Buck-Boost Controllers Arm For Industrial Applications

Renesas Electronics’ latest family of bidirectional four-switch synchronous buck-boost controllers, the ISL81601 and ISL81401, are touted as the industry’s only true bidirectional controllers that sense peak current at both ends and provide cycle-by-cycle current limit in both directions while in buck or boost mode. The controllers generate point-of-load (POL) and voltage rail conversions with peak efficiency up to 99 percent. The ISL81601 has a wide input range of 4.5V to 60V and produces a 0.8V to 60V output to support most industrial batteries: 12V, 24V, 36V and 48V. Also available is the ISL81401, a 4.5V to 40V input and 0.8V to 40V output version, and its unidirectional counterpart, the ISL81401A. The new controllers are suited for dc power backup and battery-powered medical, industrial and telecommunication systems.


The ISL81601 and ISL81401’s bidirectional peak current sensing capability promises to eliminate complex external circuitry required for charging and discharging a battery to supply power to the loads. Their proprietary algorithm provides smooth mode transitions between buck, boost and buck-boost, while reducing low frequency ripple at Vout, ensuring minimal disturbances during line or load transients. The algorithm also ensures predictable ripple voltage under all conditions. The addition of multilayer overcurrent protection and a precision control algorithm delivers constant current down to 0.1V at Vout for reliable operation. Designers can easily expand system power by paralleling an unlimited number of controllers. The ISL81601 and ISL81401 operate two switches at a time to minimize power loss and achieve higher efficiency.

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ISL81601, ISL81401, and ISL81401A feature:

  • Single inductor 4-switch buck-boost controllers
  • Bidirectional operation (ISL81601 & ISL81401) with four feedback control loops
  • Independent voltage and current feedback loop control
  • Constant current/constant voltage profile for input and output
  • Supports on-the-fly changes in parametric settings using microcontroller
  • Programmable frequency: 100kHz to 600kHz
  • MOSFET drivers with adaptive shoot-through protection
  • 8V drive (ISL81601), and 5V drive (ISL81401/A) for optimized efficiency
  • Light load efficiency mode and 2.7µA shutdown current extends battery life
  • Frequency dithering for lower EMI (ISL81601 & ISL81401)
  • Extensive multilayer protection for overvoltage, under voltage, overcurrent, overtemperature, and short circuit

All three controllers and evaluation boards are available now. The ISL81601 bidirectional 60V synchronous buck-boost controller is available in a 38-lead HTSSOP package priced at $3.99 and a 32-lead QFN package priced at $3.69 each/1,000. For more information, checkout the datasheet.


The ISL81401 bidirectional and ISL81401A unidirectional synchronous 40V buck-boost controllers are available in 32-lead QFN packages. The ISL81401 is priced at $2.79 and the ISL81401A is priced at $2.29, both each/1,000. Need more? Then peruse the ISL81401 datasheet and the ISL81401A datasheet.

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