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YwRobot 5V to 3.3V linear step-down

by Stefano on 2015.05.18, 2 comments

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How to use the YwRobot Power Supply to obtain 3.3V from a 5V source.

Tools

All the tests have been performed with

Reference

The documentation on the YwRobot board is not abundant as other pieces of electronics around. It features two AMS1117 adjustable regulator (rated at 1A) in cascade: the first stage provides the 5V starting from the input voltage (in the 6-15V range), the second stage feeds the 3.3V rail stepping down from the 5V rail.

See equivalent LDO voltage regulator REG1117 from Burr-Brown (Texas Instruments)

Connect the rails

To achieve the 5V to 3.3V conversion only the second stage of the board is used. In this slightly unconventional configuration the main input is not used (as well the first stage 5V linear regulator) and a 5V source is connected to a 5V pin to feed just the second AMS1117 to provide 3.3V.


The pictures show how to set the jumpers to have a rail-to-rail conversion where one side of the board (input) taps into the breadboard 5V rail, and the other side feed the opposite rail at 3.3V.

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2 thoughts on “YwRobot 5V to 3.3V linear step-down

  1. Thanks for the pinout and pic. Please confirm the barrel voltage input range — 5, 9, 12v. Please also confirm that the USB connecter is for 5v OUTPUT for say an Arduino or other circuit.
    Suggestions for other voltage regulators?

    Thanks in advance

    • Hi Lee,
      with a dropout of 1.3V I wouldn’t recommend a Vin of 5V but 9V, 12V and up to 15V are within the specs of the regulator. The USB connector is on the 5V output rail and is designed to power Arduino boards and alike.

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