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MSP430F2274-EP: Temperature dependency in ADC10?

Neil Tice
Prodigy 90 points
Part Number: MSP430F2274-EP

I am working on a BLDC controller using this extended-temperature MSP430 part.  Almost all of this design is adapted from a similar design that used a C2000 DSP as the controller, we swapped in the MSP430 because a different application required a low-power state.

We are now doing environmental tests on the controller and we are getting some odd behavior at ambient temperatures above about 92C*.  It appears that an incorrectly high value is being read at the ADC10 for our current sensor.  There is nothing in that signal path that is different from the previous design (which works correctly at these temperatures) other than the microcontroller.

Is there a known issue with ADC offset at high temperatures in the MSP430?

  • 0
    TI__Mastermind 27240 points

    Hello Neil,

    I just reviewed the Errata document on the MSP430F2274-EP product folder, and I don't see any errata affecting ADC performance.  

    What voltage reference are you using for the ADC?  

    What is the behaviour you are seeing and on how many devices?   

    Thanks,

    JD

  • 0 in reply to JD Crutchfield
    Prodigy 90 points

    Thanks for checking, JD.

    We have observed the same behavior in two board sets mounted on two different mechanical drivetrains.  We determined that at elevated ambient temperatures, the current limit PI loop built into our software was getting triggered and shutting down the system, although the current draw had not increased.  When ambient temperatures are reduced, operation goes back to normal.  Since the circuit design is almost entirely unchanged other than the change of microprocessor, it is possible that the MSP430 hardware is the problem.  We do not have a communications link with the controller, so we have to infer what is happening from performance.  We have the inverter power supply current instrumented with a high-bw current probe and oscilloscope.

    We are using the 3.3V Vcc as the reference.  We are working on a test harness that will allow us to instrument this voltage and other signals from inside the temperature/altitude chamber.  But we would not expect to find a problem with the 3.3V, since we used the same power supply and reference voltage in the C2000-based design.

  • 0 in reply to Neil Tice
    TI__Mastermind 27240 points

    Hello Neil,

    Thanks for the information on the reference.  The MSP430 and C2000 are entirely different MCUs, so they won't necessarily behave the same.  That said, if your 3.3V was working with C2000, then it's probably alright.    

    Do you have debug access to the MSP430 on the board?  It'll probably be helpful to actually see the ADC data from the MSP430 when at this failure point, as it can probably help point us towards the root cause.  Can confirm that it's somehow the ADC data and move from there.  

    Thanks,

    JD  

  • 0 in reply to JD Crutchfield
    Prodigy 90 points

    JD, Thanks for you reply.

    We have determined that this is not a problem with the MSP430.  As your first reply notes, there is no known issue with this part number at temperatures between 85C-125C.  We traced it back to marginal performance of the inverter high-side gate drive pumps at high temperature.  I will mark your first reply as having answered the question.

    Thanks,

    Neil

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