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Switch for ads1234

Niclas F
Prodigy 60 points
Other Parts Discussed in Thread: ADS1234, TS5A3166, ADS1232REF, TS3A4751, ADS1231

 What is the recomended switch for ads1234 that can be used to break the excitation to the bridges to save power when not converting?

  • 0
    TI__Guru** 113765 points

    Hi,

    One possibility is the TS5A3166 when using 5V bridge excitation or less.  This device was used as part of the reference design for the ADS1232REF (2 channel version).  A MOSFET could be used as well.  Generally what you are looking for is low on resistance.

    Best regards,

    Bob B

  • 0 in reply to Bob Benjamin
    Prodigy 60 points
    Thanks for the fast reply

    It sounds good. I have tried with 4 MOSFET 's, it seemed to work but I had other problem with pcb layout. After studying the ADS1232REF datasheet I ordered the 4 channel version of the analog switch.

    Should you prefere MOSFET's or an analog switch?

    analog switch: TS3A4751 0.9-Ω on resistance
    MOSFET's: 2N700 typical 1.7-Ω on resistance

    I was a bit worried about resistance temperature dependens. Maybe the offset calibraton is taking care of that?
  • 0 in reply to Niclas F
    TI__Guru** 113765 points

    Hi,

    The MOSFET is less complicated, but switch resistance is a little higher.  You can avoid issues with the switch by making sure the measurement maintains the ability to be ratiometric.  This removes the affects of the switch resistance from the measurement by making sure that the excitation of the bridge is the same as the reference voltage.  You could use something like:

    Best regards,

    Bob B

  • 0 in reply to Bob Benjamin
    Prodigy 60 points
    So logical, as described in the datasheet for ADS1231.

    Thank you Bob