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MSP430FR59691: Temperature readings during electromagnetic events

Part Number: MSP430FR59691

Hi Team,

I am posting this inquiry below on behalf of our customer.
I will paste the customer inquiry to make sure I will miss any details:

"We wrap a hand device cable from a HF Surgical Generator to our Unit Under Test that has the MSP430FR59691 on the PCBA. The test consists of wrapping the cable and firing RF to see if our device in relation to the HF Surgical Equipment.

When we do this we see a temperature spike on our software output logs, we see this rise when energy is applied to the device with the cord and before the circuit is completed creating a corona discharge.  It does not appear to be a real temperature spike because there is no ramp of the data.

We attached a thermistor to the MSP430, but I did not see any temperature spikes actually happen. Intuitively if there had been a temperature spike we would have seen the temp come down slowly. But using the thermistor, there was never a change in temp.

We are wondering why the frequency or voltage values from the HF Surgical Equipment could have cause this fake temperature reading on the MSP430?

The frequency values of the HF Surgical Equipment we were using are as follows;

Based on that info, it gives a pretty good picture of what the output frequency looks like.

Below is a list of the voltage and power of the HF Surgical Equipment.



Please let me know if you have any questions for the customer.

Thanks,

Jonathan

  • I suspect that the feature sizes within the MSP430 chip are too small for there to be much coupling into them. It seems more likely that it is entering via the power supply pins or the external reference. (If used.) Does this show up in any other ADC channels?

    That test setup with multiple turns around the DUT with the high di/di looks like a good way to magnetically couple to the DUT which means that any low impedance loops could get hit. With multiple Vcc and ground pins the MCU could be at the center of several loops.

  • Agree with David. 

    In addition, does customer use the built-in temperature sensor? The temperature sensor is referring to internal shareRef or external Vref? Do you have measure the power supply and Vref when doing the test? It is better to find ways to protect the power supply and Vref for FR59691 on the board. 

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