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ADS7959 - Unused input pin

Kawai
Guru 19775 points
Other Parts Discussed in Thread: ADS7959

Hi Team,

Could you please tell me what you should do with the unused input channel pin ?

I understand that generally you should pull down to GND or directly connect to GND, or to pull up to reference voltage. However I think the best way would depend on input structure.
What is TI recommendation ?

Another question is that our customer has their schematic with the unused input floating. In this case, would there be a possibility that the device would get damaged somehow ?

Best Regards,
Kawai

  • 0
    TI__Guru 52486 points

    Hello Kawai-San,

    The ADS7959 (8 channel) device pin out is compatible with other ADS79xx devices in the family (12ch and 16ch versions). These pins correspond to unused channels and are not connected internally.  

    In the case of the ADS7959, the 'NC' unused pins are not connected internally to the device; therefore it appears to be unlikely that damage could occur. The general recommendation is to tie these pins to AGND via a pull-down resistr (~10kOhm) to avoid any potential cross talk issue.

    Best Regards,

    Luis

  • 0 in reply to Luis Chioye
    TI__Guru 52486 points

    Hello Kawai-San,

    One clarification to the post above: I was referring to the 'NC' pins that are not connected to the device internally.

    In the case of ADS7959 channels/pins that are not used in the user application, but connected to the device, (for example CH0 to CH7), the recommendation is still to connect the unused channels to GND via a pull-down as you have mentioned.   Provided that the 'Absolute Maximum Ratings' (p4 of the datasheet) are not exceeded, no damage will occur on the device.

    Best Regards,

    Luis

  • 0 in reply to Luis Chioye
    Guru 19775 points

    Hi Luis-san,

    Thanks for the answer. I apologize for not clarifying the "unused pin", I was meaning the unused channels of CH0 to CH7 as you have answered me later.

    Our customer is worrying that if there is a possibility for the device to get damaged when they kept the unused channels in CH0 to CH7 floating. As it is floating there may be an unexpected voltage or interference, so I will ask them to connect the input pin to GND through a pull down resistor (~10kohm). I will also answer customer that there will be no damage as long as the input voltage is under Absolute Maximum Ratings.

    Best Regards,
    Kawai