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BQ25798: BQ25798 how to set the Input_Voltage_Limit Register and REG06_Input_Current_Limit

Star Xu
Expert 7895 points
Part Number: BQ25798
Other Parts Discussed in Thread: BQSTUDIO

Hi

The customer test with BQ25798EVM, they find these 2 registers are affected by the input power.

Test condition as below:

The charging power supply is 15V-300mA, the ambient temperature is 24 degrees.

1, Fully discharge the battery, from the bqstudio software, the value of REG05_Input_Voltage_Limit Register is 7100mV, and the value of REG06_Input_Current_Limit is 1010mA.

2, Modify the REG05_Input_Voltage_Limit Register to 22000mV, and the value of REG06_Input_Current_Limit to 3000mA.

3, REG05 is set successfully, and the REG05_Input_Voltage_Limit Register becomes 22000mV, but REG06_Input_Current_Limit is still 1010mA. The weirdest thing is that the power supply charges the battery at 15V - 0.007mA.

the register as below:

bq25978参数(2023-03-29).txt 
* Created: Wed Mar 29 12:00:07 CST 2023
*
* Format: Register Name  tab Character,\t  Register Address  tab Character,\t  Hexadecimal register value.
* Device: BQ25798
* BQZ Container: Charger_2_00-bq25798.bqz
*
REG00	14
REG01	05AA
REG03	00C8
REG05	28
REG06	002C
REG08	32
REG09	01
REG0A	E3
REG0B	00DC
REG0D	4B
REG0E	FD
REG0F	A2
REG10	80
REG11	00
REG12	00
REG13	85
REG14	1E
REG15	AA
REG16	C0
REG17	7A
REG18	54
REG19	002C
REG1B	4D
REG1C	70
REG1D	01
REG1E	C0
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	B0
REG2F	00
REG30	00
REG31	009C
REG33	0013
REG35	0FA6
REG37	0000
REG37	0FC6
REG3B	3406
REG3D	3422
REG3F	0253
REG41	0026
REG43	0000
REG45	0000
REG47	00
REG48	19

Another question, when EN_ICO is disabled, and the ILIM_HIZ pin is set to 1.5A, but the REG19_ICO_Current_Limit value returns 500mA, why not 1.5A?

Waiting for your reply.

Thanks

Star

  • 0
    TI__Guru*** 134230 points

    HI Star,

    The input current register is clamped to the lower of the value written to the I2C register or the value per the ILIM_HIZ resistor if EN_ILIM bit = 1.  To write a higher value to the input current limit register, set EN_ILIM=0.  The ILIM from ICO reports the actual current limit after ICO.  ICO starts at 500mA and sweeps up if V(BAT)<MINSYS or starts at max input current limit (3.2A) and sweeps down if V(BAT)>MINSYS.

    Regards,

    Jeff