ISO7742: 6kV ESD Test failure when using ADS1216 and ISO7742 in a RTD application

Part Number: ISO7742


My customer has met a problem when taking a 6000V ESD Test in a RTD application by using ADS1216 and ISO7742.

MCU will make a self-test for the register, and if there's something wrong in the register, MCU will write a RESET signal to RST pin of ADS1216. when taking a 6000V radiation ESD test, ADS1216 keeps Reset. My customer has done some methods to protect the devices, like adding protection diode before ADS1216, but it's useless. They have made a test on ADC, and it's OK, so they are doubting there's something wrong in SPI, which caused a timing issue. What's more, when using ISO7242, the ESD test is good, but a 1000V EFT test is failed, so maybe there's a large effect on the ISO.

The frequency of SPI is 750kHz, and there's 22ohm resistor between ISO7742 and ADS1216, ISO7742 and MCU.

If the ISO will effect the result of ESD test, and how to solve the problem? 

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