digitally programmable warning and fault thresholds
  • Dual-output Flyback controller
  • 200mA adjustable output linear regulator
  • 10mmx10mm 64-TQFP with exposed pad thermal interface
  • AEC-Q100 Grade 1


The ISL78226 is a 6-phase, bidirectional, synchronous PWM controller designed to perform power conversion between 12V and 48V buses up to 3.75kW at >95% conversion efficiency. One ISL78226 supports both Buck and Boost power conversion enabling a compact and robust design with minimum components.

ISL78226 regulates both voltage and current to control power transfer from bus to bus. The multiphase architecture uses interleaved timing to support up to six parallel power stages per ISL78226. By interleaving the power stages, the ripple frequency is multiplied, reducing input and output ripple voltage and current. Lower ripple results in fewer input/output capacitors and therefore, lower component cost and smaller circuit implementation.

The IC is designed to be interleaved in a master/slave architecture to be scaleable for higher power. Also integrated within the device is a dual-output Flyback controller that generates both a 12V supply for the power stage FET drivers as well as a 6V supply for the ISL78226 from either of the two buses. A 200mA auxiliary linear regulator is provided to supply a local microcontroller or interface devices.

A PMBus interface provides system control and diagnostics to support functional safety requirements. This digital interface offers the system controller the ability to program operating modes, voltage and current limit warning, protection thresholds, individual fault response, and rapid fault condition detection.


  • Automotive Bidirectional DC/DC Converter
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