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BQ25120A: Clarification on safety timer and BAT_OVP fault documentation

Vic Thompson
Prodigy 20 points
Part Number: BQ25120A

Good morning,

I have 2 questions related to documentation of the safety timeout and an incompletely documented fault relating to battery overvoltage.

1. The safety timer is described as having a programmable range of tMAXCHG between 2 - 540 minutes on datasheet pg 12, but the selectable timeouts in the VIN_DPM and Timers register appear to be 30 minutes/3 hrs/9 hrs.  Please clarify the timeout range and, if different than the register description, how the full range may be selected.

pg.12

pg. 46

2. The state diagram on pg 32 implies Battery Overvoltage causes a fault when the IC is in Ready state or Done state.  However there is no mention of Battery overvoltage elsewhere in the documentation nor is this fault described in the Faults/Fault Mask register on pg 37.  Please clarify what this fault is, what are the limits on BAT_OVP, and if it is reported as a fault.

pg. 32

  • 0
    TI__Genius 12485 points
    Hi Vic,

    Safety timer bit: The full 9hour can be selected by using bits 10 for the safety timer bits.

    BATOVP: Sorry about that, BAT_OVP is an internal signal and shouldn't see a mention on the datasheet. The device will terminate charging when the charging process is complete. I will update the datasheet to reflect this change. The device only has BAT_OCP which can be read on the faults register.

    regards,
    Gautham
  • 0 in reply to Gautham
    Prodigy 20 points

    Hi Gautham,

    Thanks for the reply, but would you please provide a bit more detail on the safety timer?  I know about the selection of 9 hrs by specifying TMR_1:TMR_0 as 10. 

    What I would like to know is how to decrease the time to a timeout less than 3 hours.  As I wrote earlier, the documentation states that the safety timer has a programmable range which can be decreased to as low as 2 minutes (pg. 12) -- but there is no indication on how to select this in the VIN_DPM and Timers register description on pg. 46.

    So, how is a timeout less than 3 hours selected?  Or is there an error in the programmable limits shown on pg. 12?

     

  • 0 in reply to Vic Thompson
    TI__Genius 12485 points

    Vic,

    The electrical spec table indicates only the min/ max on the timer by design the smaller end is coming for precharge which is 0.1x fast charge timer. The device only has the bits you have identified. 

    What is the exact value you are looking for? There is a 30 min option. 

    regards,

    Gautham