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Original question:

BQ40Z50-R2: wakeup from Shutdown mode question

BQ25792: BQ25792 drive BQ40Z50

Steven(Shenzhen) Shi
Mastermind 30515 points
Part Number: BQ25792
Other Parts Discussed in Thread: BQ40Z50, , , BQ40Z50-R2

Hi team，

There is a issue for BQ25792 to drive BQ40Z50.

When I disconnected 5V to BQ40Z50 it became shutdown mode.

Then when I used 5V to wake up BQ40Z50 I found VBAT was 5V for 2.2S then drop to 0V which was not able to wake up BQ40Z50(Need 3V to wake up).

When I removed battery pack BQ40Z50 the VBAT was stable at 5V.

Could you help me fix this issue? Does this related to the current limit of BQ25792?

  • 0
    TI__Guru**** 170026 points

    Hi Steven,

    What voltage is the scope plot of?  I see 7 pulses of something which implies that one of a protection features that allow 7 retries has activated and then put the device in HiZ.  Can you read the I2C status and fault registers (REG0x1B to REG0x27) one time immediately after this occurs and reply back? 

    Regards,

    Jeff

  • 0 in reply to Jeff F
    TI__Mastermind 30515 points

    Hi Jeff，

    This voltage is VBAT voltage for BQ25792. The below is the REG value after the device enter HIZ mode.

    REG_NO VALUE
    00 12
    01 0348
    03 0032
    05 2b
    06 00C8
    08 C3
    09 05
    0A 01
    0B 00DC
    0D 03
    0E FB
    0F A2
    10 10
    11 40
    12 00
    13 21
    14 16
    15 AA
    16 A0
    17 74
    18 41
    19 00C8
    1B 4F
    1C 2A
    1D 00
    1E 10
    1F 10
    20 00
    21 00
    22 00
    23 00
    24 00
    25 00
    26 00
    27 00
    28 00
    29 00
    2A 00
    2B 00
    2C 00
    2D 00
    2E 30
    2F 00
    30 00
    31 0000
    33 0000
    35 13AB
    37 0000
    39 0000
    3B 0000
    3D 0000
    3F 0000
    41 0000
    43 0000
    45 0000
    47 00
    48 08

    Best,

    Steven

  • 0 in reply to Steven(Shenzhen) Shi
    TI__Guru**** 170026 points

    Hi Steven,

    The registers are not reporting HiZ state but are reporting VINDPM (meaning too much load on SYS+BAT for the input adapter). Does VBUS voltage dip below 4.3V during the pulses above?  Are you certain that there is only one I2C read after either one of the 7 pulses or at the end after the device enters HiZ?  A second register read clears the fault registers.

    Regards,

    Jeff 

  • 0 in reply to Jeff F
    TI__Guru**** 170026 points

    HI Steven,

    I just now attached a 2S battery with BQ40Z50 that was in shutdown to my BQ25792EVM and it started up without an issue.  Are you using the EVM or your own board?  If EVM, is the shipFET attached and working as expected?  If your own board, can you send the schematic?

    Regards,

    Jeff

  • 0 in reply to Jeff F
    TI__Guru** 106020 points

    Hello Steven,

    Here are some of the tests we performed to try to re-create your issue with the EVMs:

    • Tested with both DSG FET and CHG FET off using manual control on the BQ40z50.
      • Charger went to OVP then UVP, cycled forever (not 7 pulses).
    • Tested with CUV protection triggered.
      • Gauge still allowed pre-charging normally through only the CHG FET.
    • Shutdown the gauge manually to let the charger wake the gauge up.
      • Woke up normally and began charging.

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    TI__Mastermind 30515 points

    Hi Jeff and Wyatt,

    The attachment is the schematic.

    I tried to use EVM to test the bug but BQ25792 waked up BQ40Z50 as normal.

    Best,

    Steven

  • 0 in reply to Wyatt Keller
    TI__Mastermind 30515 points

    Hi Jeff and Wyatt,

    Here is the block diagram for the system.

    My test process is shown as below:

    1.Remove DC input of the BQ25792.--Success.

    2.BQ40Z50-R2 enter Shutdown mode. --Success.

    3. Apply 5V DC input to BQ25792, BQ40Z50 will not recover from Shutdown mode. 

    -----BQ40Z50 not recover from Shutdown mode since vPack is smaller than Charger Present Threshold(3V). 

    4. But when we remove the BQ40Z50 battery pack from BQ52792, and apply DC input to BQ25792,BQ25792 can have 5V output. I suspect that the BQ40Z50 sink current is too high and pull the 5V output down. So BQ40Z50 will not recover.

    Best,

    Steven

  • 0 in reply to Steven(Shenzhen) Shi
    TI__Guru**** 170026 points

    Steven,

    The BQ40Z50 sink current is very low.  What is the current of the MCU which is also pulling current from the BAT pin?  When in trickle charge, the charger BAT output current is only 100mA and then precharge is default set low as well.  If you lower VBAT_LOWV % and increase precharge current both in REG0x08 of BQ25792, does that help?

    Regards,
    Jeff