• State Resolved
  • Locked Locked
  • Replies 5 replies
  • Answers 1 answer
  • Subscribers 62 subscribers
  • Views 447 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

BQ25792: Vsys voltage VS Vbat voltage

Fabio Gou
Intellectual 2500 points
Part Number: BQ25792

I want to know whether this picture is wrong. This is Figure 9-6. Typical System Voltage vs Battery Voltage for a 2S Battery Configuration.

The purple curve(charge enabled curve),  Vsys=Vbat+Icharge*Rds

Why Vsys is smaller than Vbat ?

  • 0
    TI__Intellectual 2500 points

    Two more question:

    1. 

    I noticed the REGN LDO output voltage is 5V. 

    In battery only condition, if Vbat is just 3.5V or 4V, how could the battery turn on the LDO?   and drive Q1 Q2 Q3 Q4?

    2.

    In the ship mode, the  i2C is still working. And shutdown mode, I2C is closed.

    Both turn off the BATFET and Extern FET. 

    So, In the ship mode, How does the battery power the I2C circuit diagram? Via the BATP pin?

  • +1 in reply to Fabio Gou
    TI__Guru*** 143910 points

    Hi Fabio,

    I think you are correct about Figure 9-6.  I am currently updating the datasheet and will submit this for correction.

    Regarding REGN output, in battery only the REGN voltage is not provided.  The battery powers an in internal linear regulator, i.e. the internal rail is not higher than the battery voltage, except for the SDRV pin as explained below.

    The internal BATFET cannot be turned off (I have updated that in the soon-to-release datasheet update).  In ship mode, BATP is the input to a charge pump that powers the SDRV pin.

    Regards,

    Jeff

  • 0 in reply to Jeff F
    TI__Intellectual 2500 points

    question2: But the REGN voltage power Q1 Q2 Q3 Q4. In the OTG mode, How could the MOSFET work when battery voltage is 4V?  The another internal linear regulator power Q1Q2Q3Q4 too?

    qustion3: But how the battery power the I2C circuit?

  • 0 in reply to Jeff F
    TI__Intellectual 2500 points

    question2: But the REGN voltage power Q1 Q2 Q3 Q4. In the OTG mode, How could the MOSFET work when battery voltage is 4V?  The another internal linear regulator power Q1Q2Q3Q4 too?

    qustion3: But how the battery power the I2C circuit?

  • 0 in reply to Fabio Gou
    TI__Guru*** 143910 points

    Hi Fabio,

    The high side FETs are driven by BTST cap voltage.  In OTG, REGN is the higher of BAT or PMID voltage, clamped to 5.2V.

    Regards,

    Jeff