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BQ24195 battery discharge in boost mode

Carlos Grangeia
Prodigy 40 points
Other Parts Discussed in Thread: BQ24195, BQ24295

Hi there,

I designed 4-layer PCB that contains a single cell battery charger BQ24195 and is controlled by I2C commands, so I'm able to set up into boost mode operation from battery, getting a PMID output voltage of 5.1V.

However, on the scenario of IPMID = 0, the battery is discharged at rate of 15mA (typ) as stated on the datasheet:

I notice that in boost mode, REGN LDO is still ON (~5V) when the input is removed and therefore BQ24195 isn't in high impedance ... I tried to set to REG00[7] = 1, but then boost mode is disabled.

Since my board is mainly to be used as power bank (in boost mode), I wonder is there a way to decrease the constant battery discharge current when no device is connected to the PMID output?

Thank you in advance!

Regards,

Carlos.

 

  • 0
    TI__Guru**** 166626 points
    Can you change to bq24295 which has 3.5mA typical IBOOST instead of 15mA?
  • 0 in reply to Jeff F
    Prodigy 40 points

    Hi Jeff,

    thanks for the fast reply!

    On my board, I connected 2 USB Port Controllers mainly for current limiting to allow intelligent management of system power and therefore to avoid draining the battery excessively. Both of them are configured to handle up to 1.1A (max), so if 2 devices are connected, BQ24195 is perfect since it can provide at least 2.1A on the PMID output.

    According with the datasheet, BQ24295 can only provide 1.5A (min.) at the PMID output ... so, I'm assuming that it would be a bad idea to overload BQ24295 with a boost current around 2.1A - 2.2A, right?

    With a constant boost current drain of 15mA, the batteries will drain quickly so I came up with the idea to turn on-off the Boost Mode every 5-10 seconds and use the USB Port Controllers to detect if a device is connected to the power bank through the current monitoring process. By this way, I think I will increase the battery lifetime ...!

  • 0 in reply to Carlos Grangeia
    TI__Guru**** 166626 points
    Great idea! Another idea might be to monitor the PMID pin with an SVS like TPS3839K50 and only turn on the boost when V(PMID) droops below a certain voltage.
  • 0 in reply to Jeff F
    Prodigy 40 points
    Thanks Jeff for the great support!!