ISO7742: ESD Diode spec.

Hi Ben,

Thank you for using E2E. The ESD diodes given in Figure 8.4.1 are primarily meant for ESD protection & clamping, it is not recommended to pass continuous current  through these diodes. Applying INx higher than its respective VCC violates the absolute maximum rating of INx pin as shown below hence passing continuous current through ESD diodes will violate device absolute max specs.

These ESD diodes are designed to meet 6kV HBM ESD.

Regards,

Koteshwar Rao

Hi, Koteshwar

marked with green frame, it has 985 ohm to limit current but not protect ESD Diode.

i have a trouble, the pin 12 & 16 is broken. 

so we want to know the spec.

or it must add an extra resistance?

regards,

Ben

Hi Ben,

Thank you for sharing additional information related to the issue you are facing. You are right, the 985Ω resistor in series is to limit the current into INx pin.
Since the ESD diodes are not built for continuous operation, we do not characterize them for continuous current spec and I do not have a number to quote you to guarantee the spec. I would say even 10mA of continuous current for few hours could reduce the effectiveness of ESD diodes for ESD protection.

To better address your issue and find our the root cause for Pins 12 & 14 getting damaged, please share us with the below information so that we can try help you.

1. What is your end application and how is ISO7742 used in the application?
2. Please share us the schematic for review.
3. Please describe when did you find out OUTA (Pin 14) & INC (Pin 12) are damaged? What are the tests did you conduct before the device was damaged?
4. Please also share if you have waveform related to the issue.

Please share as much information possible for us to understand your application to help you with the root cause. Thank you.


Regards,
Koteshwar Rao