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Original question:

BQ40Z80: SMB connection error

BQ40Z80: bqStudio for in-house testing

Adam Drewery69
Prodigy 110 points
Part Number: BQ40Z80
Other Parts Discussed in Thread: BQSTUDIO,

Hello,

I was able to get through configurations with the BQ40Z80EVM-020, and I moved to our custom PCB. The circuitry is nearly an exact replica of the EVM circuitry with a few exceptions on the CHG FET drive circuit. We are not using a PRE-CHG or PRE-DSG circuit.

My question is, when we go through checkout is there a way to have to avoid having pack voltage connected? I have seen several postings () saying to keep the device communicating reliably we need to have PACK voltage connected. I have configured the device to not go into sleep mode, and I am using a *PRESENT pin to detect the pack is enabled. I have ensured that the pin is < 0.55V per the data sheet. It seems to me that this should be sufficient to bring the device on and start communicating with bqStudio. What is the reasoning behind requiring voltage at the PACK pin?

I have attached my configuration settings in case I am missing something.

5265.test.gg.zip

Thanks,

Adam Drewery

  • 0
    TI__Mastermind 24870 points
    Can you also share the schematic?
  • 0 in reply to Kang Kang
    Prodigy 110 points
    Hi Kang,

    I am unable to share the schematic as I do not have ownership of it. Suffice it to say, I am not sure how my schematic is even relevant. The issue is also present on the BQ40Z80EVM-020.

    On our BQ40Z80EVM-020, I have loaded the configuration settings in the post above. I have the jumpers set as listed below.

    Jumper settings:

    J5.1 - J5.2
    J6.1 - J6.2
    J7.1 - J7.2
    J10.1 - J10.2
    J18.1 - J18.2
    J20.1 - J20.2
    J21.1 - J21.2
    J22.2 - J22.3

    Unless I am missing something, it would seem to me that holding the PRES pin low with these settings should automatically bring the BQ40Z80 up.

    Thanks,
    Adam
  • 0 in reply to Adam Drewery69
    TI__Mastermind 24870 points
    It is just a first step for us to do a comparison. You said a near replica.

    Can you share your battery pack information. What voltage is the battery at?
  • 0 in reply to Kang Kang
    Prodigy 110 points
    I understand.

    The battery stack on the end product is 21.0 - 29.4V. It is a 1P7S cell configuration. The actual testing I am currently doing is at 25.6V.

    For the time being, I am working with 7 1kΩ resistors in series to simulate the cells on the EVM for this issue.
  • 0 in reply to Adam Drewery69
    Prodigy 215 points
    Adam,

    I am having the same issue with the EVM. Were you able to find a solution to your problem?

    Sean
  • 0 in reply to Sean Chen79
    Prodigy 110 points

    Sean,

    I have not found a solution to this yet. For the evaluation kit it can be done by permanently connecting power to the PACK+ pin.

    In our own design, I think our only option will be to re-purpose the circuitry to short the stack to the PACK+ pin momentarily.

    Thanks,

    Adam

  • 0 in reply to Adam Drewery69
    Prodigy 110 points

    After digging more in to this issue, it appears to me that the PRES* pin functionality is very misleading. The way I originally interpreted the point of this pin is that it was to signal to the BQ series that the battery is inserted, and the BQ40Z80 should power up and begin normal operation.

    However, from reading the manual several more times and looking at section 6.4 (SHUTDOWN Mode) of the manual, I am not sure what the point of the pin is. We have been performing tests these last few days with this pin pulled high.

    From the manual, "If PRES is low for four samples (one second), OperationStatus[PRES] is set, indicating the system is present (the battery is inserted)." We have been doing testing with this pin pulled up to pack voltage."

    Also, from section 6.4, if the device is entered in to SHUTDOWN mode, then the only way for it to exit that mode is to have the PACK pin (pin 25) > VSTARTUP. If I couple these two things together, it seems to me that the present pin is useless.