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Renesas ISL81801 Synchronous Buck-Boost Controller

Power controller switches smoothly between buck and boost modes

Renesas’ new ISL81801 is a true bidirectional synchronous buck-boost controller which maintains reliable operation by performing peak and average current sensing and monitoring at both ends.

The ISL81801 operates over wide input- and output-voltage ranges: 4.5V to 80V at the input, producing an output between 0.8V and 80V. To perform buck-boost conversion, the ISL81801 uses a proprietary control algorithm: it implements valley current modulation in boost mode, and peak current modulation for buck mode control, and switches smoothly from one mode to the other.

The ISL81801 controller by Renesas has four independent control loops for input and output voltages and currents. Inherent peak-current sensing at both ends and cycle-by-cycle current limiting ensure high operational reliability, as they provide an instant current limit in fast transient conditions at either end, and in both directions.

The Renesas buck-boost controller also has two current monitoring pins at both input and output to facilitate constant-cCurrent limiting and other system-management functions. As well as providing multi-layer over-current protection, the ISL81801 also offers a full range of protection features including:

  • Over- and under-voltage protection
  • Over-temperature protection
  • Average and peak current limit on both input and output

The ISL81801 controller is available in two package options:

  • A space-saving, 32-lead 5mm x 5mm TQFN
  • A 38-lead 4.4mm x 9.7mm HTSSOP package which is easy to mount in a PCB assembly

Renesas also supplies the similar ISL81802, a dual synchronous buck controller which generates two independent outputs, or one output with two interleaved phases.

ISL81801 Features

  • Consistent output ripple at various load levels
  • MOSFET drivers with adaptive shoot-through protection
  • Supports start-up into pre-biased rails
  • Programmable frequency range: 100kHz to 600kHz
  • Output and input current monitor
  • Low stand-by power consumption
  • 2.7µA shut-down current

ISL81801 Applications

  • Battery back-up power supply
  • Uninterruptible power supplies
  • Storage systems
  • Battery-powered industrial equipment
  • Renewable energy
  • Automotive aftermarket products
  • Redundant power supplies
  • Robots
  • Drones
  • Medical equipment
  • Building automation
  • Industrial automation
  • Security and surveillance systems

Evaluation Kit

The ISL81801EVAL1Z evaluation board is designed for high current applications - the maximum output current is 10A. The current rating of the ISL81801EVAL1Z is limited by the FETs and inductor selected.

The ISL81801EVAL2Z performs bi-directional buck-boost power control and operates over a wide input-voltage range of 32V to 80V

Renesas ISL81801EVAL1Z Evaluation Kit