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BQ25504: Regarding the Current Available from the VSTOR Pin

Ryuchi Tetsuya
Prodigy 10 points
Part Number: BQ25504

Tool/software:

Regarding the Current Available from the VSTOR Pin of the BQ25504

When a battery is connected to the VBAT pin (pin 14) and the system load is connected to the VSTOR pin (pin 15),
what is the maximum current that can be drawn from the VSTOR pin (pin 15)?

I referred to the datasheet, Section 7 Specifications – 7.5 Electrical Characteristics,
but could not find any description regarding the current value that can be supplied to the system load from the VSTOR pin.

Thank you.

  • 0
    TI__Mastermind 40845 points

    Hello,

    If there is no battery, the limiting factor will be the input power. If there is a draw form VBAT, keep in mind the resistance between VSTOR and VBAT is max 2Ohms. Drawing a lot of current through 2Ohms will cause VSTOR to drop.

    Regards,

    Mike Emanuel

  • 0 in reply to Michael Emanuel35
    Prodigy 10 points

    Thank you for your response.

    I understand the point about the maximum resistance of 2 ohms between VBAT and VSTOR.

    This time, we are considering a circuit that uses a battery.
    The battery will be connected to VBAT (pin 14), and the load will be connected to VSTOR (pin 15).

    Regarding the current flowing to the load:
    At startup, the load is expected to draw approximately 200 mA for about 2 msec. After that, the current will drop to around 10–20 mA over the next 50 msec. The 10–20 mA state will last for about 1 second, after which the load will stop.

    Since the current from the battery flows from VBAT through VSTOR on the BQ25504, could you provide information on the allowable current that can flow in this path?

    Best regards,

  • +1 in reply to Ryuchi Tetsuya
    TI__Mastermind 40845 points

    Hello,

    The most likely problem you are going to experience is hitting VBAT_UV. 2 ohms with 200 mA is 400 mV drop from battery to VSTOR. When VBAT_UV is hit the FET connecting VBAT to VSTOR is disconnected. There is no internal current limit circuit from battery to VSTOR, just high Rdson.

    Regards,

    Mike Emanuel

  • 0 in reply to Michael Emanuel35
    Prodigy 10 points

    Hello,

    I apologize for the delayed response, and thank you for your reply.

    I appreciate your advice regarding the absence of an internal current limiting circuit and the potential issue with the 2-ohm resistance value.

    As the next step, we plan to create a prototype for evaluation and verify the impact of the voltage drop.

    Thank you very much.