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BQ76952EVM: Breaking then replacing the MPS430 MCU

Harry McNally
Intellectual 440 points
Part Number: BQ76952EVM
Other Parts Discussed in Thread: BQSTUDIO, EV2400, ISO1540

Hello

We were charging a 16S pack connected to the EVM with about 700mA and the ground connection to the charger came adrift. We speculate this provided return current through the USB cable with the MSP430 MCU taking a hit; the PC running BQStudio, PSU, charger, battery load unit, etc are all grounded to the mains.

Re-reading the following CAUTION from the User Guide proves that hindsight is belatedly perspicacious !

-------------------------

                                                                 CAUTION
The communication interface is not isolated on the EVM. Be sure no ground potential exists between
the computer and the EVM. Also be aware that the computer is referenced to the Battery- potential
of the EVM.

-------------------------

What the CAUTION also tells us is that an error in the charging current reported by BQStudio was because we were directing some return current away from the sense resistor through the alternative USB cable path.

We are now considering a little USB isolator to use the EVM properly:

www.amazon.com/.../ref=sr_1_5

So .. now plugging in the USB cable has the MPS430 MCU heating quickly to high temperature and (naturally) no response when scanned by BQStudio.

I have a copy of the latest v0.32 from Matt after we downgraded the MCU to v0.28. So my question is whether I can simply replace the MSP430F5529IPN and rely on the preloaded USB BSL to load v0.32 into the new part ?

We don't know if this is the only damage but there is no other heating or obvious damage to other EVM components.

With your advice, I can buy the MCU from TI and I think it will come out of Singapore to us in a few days.

All the best as we munch forlornly on our humblest pie ..
Harry

  • 0
    TI__Guru 54715 points

    Hi Harry,

    It is unfortunate to have damage. Yes, replacing the MSP430 should be an option.  Check the power system with the IC removed to be sure it can still provide the 3.3V, and inspect for any damaged components. 

    The EV2400 version 0.32 is now available for download on the tool folder.  Yes, it will run to program the new MSP430.

  • 0 in reply to WM5295
    Intellectual 440 points

    Yes on the unfortunate. Lesson learned about working with the EVM. I have since wondered if a TI I2C isolator may be useful on the EVM between the BQ and USB/MCU subsystem. I haven't considered SPI so it may not be feasible.

    I have found TI has no stock of the MSP430F5529IPN and looking at stock at WinSource from HK. Is Rev K important for the part ?

    Alternatively, is there some stock you have access to for the repair ?

  • 0 in reply to Harry McNally
    Intellectual 440 points

    WinSource have Rev E parts so, if there are no Rev K, it would be helpful to know if any errata will prevent me using the Rev E part.

    I would prefer Rev K if they are available for the EVM.

  • 0 in reply to Harry McNally
    TI__Guru 54715 points

    Hi Harry,

    Thanks for the suggestion on the isolation.  In the simple and perhaps naive view the battery is in an insulated enclosure and accessible references are thought of as the pack-.  Of course with an EVM everything is exposed.  SPI signals are unidirectional and in one sense easier to isolate.  I2C can be more challenging for isolation due to the bi-directional signal(s), but the ISO1540 devices and others are available for I2C.

    The EV2400 has always used the MSP430F5529IPN back to 2011 so I would expect any version to work, but I'm not personally knowledgeable of the details of the EV2400 or MSP430 revisions.  There are no apparent limitations of the newer firmwares being installed on older EV2400 from the EV2400 tool folder or user guide.  For details on the MSP430 revisions you might ask a question for those experts. 

  • 0 in reply to WM5295
    Intellectual 440 points

    Thank you WM, that is the information I need. I will go ahead and repair. I forgot to say that the 3.3V regulator is working fine with the MCU removed.