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CCS/MSP430F67491: latch up and watch dog in low power mode problems

Emad Hamdy
Prodigy 20 points
Part Number: MSP430F67491
Other Parts Discussed in Thread: TIDM-AUX-MODULE, ,

Tool/software: Code Composer Studio

Dears

we face a serious problems in the MCU MSP430F64791A

1-When a fast transients is applied to the 220V terminals of the single phase meter, the MCU enters a latch-up state and VDSYS becomes 2.5v instead of 3.3v and the battery terminal AUXVCC1 consumes 4 mA although the  DVCC is exactly 3.3V. This state does not release with HW reset (RST pin) and we must disconnect both the battery and the 220V to return true case.

2- When in normal mode we enable the watch dog , upon entering the low power mode 3 we disable the WD not to wake up the CPU but we noticed high battery consumption about 600uA How we can operate the WD and still reduce the consumption in low power mode 3

BR

Emad Hamdy

  • 0
    TI__Mastermind 49692 points

    Hi Emad,

    Let's focus on one issue at a time here.

    To start, fast transients on the inputs are never ideal. From your description, the input voltage to the MCU is either exceeding the absolute maximum values or trying to power up and down too quickly. This depends on if you're supplying a constant 220V input voltage and superimposing the transients on the inputs or actually pulsing the 220V causing the power to the MCU to cycle on and off. Both of these scenarios should be avoided.

    Can you share more details about these transients? Are you introducing them during a test or is this during normal operation? Have you followed all the recommended capacitor values for various pins on the device (e.g. VCORE, VCC, etc.)? Have you added any type of ESD protection devices like varistors, TVS diodes to help clamp the transients?

    Since you mentioned the AUXVCC1 module, I would highly recommend that you carefully read through our TIDM-AUX-MODULE user's guide and make sure you're following the guidelines (both hardware connections and software configurations). It's an excellent reference.

    Regards,

    James

  • 0 in reply to James Evans
    Prodigy 10 points

    1- The supply is not interrupted and the transients are caused by disconnect and reconnect a PLC modem that contains a capacitive coupling circuit

    2- The problem happens in the field 

    3- The VDsys is suddenly loaded and drops to 2.6v and remains untill the power is disconnected 

    a- Does these symptoms indicate Latchup or not?

    b- What is the most probable weak point (VCC, GPIO's, Battery socket, ADC, ....) 

     

  • 0 in reply to Yasser Fathi
    TI__Mastermind 49692 points

    Hi Yasser,

    Thanks for the additional details. It sounds like a possible latch-up condition that's being triggered by rapid fluctuations on the supply voltage or exceeding the recommended maximum inputs on the supply voltage or other I/O's.

    I'm assuming you're powering the MSP430 from the AC mains. Could you try disabling the on-board power supply and use a battery to power the device? This way, you can figure out if the transients are affecting the power supply circuitry or the sensing circuitry. If the latch-up condition goes away using battery power, then you can work on implementing additional protection on that circuitry. Similarly, if you open the sensing inputs and the issue goes away, then you can focus on that circuitry.

    Last but not least, are you using the MSP430F67491 or MSP430F67491A? Your initial post contains both part numbers, and I would recommend using the A-version.

    Regards,

    James

  • 0 in reply to James Evans
    TI__Mastermind 49692 points
    Due to the upcoming US holidays, I'll be out of office from now until January 2nd. Unfortunately, responses will be delayed, so we appreciate your patience.

    Regards,

    James

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