Error with CN0381

I think there is a mistake in design CN0381 with the IOV_DD voltage regulator. The ADJ resistor pair for the ADP1720ARMZ-R7 is shows R1=57.6k and R2=27k. If I am reading ADP1720.pdf page 10 correctly, this produces a voltage of 3.8V instead of the desired 1.8V.

This would also exceed the IOV_DD to GND spec of max=3.6V on page 94 of ad7124-8.pdf.

Swapping them around would solve the problem.



  • +1
    •  Analog Employees 
    on Sep 7, 2020 6:27 AM

    Hi Eric,

    Apologies, this is a mistake in the block diagram representation. You are correct in both that the resistors should be swapped and that this would violate the AD7124 abs max specs.

    The schematic has them in the correct positions. R1 = 27k and R2 = 57.6k. You can get the schematic from the Design Support Files.



  • 0
    •  Analog Employees 
    on Dec 8, 2020 4:02 PM

    Hi Eric,

    To add onto what Nikko said a few months ago, the CN0381 and the CN0383 were combined into an updated CN0383 document which is an all encompassing RTD + AD7124 document.  The CN0381 doesn't exist anymore and all links to the CN0381 now point to the CN0383.  You should go have a look at the updated document.