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THS4631: THS4631 offset voltage drift

Jerry Hsueh
Expert 2730 points
Part Number: THS4631
Other Parts Discussed in Thread: THS4531

Testing In ths4631 EVM, when the input voltage of the chip pin is 0V, then measured the output voltage is 0.3V.

What is a good solution to compensate the drift offset voltage?

thank you

  • 0
    TI__Expert 7875 points
    Hi,

    Typically offset drift refers to the change in offset with temperature. Are you trying to compensate for temperature changes or just eliminate the nominal offset at room temperature?

    Regards,
  • 0 in reply to Jacob Freet
    Expert 2730 points
    Hi Jacob

    Is 0.3V offset voltage normal in ths4631 EVM board at room temperature?
    I want to eliminate the nominal offset at room temperature to reduce the output voltage 0.3V to 0V.
    How to compensate it?
    thank you
  • 0 in reply to Jerry Hsueh
    TI__Expert 7875 points
    Hi,

    The have you re-configured the EVM from it's default configuration at all? The typical input offset of the THS4631 is 260uV. You could expect to see an offset around 0.3V if you are in a gain of 10 V/V for example. However, if you are in the default gain of 1 V/V, then it is showing much higher than expected.

    Regards,
  • 0 in reply to Jacob Freet
    Expert 2730 points
    Hi Jacob,

    No re-configured the EVM from it's default configuration
    How to compensate the output voltage from 0.3V to 0V by hardware or...?
    thank you

    Jerry
  • 0 in reply to Jerry Hsueh
    TI__Expert 7875 points
    Hi Jerry,

    Just to confirm, is the part in a unity gain configuration? 300mV would be a much higher than expect offset in that case. You can eliminate it by providing a DC bias to the non-driven input pin, but I think there may be something else going on if you are seeing that much offset in unity configuration.

    Regards,
    Jacob
  • 0 in reply to Jacob Freet
    Expert 2730 points
    Hi Jacob,

    The gain is 1 V/V in the EVM, 0.3V is much higher? so need to eliminate it by providing a DC bias to VIN− pin, right?
    Could you provide THS4631 EVM Schematic to us? thank you.

    Jerry
  • 0 in reply to Jerry Hsueh
    TI__Expert 7875 points
    Hi Jerry,

    I would expect a much lower offset than 0.3 V from a gain of 1 V/V configuration so I think that may be another issue going on. The EVM schematic is shown in Figure 50, Page 19 of the THS4531 Datasheet. Can you compare the schematic to your board and see if there are any changes?

    Thank you,
  • 0 in reply to Jacob Freet
    Expert 2730 points
    Hi Jacob,

    Offset voltage 0.3 V is because use single power VS+ 24V/ VS- 0V, if the input with dual power supply VS+ 12V/ VS- -12V, then output voltage is less than 5mV, Currently customer is using AD8065, Do you have any recommended OP to replace AD8065, which can use for single power supply VS+ 24V/ VS- 0V application.
    Thank you.
  • 0 in reply to Jacob Freet
    Expert 2730 points
    Hi 
    Now we are using AD8065 in single power supply VS+ 24V/ VS- 0V, the output voltage is less than 5mV.
    Do you have any suggestion for OP which can replace AD8065 with low offset voltage in single power supply VS+ 24V/ VS- 0V application? 
    thank you
  • 0 in reply to Jerry Hsueh
    TI__Expert 7875 points
    Hi Jerry,

    What is the common mode (DC) voltage of your output when you are measuring the offset? The offset shouldn't change in +/- 12 vs. 0-24 V if the common mode is kept at mid-supply. If it is kept at 0V, then that would be what is causing the issue.

    Regards,