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BQ25898: Power Path function

Danilo A.
Mastermind 28710 points
Part Number: BQ25898

Hi Team,

A customer would like to understand better how the Power Path technology works specially the SYS output voltage will be for each point of the battery cycle. In the datasheet, it has some guidance that says Vsys = Vbat + 50mV as long as Vbat > Vsysmin. Then, when Vbat<Vsysmin, Vsys = Vsysmin + 250mV.


So, assuming the typical values, as the battery discharges from 4.2V to 3.75V, Vsys = Vbat+50mV. Then, when Vbat drops below 3.75V, Vsys will jump up to Vsysmin + 250mV = 4.0V, and it will stay regulated at 4.0V as the battery discharges from 3.75V down to 3.0V. Is this correct?

Please confirm the following:
USB power present, battery charging: Vsys = ?
No USB power present, battery fully charged at 4.2V: Vsys = ?
No USB power present, battery nearly empty at 3.0V: Vsys = ?

What is the SYS output voltage going to be in each of these states?

Regards,

Danilo

  • 0
    TI__Guru 57701 points

    Danilo,

    9.2.6.1 Narrow VDC Architecture on the d/s applies when valid VBUS is present.

    If only battery is present and the voltage is above depletion threshold (VBAT_DPLZ), the BATFET turns on and connects battery to system. VSYS is VBAT minus BATFET voltage drop. Please refer to 9.2.6.3 Supplement Mode on the d/s for the details.

     

    USB power present, battery charging: Vsys = ? => Please refer to Figure 12. V(SYS) vs V(BAT) on the d/s
    No USB power present, battery fully charged at 4.2V: Vsys = ? => similar to VBAT (BAT pin voltage)
    No USB power present, battery nearly empty at 3.0V: Vsys = ? => Similar to VBAT (BAT pin voltage)

     

    It is highly recommended to get familiar with the charger operation by evaluating the EVM.

    Thanks,

    NIng

  • 0 in reply to Ning T
    Prodigy 50 points

    Hi Ning, thanks for the information. This is very helpful. 

    What about the BQ25898C variant? The datasheet for the C version does not have a section on Narrow VDC architecture. Can I assume that the Vsys behavior is similar? 

  • 0 in reply to Chris Fernandez1
    TI__Guru 57701 points

    Danilo,

    Yes, the principle of BQ25898C is similar to other BQ25898x devices.

    Thanks,

    Ning.

  • 0 in reply to Ning T
    Prodigy 50 points

    This resolved my issue. It says there's a button to click, but I don't see such a button. 

    Thanks for the help!

  • 0 in reply to Chris Fernandez1
    TI__Guru 57701 points

    Hi,

    It's great that your question is resolved. This thread is closed.

    Thanks,

    Ning,