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BQ25798: Questions about the Power-On Reset (POR)

Mathis CEDRA
Prodigy 30 points
Part Number: BQ25798
Other Parts Discussed in Thread: BQ25790,

Hi,

I have several inquiries related to the Power-On Reset (POR) feature in the BQ25790/92/98 charging controllers:

[Q1]: Why is POR present across all ranges of USB-C Power Delivery chargers? I am curious about the rationale behind including POR in all USB-C Power Delivery charger models.

[Q2]: Why is POR not user-disableable? Is this related to any industry standards? I would like to understand why the POR functionality cannot be disabled by the user. Is there a specific industry norm governing this?

Currently, I am evaluating the feasibility of integrating a USB-C Power Delivery architecture (using BQ25798 + TPS25750D) for designing a Li-ion power bank (ranging from 1S to 4S). Each Li-ion cell in the bank has its own individual protection circuitry (including Under Voltage Protection (UVP), Over Voltage Protection (OVP), Over Current Protection (OCP), and thermal protection). Unfortunately, all available charger families include a POR. Specifically, if the battery pack enters an undervoltage protection state, the BQ25798 loses power and subsequently loses its configuration settings.

[Q3]: Are there any USB-C Power Delivery solutions available that do not include a POR? or a solution to reprogram the charger in standalone?


Thank you for your assistance.

Mathis

  • 0
    TI__Guru**** 166306 points

    Hi Mathis,

    All of TI's (and competitors that I am aware of) use registers to configure analog control loops and digital state machine.  These registers reset to defaults at POR. The default settings are intended to be a safe configuration for standalone charging.  The BQ25798+TPS25750D solution has TPS25750D firmware that programs the BQ25798 registers over I2C at power up.

    Regards,

    Jeff