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BQ25101H operation without Battery

Rajesh Ravnikar
Prodigy 70 points
Other Parts Discussed in Thread: BQ25101H

Hi Ti Team,

This is Rajesh from Happiest Minds.

We are using BQ25101H in one of our designs.

Without battery connected we would get 4.2V regulated output and 22mA of initial output current .

Does the charger remain in this state if battery is not present or will it change into a different charging state.

I wanted to know , what will be the state of BQ25101H without battery . Can I power up my system without battery using BQ25101H ? and yes 5V input would be present.

Regards,

Rajesh N

  • 0
    TI__Genius 14890 points

    Rajesh,

    The best way to put the bq25101H into a regulated supply mode is to tie TS high as stated in Section 8.3.8 when discussing the TS pin.  TTDM is discussed throughout the datasheet as "Termination and Timer Disable Mode".  In this mode, the current is still limited by the current set with the ISET pin.

    If TS is not high, you may get different behavior under different conditions.

    Look at the OUT if TS is not pulled high and you have no load.  The meter will show about 4.2V, but if you use an oscilloscope, you'll see a pulsed OUT pin which averages to 4.2V. As you change the load (resistive load is easiest to see), the behavior will change.  Decreasing the resistor value will get to a high enough current to put the device into constant output voltage.  Increasing the resistance does not go back to the pulsed mode.

    What is the goal of your system?

    Regards,

    Dick

  • 0 in reply to Dick Stacey
    Prodigy 70 points
    Hi Dick,

    Thank you for your quick response.
    Our system is a developers kit , so with Bq25101H I need to power up the system even without battery.
    Battery is optional.
    So trying to understnad , does BQ25101H supports this without battery.

    Regards,
    Rajesh N
  • 0 in reply to Rajesh Ravnikar
    Prodigy 70 points
    Hi Dick,

    One more question, does keeping the TS pin floating also puts the charger in TTDM mode or do I need to pull it high to 1.6V.
    Or is there a way to configure TS pin to enter TTDM mode when battery not present and exit TTDM mode when battery is present.

    I was thinking , if TS pin is left floating the charger enters TTDM mode and if the battery pack is connected with 10K NTC thermistor then it exits the TTDM mode.

    Is my understanding is correct.
    Datasheet is confusing , in the pin description it says TTDM mode is entered if TS pin is floating or pulled high and rest of the other sections it only says pull TS pin high to enter TTDM mode.

    Please educate me on this.

    Thanks for your time and consideration.

    Regards,
    Rajesh N
  • 0 in reply to Rajesh Ravnikar
    TI__Genius 14890 points

    Rajesh,

    Section 8.4.5 in the Device Function Modes discusses Termination and Timer Disable Mode (TTDM).

    The first sentence should answer your question:

    The battery charger is in TTDM when the TS pin goes high from removing the thermistor (removing battery pack/floating the TS pin) or by pulling the TS pin up to the TTDM threshold.

    If the thermistor is embedded in the battery and will connect to the system when the battery is inserted, the bq25101H will be in TTDM when you don't have a battery and in regular mode with the battery pack.

    Regards,

    Dick