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ISO7821: Dead Short from pin 16 to pin 9

Dan Lukas
Intellectual 750 points
Part Number: ISO7821

Every one of the parts that I received has a short from pin 16(Vcc2) to pin 9(Gnd2).

Measuring with a Fluke 179 I have high resistance from pin 16(Vcc2) to 15(Gnd2) and high resistance from pin 15(Gnd2) to 9(Gnd2) but zero Ohms from pin 16(Vcc2) to pin 9(Gnd2).

These are cut-tape parts from Digikey ordered about 3-weeks ago.

  • 0
    TI__Intellectual 2325 points

    Hi Dan,

    Thank you for using our E2E forum.

    Could you please clarify the full part number you received?

    We have two different pinouts in the 16SOIC footprint. One is a 16DW and another is a 16DWW. The pinout is not the same between the two options and perhaps a mix-up may have happened?

    Please refer to the comparison diagram below I put together based  on page 6 of the ISO7821 datasheet. The 16DW package may have been delivered and the impedance measurements you are seeing align with the diagram/pinout on the left:

    For 16DW:

    • Pin 16: GND2 <> Pin 15: NC : High-impedance  - this is normal
    • Pin 16: GND2 <> Pin 09: GND2 : Dead short      - this is normal
    • Pin 15: NC      <> Pin 09: GND2 : High-impedance  - this is normal

    The DWW package has the pinout where pin 16 = Vcc2, pin 15 = gnd2 = pin 9.

    I realize/acknowledge that this small difference can be confusing. Hope this helps!

    Best regards,

    Abhi

    PS:  Fixed Typo. Clarified post to say that Pin 15 (NC) impedance to pin 09 (GND2) : expected impedance is high.