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Original question:

BQ2980: wake it up after inserting battery without signal on PACK+

BQ2980: Wake up on battery connect without charger

Friedolin Gröger
Prodigy 10 points
Part Number: BQ2980

I want to use the BQ298015 as a system-side protector in a product with a replaceable 18650 Li-Ion cell.

The product should be able to turn on after inserting a full battery cell, even if there is no charger attached.

According to the datasheet, this should be possible on a BQ2980 variant without UV_SHUT enabled, however all the variants of the datasheet have UV_Shut enabled.

Is there a reason for that? Are there variants without UV_Shut available that are not listed in the datasheet?

According to some previous answers in this forum, it should be possible to power-up the protector without a charger, even with UV_Shut enabled, if the load current is low enough.

My standby load current (device switched off) would be around 25-30µA. However even with the protector running isolated without any load, it does not turn on without a voltage on the charger side.

Can you provide a workaround to supply the charger side from the battery during battery connect, without impeding the protection function of the chip?

However I would prefer to acquire a variant with UV_Shut disabled, where no workaround is needed.

The BQ297 also needs a charger to power up, as do protection chips from maxim/analog. Diodes inc do not produce battery protection chips anymore.

I don't understand why nobody wants to manufacture a system-side battery protection chip that doesn't need a charger to power on, but I do believe there is a market for this, as other questions in this forum also asked for this behavior.

Thanks, Friedolin

  • 0
    TI__Mastermind 20670 points

    Hi Friedolin,

    Our devices are meant to be pack-side protectors and a charger voltage is typically required to power on the device, so a replaceable battery would not work well with the device. There isn't a workaround for this unfortunately, as this is just how our parts are designed to function.

    Regards,

    Max Verboncoeur

  • +1 in reply to Maxwell Verboncoeur
    Prodigy 10 points

    This is unfortunate, however so far the BQ298 is still the best solution to my application. I found a workaround myself. I'd appreciate some feedback, but I'll post this also as inspiration for other people with a similar problem.

    This pulls up the PACK  pin to battery voltage (Even with some standby current on VBAT) when the button is pressed, simulating charger detection. It should not influence normal operation while the button is not pressed, and only influence fault recovery and not fault detection while the button is pressed.

    The replacable battery is connected on the left side. The power button is also used by an on/off controller, which switches on the voltage regulators. The value of R33 depends on the standby current at VBAT. The 2 p-Fets are needed because of the body diodes.

    Alternatively, a single PNP transistor with a gain of around 300 and a base resistor of 1MΩ (depending on the standby load) works as well:

  • +1 in reply to Friedolin Gröger
    TI__Mastermind 20670 points

    Hi Friedolin,

    This looks good and should work.

    Regards,

    Max Verboncoeur