• State Resolved
  • Locked Locked
  • Replies 9 replies
  • Answers 3 answers
  • Subscribers 65 subscribers
  • Views 1339 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

BQ40Z80: How to get gauge up and running?

andre_
Prodigy 80 points
Part Number: BQ40Z80
Other Parts Discussed in Thread: BQSTUDIO

Hi there

We are currently working on a battery powered project. For this we used the bq40z80 fuel gauge to measure remaining capacity and also to protect the battery from overvoltage and undervoltage.

Our problem is that we cannot get the gauge to do anything. It doesn't respond to SMBus reads or writes(no ack) and it also doesn't open the protection FETs to allow the battery to be drained, even though the battery is fully charged. But of course we were unable to tell the bq40z80 the cutoff voltage levels because the SMBus connection is not working.

Can you please explain in more detail how to do the initial setup and please also explain how to program the levels using the bqStudio and ThumBus2300 SMBus adapter.

PS: I attached the circuit arround the bq40z80. Its nearly identical to the one of the EVM.

Thanks for your help.

Regards André

  • 0
    TI__Mastermind 24870 points

    Hello User,

    Make sure you are waking the device up. You will need to your VC5 to Pack pin.

  • 0
    TI__Genius 12760 points

    Andre,

    please consider VC6 connection mentioned in the datasheet ( 6 Pin Configuration and Functions ).

    Regards Bernd

  • 0 in reply to Kang Kang
    Prodigy 80 points

    Kang Kang said:

    Hello User,

    Make sure you are waking the device up. You will need to your VC5 to Pack pin.

    Hi Kang Kang

    I tried your answer and it helped in the sense that I am now able to communicate with the device over BQStudio. The problem is that this connection form PACK to VC5 causes the discharge fet to allways be open(Vgs allways arround 2V in off state and 12V in on state). I connected PACK through a 10k Resistor to VC5.

    Can you tell me how this function is intended to be used because I can not imagine how this should work. If you have a battery powered device on the protected side, why should PACK ever be a positive voltage??? Maybe you can tell me how to connect the PACK pin so that the bq40z80 starts communicating as soon as the battery is connected.

    Thanks for your help and have a nice day.

    Regards André

  • 0 in reply to andre_
    TI__Mastermind 24870 points

    Hello Andre,

    Can you take a screenshot of bqStudio? What protections bits are being set?

  • 0 in reply to Kang Kang
    Prodigy 80 points

    Hi Kang Kang

    For now I only use the basic protections(CUV,COV). For testing I controll the DSG mosfet over bqStudio. As you can see on the screenshot it is currently in OFF, but there is still some reamining Vgs on the Q202(2V).

    This is the memory file: https://gofile.io/?c=pPWiem

    Thanks a lot for the support.

    Regards André

  • 0 in reply to andre_
    TI__Mastermind 24870 points

    Thanks, this schematic doesn't make sense to me.

    Why do you have VCC between the protection FETs?

    There should not be any residual charge on CHG FET, can you try blue-wiring a 10 kOhm pull down to ground to see if that residual charge is dissipated.

    I recommend doing the placement similar to what we have on the bq40z80 EVM.

  • 0 in reply to Kang Kang
    Prodigy 80 points

    Please take a look at the schematic you mentioned. The attached schematic is the one from BQ40z80EVM. As you can see Vcc is connected after the first protection FET as well. I assume this is to protect from reverse polarity.

    What you can see to is the fact that PACK is for some reason connected after the protection FETs. This means the part needs to be "activated" by an external power source connnected to PACK+ and PACK-, like a charger or something. The big button marked with "Wake" supports this therory I guess.

    Connecting the PACK pin to any other location than PACK+ probably changes the Vgate of Q3 because PACK is used as the reference for this voltage.

    Please explain to me how this IC is normally used. Can I Wake it with PRES? Id rather understand this than to just try and connect pulldown resistors to FET.

  • 0 in reply to andre_
    TI__Mastermind 24870 points

    Hello Andre,

    Yes, the IC can be woken up. All you need to do is short the top of the cell stack to the Pack+ pin.

  • 0 in reply to Kang Kang
    Prodigy 80 points

    Hi Kang Kang,

    Sadly I don't think you really understand my issue here. Guess I will have to live with the fact that the IC can only be woken up with an external power source or by shorting the pack pin.

    Thanks for your help anyway.

    Regards André