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BQ24171: STAT operation quesiton

Patrick Chen
Mastermind 8875 points
Part Number: BQ24171
Other Parts Discussed in Thread: BQ24172

Hello

             Customer set TS temperature is 45°C and it is indicate blinking of STAT pin and charge suspend while  45°C. But if on 43°C ~44°C , customer to do AC plug (AC to 12VDC to battery charge). They will find STAT waveform from Fig 1 to Fig2. The STAT happen blinking while AC plug under 43°C ~44°C . But if under 43°C, STAT pin will not happen blinking while AC plug. What is the issue root cause? Thank you. 

Fig1

Fig2

BR

Patrick

  • 0
    TI__Guru**** 166936 points

    Hi Patrick,

    What is the battery voltage and charge current when this happens?  Can you repeat the test, adding charge current and battery voltage to the plot above? 

    Regards,
    Jeff

  • 0 in reply to Jeff F
    Mastermind 8875 points

    Hello

               Below has two different battery condition. Please refer to below waveform. Has any comments for it? Thank you. 

    1. battery 8.08V

    2. Battery 7.2V

     


    BR

    Patrick

  • 0 in reply to Patrick Chen
    TI__Guru**** 166936 points

    Patrick,

    I am confused as to where the channel 4 ground really is.  Is it at the marker or at the point where channel 1 goes low?

    I have been able to duplicate on the bench.

    Regardless, BQ24171 is JEITA and so 45C should not result in 1HZ blinking.  I tried to reproduce using an EVM but cannot.  You agree that the 2 plots on the left are correct, with the top going into CV with reduced VFB and the bottom resuming charge, yes? 

    The plots on the right are behaving as if TS decision is being made and latching when the TS is at VT5 instead of VT4.  If you toggle /CE, does charge resume? If there you add a 1-100nF capacitor from TS to ground, does the behavior change?  Are we certain the ICs are BQ24171 and not BQ24172, which is not JEITA and therefore should stop charge at VT4?

    Regards,

    Jeff

  • 0 in reply to Jeff F
    Mastermind 8875 points

    Hello

                Customer have some questions as below. Thank you. 

    1. At 44°C, STAT pin signal is normal while AC plug in. But if AC plug out, STAT pin will blinking. What is the behavior root cause? 

    2. STAT pin is High and charging current is zero while AC plug in. But AC plug out, why device start to charging again? 

    BR

    Patrick

  • 0 in reply to Patrick Chen
    TI__Guru**** 166936 points

    Patrick,

    I am unable to reproduce this behavior on the bench using an EVM.  It appears that the BQ24171 is behaving as a BQ24172 due to noise on TS.  Can you add a 10-100nF from TS pin to ground and is if that fixes the issue?

    Regards,

    Jeff