Surge damage in ADG1402

Hi,

     In my project to measure analog voltage or current,  I'm using ADG1402 analog switch to connect or not a shunt resistor used to measure input current in a system with a ADC. My input is differential and protect against differential surge using a tranzorb, overcurrent by using a PTC and schottky diodes are present between ADG1402 inputs and power supplies  (Vdd=+15V and Vss=-15V). When I apply a 500V surge in common mode (input signal and ground), ADG1402 is damaged by this surge and my system crashs. After ADG1402 is removed, system works well.

     My question is what is causing this damage with respect to ADG1402 ?

Thanks,

Mateus.

  • Hi Mateus,

    Can you send me a screeshot of your input protection to the ADG1402?

    Is it possible to monitor the voltage on the ADG1402 inputs during the surge test?

    The transzorb and the schottkys should be clamping this to within 0.3V of Vdd, correct?

    What is the duration of your 500V pulse?

    What is current limited too?

    What is clamp voltage of Transzorb?

    Rgds,

    Theresa.

  • Hi Theresa,

    Thanks for your reply. Please send me your e-mail, so I can send you our input protection schematic. About the questions:

    Test is perfomed according to IEC61000-4-5, 1.2/50us, 10 pulses with interval of 60s. In coupling method, we are using 0.5uF in series with 40 ohms. Yes, schottkys and transzorbs are clamping the voltage within component limits. Tranzorb is 1.5SMC15CA. Just add some information, in differential mode there is no damage, only in common mode.

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