STM32L431RCT reads out Zero Value from ADC after EMC/ESD Testing. After a manually disable and enabling adc cycle everything is fine again.

[MGehr.3]

Do you have any ideas what's going on with STM32L431RCT. After ESD Testing ADC of STM32L431RCT reads back 0 Values at all Input Channels. A manually disable and enabling cycle in debugging mode helps. ADC is reading values then correct again.

We also checked ADC Registers(ADC Mode, Channel Selection and so on). But everything looks fine. Only the read back ADC Value are on all channels Zero :-(. . Any ideas what did happen? I can repeat this bahavour pretty well :-)! Thany you in advance for your feedback/help!

[waclawek.jan]

> After ESD Testing

What is ESD testing?

JW

[ABan.1]

electrostatic discharge

[MGehr.3]

We are testing the whole device. We apply ESD Pulses on our Housing.... After a couple of ESD Pulses inside the ADC Measurements of STM32L431 are measuring continuesly 0 Values... :(

[MHAJJ]

Hi,

Can you share/send me schematics and PCB, also at what level (1kV, 2KV..) the ADC start to read back a 0 ?

As you said that the pulses are applied to the housing, is it connected to the ground ? can you check the VSS and VSSA are well decoupled ?

Regards,

Mahmoud.

[MGehr.3]

[MGehr.3]

I've attached the above Schematic where we have problems after ESD Test. we tested applying ESD Pulses without Housing straight to PC10/PC11 used as USART (because these Signals are wired to another PCB in the same housing). We got the same behavior. We also tried external TVS Diodes on these Signals. Did'nt improved something... :-(. Hope you can help us finding the issue of this behavour :-)!

[MGehr.3]

Interesting for us is what's going on inside the STM32L431? Why is it measuring always Zero Values??? Afterr disabling and enabling ADC everything is fine again...

[waclawek.jan]

MHAJJ asked for details (e.g. PCB drawing, and the method/voltage of ESD testing used) for a reason.

It's more the PCB/enclosure layout than schematics what is needed here. Draw into it a line showing the most probable (shortest) current path from the gun's tip, through the protection diodes inside the mcu, through the ground tracks/wires/whatever, to the gun's ground/earth point.

JW

[#10]

Can you percentage/ship me schematics and PCB, also at what degree (1kV, 2KV..) the ADC begin to examine again a zero ? As you said that the pulses are carried out to the housing, is it linked to the floor ? Can you check the VSS and VSSA are well decoupled ?