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Original question:

BQ25792: No charge current

BQ25792: Unable to re-enter charging normally

Lumina Gui
Genius 3650 points
Part Number: BQ25792

Tool/software:

Dear TI Engineer,

We encountered a new issue when using BQ25792, which is that some devices cannot enter charging mode normally after the battery is discharged. We set the charger voltage to 16.8V for 4s battery, and the battery voltage is about 11.4V when the battery is fully discharged.

We have read the values of all registers that can and cannot be charged normally, and the comparison data obtained is as follows:

Fullscreen Register data recording.txt Download 
Abnormal charging register data 
Regaddr: 00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F 10 11 12 13 14 15 16 17 18 19 1A 1B 1C 1D 1E 1F 20 21 22 23 24 25 26 27 28 29 2A 2B 2C 2D 2E 2F 30 31 32 33 34 35 36 37 38 39 3A 3B 3C 3D 3E 3F 40 41 42 43 44 45 46 47 48 
data:	 26 06 90 00 64 8B 00 9A C3 05 EA 00 DC 4B 3D A2 85 78 00 61 36 AA C0 7A 55 00 9A 0B 0A 01 C0 00 20 40 00 80 10 00 20 40 00 00 00 00 00 00 B0 00 00 00 31 00 00 3B 04 3B 14 00 00 2C BC 33 14 02 BC 00 4E 00 1E 00 1C 00 08 
data:	 26 06 90 00 64 8B 00 9A C3 05 EA 00 DC 4B 3D A2 85 78 00 61 36 AA C0 7A 55 00 9A 0B 0A 01 D0 00 00 00 00 80 10 00 20 40 00 00 00 00 00 00 B0 00 00 00 41 00 00 3A E6 3B 88 00 00 2C 42 40 88 02 D8 00 5A 00 1D 00 1D 00 08 
data:	 26 06 90 00 64 8B 00 9A C3 05 EA 00 DC 4B 3D A2 85 78 00 61 36 AA C0 7A 55 00 9A 0B 0A 01 D0 00 00 00 00 80 10 00 20 40 00 00 00 00 00 00 B0 00 00 00 2D 00 00 3B 76 3A 62 00 08 2A EE 44 62 02 1C 00 56 00 00 00 1E 00 08 
data:	 26 06 90 00 64 8B 00 9A C3 05 EA 00 DC 4B 3D A2 85 78 00 61 36 AA C0 7A 55 00 9A 0B 0A 01 C0 00 20 40 00 80 10 00 20 40 00 00 00 00 00 00 B0 00 00 00 2D 00 00 3B AA 3A F0 00 14 29 D4 44 F0 02 64 00 4B 00 00 00 03 00 08  
data:	 26 06 90 00 64 8B 00 9A C3 05 EA 00 DC 4B 3D A2 85 78 00 61 36 AA C0 7A 55 00 9A 0B 0A 01 D0 00 00 00 00 80 10 00 20 40 00 00 00 00 00 00 B0 00 00 00 2D 00 00 3A E8 3A 9E 00 16 29 DA 44 9E 01 B8 00 4F 00 1D 00 00 00 08 
data:	 26 06 90 00 64 8B 00 9A C3 05 EA 00 DC 4B 3D A2 85 78 00 61 36 AA C0 7A 55 00 9A 0B 0A 01 C0 00 20 40 00 80 10 00 20 40 00 00 00 00 00 00 B0 00 00 00 2D 00 00 3B 04 3A 18 00 00 29 DA 45 18 01 96 00 4B 00 1D 00 00 00 08 
data:	 26 06 90 00 64 8B 00 9A C3 05 EA 00 DC 4B 3D A2 85 78 00 61 36 AA C0 7A 55 00 9A 0B 0A 01 D0 00 

Normal charging register data ：
Regaddr: 00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F 10 11 12 13 14 15 16 17 18 19 1A 1B 1C 1D 1E 1F 20 21 22 23 24 25 26 27 28 29 2A 2B 2C 2D 2E 2F 30 31 32 33 34 35 36 37 38 39 3A 3B 3C 3D 3E 3F 40 41 42 43 44 45 46 47 48 
data:	 26 06 90 00 64 8B 00 9A C3 05 EA 00 DC 4B 3D A2 85 78 00 61 36 AA C0 7A 55 00 9A 0B 4A 01 D0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 B0 00 00 00 AD 00 42 3A FA 3A EE 00 12 2D 82 2F EE 02 EE 00 4F 00 1B 00 2F 00 08 
data:	 26 06 90 00 64 8B 00 9A C3 05 EA 00 DC 4B 3D A2 85 78 00 61 36 AA C0 7A 55 00 9A 0B 4A 01 D0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 B0 00 00 00 AC 00 42 3B 16 3A EE 00 06 2D 82 2F EE 02 EE 00 4E 00 1B 00 2D 00 08 
data:	 26 06 90 00 64 8B 00 9A C3 05 EA 00 DC 4B 3D A2 85 78 00 61 36 AA C0 7A 55 00 9A 0B 4A 01 D0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 B0 00 00 00 AC 00 44 3B 18 3A EE 00 14 2D 82 2F EE 02 EE 00 4F 00 1A 00 2C 00 08 
data:	 26 06 90 00 64 8B 00 9A C3 05 EA 00 DC 4B 3D A2 85 78 00 61 36 AA C0 7A 55 00 9A 0B 4A 01 D0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 B0 00 00 00 AF 00 3E 3B 18 3A EE 00 14 2D 82 2F EE 02 EE 00 4F 00 19 00 2F 00 08 

Compare the differences in register data：
Regaddr:                 1E  20  21  23  24  26  27  3132  3334
Abnormal charging data： C0  20  40  80  10  20  40  0031  0000
Normal charging data：   D0  00  00  00  00  00  00  00AD  0042


Functional definition of differentiation:
1Eh[bit4]：
VSYS Regulation Status (forward mode)
Type : R
POR: 0b
0h = Not in VSYSMIN regulation (VBAT > VSYSMIN)
1h = In VSYSMIN regulation (VBAT < VSYSMIN)


20h[bit5]：
VBAT over-voltage status
Type : R
POR: 0b
0h = Normal
1h = Device in over voltage protection

21h[bit6]：
VSYS over-voltage status
Type : R
POR: 0b
0h = Normal
1h = Device in SYS over-voltage protection

23h[bit7]
Charge status flag
Type : R
POR: 0b
0h = Normal
1h = Charge status changed

24h[bit4]
VSYSMIN regulation flag
Type : R
POR: 0b
0h = Normal
1h = Entered or existed VSYSMIN regulation

26h[bit5]
VBAT over-voltage flag
Type : R
POR: 0b
0h = Normal
1h = Enter VBAT OVP

27h[bit6]
VSYS over-voltage flag
Type : R
POR: 0b
0h = Normal
1h = Stop switching due to system over-voltage

From the register recording, there are some protection happens when the battery cannot charing. Do you have any ideas about this question?

The schematic is as below:

The link to another post on my case is

https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/1479775/bq25792-no-charge-current?tisearch=e2e-sitesearch&keymatch=BQ25792#

Thanks,

Best Regards

  • 0
    TI__Guru**** 166626 points

    Hi Lumina,

    On the schematic, what the 10kohm resistor from SWx to GND for?  I do not recommend those.

    Does the converter stop switching completely or does only charging stop?  If the host toggles the EN_HIZ bit, does switching/charging resume?

    Regards,

    Jeff

  • 0 in reply to Jeff F
    Genius 3650 points

    Hi Jeff,

    This resistor is used to reduce EMI. SW is connected to GND with RC and 10k resistors.

    Jeff F said:
    On the schematic, what the 10kohm resistor from SWx to GND for? 

    We captured the waveform and found that there is an output. VC2 is a Type-C charging port that can charge the battery when plugged into an adapter. VC1 is connected to a DC port and cannot charge the battery when the adapter is inserted.

    Jeff F said:
    Does the converter stop switching completely or does only charging stop?

    Thanks,

    Kind Regards

  • 0 in reply to Lumina Gui
    TI__Guru**** 166626 points

    Hi Lumina,

    The BAT and SYS OVP are not unexpected if the battery pack protector FET opens while charge is enabled.  The charger only sees the minimum recommended capacitance at BAT, charges to OVP, turns off for 30ms, restarts and repeats.  To prevent, you can add 200uF cap to BAT pin. 

    Regarding VAC1 port not charging, ACDRV1 does not auto turn on unless VAC2 < UVLO voltage, i.e. applied voltage at VAC2 must be removed.  The input current limit on VAC1 is set to the lower of D+/D- negotiated value (lowest is 500mA) or ILIM_HIZ resistor clamp (set to 1.5A on the schematic.  If D+/D- are floating, the negotiated value is 3A.  What do the status and fault registers report immediately after VAC1 is applied?

    Regards,

    Jeff