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Original question:

BQ25713: BQ25713 is not able to trigger the charger side High Drive Mosfet Q6 resulting no movement of charge into the battery...

BQ25713: BQ25713

Akhil Hegde
Prodigy 70 points
Part Number: BQ25713
Other Parts Discussed in Thread: BQSTUDIO

Hi there,

Recently I had purchased a BQ25713 EVM and had tested the working of the same with the help of the guide given out by the TI. 

The datasheet of BQ25713 was referred to set the configuration to the EVM. The complete working of the EVM with a battery pack and system was tested and verified.

After understanding the working, We have developed custom pcb using BQ25713  exactly as EVM schematic, which has been posted below. 

The working of the pcb for the given schematic was verified with a few sets of same boards. The components used for pcb was same throughout the batch . But, one of the board of the same batch was not able to charge the battery pack. Probable reason found out while debugging the board, was that the mosfet Q6 doesnt seem to be switching.  The voltage between drain and source of mosfet Q6 in this particular board is 12.3 when 14 volts was given on input from charger whereas in the other WORKING boards, its 1.7620 V with same input .With charger connected and battery disconnected, the system voltage observed was 1.24 V(instead of12.3V which was set using using bqstudio also the working of the mosfet was verified by verifying the diode drop and Drain source resistance). This part seems to be causing the whole issue as the Vsys voltage in the faulty board 1.3V whereas in that of other working boards, its 12.3 V and the battery pack doesnt charge even when supply voltage is given. Some of the other observation are that REGN is giving regulated 6V output properly and when the battery pack is connected the VSYS voltage is equal to pack voltage(which is expected and correct) irrespective of the charger source being connected or not. 

Just wanted to know what could be possible reason for this behavior of the board.

Thanks in advance!!.

  • 0
    TI__Expert 4285 points

    Hi Akhil,

    It seems on the "bad" board, Q6 is not turned on. Can you check voltage at HDRV1? If you see same gate voltage, then Q6 itself is faulty.

    On top of that, here are some other tips for debug:

    - it is always a good practice to check status registers, 0x20 and 0x22, making sure there is no fault reported, which will otherwise help debug as well.

    - read back ADC, making sure what device "sees: are the same as you've applied.

    Best Regards,

    Linhong

  • 0 in reply to Linhong Qin
    Prodigy 70 points

    Hi Linhong,

    As u mentioned , the voltage at HDRV1 in the faulty board is 1.2V where in other working boards, its around 10V. So definitely the available gate voltage is not sufficient to turn on the mosfet.

    And coming to status registers, there is a fault popping up in 0x20 register, the adapter seems to be recognized with its voltage (as seen in VBUS voltage readback) but the ic seems to detect some kind of system short( because sys_short bit in charge status register is high ).Also system voltage and battery voltage readback registers are not updating in the bqstudio even with adc's set. Even when i try to set system short disable to high in the charge option 0 register, in charge status register the sys short is still remains high. Just to mention, there is no load connected to the system side output and just the battery and the charging source are connected to the charger pcb.

    Best Regards,

    Akhil

  • 0 in reply to Akhil Hegde
    TI__Expert 4285 points

    HI Akhil,

    If there is a short, converter won't turn on. We need to clear the faults first.

    Please measure the voltages of below pins and compare to a "normal" board, I suspected some problems on the output side(BAT/SYS).

    • CELL_BATPRES
    • SRP/SRN
    • BATDRV 
    • SYS( I think you said it's low, which is abnormal because there is no load connected. it might get short from BAT)

    and related circuit if needed.

    Best Regards,

    Linhong

  • 0 in reply to Linhong Qin
    Prodigy 70 points

    hey,

    My argument here is that if its really a shorting fault, then how is Vsys giving battery voltage whenever the battery is connected (we get battery voltage through Vsys even  when the battery is connected after charger is connected).I have done a comparison of voltages in working and faulty boards which is tabulated below. 

    Working Faulty

    CELL_BATPRES

    (for 4s config)

    		 1.5 V/4.5 V   1.5 V/4.5 V 
    SRP/SRN 12.5V 0V
    BATDRV  6.36V 0V
    VSYS 12V 1.32V

    The above test was performed with just the charger connected (battery unconnected). 

      

    In general, no shorts or wrong mounting of components on the board.

    One more observation - I tried to change the Sys Short bit in the Charger Status Register to zero (by default it was one when board was initialized) and tried to write it. While reading the registers, sys short was low but  IINDPM bit was set high and when i tried to set current charge current, the communication was getting disabled (stopped getting Acknowledgement from the board) and when i reset it , the board gets acknowledgement but current would be set to zero. Changing current would again result in communication loss.

  • 0 in reply to Akhil Hegde
    TI__Expert 4285 points

    Hi Akhil,

    SRP/SRN and VSYS voltages are not normal. I recommend you remove components one by one on these pins to isolate the problem. Forcing charge under such condition may cause damages.

    And I assume IC soldering is solid good.

    By the way, do you monitor current as well? What's the current for IBUS, IBAT and ISYS?

    Best Regards,

    Linhong

  • 0 in reply to Linhong Qin
    Prodigy 70 points

    Hey Linhong,

    The issue was with the Capacitor C40 which is placed in between pins SRP and SRN. I just had to replace it with a new capacitor of same capacitance and all parts of the circuit started working fine. 

    Thanks a lot!!