I'll be using an ADA4851-1 (supplied +5V) in a high-voltage (up to 60V during a small-time during which the OA isn't supplied, then max 38V in nominal operation) sensing application, with a bridge divider (1:11 with a 100kOhms and a 10kOhms which middle node is linked to the positive input of the OA used as a voltage follower.
I have two questions regarding my design :
-First, when the amp is not supplied (battery not connected to the DCDC converter supplying the OA in 5V), but that there is voltage on the sensed node, and given that I use a 5V Zener diode between the positive input and the GND, will the internal ESD diode of the ADA4851 send the (60V-5V)/100k = 550µA to the 5V node, thus potentially powering the 5V electronics ? Will the AO break down ? Or will it handle this problem properly ?
-Secondly, during nominal operation (ADA supplied with 5V), in the case where the "bottom" resistor of the bridge divider breaks in open-circuit, the Zener and the ESD diodes will limit the V+ voltage at 5V, but will the ADA support the (38V-5V) / 100k = 330µA input current ? Unfortunately there is no specification for the maximum allowable input current in the datasheet.
I hope that you will be able to help me regarding these two issues.