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TPS65987D: TIDA-01627 Powerbank not charging with dead-battery

Angel Sanchez Garcia
Prodigy 200 points
Part Number: TPS65987D
Other Parts Discussed in Thread: BQ40Z50, TPS65987, , BQ25703

Hi.

I'm developing a TIDA-01627 based powerbank using the TPS65987 and a BQ25073 charger. Battery protection is handled by a BQ40z50.

The idea is having the powerbank by default in sink configuration.

When I unlock the battery protections with an external charger I can initialize the BQ25073 and get it to charge the battery correctly, but when the battery is in a protected/discharged state (0V VSYS and no VIN_3V3) I cannot get this to work.

I have inspected the communication between TPS65987 and BQ25073 and there is no I2C traffic (lines idling high, 3V3_LDO goes on correctly) when plugging the USBC with dead battery, however the sequence is as expected when the battery is active.

I have tried setting the charger configuration packets to be triggered in power-on reset, hard reset, and PP1 switch on. This 3 events work with active battery but not with dead battery.

What can be the cause of this problem? It looks like something is preventing the I2C to send packets.

Thank you.

  • 0
    TI__Mastermind 36751 points
    Hi Angel,

    Does the BQ25703 support this mode of operation? It could be holding the I2C lines low when the battery is completely dead. There is nothing that would prevent the TPS65987D from sending I2C Data during dead battery mode. I have tested the dead battery behavior with other I2C Slave devices and have not seen this issue.

    Thanks,
    Eric
  • 0 in reply to Eric Beljaars
    Prodigy 200 points
    Hi Eric.

    As explained BQ25703 datasheet, page 24, the power-up from source feature requires a minimum voltage (VBUS_CONVEN) of 3.5V in VBUS, VBUS is at 5V. I can see the internal LDO is activated, though it only outputs 4.8V as VBUS is under the 6V regulation voltage, but this should be a valid working condition and it works at this voltage when battery is enabled.

    I2C lines are not held down as they rise at the same time as LDO_3V3, which is their pull-up rail, when connecting the USBC.

    There must be some configuration I'm missing in the TPS65987. For this test I'm using a legacy USB-C charger, not a PD enabled charger, from an LG/Google Nexus 5X but this shouldn't affect if I try to trigger the commands from a reset event right?

    Thanks.
  • 0 in reply to Eric Beljaars
    Prodigy 200 points
    Hi again Eric.

    Finally resolved the issue, my problem was that the boot mode resistor was changed in a previous test and was not allowing the TPS65987 to boot without VIN_3V3.

    Also had to disable the LDO output mode of the BQ25703 as the battery precharge is handled by the BQ40z50.

    Thanks for your help!