I'm doing right now a redesign of an old product which was developed by our customer. The AD421 is used to implement a current loop output with HART capability.
According to the customer, there was a problem with this chip in earlier silicon revisions when using the DRIVE/COMP pin with an external FET to regulate VCC, so an external voltage regulator was added in their old design. We would like to remove the external regulator. Is there something like an revision history with old silicon erratas of the AD421? I only found out that the datasheet is Rev. C and from the year 2000.