MSP430FR6047: USS ADC Capture Issue: Flat High Amplitude Capture Observed

Kamlesh Bharodiya

Part Number: MSP430FR6047

Hi Team,

In out water meter product, we are using MSP430FR6047. In some cases, the ADC capture on USS shows this:

(Sorry for the bad picture as it was taken in field)

You can clearly see some signal on UPS, but DNS is 2047. I got the PCB back from field and tested by applying small amplitude signals (200mv, 1MHz) on the CH0IN and CH1IN pins. Here is the output:

As can be seen, the DNS Channel is showing 2047 value - replicates the field issue.

Through some forums, I got to know that the USS Module Input channel is damaged in this case. What could be the possible reasons and how can they be avoided? As this issue has been seen in multiple times, it has become a critical issue. The Schematic for the USS analog part is designed as per EVM. Please help in this regard.

Regards,

Kamlesh

over 1 year ago

0 Cash Hao11 over 1 year ago

TI__Mastermind 27635 points

Hi,

Is this phenomenon only observed on one single meter?

If so, have your tired to replace the MCU on that board with the same firmware and test again?

Best regards,

Cash Hao

0 Kamlesh Bharodiya over 1 year ago in reply to Cash Hao11

Prodigy 180 points

There are several meters with this issue. replacing the MCU solves the issue. However, we would like to understand the cause behind this situation and handle it prior to device failure.

Please help.

Regards,

Kamlesh

0 Cash Hao11 over 1 year ago in reply to Kamlesh Bharodiya

TI__Mastermind 27635 points

Hi,

There would be a lot of things which could cause the device failure on those MCU. However, the most frequent root cause would be the ESD damage through the pins. I would suggest you to check if there is any ESD hazard around.

And if the water pipe is made of metal or the transducer has a shield wire, you can connect those to the board's GND.

Best regards,

Cash Hao

0 Kamlesh Bharodiya over 1 year ago in reply to Cash Hao11

Prodigy 180 points

Hi Cash Hao,

Thank you for the prompt response. The devices are deployed in field. There might be ESD sources around - not quite sure. Are there any methods recommended by TI to protect the USS analog circuitry from getting damaged especially for the USS Analog Part of MSP430?

Regards,

Kamlesh

0 Kamlesh Bharodiya over 1 year ago in reply to Kamlesh Bharodiya

Prodigy 180 points

Also, currently the PCB and Transducers are isolated from the surrounding (including enclosure) to reduce any chances of ESD events.

0 Cash Hao11 over 1 year ago in reply to Kamlesh Bharodiya

TI__Mastermind 27635 points

Hi,

We do not have much methods to protect the USS part for the MCU. Like I said before,

Cash Hao11 said:
if the water pipe is made of metal or the transducer has a shield wire, you can connect those to the board's GND.

Best regards,

Cash Hao

0 Kamlesh Bharodiya over 1 year ago in reply to Cash Hao11

Prodigy 180 points

Hi Cash Hao,

Thanks for your response. I have contacted the Transducer manufacturer. We will go ahead with connecting the shield with Board's GND. What =would be better connection - connecting the shield with AGND or any nearest pin to the Power GND of the PCB?

Also, Can we put Diode on CHxOUT and CHxIN pins to protect the pins from voltage surge? Would it help?

Regards,

Kamlesh

0 Cash Hao11 over 1 year ago in reply to Kamlesh Bharodiya

TI__Mastermind 27635 points

HI Kamlesh,

Connect to the USS_GND is more preferred. But any other GND should be fine.

Kamlesh Bharodiya said:
Can we put Diode on CHxOUT and CHxIN pins to protect the pins from voltage surge? Would it help?

I do not suggest to add any other circuit on the CHxOUT and CHxIN pins. Adding more component may affect the USS performance.

Best regards,

Cash Hao

0 Kamlesh Bharodiya over 1 year ago in reply to Cash Hao11

Prodigy 180 points

Great! Thank you for the response. Will keep the above points in mind.

Regards,

Kamlesh

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MSP430FR6047: USS ADC Capture Issue: Flat High Amplitude Capture Observed