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BQ40Z60 turn on

tommy madsen
Prodigy 30 points
Other Parts Discussed in Thread: BQ40Z60

Dear TI & Supporting engineers.

I have a quick question.

We have designed a 4P4S battery pack with your BQ40Z60 inside as a "pack side solution" pretty much 100% "copy'n'paste" from the EVM except for the push button and IRQ signals which are not connected

I do have the following signals out of the pack connector:

VSYS, VAC, SDA, SCL, GND

In my application I need to have power from the battery available at all times (as long as there's charge on it at least) and then my system MCU will control power management in my application and talk to the BQ40Z60 etc..

Now I'm a bit concerned as I've been reading your forum and it seems to be suggested that it's not possible to have VSYS available at all times from power on reset?

What I mean is...

Image I have a fresh battery pack (with BQ40Z60 programmed inside) if I then insert that into my product/application I want it to immediately feed voltage on VSYS so that my MCU can boot and monitor the on/off button on my product and take further action if needed

Is this possible?

Have I overlooked something??

  • 0
    TI__Guru 73830 points
    Voltage should be available at VSYS, if the CHG and DSG FETs are enabled and they can be enabled if the gauge is powered up. Most users take advantage of the SYSPRES pin to allow the FETs to be disabled when the pack is removed from the system. This is for safety to prevent voltage from being present on the pack connector. You can keep these FETs on, if necessary. If you reset the gague, then the FETs will be disabled during the reset period and will turn back on after the firmware is back online. if the device is in shutdown, then the FETs will be off until the adapter voltage is applied to allow the device to wake up. Does this answer your concern?
  • 0 in reply to ThomasCosby
    Prodigy 30 points
    Hi Thomas,
    Thanks for your good reply, very well written and informative.

    I'm planning that in the event that the battery shall be removed one must hold the power button for X amount of seconds and then the MCU will send a shutdown command to the BQ40Z60.

    One additional question if I may.

    We need to obtain approvals for this battery pack in order to be able to ship it with a courier (I believe it's called UN38.3) - we use 16pcs Samsung ICR18650-30Q cells inside which are all UN38.3 approved.

    One of the UN38.3 tests requires you to short circuit the battery pack - do you know if it's allowed to perform this test while the battery pack is in shutdown state? - and regardless - what happens if the pack is in shutdown state and you apply a short circuit between any or all terminals (VSYS, VAC, GND, SDA, SCL) - My guess is "nothing" happens as the FET's are off.

    Thanks Thomas, I appreciate your time.

    Best regards
    Tommy L. Madsen
  • 0 in reply to tommy madsen
    TI__Guru 73830 points
    The FETs will be disabled when the device is in shutdown, so a shorted load should have not effect. The device also provides shorted load protection, so it should protect the pack should a short occur when the FETs are enabled.