Exar: XR79120: Industry’s Smallest 20A Power Module

The XR79120 is a synchronous step down controller for point-of load supplies up to 20A. A wide 4.5V to 22V input voltage range allows for single supply operation from industry standard 5V, 12V, and 19.6V rails. With a proprietary emulated current mode Constant On-Time (COT) control scheme, the XR79120 provides extremely fast line and load transient response using ceramic output capacitors. It requires no loop compensation, hence simplifying circuit implementation and reducing overall component count.


  • 3V to 22V PVIN with 5V bias
  • 4.5V to 5.5V single supply operation
  • ≥0.6V adjustable output voltage
  • Programmable 200ns to 2μs on-time
  • Selectable CCM or CCM/DCM modes
  • Precision enable and power-good flag
  • >93% efficiency
  • Constant on-time control
  • Stable ceramic output capacitor operation
  • Constant 400kHz to 600kHz switching frequency
  • Programmable current limit with thermal compensation
  • Programmable soft start