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Thread: Questions about Level shifting for DAC, and using two different power sources

  1. #1

    Questions about Level shifting for DAC, and using two different power sources

    Hello all,

    I am powering an MCP4725 DAC using the Teensy 4.1. I would like to boost the 3.3v output of the DAC to 5v, to produce control voltage for use in a modular synth environment.

    My first question is simple: Can I power the DAC straight from a 5v rail, or should I use something like a logic level shifter to get a 5v output? If neither of those are correct I assume I need to build an amplifier circuit following the DAC.

    Secondly, while I'm still prototyping I'd prefer to power the Teensy using USB. If level shifting is necessary to amplify the DAC output, I have an Arduino to supply 5v from the pin. And if level shifting is necessary, is it safe to use the Teensy's 3.3v pin for the LV of the level shifter, and the 5v pin from the Arduino as the HV?

    Going off of total guess work here, so if this is way off the mark, I'm open to any suggestions. Thanks!

  2. #2
    Senior Member
    Join Date
    Jul 2020
    With I2C the bus signals are shared and bidirectional, and the MCP4725 requires logic HIGH signals to be > 0.7Vcc (3.5V if powered from 5V).
    Thus you'll need bidirectional level shifter for the I2C bus if powering the DAC from 5V. Something like this perhaps:

    Yes so long as grounds are shared your 5V source can be the Arduino, although you might want a cleaner 5V for the DAC to minimize audible
    noise from a digital power rail - this might mean some extra filtering of the 5V.

  3. #3
    Perfect, I just happen to have one of those on hand. Thank you!

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