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ADS1278-SP: ADS1278 DGND to AGND 10E @pin34.

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Replies: 5

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Part Number: ADS1278-SP

Hi Team,

One of my customer is having issue with DGND to AGND resistance, in the device the resistance @pin 34 (DGND) to any AGND pin is 10E. Is this correct?

( The device is mounted on PCB and customer is having separate AGND and DGND, for checking resistance they removed shorting b/w the grounds).

What should be ideal resistance between AGND to DGND pins, is it open or short (internally).

Can you please help with your inputs.

Regards, Shinu Mathew.

  • Hi Shinu,

    AGND and DGND are internally isolated from each other, but have a parasitic diode connection between them.  For a voltage potential less than 0.3V, the impedance should be very high, but once the voltage exceeds about 0.6V, it will appear very low due to the forward current through the diode.

    Regards,
    Keith Nicholas
    Precision ADC Applications

  • In reply to Keith Nicholas:

    Hi Keith,

    Thanks for the inputs.

    Regards, Shinu Mathew. 

  • In reply to Shinu.V.Mathew:

    Hi Keith,

    Can the parasitic diode formation is bidirectional ? Since observe same impedance in both forward and reverse diode mode.

    Regards, Shinu Mathew. 

  • In reply to Shinu.V.Mathew:

    Hi Shinu,

    Yes, the parasitic diode looks like two diodes that limits the voltage from AGND to DGND from +0.3V to -0.3V, per the ABS specs in the datasheet.

    Regards,
    Keith

  • In reply to Keith Nicholas:

    Hi Keith,

    Thanks for the reply.

    Regards, Shinu Mathew.