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ADS131M06: input impedance variation over temperature

James Dupre
Prodigy 120 points
Part Number: ADS131M06
Other Parts Discussed in Thread: ADS131M04, ADS131E06

Tool/software:

Hi,

The datasheet specifies the input impedance as a function of the gain, but can you provide any insight into the input impedance variation in response to changes in temperature? Should I expect something like +/- 1% change in the input impedance over the operating ambient temperature range? And is the change in input impedance linear with temperature?

Regards,

James

  • 0
    Prodigy 120 points

    I should have mentioned that I will drive all ADC inputs with a low output impedance source, but the 1K resistors in the anti-aliasing filters could create discrepancies between the readings at high and low temperature if the input impedance varies significantly.

  • 0 in reply to James Dupre
    TI__Mastermind 45555 points

    Hi James,

    The impedance changes with the temperature, but the spec was not characterized so unfortunately we do not have the data for that. If the input impedance is a concern, you can consider ADS131E06 that is a 6-Channel, 24-Bit, simultaneously-sampling ADC with much higher input impedance (200Mohm).

    If you are still interested in ADS131M06, you can see the more accurate input impedances as shown in this graph from the datasheet of ADS131M04:

    BR,

    Dale

  • 0 in reply to Dale Li
    Prodigy 120 points

    Hi Dale,

    Thanks again for your detailed response. Unfortunately, I have a very limited amount of board space for this device, so the ADS131E06 is just too large for my design.

    I plan to move ahead with the ADS131M06 but would like to minimize the impact of any input impedance variation. Therefore, I plan to use 100 ohm resistors and a 100 nF capacitor for the antialiasing filter instead of the recommended 1 K resistors and 10 nF capacitor recommended in the datasheet (see below). Is there some reason why this would not work? The cutoff frequency will be the same, but the lower value resistors will mitigate the effects of any changes input impedance.

    Regards,
    James