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BQ25892: Large surge voltage when battery is asserted and de-asserted

Ruixin Feng
Intellectual 1765 points
Part Number: BQ25892

Hi team,

customer use BQ25892 and test a large surge voltage on VBAT pin when the battery is asserted or de-asserted. SCH and test results are shown as below. Could you give any advice on it? Thanks!

When battery is de-asserted, yellow line is VBAT waveform.

When battery is asserted, yellow line is VBAT waveform.

Thanks!


Rayna

  • 0
    TI__Genius 15155 points

    Hi Rayna,

    Could you please advise the following?

    1. Are you using a real battery or a battery simulator for these tests? It looks like VBAT has about ~1V variation at the beginning of the last scope capture. A real battery should hold VBAT steady.

    2. When you say the battery is asserted / de-asserted, are you disconnecting the battery using an external circuit element or are you simply disconnecting the battery by hand? Is the battery far away from the BAT pin of the charger IC?

    3. What is your battery voltage (voltage across battery / battery simulator terminals) when you apply the battery to the system?

     Regards,

    James

  • 0 in reply to James Steenbock
    TI__Intellectual 1765 points

    Hi James,

    1. real battery.

    2.By hand. not too far.

    3. 3.8V-4.0V

    Rayna

  • 0 in reply to Ruixin Feng
    TI__Genius 15155 points

    Hi Ruixin,

    1) Can you provide a scope capture of VBAT, IBAT (current flowing into battery), VBUS, and IBUS (input current to charger) when you see the voltage spike? Please have all the signals labeled and in one scope picture.

    2) Can you also provide a scope capture of VBAT, IBAT, VSYS, and ISYS (SYS load current) when you see the voltage spike?

    3) Please provide a full register dump of your charger settings right before the battery is removed, and another register dump from after the battery is removed.

    3) Do you have any higher voltage connections in your system that could be contributing to ~5.5V at BAT pins?

    4) Does the behavior remain the same when you connect a simulated battery (source meter for example) or a different type of battery (if available)?

    Regards,

    James