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BQ25792: Charging Current Not Increasing

Nishanth M32
Intellectual 295 points
Part Number: BQ25792
Other Parts Discussed in Thread: EV2400, ,

Hi,

I am using the BQ25792 as a boost charger for my 3S1P battery charging system. I changed the charging current REG03 register to 3000mA using EV2400 & Battery management Studio. But the charging current is not going more than 1.2A. For example If I set the charging current to 500mA means, it working perfectly, the charging current comes to 500mA. But in my case charging current must be 3A. Help me to solve the problem:

Input: 12V/5A Max

Battery: Li-Ion - 3Series & 1 Parallel

Charging Voltage: 12.6V

Required Charging Current: 3A

Current Situation:

Input Current Max: 1.240A

Battery Charging Current: 1.186A

I attached the register file and schematic.

BQ25792_3S_1P.txt 
* Created: Sun Apr 11 19:00:12 IST 2021
*
* Format: Register Name  tab Character,\t  Register Address  tab Character,\t  Hexadecimal register value.
* Device: BQ25790_92
* BQZ Container: Charger_2_00-bq25790_92.bqz
*
REG00	1A
REG01	04EC
REG03	012C
REG05	6A
REG06	0091
REG08	F2
REG09	05
REG0A	A3
REG0B	00DC
REG0D	4B
REG0E	3D
REG0F	A2
REG10	80
REG11	40
REG12	00
REG13	21
REG14	16
REG15	AA
REG16	C0
REG17	7A
REG18	54
REG19	0091
REG1B	0F
REG1C	6A
REG1D	01
REG1E	40
REG1F	00
REG20	00
REG21	00
REG22	00
REG23	00
REG24	00
REG25	00
REG26	00
REG27	00
REG28	00
REG29	00
REG2A	00
REG2B	00
REG2C	00
REG2D	00
REG2E	30
REG2F	00
REG30	00
REG31	0000
REG33	0000
REG35	2F1C
REG37	0000
REG37	0000
REG3B	0000
REG3D	0000
REG3F	0000
REG41	0000
REG43	0000
REG45	0000
REG47	00
REG48	08


Battery Charger 3S4P_REV.pdf

Regards,

Nishanth M

  • +1
    TI__Guru*** 143880 points

    Hi Nishanth,

    Input current limit is the lower of the value set by the ILIM_HIZ pin or IINDPM register.  From you schematic, input current limit is set to ~1.45A.  From your register dump, REG14 is reporting ILIM pin is enabled so input current limit is 1.45A which is what REG19 reports.  I am puzzled though because the status register 1B isn't showing that the charger's IINDPM is in control.  Did your board layout follow the BQ25792EVM board layout, especially the PMID and SYS capacitors?  If not, the charger may not regulate current properly.

    Regards,

    Jeff

  • 0 in reply to Jeff F
    Intellectual 295 points

    Hi Jeff,

    Thanks for the reply...Regarding the heat issues and current regulation, I have updated PCB layout, please check and let me know to go further for PCB Version2 fabrication.....

    BOOST CON-V2-gbr.rarBOOST CON-V2-GERBER.pdfLI-ION_BATTERY_CHARGER_BB_V02_02.pdf

    Regards,

    Nishanth M

  • 0 in reply to Nishanth M32
    TI__Guru*** 143880 points

    Hi Nishanth,

    The board layout top and bottom layers look similar to the top and bottom layers of the EVM.  But, the EVM has 2 internal layers with redundant power (VBUS, PMID, SYS, BAT, GND) planes/pours that help with power dissipation.  On this package, the power dissipation occurs through all of the pins.  So, if even the pin is a low current digital pin, connecting to those pins through wider traces/pours will help with power dissipation.  Please add more copper/wider traces to as many pins as possible.

    Regards,

    Jeff