STMicroelectronics — ST1PS03 Step-Down Converter

STMicroelectronics ST1PS03 Step-Down Converter

Tiny and efficient: 400 mA converter ideal for wearable and battery-powered products

The ST1PS03 from STMicroelectronics is a 400 mA synchronous step-down converter which is ideal for wearable and portable electronic devices because of its small size, high conversion efficiency, and low quiescent current.


Operating from an input-voltage range of 1.8 V to 5.5 V, the ST1PS03 can supply up to 400 mA to the load. The output voltage can be set dynamically to a value between 1.6 V and 3.3 V using three digital control inputs. The device can also supply a sub-system via a control switch accessible from the Vin_Aux pin.


The ST1PS03 peak current-control method of regulating power conversion enables it to achieve very high efficiency using just a 2.2 µH inductor and two small capacitors. Efficiency is 92% when supplying a 10 mA load at 2.5 V from an input at 3.6 V. Quiescent current, when the device is not switching, is just 500 nA at an input voltage of 3.6 V.


The ST1PS03 is supplied in a 12-pin TQFN package which is 0.55 mm high, and has a 2.0 mm x 1.7 mm footprint.


  • 100% duty cycle
  • Under-voltage lockout protection
  • Soft-start circuit
  • ±1.5% output-voltage accuracy


  • Wearable devices
  • Portable products
  • Personal tracking monitors
  • Smart watches
  • Sport bands
  • Energy-harvesting devices
  • Industrial sensors
STMicroelectronics — ST1PS03 Step-Down Converter

Development Kit

Kit Part Number: STEVAL-1PS03A

The STEVAL-1PS03A is an evaluation board for a smart converter design which supplies up to 400 mA from a 1.8 V to 5.5 V input. The board demonstrates how highly efficient conversion can be achieved with just the ST1PS03AQTR converter, a 2.2 μH inductor and two small capacitors.

STMicroelectronics — ST1PS03 Step-Down Converter

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