We have been using the AD5422 DAC in a production board for over 4 years and recently have been experiencing a fault with around 10% of the boards. The fault affects Iout and Vout, for Iout it has a negative 4mA offset so the full range goes from -4 to 20mA instead of 0 to 24mA, while for Vout it is stuck at –22Volts regardless of which Voltage mode it is currently in.
We have this problem occur on different batch numbers and both packages (TSSOP & LFCSP) of the AD5422 chip. We have no issues communicating to the chip and have read back the registers and found that that they have been set correctly. We have also tested the surrounding parts which connect to the chip but have found them to be working correctly.
We have checked the voltage rails, Refout and Refin and all of them are at the correct voltages.
Any ideas to what could be causing this problem or solutions to fix it will be greatly appreciated.
Thanks for the help.
adding circuit diagram
[edited by: LukeAW at 3:55 PM (GMT 0) on 2 Sep 2019]