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Original question:

BQ24295: VSYS stays off if PMID has load on startup, w/o battery.

BQ24295: BQ24295 Q4 turn off conditions when discharge status

Julian Chen
Expert 2550 points
Part Number: BQ24295


Hi E2E,

Our customer test "Battery discharge test"  in chamber(-25 degree C) find that IC reach for NTC protection early.

The test table as below,

*We find the VREGN=0V @ 67%.

After this test, I ask for customer use  10K Variable resistance to test then find the NTC protection is 76% and 36% normally.

First, I doubt the battery can't work at -25 degree C lead to VREGN no output. But the PMIC still have voltage (2.997V). So MAYBE battery is normally.

Now Customer want to us to explain "what conditions will lead to Q4 be turned off when battery discharge"

I study the conditions and arrange it as below,

1. Battery voltage under 2.0V

2. NTC protection

Did I miss others conditions?

  • 0
    TI__Guru 57541 points
    Hi,

    Rereferring to 8.3.5.5.3 System Over-Current Protection on the d/s:
    If the system is shorted or exceeds the over-current limit, the device latches off BATFET. DC source insertion on VBUS is required to reset the latch-off condition and turn on BATFET.

    Thanks,

    Ning.
    Please click "This Resolved my issue" button if this post answer your question.
  • 0 in reply to Ning T
    Expert 2550 points

    Hi Ning,

    Thanks to your reply. I have another question.

    I study the REGN enable conditions,

    ==

    The REGN is enabled when all the conditions are valid.

    1. VBUS above VVBUS_UVLOZ

    2. VBUS above VBAT + VSLEEPZ in buck mode or VBUS below VBAT + VSLEEP in boost mode

    3. After typical 220-ms delay (100 ms minimum) is complete

    ==

    So in boost mode, VBUS need to above VVBUS_UVLOZ-and below VBAT+VSLEEP ?? BUT VBUS no output when boost mode. (Use Battery supplied)

    BTW, when use Battery supply, does PMID supply to LDO then convert to VREGN?

  • 0 in reply to Julian Chen
    TI__Guru 57541 points
    Hi,

    1) In boost mode, the condition 2 is "VBUS below VBAT + VSLEEP in boost mode".
    2) REGN ramps up before the device starts switching to support PMID voltage.

    Thanks,

    Ning.
    Please click "This Resolved my issue" button if this post answer your question.