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LMP8601-Q1 Output offset voltage

Lukas Burgstaller
Prodigy 20 points
Other Parts Discussed in Thread: LMP8601

Hello,

I would need further information about the offset output voltage of the LMP8601.

In the datasheet it is briefly mentioned, that a power supply with an internal resistance lower than 10 Ohm should be used.

What is the consequence, if an higher impedance source is used?

Can a higher impedance source be used?

The application would be for an ADC input.

Is the output current influenced be the impedance of the power supply?

  • 0
    TI__Mastermind 18790 points

    Lukas,

    As it states in the datasheet, the reason a small impedance source is required to drive the offset pin is due to the fact that this pin is wired internally into the resistive feedback network that provides the gain of the part. You can think of the output impedance (in the simplest of cases) as an additional resistor you would then be introducing into the network. By doing this, you are effectively increasing the gain error of the part. The larger the impedance of the source used, the larger the error you would introduce. So while, theoretically, you should be able to use a larger impedance source, I would not recommend it to maintain accuracy in the measurement. Hope this helps.

    Carolus

  • 0 in reply to Carolus Andrews
    Prodigy 20 points
    Okay, as far it is understandable.
    But how would it interfere in reality?
    An 0,5V offset shift is required for the application, but the accuracy is not highly required.
    If the accuracy is still 20% it would be okay. Every interference in shifting the input offset voltage would be much higher.

    The possibility of usable current sensing amplifiers is restricted due to the timeline.
    Is there a somehow use full application to shift the output voltage by 0,5V if there is only low accuracy necessary.
  • 0 in reply to Lukas Burgstaller
    TI__Mastermind 18790 points
    Lukas,

    unfortunately, we don't characterize that curve. We only stipulate that a low impedance source should be used. Were you wanting to divide a voltage into the pin? If your tolerable range of error is +/-20% as you say, you may be able to get away with this, but that is my opinion. You would need to characterize the system and see if it is within a range of tolerance you can accept. I would advise that you use resistors that are as low as the current stresses of your system can tolerate to mitigate the error you're bringing in. Hope this helps.

    Carolus