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BQ25895: The SYS pin of BQ25895 has no power output

user6330332
Prodigy 50 points
Part Number: BQ25895

Hi

1. After disconnecting the external input source, write ‘1 ’to 'BATFET_DIS' of register Reg09 of BO25895, and make the chip enter sleep mode (with battery at this time), then input 6V/2A power to VBUS terminal. I have ensured that there is power input to VBUS, but found that there is no power output of SYS pin in some machines.At the same time, the BAT pin is not charging. Only when the external input power supply and battery are disconnected at the same time, and then the battery or external power supply is connected, the SYS pin will have the power output. For example, the BQ25895 can output or charge normally if the power is reset.

2. Question 1 appears probabilistically, we guess whether it is related to DMDP or I2C Watchdog Timer Setting, because I wrote 'I2C Watchdog Timer Setting' as' 00 '.

3.'I2C Watchdog Timer Setting' is written as' 00 '，What are the effects?

4.What is the effect of writing 'I2C Watchdog Timer Setting' as' 01 '?

The register configuration of BQ25895 when external power is connected

0X0 = 0X3F
0X1 = 0X5
0X2 = 0XBC
0X3 = 0X3A
0X4 = 0X10
0X5 = 0X7
0X6 = 0X5E
0X7 = 0X8D
0X8 = 0X3
0X9 = 0X54
0XA = 0X93
0XB = 0X16
0XC = 0X0
0XD = 0X94
0XE = 0X4C
0XF = 0X4E
0X10 = 0X50
0X11 = 0XA3
0X12 = 0X14
0X13 = 0X1B
0X14 = 0X39

BQ25895 register configuration when external power is not connected（NO ship mode）

0X0 = 0X3F
0X1 = 0X5
0X2 = 0XBC
0X3 = 0X3A
0X4 = 0X10
0X5 = 0X7
0X6 = 0X5E
0X7 = 0X8D
0X8 = 0X3
0X9 = 0X54
0XA = 0X93
0XB = 0X2
0XC = 0X0
0XD = 0X94
0XE = 0X4C
0XF = 0X4F
0X10 = 0X4F
0X11 = 0X23
0X12 = 0X14
0X13 = 0X3F
0X14 = 0X39

  • 0
    TI__Guru 57341 points

    Hi,

    We are working on it and will get back to you.

    Thanks,

    Ning.

  • 0 in reply to Ning T
    Prodigy 50 points

    Hi，Ning

    Any answers to the above questions?

  • 0 in reply to user6330332
    TI__Guru 57341 points

    Hi,

    We will get back to you later today.

    Thanks,

    Ning.

  • 0 in reply to Ning T
    TI__Guru** 105590 points

    Hello,

    Setting the watchdog timer setting to 00 means you do not need to reset the timer with the host. For the other settings of 40 seconds, 80 seconds and 160 seconds you will have to toggle the watchdog bit in REG03 to reset the timer, otherwise the default config will be loaded into the registers.

    I uploaded your register settings and tested with our EVM, when the VBUS is supplied the charger enables VSYS and begins charging. Can you explain your testing and the procedure you followed so I can try to replicate better?

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    Prodigy 50 points

    We found that only when VBUS was powered on, there was a probability that ship mode could not be exited. However, IIC was tried to wake up BQ25895, which indicated that it was possible to access VBUS without exiting ship mode.
    Test steps: After entering ship mode, access the VBUS power supply (adapter 6V/2A), and the cycle will occur after more than 1000 tests
    1. In terms of hardware, there is a little wrong design. There will be a 3.3V voltage between D+ and D- when the power is on.

  • 0 in reply to user6330332
    TI__Guru** 105590 points

    Hello,

    Are you testing with an EVM? I have tried to replicate but I do not see the same behavior, if you are using a custom board there may be something else preventing the chargers normal behavior when the adaptor in plugged in.

    It looks like in REG09 you have a reserved bit set to one, was this modified by your host?

    It also looks like you have power good and fast charging when the adaptor is plugged in which should mean the charger is working properly. It is in VBAT is below VSYSMIN.

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    Prodigy 50 points

    I haven't tried EVM entry test, REG09 sets a to 1 is sent by my host, and now found some problems on the host the program logic that it after send REG09 dormancy r, also read the battery voltage and other set operation immediately, so I doubt whether the host software logic make wrong BQ25895 appear on electricity

  • 0 in reply to user6330332
    TI__Guru** 105590 points

    Hello,

    I'm not sure I follow your wording, if you have charge enabled and the adaptor is plugged in with BATFET off, the charger should enable the BATFET. Can you share scope captures of VBUS, VBAT, and VSYS when you plug in the adaptor?

    Sincerely,

    Wyatt Keller