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ADS52J90: AVSS & DVSS Connected within chip?

Amanda Ross95
Intellectual 2740 points
Part Number: ADS52J90

Hello,

I have a customer who is currently using the ADS52J90 device. On his unpopulated board he shows that the analog and digital grounds are not connected while on a fully populated board, there is a zero ohm connection showing between AVSS and DVSS. 

Would you be able to tell me if there is a connection between AVSS and DVSS internal to the ADS52J90?

Thanks,

-Amanda

  • 0
    TI__Mastermind 49676 points

    Hi Amanda,

    I am checking with design and will get back to you as soon as possible.

  • 0 in reply to Praveen Aroul
    TI__Intellectual 2740 points
    For anyone reading this, Praveen and I ended up taking this offline but I wanted to post an update on the forums just as an FYI for anyone else with the same question. We ended up reaching out to our design team to explain this and this was their response--

    "The analog and digital blocks are present in the same substrate, because of which, we see a 1ohm resistance between AVSS and DVSS. This is like a DC short and will be high impedance for AC response. The digital switching current that will be present in the DVSS balls of the device will see the substrate 1ohm to AVSS and a 0ohm to the board DVSS plane; so the path taken by the current will be the DVSS plane. When this current reaches the power connector (the ideal ground), the current will exit the board and won’t enter the AVSS plane even if we short the two planes here. Hence, we recommend the customers to have two different planes for AVSS and DVSS because we don’t want any coupling in Analog because of Digital switching (which is an AC signal). "

    Thanks,
    -Amanda