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BQ25798: Battery Charge Does not Start

Egemen Aksoy
Expert 1005 points

Part Number: BQ25798

Tool/software:

Hello,
We are using the BQ25798 battery charging IC in our project. VBUS = 5V, and the battery pack we use is a 1s5p Li-ion 3.6V.

Firstly, when the battery is connected and then VBUS is supplied, the battery does not start charging.
Similarly, if the battery is connected first and the device is then powered on via VBUS, the VBUS side does not become active and no current is drawn.
Afterward, if the battery is removed while VBUS is connected, the device shuts down.
However, if VBUS is applied first and then the battery is connected, current is only drawn from the VBUS side.
Then, if VBUS is turned off, the device continues to operate without shutting down.
In all cases, whichever power source is connected first takes priority.

I have attached the charger register that we using.

Fullscreen charger registers.txt Download 
Just VBus
 REG0 -> 0x5
 REG1 -> 0x1
 REG2 -> 0xa4
 REG3 -> 0x1
 REG4 -> 0x2c
 REG5 -> 0x2b
 REG6 -> 0x0
 REG7 -> 0xb6
 REG8 -> 0x43
 REG9 -> 0x5
 REGa -> 0x23
 REGb -> 0x0
 REGc -> 0xdc
 REGd -> 0x4b
 REGe -> 0x3d
 REGf -> 0xa2
 REG10 -> 0x30
 REG11 -> 0x41
 REG12 -> 0x0
 REG13 -> 0x1
 REG14 -> 0x0
 REG15 -> 0xaa
 REG16 -> 0x70
 REG17 -> 0x7a
 REG18 -> 0x54
 REG19 -> 0x0
 REG1a -> 0xb6
 REG1b -> 0xf
 REG1c -> 0xa
 REG1d -> 0x0
 REG1e -> 0x10
 REG1f -> 0x18
 REG20 -> 0x0
 REG21 -> 0x0
 REG22 -> 0x0
 REG23 -> 0x0
 REG24 -> 0x0
 REG25 -> 0x0
 REG26 -> 0x0
 REG27 -> 0x0
 REG28 -> 0x0
 REG29 -> 0x0
 REG2a -> 0x0
 REG2b -> 0x0
 REG2c -> 0x0
 REG2d -> 0x0
 REG2e -> 0x0
 REG2f -> 0x0
 REG30 -> 0x0
 REG31 -> 0x0
 REG32 -> 0x0
 REG33 -> 0x0
 REG34 -> 0x0
 REG35 -> 0x13
 REG36 -> 0xb6
 REG37 -> 0x0
 REG38 -> 0x0
 REG39 -> 0x0
 REG3a -> 0x0
 REG3b -> 0x0
 REG3c -> 0x0
 REG3d -> 0x0
 REG3e -> 0x0
 REG3f -> 0x0
 REG40 -> 0x0
 REG41 -> 0x0
 REG42 -> 0x0
 REG43 -> 0x0
 REG44 -> 0x0
 REG45 -> 0x0
 REG46 -> 0x0
 REG47 -> 0x0


VBus+Vbat

 REG0 -> 0x5
 REG1 -> 0x1
 REG2 -> 0xa4
 REG3 -> 0x1
 REG4 -> 0x2c
 REG5 -> 0x2b
 REG6 -> 0x0
 REG7 -> 0xb6
 REG8 -> 0x43
 REG9 -> 0x5
 REGa -> 0x23
 REGb -> 0x0
 REGc -> 0xdc
 REGd -> 0x4b
 REGe -> 0x3d
 REGf -> 0xa2
 REG10 -> 0x30
 REG11 -> 0x41
 REG12 -> 0x0
 REG13 -> 0x1
 REG14 -> 0x0
 REG15 -> 0xaa
 REG16 -> 0x70
 REG17 -> 0x7a
 REG18 -> 0x54
 REG19 -> 0x0
 REG1a -> 0xb6
 REG1b -> 0xf
 REG1c -> 0xa
 REG1d -> 0x1
 REG1e -> 0x10
 REG1f -> 0x0
 REG20 -> 0x0
 REG21 -> 0x0
 REG22 -> 0x0
 REG23 -> 0x0
 REG24 -> 0x0
 REG25 -> 0x0
 REG26 -> 0x0
 REG27 -> 0x0
 REG28 -> 0x0
 REG29 -> 0x0
 REG2a -> 0x0
 REG2b -> 0x0
 REG2c -> 0x0
 REG2d -> 0x0
 REG2e -> 0x0
 REG2f -> 0x0
 REG30 -> 0x0
 REG31 -> 0x0
 REG32 -> 0x0
 REG33 -> 0x0
 REG34 -> 0x0
 REG35 -> 0x13
 REG36 -> 0xb6
 REG37 -> 0x0
 REG38 -> 0x0
 REG39 -> 0x0
 REG3a -> 0x0
 REG3b -> 0x0
 REG3c -> 0x0
 REG3d -> 0x0
 REG3e -> 0x0
 REG3f -> 0x0
 REG40 -> 0x0
 REG41 -> 0x0
 REG42 -> 0x0
 REG43 -> 0x0
 REG44 -> 0x0
 REG45 -> 0x0
 REG46 -> 0x0
 REG47 -> 0x0

Vbat

 REG0 -> 0x5
 REG1 -> 0x1
 REG2 -> 0xa4
 REG3 -> 0x1
 REG4 -> 0x2c
 REG5 -> 0x2b
 REG6 -> 0x0
 REG7 -> 0xb6
 REG8 -> 0x43
 REG9 -> 0x5
 REGa -> 0x23
 REGb -> 0x0
 REGc -> 0xdc
 REGd -> 0x4b
 REGe -> 0x3d
 REGf -> 0xa2
 REG10 -> 0x30
 REG11 -> 0x41
 REG12 -> 0x0
 REG13 -> 0x1
 REG14 -> 0x0
 REG15 -> 0xaa
 REG16 -> 0x70
 REG17 -> 0x7a
 REG18 -> 0x54
 REG19 -> 0x0
 REG1a -> 0x32
 REG1b -> 0x0
 REG1c -> 0x0
 REG1d -> 0x1
 REG1e -> 0x0
 REG1f -> 0x0
 REG20 -> 0x0
 REG21 -> 0x0
 REG22 -> 0x0
 REG23 -> 0x0
 REG24 -> 0x0
 REG25 -> 0x0
 REG26 -> 0x0
 REG27 -> 0x0
 REG28 -> 0x0
 REG29 -> 0x0
 REG2a -> 0x0
 REG2b -> 0x0
 REG2c -> 0x0
 REG2d -> 0x0
 REG2e -> 0x0
 REG2f -> 0x0
 REG30 -> 0x0
 REG31 -> 0x0
 REG32 -> 0x0
 REG33 -> 0x0
 REG34 -> 0x0
 REG35 -> 0x13
 REG36 -> 0xb6
 REG37 -> 0x0
 REG38 -> 0x0
 REG39 -> 0x0
 REG3a -> 0x0
 REG3b -> 0x0
 REG3c -> 0x0
 REG3d -> 0x0
 REG3e -> 0x0
 REG3f -> 0x0
 REG40 -> 0x0
 REG41 -> 0x0
 REG42 -> 0x0
 REG43 -> 0x0
 REG44 -> 0x0
 REG45 -> 0x0
 REG46 -> 0x0
 REG47 -> 0x0

Could you review our register settings and help us if there is any issue?

Best regards,

Egemen

  • 0
    TI__Guru**** 180116 points

    Hi Egemen,

    REG0x1F is reporting TS Cold meaning the TS pin voltage is reporting the battery pack is too cold to charge.  To hardware disable TS function, use same resistors for the resistor divider from REGN to TS to GND.  To software disable TS, use set REG0x18[0]=0.

    Regards,

    Jeff

  • 0 in reply to Jeff F
    Expert 1005 points

    Hello Jeff,

    REG1b -> 0xf
    REG1c -> 0xa
    REG1d -> 0x1
    REG1e -> 0x0
    REG1f -> 0x0
    REG20 -> 0x0
    REG21 -> 0x0

    Charger status registers and fault registers is read like above.

    According to the status registers, VBUS_STAT_3:0 5h: Unknown adaptor (3A) and charge does not start.

    Why the status register responds unknowing adaptor?

    Best regards,

    Egemen

  • 0 in reply to Egemen Aksoy
    TI__Guru**** 180116 points

    HI Egemen,

    Unknown adapter simply means the charger could not identify the adapter's current rating and IINDPM defaults to 3A.  If charge status is NOT charging then either

    1. /CE pin = high or CE bit=0 has charge disabled.

    2. EN_HIZ bit = 1 which can be autoset if there is an over current fault

    Regards,

    Jeff