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TS12A12511 GND connection

Stuart Borden
Prodigy 180 points
Other Parts Discussed in Thread: TS12A12511

I am using a pair of  TS12A12511 switches in an analog signal line switching application.  An  ADC directly controls the switches.  I am using +/- 2.5V signal voltage levels.  Unfortunately the converter does not understand polarity, just  AGND  to AVDD differential.  Since  the application is bipolar, this requires that the converter's AGND pin be tied to -2.5V and AVDD pin tied to 2.5V.  None of this is the problem.

Problem is the converter data sheet failed to mention that the converter's "Digital Output Control Lines" are NOT referenced to the converter's DGND pin, but to the AGND pin.  This means, that instead of a simple 0-5V signal (the converter's digital VDD pin is tied to 5V), I get -2.5V to +2.5V.

Because of an error when I generated the symbol for the TS12A12511, the switches' control lines are not connected on the PCB.  And maybe this is good.

Can the TS12A12511 control line accept this level (-2.5V ~ +2.5V) of signals?  Should I tie the TS12A12511 GND pin to -2.5V? Should I add some sort of level translator or find another switch?

Hopefully I can get some insight into this dilemma.

Regards to the community,

Stuart Borden.

  • 0
    TI__Expert 6395 points

    Hello Stuart,

    Based on what you stated above I think your best bet is to tie the GND and V- pin of the TS12A12511 to - 2.5 V and have the V+ pin tied to 2.5 V. 

    Just be careful that there will never be any signal greater than V+ or less than V-/GND and you won't have any problems.  Another gotcha is to make sure your Digital input thresholds of the TS12A12511(Which are now referenced to -2.5 V) work with the ADC's digital output thresholds.

    Regards,

    Andrew