ISO7231C: flashing failure

Hi Pavan:

Thanks for posting your question on E2E!

Can you please repost the error message to the thread?

Is it possible for you to probe the isolator inputs and outputs after the device fails? If you suspect that the isolators sustain permanent damage, can you please measure the pin resistances with respect to each GND on a failed device to isolate the failure location?

Lastly, please note that these digital isolator IO pins are only protected against device level HBM ESD. If your system has an exposed JTAG connector, there is potential that system level noise transients (for example, IEC ESD due to a human accidently touching the JTAG connector) to enter the isolators and create permanent damage. If this is the case, I'd recommend adding a 5V TVS diode with a 1kOhm series resistor to each IO pin.

Thanks,

Dushmantha  

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please find the attached error image.

Hi, we are not touching the board and JTAG with bare hands, and once this error coming it is not flashing and we have check all pins impedances also. but we are getting same as working board.

please do needful support

Hi Pavan:

Thanks for proving the additional details!

The error message confirms that one or multiple isolator IO pins are not working as expected.

Can you please confirm if the non-functional isolators show permanent damage? In other words, would the non-functional isolators start working after a full power cycle? 

As I mentioned in my earlier post, it would be useful to have isolator IO waveforms to isolate the non-functional isolator channel.

What is the exact condition where the isolators stop working? Is this during an EMC test or just normal operation over time? Do you connect and disconnect the JTAG in your system?

Regarding the application details, can you please share the schematic? What's the data rate/clock frequency in your application?

Regards,

Dushmantha

Hi Pavan,

I wanted to check back with you to see if you had a chance to share us more details related to the issue so that we can help you debug the issue. Like Dushmantha already mentioned, we would require below information to understand the situation and issue better and root cause it accordingly.

1. Share schematic showing MCU, isolator and JTAG connector
2. Share PCB layout
3. Let us know when does device fail exactly. Was it after a particular EMC test or after running any other particular test? It is important to know more details about the incident that could have caused the issue
4. After the device has failed, please monitor waveform at both input and output of isolators
5. After monitoring waveform, if you do not see output following the input then you can de-solder the device and then check each pin resistance its local GND and share us the information.

Please do share above information for us to help you debug the issue, thanks.

Regards,
Koteshwar Rao

Hi Pavan,

I am hoping that you were able to resolve the issues that you are facing in flashing the MCU, I will go ahead and close this E2E thread. If you still see the issue then please do not hesitate to reply back to this post with the information requested. Thanks.

Regards,
Koteshwar Rao

Hi,

I can share the scheamatic part of MCU and jtag.

To share the layout i need to check the approval from higher manager. i will check and let you know.

We are not performing any EMC test as of now, we are just performing functional test of OBC.

I have checked each pin resistance to its local ground but it is not showing any short w.r.to gnd.JTAG_ISOLATORS.pptx

Hi Pavan,

Thank you for sharing the schematic. Thank you also for confirming that you are not performing any EMC when the fail occurs. It is still important for us to know the exact situation when the devices fails, like if it was halfway during flashing the MCU, if it was already damaged while trying to flash MCU or any other specifics related to the moment device is seen as failed.

Along with the PCB layout, please try to answer all the questions listed below with as much clarity as possible. For us to be able help you debug, it is important that I understand as much as you about the situation.

1. Share PCB layout
2. Let us know when does device fail exactly. Was it after a particular EMC test or after running any other particular test? It is important to know more details about the incident that could have caused the issue
3. After the device has failed, please monitor waveform at both input and output of isolators. Please do check for this.
4. After monitoring waveform, if you do not see output following the input then you can de-solder the device and then check each pin resistance to its local GND and share us the information. Please do also mention the exact resistance that you read from pins to local GND for the assumed failed device and a new device. This helps us narrow down the issue to a particular pin and helps debug faster.

Regards,
Koteshwar Rao