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ADS131M08: Can the internal reference on REFIN pin be used for external circuits?

Ken Henderson
Intellectual 670 points
Part Number: ADS131M08
Other Parts Discussed in Thread: LMZ10500

Hello,

I would like to use the internal 1.2V reference for external circuits. What is the maximum load current that can be safely supplied?

And can the pin sink current, if so, how much?

I'm asking about sinking current because I would like to make a 1.44V reference with a divider from 3.3V to REFIN. There will be some error introduced by the 3.3V supply voltage but at least this is reduced by the divider ratio ((1.44-1.2)/(3.3-1.2)=0.114). Resistors could be 10k+1.3k, so sink current would be 190uA.

Thanks, Ken

  • 0
    TI__Guru 66466 points

    Hi Ken,

    Thanks for your post.

    The REFIN pin can sink and source current since it also accepts external reference voltage sources. However, I would not try to draw more than a couple hundred microamps to use for external circuits. If you already need to connect the circuit to the 3.3-V supply, why not increase the resistors and connect the low side to ground?

    Regards,

  • 0 in reply to Ryan Andrews
    Intellectual 670 points

    Hi Ryan,

    Thanks for the reply. The 3V3 supply comes from a LMZ10500 which with the feedback resistors will have an error of about +/-2%.

    If I use a divider to ground with 0.1% resistors the error on 1.44V would be approx +/-2.2% or +/-32mV.

    Using the 1.2V ref at the bottom of the divider, the error due to the 3V3 supply is reduced to +/-2.2% of (1.44-1.2) or +/-5.3mV. Add to this the +/-0.1% error of the 1.2V ref +/-1.2mV and I get a total error of +/-6.5mV.

    (unless I'm doing the maths wrong...)

    Best regards, Ken