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BQ4050: How to activate the BQ4050 chip and make it turn on the mosfet to form connection between the battery and pack side

Wasir Muhammad Rumi
Prodigy 35 points
Part Number: BQ4050
Other Parts Discussed in Thread: TIDA-00982, , BQSTUDIO, EV2400

Tool/software:

Hello, I have been designing a robot for my final year project. As such, I wanted to use a BMS and selected the BQ4050 based on the reference design of TIDA-00982 (https://www.ti.com/tool/TIDA-00982) and expanded it to a 4s1p design.

However, I cannot seem to be able to wake up the device to make it just turn on the MOSFETs and drive a circuit on the pack side. 

I designed a restart button but pressing it does not seem to be doing anything.

I have attached my schematic. Do I need to buy the SMBUS ev2300 communicator to activate the chip or some other ways? 

It would help me very much if you can help me troubleshoot on this.

  • 0
    TI__Mastermind 37761 points

    Hello Wasir,

    Usually you will need to hold down the "RESTART" button to short between PACK and BAT while communicating to the device.

    Also, I am trying to follow your schematic and want to ask if you have implemented the sense resistor on the high side. This gauge is not able to do high side current sensing and will cause issues.

    Regards,

    Adrian

  • 0 in reply to Adrian
    Prodigy 35 points

    Hello Adrian,

    Thanks for replying back to my issue and thanks for noticing my mistake on the sense resistor. For now, I have just scratched out the traces and rewired them manually.

    As for what you said here:

    Adrian said:
    Usually you will need to hold down the "RESTART" button to short between PACK and BAT while communicating to the device.

    Does this mean that the 'RESTART" button just wakes the bq4050 chip to start communicating through the SMBUS to our PC and the BqStudio? But it does not turn on the chip and start functioning, like in Layman's terms, its not a plug an play device, if I am getting this correctly?

    I ned to use the BqStudio to activate the chip and load the chemistry tables before it starts to work and connect the pack and battery side using the MOSFETS, is that correct?

  • 0 in reply to Wasir Muhammad Rumi
    TI__Mastermind 37761 points

    Hello,

    Shorting the PACK and BAT pin allows there to be a voltage applied on the PACK pin, and this allows the gauge to start communicating with the device. If the gauge doesn't sense voltage on the PACK pin then it is most likely entered sleep or shutdown mode. You will need to short BAT to PACK while communicating to turn on the FETs. After that, you should be able to release the RESTART button and communicate with the device normally. To turn the FETs on, you can use BQStudio and the host MCU to communicate the commands.

    Regards,

    Adrian

  • 0 in reply to Adrian
    Prodigy 35 points

    Thank you again for your reply. If it's no issue, I would like to clarify one last question:

    Do we need a host processor (suppose STM) to always turn on the FETs or should it be self-sufficient to power on the MOSFETS?

    I have got the EV2400 and have been able to communicate with the BQ4050 so the RESTART button should be working. But disconnecting from the BQStudio and then using the chip as a standalone unit again deactivates the chip and pack side does not turn on which I am using to power on another circuit.

    I was reading through the datasheet and found the command "FET_EN" on the BqStudio which does turn on the MOSFETS and I am able to power my external circuit from the pack side.

    However, I then disconnected the EV2400, disconnected the battery (to simulate shutdown) and reconnected the battery again to see if it now worked without BqStudio. Something was wrong and one of the MOSFETS (the pack side) burned down.

    Sorry for disturbing you and I am going through the complete datasheet right now, but if you have any idea how I can make the bq4050 work independently, it would help me immensely if you can provide your expertise.

    Best regards,

    Wasir Rumi

  • 0 in reply to Wasir Muhammad Rumi
    TI__Mastermind 37761 points

    Hello Wasir,

    Please allow me some time to look into this.

    Regards,

    Adrian

  • +1 in reply to Wasir Muhammad Rumi
    TI__Mastermind 37761 points

    Hello Wasir,

    We believe the FET burning down could be due to a short in the circuit and we also do not recommend disconnecting the battery to simulate shutdown mode, you can simply send the shutdown command to send the gauge to shutdown.

    Regards,

    Adrian

  • 0 in reply to Adrian
    Prodigy 35 points

    Thank you, Adrian.

    I will try to use your instructions to carry further tests on the chip during the weekends. In the meantime, I think that's all and mark the thread as resolved.

    Thanks again.

    Best regards,

    Wasir

  • 0 in reply to Wasir Muhammad Rumi
    TI__Mastermind 37761 points

    Your welcome, please don't hesitate to post more questions.

    Regards,

    Adrian