What is it?

This is a utility board based on ST's ST1PS03 "nano-quiescent synchronous step-down converter with digital voltage selection, Power Good and load switch", to quote from the data sheet.

The ST1PS03 is ST's latest buck converter, which converts input voltage into a lower output voltage. The ST1PS03 converts input voltage (3V3 to 5V5) into one of eight fixed output voltages depending on the digital inputs of three pins. The output voltage can be changed dynamically (ie., at any time even while powered up) and covers all of the typical low voltages one might need for embedded devices: 1.6, 1.8, 2.1, 2.5, 2.7, 2.8, 3.0, and 3.3 V.

The ST1PS03 can support up to 400 mA current output as well. This is enough to power an ESP8266 or ESP32 device and most any other embedded system.

In addition, there is an embedded load switch which outputs the input voltage for use in your application. This means that for USB or LiPo battery input voltage you can have access to the above eight output voltages as well as access to the 5 V or 3.7 V input voltage, respectively, as auxiliary outputs through convenient ports on the side of the utility board.

The utility board has an on/off power switch, a USB 2.0 connector and an SMD JST connector for a LiPo battery. The voltage is selected by positioning the three dip switches according to the voltage table (also on the back of the utility board):

The output voltage settles on the new value within seconds after changing the dip switch pins. There is a power good output from the ST1PS03 that is used to control a green indicator led; led on means the selected voltage was achieved.

The board design allows for mounting on a breadboard using pin headers or simply soldering wires to the output ports for use in your application.

The ST1PS03 is an ultra-low-power (i.e., nano-quiescent) device. In the utility board implementation, this is compromised somewhat by the 1M Ohm pullups on the three dip switches and power good output. In the worst (2.50 V output) case, these would add 4 x ~5 uA ~ 20 uA to the ~1 uA ST1PS03 Iq. Of course, disabling the led is required for even this current usage.

As a utility board intended for diagnostic and debug usage, nano-quiescence is not imperative. In an application where the ST1PS03 is intended as a permanent power element, however, it is straightforward to get the benefit of variable power output and power good indication (via GPIOs) and preserve the ~1 uA nano-quiescence. For breadboard use, < 20 uA current draw leaves the majority of the 400 mA output capacity for the application itself.

Why did you make it?

There are many sensors and MCUs that require voltages other than 3V3 or 5V0. Most commonly 2.8 V for ST's time-of-flight sensors and 1V8 for many IMUs, etc. It is convenient to have a small, simple-to-use utility board that can provide a range of voltages between 1V8 and 3V3 using readily available power source like USB and LiPo batteries. Even better, when using USB the auxiliary output provides a convenient 5 V source for addressable leds and motor drivers, etc. Having convenient access to up to 9 different voltages from one small pcb provides useful flexibility when testing and debugging circuits.

One could simply use a variable power supply, and I make good use of mine. But this requires I haul it out to a testing table along with the device I am building or debugging, which is not always convenient.

The ST1PS03 utility board is something that can become a useful tool on your prototyping work bench; easy to use, small and convenient, powered by sources you are already using. This is the idea, anyway.

What makes it special?

The ST1PS03 utility board is a small, easy-to-use, convenient source of up to 8 user-selectable low voltages that can provide up to 400 mA of current.

In addition to the low voltage outputs, the embedded load switch makes the input voltage available as an auxiliary output for use in your application.

Power source can be USB 2.0 cable or LiPo battery.

The ST1PS03 utility board makes testing and debugging low-voltage circuits easier!

Order the pcb from OSH Park and assemble some of your own ST1PS03 utility boards.

Adapt the design to your specific application.

Or order the fully assembled and tested boards here and see how a convenient low voltage source can help with your project development!