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BQ24195: Can BQ24195 buck run without battery

Tulio Pires Oliveira
Prodigy 40 points
Part Number: BQ24195

Hello,

I´m trying to run BQ24195 with and without battery but I still need the SW pin to output 3.8V  that will be used for a SIM module. Is that possible?

If not what will be a way of having the system running with and without battery?

Thank you for your attention.

  • 0
    TI__Expert 8230 points
    Hello Tulio,

    When using the bq24195, if no battery is present, you will observe the BAT output voltage toggling between the battery charge and battery re-charge threshold, since the decoupling cap at BAT will be constantly charging and discharging. The SYS output will also behave similarly, since it tracks the battery voltage when charge's enable.

    If no battery is present, we recommend charging to be disabled; with this configuration, the SYS output will be regulated to MINSYS when an adapter is present. The highest MINSYS threshold on this device is 3.7V however, you might need an additional power stage at SYS if your system needs 3.8V.
  • 0 in reply to Fernando Lopez
    Prodigy 40 points

    Ok great!
    Actually the module SIM5360 that I´m using goes from 3.4 to 4.2V. So it´s OK.
    Two more short question:
    1- How can I disable the charging, if the microcontroller will not be fully on due the pulsed output?
    2- If I save the configuration as charging disable, will it stay as it even after power-off?

    I ask it because I have a 3.3V regulator after the SYS that is used to the uC(ESP8266), and it takes some 10sec to get started.!

  • 0 in reply to Tulio Pires Oliveira
    TI__Expert 8230 points

    Hello Tulio,

    The bq24195 has a charge enable pin (/CE) you can use to control charging enable/disable. If pulled low, charge's enabled. You could tie this to a pull-up voltage and then drive a FET to ground the pin with the MCU once it boots up. Another option is to disable charging via I2C, there's a bit to disable charging, and the MCU can clear it once it boots up; only caveat with this option is that the bit will stay set as long as the battery voltage applied to the device is within the range for valid I2C communication (typically around 2.3V). If the battery voltage drops too low, the device registers will go back to default once power is restored.