Why does it recommended to place schottky diodes in series with the AD7324 VDD and VSS supply signals.
Doesn't it prevent to carry current out from IC through the ESD diodes when Over voltage is applied to the analog input pins?
It not guaranteed that the ESD diode could hold overvoltage for a longer period. The AD7324 uses dual supply that ranges form Vdd=12V to 16V and Vss = -12V to -16V to operate. The schottky diode is a recommendation to protect Vdd and Vss pins to have an opposite voltage to enter. The schottky also has a low forward voltage drop.
This question relates to Figure 54. of data sheet.
It is always recommended to place the Schottky diodes in series with the VDD and VSS supplies on the AD732x family. This prevents any latchup condition from occurring in cases where VCC is brought high prior to VDD.
An exception occurs in cases where VSS is tied to 0V. In this case the diode on that supply (only) may be omitted.