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MSP430F235 Brownout Reset

Roman T.
Prodigy 150 points
Other Parts Discussed in Thread: MSP430F235

Hi

In one of our applications using the MSP430F235, the supply voltage somtimes drops with a rate of about 100 mV/s towards 0 V. In that case the Brownout Reset is not triggered, which causes some problems. Is the above drop rate too slow for the Brownout Circuit?

Regards

Roman

  • 0
    Guru 227245 points

    The brownout level is way below the required operating voltage. On some devices well below 1.5V or even less. But it should trigger eventually.
    And usually, the slower the voltage falls, the higher the trigger voltage is.
    Problem is if it rises again before it has crossed the BO threshold but the CPU has already crashed because of the low voltage. Then the BOR is not triggered and the CPU won't startup again.

  • 0
    TI__Intellectual 2595 points

    The Vcc of a 2xx chip can fall and rise at 100mV per hour and the brownout will still trigger. In applications work we often test MSP430 chips with super slow Vcc rise and fall times, as it is an important issue in some high volume applications. The brownout module provides very robust Vcc protection, as long as the chip is running at low speed (below about 4MHz for the chip you are using). If you program the SVS module correctly you can achieve similar robust protection when running the chip at any speed up to its maximum specified frequency (16MHz for the chip you are using).

    The only related issue I recall with any 2xx chip is issue BCL13, which you will find in some of the errata documents. This bug was caught a long time ago, so it should only be present if you have a rather old sample of the device. If you look at the errata document for the MSP430F235 you will see it was fixed in revision D of that device.

    Regards,

    Steve

     

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