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THS4541: Setting Vocm to 1.4V using pull-down resistor

Nir Alon
Intellectual 650 points

Part Number: THS4541

Tool/software:

Hello all,

In my application, I use the THS4541 in a single-ended to differential configuration.

The FDA is connected to a DAC, and both use a 3.3V single supply.

The differential signals are typically biased at 1.4V.

By default, the Vocm is 1.65V with a 3.3V supply (mid-supply voltage divider).

Is it good practice to adjust the voltage divider using an external pull-down resistor to achieve 1.4V?

(Assuming that Vocm does not need to be highly accurate.)

Thanks,

Nir

  • +1
    Guru 327760 points

    The internal divider resistor values are matched, but their absolute values are not guaranteed and can vary, and there is no specification for their limits. You are supposed to actively drive the Vocm pin to the desired voltage, i.e., use a divider and buffer it with any cheap opamp.

  • +1
    TI__Mastermind 24524 points

    Hello Nir,

    Depending on the accuracy needs for the project, it may be best to use a separate amplifier or reference voltage with known good (enough) precision to provide the external VOCM signal.  

    If a simple voltage divider or pull-up (or down) resistor is sufficient you may use these, though I recommend determining the project tolerance for accuracy.

    Best,

    Alec

  • 0 in reply to Alec Saebeler
    Intellectual 650 points

    Hi Clemens and Alec,

    I think I'll conduct a practical test with the evaluation board across the entire temperature range and decide whether to go with a simple solution like a resistor alone or a resistor divider and buffer, depending on the deviation observed.

    Thanks!

    Nir