EVAL-AD5791 board has EPAD of ADP7182 not connected as per datasheet.

EPAD of ADP7182 on EVAL-AD5791 is connected to GND while datasheet of ADP7182 mentions it is internally connected to VIN and externally it should be connected to VIN.

Which one is correct? and if datasheet is correct I wonder how evaluation boards are even working if at any point GND is connected to VIN then there must be some damage, either on circuit or to the ADP7182?

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  • +1
    •  Analog Employees 
    on Apr 19, 2021 5:39 AM

    Hi Mayankgour13,

    The EPAD/backside of the die should be connected to the lowest potential, which is “VIN” for the ADP7182. Connecting the EPAD to “GND” will definitely create issues with its operation, since this will forward bias diodes in the silicon. The backside of the die is in a p-substrate, and this is directly connected to the EPAD. Therefore, this p-substrate/EPAD pin needs to be connected to the lowest potential to prevent any forward biasing of PN junctions on the IC.

    The reason why you are not seeing a hard short between VIN and EPAD is because the conductive material between the EPAD and substrate is not really low impedance. The electrical connection between the EPAD and VIN/substrate connection on the die is a high impedance path, therefore you will not generate a significant amount of noticeable current.  

    For proper operation of the ADP7182, the EPAD must be connected to VIN.

    Best Regards,

    Alex

Reply
  • +1
    •  Analog Employees 
    on Apr 19, 2021 5:39 AM

    Hi Mayankgour13,

    The EPAD/backside of the die should be connected to the lowest potential, which is “VIN” for the ADP7182. Connecting the EPAD to “GND” will definitely create issues with its operation, since this will forward bias diodes in the silicon. The backside of the die is in a p-substrate, and this is directly connected to the EPAD. Therefore, this p-substrate/EPAD pin needs to be connected to the lowest potential to prevent any forward biasing of PN junctions on the IC.

    The reason why you are not seeing a hard short between VIN and EPAD is because the conductive material between the EPAD and substrate is not really low impedance. The electrical connection between the EPAD and VIN/substrate connection on the die is a high impedance path, therefore you will not generate a significant amount of noticeable current.  

    For proper operation of the ADP7182, the EPAD must be connected to VIN.

    Best Regards,

    Alex

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