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How can BQ40Z60 work without Battery pack?

Pietro Di Buono 88
Intellectual 360 points
Other Parts Discussed in Thread: BQ40Z60

Our application need to work also when the battery pack isn't present.

BQ40Z60EVM work without battery with VSYS at precharge voltage and ISYS at precharge current. But, if I upload the same firmware on our custom board, BQ40Z60 reset every few seconds, maintaining VSYS to 0 V, as I can see from the message "Timeout or unexpected response communicating with device" and the INIT bit of OperationStatus Register setted.

With a oscilloscope, I have seen that BQ40z60 tries to turn on the charger (it starts switching high side driver) but, after about twenty cycle, it switches off.

How can I solve this problem?

  • 0
    TI__Mastermind 27105 points
    Hi Pietro,

    If you could attach a schematic for your custom board and your gg.csv file, I can take a look.

    Best Regards,
    Ben Lough
  • 0 in reply to Benjamin Lough
    Intellectual 360 points

    if you give me your email, I can send the requested files.

    Thank you

  • 0 in reply to Pietro Di Buono 88
    TI__Mastermind 27105 points
    Hi Pietro,

    I sent you a private message.

    Best Regards,
    Ben Lough
  • 0
    Intellectual 360 points

    FURTHER INFORMATION

    In my board, I've left SYSPRES floating. Also in the evaluation board, SYSPRES has been left floating during my tests (SLUUA04C said "If the [NR] bit is set, the SYSPRES input can be left floating, as it is not monitored."), and the evaluation board works fine without battery and with [NR] = 1!
    Nevertheless, I've tested my board with all possible configurations:

    • Case 1: [NR] = 0, SYSPRES = GND , with battery -> battery is charging
    • Case 2: [NR] = 0, SYSPRES = GND , without battery -> @ power-on, charger doesn't start, but if I insert battery for a moment, it starts and it seems works fine. If the current slowly rises it works, also with heavy load current (> 1A); but, if the current rises suddenly, the charger stops (even with only 100 mA).
    • Case 3: [NR] = 0, SYSPRES = FLOAT, with battery -> charger is on, current on load is handled properly, battery doesn't charge.
    • Case 4: [NR] = 0, SYSPRES = FLOAT, without battery -> @ power-on, charger doesn't start, but, if I insert battery for a moment, it starts but works bad, because it stops immediately when load current increases.
    • Case 5: [NR] = 1, SYSPRES = GND , with battery -> like case 1
    • Case 6: [NR] = 1, SYSPRES = GND , without battery -> like case 4
    • Case 7: [NR] = 1, SYSPRES = FLOAT, with battery -> like case 1
    • Case 8: [NR] = 1, SYSPRES = FLOAT, without battery -> like case 4

    As you can see, with [NR] = 1, the chip doesn't care for the SYSPRES level (as it should be), and case 6 and case 8 are treated as case 4, that has a different behavior than the evaluation board.
    Why do case 4 work differently?
    If we answer this question, we will have solved a problem.
    However, there is another problem! In cases 2, 4, 6, and 8, in the evaluation board, the charger starts immediately. Contrariwise, in my board, it starts it only if batteries are inserted for a moment. Why is it?

  • 0 in reply to Pietro Di Buono 88
    Intellectual 360 points
    If I decrease the power supply voltage, the current, that the charger is able to supply, before stopping, increases. Maybe, there is something of wrong with LDRV?