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BQ24195L: Configuring of VSYS Voltage Thresholds

Josh Homerston
Prodigy 10 points

Part Number: BQ24195L

Tool/software:

Hi all,

hoping someone can confirm the configuration required for the BQ24195L charger IC to achieve a certain functionality. Having read the DS thoroughly and also having reviewed the reference schematics I remain uncertain on how to set VSYS to a desired voltage.

I'm aware the BQ24195L supports a minimum voltage level ( SYS_MIN[2:0] ), but my question is more related to limiting the upper value of VSYS. Is this accomplished using the VREG[5:0] values ( Charge Voltage Limit ), or the VINDPM[3:0] values (Input Voltage Limit).

My goal is to achieve a regulation of 5V (VBUS) -> 3.6V, and have the Li-Ion cell take over the power-path supply (if present, of course) when VBUS is removed. However various devices attached to VSYS only have a VMAX rated to 4.1V, I am hoping to ensure the BQ24195L can be configured to never deliver more than this value even if a 5V VBUS supply is present.

Many thanks in advance.

  • 0
    TI__Guru 60341 points

    Hi,

    Referring to the spec below, the VSYS is up to VBAT+150mV.

    In 8.3.2.1 Narrow VDC Architecture on the d/s, When the battery is below minimum system voltage setting, the BATFET operates in linear mode (LDO mode), and the system is 150 mV above the minimum system voltage setting. As the battery voltage rises above the minimum system voltage, BATFET is fully on and the voltage difference between the system and battery is the VDS of BATFET

    Thanks,

    Ning

  • 0 in reply to Ning T
    Prodigy 10 points

    Hi Ning,

    thanks for your reply.

    To follow on, how is the 'VBAT' upper threshold managed? Is that the value held across the VREG[5:0] registers, or the value held in the VINDPM[3:0] registers?

    Kind regards,

    Josh

  • 0 in reply to Josh Homerston
    TI__Guru 60341 points

    Hi Josh,

    When VREG[5:0] setting is 4.2V, the max VSYS is up to 4.35V typically.

    Thanks,

    Ning