STMicroelectronics – Step-down converter IC features small system footprint and high efficiency


The ST1S15J18R step-down converter IC from STMicroelectronics is intended for use in applications in which high efficiency and a small board footprint are important requirements.

The converter can provide a 500mA output current from an input voltage ranging between 2.3V and 5.5V. It has a fixed output voltage of 1.82V. Efficiency at an input voltage of 3.6V and an output current of 150mA is 83%.


It runs at a 6MHz switching frequency, which means that it can operate with a tiny inductor that has a nominal value of just 470nH, and an output capacitor of only 4.7μF. The ST1S15 itself is housed in a Flip Chip 6 package measuring 1.2mm x 0.9mm.

This means that the total footprint of a buck converter circuit based on the ST1S15 is extremely small.

At the same time, the device’s high-frequency operation provides for very fast response to both load and line transients.

A pulse frequency mode can be selected to provide high efficiency under light-load conditions. In normal operation, the ST1S15 uses PWM mode for tight regulation and the best dynamic performance.


  • 45μA quiescent current in PFM mode
  • 10mV peak-to-peak output-voltage ripple in PWM mode
  • Short-circuit protection
  • Thermal-overload protection
  • 130°C/W junction-to-ambient thermal resistance


  • Core supply for DSP or multimedia processor
  • Portable electronics devices


The STEVAL-ISA131V1 is an evaluation board for the ST1S15, providing 500mA of output current from an input voltage of 2.3V to 5.5V.

Orderable Part Number: STEVAL-ISA131V1