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Original question:

BQ25100: BQ25100 Oscillations at Startup

BQ25100: Oscillation at startup issue - similar circuit - Solution?

Karthick Sivakumar
Prodigy 10 points
Part Number: BQ25100

Hi,

We are planning for a similar configuration described in below thread - TI Charger IC followed by PCM.

PCM will be in ship mode initially isolating battery from charger and rest of circuit.

Once charger is connected for the first time PCM will be enabled and battery voltage will appear at VBAT_SW.

Our charging current range will be limited to 75mA.

Our circuit is similar to below thread, we just need to understand if the issue is resolved and what was the solution?

https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/1124753/bq25100-bq25100-oscillations-at-startup?tisearch=e2e-sitesearch&keymatch=BQ25100#

Regards,

Karthick

  • 0
    TI__Genius 12015 points

    Hello Karthick,

    When an adapter is applied to the BQ25100 with appropriate external components, you can typically expect VBAT_SW to oscillate between 3.8V and 4.2V without current draw as the output capacitor rapidly charges and discharges.

    For the PCM, what is the threshold for exiting shipping mode? Also, I'm unable to find in the datasheet what happens to VOUT during ship mode, if the pin is placed in a high-impedance mode or if 'VOUT' is shorted to ground. When current is applied, what is the expected current draw from the PCM?

    Best Regards,

    Juan Ospina

  • 0 in reply to Juan Ospina
    Prodigy 10 points

    Hi Juan,

    Thanks for your reply. Please find below our answers.

    For the PCM, what is the threshold for exiting shipping mode?

    • Threshold is greater than 3.6V. 

    Also, I'm unable to find in the datasheet what happens to VOUT during ship mode, if the pin is placed in a high-impedance mode or if 'VOUT' is shorted to ground.

    • VOUT will be in high impedance mode. 

    When current is applied, what is the expected current draw from the PCM?

    • Is your question about VOUT sink current of PCM to exit from ship mode? In that case as I mentioned above VOUT will be in high impedance state.

    Regards,

    Karthick

  • 0 in reply to Karthick Sivakumar
    TI__Genius 12015 points

    Hi Karthick,

    I believe this configuration is fine as the threshold for exiting shipmode is low enough. I would recommend testing this with an evaluation module prior to board construction, but from a high level the system should work as intended.

    Best Regards,

    Juan Ospina