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Original question:

BQ25798: IINDPM

BQ25798: IINDPM

Yoshinobu Kagawa
Expert 2030 points
Part Number: BQ25798

Background:
In the following flow, the host overwrites the IINDPM register with 0xa0 (1.6A) at the timing when the power supply is switched to the VAC1 side, but the value does not switch to 1.6A after the overwrite and always becomes 1.7A, which is based on the resistance value of the ILIM_HIIZ pin.

IINDPM.pptx

Question:
(1) Are there any conditions that could cause the ILIM_HIZ pin input current limit to take priority over the ILIM_HIZ pin input current limit, even though the input current limit set by the host is smaller than the ILIM_HIZ pin input current limit?
(2) When setting a smaller value than the ILIM_HIZ pin by overwriting the IINDPM register, if it depends on the timing after reading the VBUS0 voltage or enabling EN_ACDRV1, etc., what conditions and waiting time are necessary to reflect it correctly?

ILIM_HIZ.pptx

Regards,
Kagawa

  • 0
    TI__Mastermind 31551 points

    Hello Yoshinobu,

    Yoshinobu Kagawa said:
    (1) Are there any conditions that could cause the ILIM_HIZ pin input current limit to take priority over the ILIM_HIZ pin input current limit, even though the input current limit set by the host is smaller than the ILIM_HIZ pin input current limit?

    The ILIM_HIZ pin sets a high clamp for the IINDPM register. The host cannot program the IINDPM register to any values higher than this ILIM clamp after POR, unless the register bit EN_EXTILIM is set to 0.

    Yoshinobu Kagawa said:
    2) When setting a smaller value than the ILIM_HIZ pin by overwriting the IINDPM register, if it depends on the timing after reading the VBUS0 voltage or enabling EN_ACDRV1, etc., what conditions and waiting time are necessary to reflect it correctly?

    The host should be able to over-write the IINDPM register to change the input current limit at any time and it should automatically update with  the new current limit.

    Best Regards,

    Christian.

  • 0 in reply to Christian Moyer
    Expert 2030 points

    Hello Christian-san,

    We will send you the current register settings.
    The problem is that IINDPM cannot be set to a lower value than what is clamped by ILIM_HIZ.
    This symptom no longer occurs when the wait time for writing the new IINDPM setting value from the host after power is supplied to VAC1 is changed from the current 800ms to 1s or more.
    Therefore, we believe that a waiting period is required before overwriting the IINDPM register again after reading ILIM_HIZ is completed.
    Could you please specify the specific waiting time?

    Fullscreen BQ25798_Register setting values_20240402.txt Download 
    * Created: Tue Apr 02 09:20:47 JST 2024
*
* Format: Register Name  tab Character,\t  Register Address  tab Character,\t  Hexadecimal register value.
* BQZ Container: Charger_2_00-bq25798.bqz
*
REG00	00	10
REG01	01	2D0
REG03	03	64
REG05	05	6D
REG06	06	AA
REG08	08	C3
REG09	09	23
REG0A	0A	63
REG0B	0B	DC
REG0D	0D	4B
REG0E	0E	3B
REG0F	0F	B2
REG10	10	90
REG11	11	41
REG12	12	10
REG13	13	61
REG14	14	B6
REG15	15	AA
REG16	16	C0
REG17	17	06
REG18	18	54
REG19	19	45
REG1B	1B	0F
REG1C	1C	8A
REG1D	1D	41
REG1E	1E	C0
REG1F	1F	00
REG20	20	00
REG21	21	00
REG22	22	00
REG23	23	00
REG24	24	00
REG25	25	00
REG26	26	00
REG27	27	00
REG28	28	FD
REG29	29	D7
REG2A	2A	7F
REG2B	2B	1F
REG2C	2C	FF
REG2D	2D	F4
REG2E	2E	80
REG2F	2F	00
REG30	30	00
REG31	31	260
REG33	33	3F6
REG35	35	2F8A
REG37	37	2F86
REG37	39	12EB
REG3B	3B	1C26
REG3D	3D	1C5C
REG3F	3F	25C
REG41	41	26
REG43	43	3F
REG45	45	57
REG47	47	00
REG48	48	19


    Regards,
    Kagawa

  • 0 in reply to Yoshinobu Kagawa
    TI__Mastermind 31551 points

    Hello Kagawa,

    Please refer to section 9.3.4 Device Power Up from Input Source of the datasheet:

     

    We don't have a specific waiting time on when you can write to the IINDPM register. It is dependent on the other variables specified above.

    Best Regards,

    Christian.