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bq24297 VSYS

Nikolaus Schaller
Intellectual 330 points
Other Parts Discussed in Thread: BQ24297

What is the voltage of VSYS? I just see 3.35V when operating w/o battery and external USB (5.05V). 3.35V looks like an almost empty battery to the system.

Is it possible to program the VSYS voltage?

  • 0
    TI__Guru 57341 points

    Yes, you may program VSYS by REG01[3:1]. Thanks!

  • 0 in reply to Ning T
    Intellectual 330 points

    NT35830 said:

    Yes, you may program VSYS by REG01[3:1].

    Ah, thanks!

    What I am now not understanding is that these bits are called "minimum voltage limit".

    What does "minimum" mean in this context? Does it mean that the bq24297 switches off if it can't maintain VSYS at this level?

    And what happens if the system is powered by battery (seems to be indicated by VSYS_STAT in REG08[0:0]). Is this then treated as "empty" battery? Or does the bq24297 then work as an upward converter from VBAT to VSYS to maintain this voltage?

    BR,

    Nikolaus Schaller

  • 0 in reply to Nikolaus Schaller
    TI__Guru 57341 points

    Please refer to Section 9.3.2.1 on page 20 and Fig13 of the d/s for the details. 

    The device deploys Narrow VDC architecture (NVDC) with BATFET separating system from battery. The minimum system voltage is set by REG01[3:1]. Even with a fully depleted battery, the system is regulated above the minimum system voltage (default 3.5 V).

    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.

    When the battery charging is disabled or terminated, the system is always regulated at 150 mV above the minimum system voltage setting. The status register REG08[0] goes high when the system is in minimum system voltage regulation.

    Thanks!