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Original question:

BQ25730: About Vsys voltage control when BATFET is not used

BQ25730: About increased current consumption than BQ25731

Tsukui Yusuke
Guru 21930 points
Part Number: BQ25730
Other Parts Discussed in Thread: BQ25731

Hi,

We are considering replacing BQ25731 with BQ25730 by referring to the thread below.
https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/1053359/bq25730-about-vsys-voltage-control-when-batfet-is-not-used/3897374#3897374

Customer is verifying by replacing BQ25731 with BQ25730.
As a result, the phenomenon that the current consumption of BQ25730 became larger than that of BQ25731 occurred.
For both BQ25730 and BQ25730, the default registers are rewritten as follows.

Under this setting condition, BQ25731 was on the order of several tens of μA.
On the other hand, BQ25730 was on the order of several hundred μA.
Is there a way to reduce the current consumption of BQ25730?
And Could you give me some advice on the cause of the increase in current consumption?

ChargeVoltage 05/04h 16.608V:40E0h
ChargeCurrent 03/02h 0000ｈ
OTGVoltage 07/06h 0000ｈ
OTGCurrent 09/08h 0000ｈ
IIN_HOST 0F/0Eh 1B00h ＠10mΩ
ChargeOption0 01/00h E31Bh
ChargeOption1 31/30h 3300h
ChargeOption2 33/32h 00BAh
ChargeOption3 35/34h 0434h
ChargeOption4 3D/3Ch 0040h
ProchotOption0 37/36h 0A81h
ProchotOption1 39/38h 1900h
ADC Option 3B/3Ah 2040h


Best regards,
Yusuke

  • 0
    TI__Mastermind 18685 points

    The quiescent current spec for BQ25730 and BQ25731 are the same. Please make sure they are operating under the same condition, in the same operation mode. 

  • 0 in reply to Tiger Zhou
    Guru 21930 points

    Hi Tiger,

    Thank you for your kind support.
    >Please make sure they are operating under the same condition, in the same operation mode. 

    We checked the behavioral differences between BQ25730 and BQ25731.
    As a result, the current consumption was reduced by changing "34h bit7 (BATFET_ENZ)" of BQ25730.
    By setting BATFET_ENZ to 1, the VREG voltage becomes 0V and it seems that the current consumption can be suppressed.

    I have a question about this confirmation result.
    BQ25730 BATFET will not be installed due to the background of the previous consultation.
    Is it okay to use BATFET_ENZ to reduce battery consumption in that situation?
    And Could you tell me some points to note when using BATFET_EN?

    Best regards,
    Yusuke

  • 0 in reply to Tsukui Yusuke
    TI__Mastermind 18685 points

    Okay, I don't see any issue in your application. 

    BATFET_ENZ:Turn off BATFET under battery only mode. If charger is not in battery only mode this bit is not allowed to be written to 1. Under battery only OTG mode, this bit is forced to be 0b.
    BATFET_ENZ=0b: Not force turn off BATFET <default at POR>
    BATFET_ENZ=1b: Force turn off BATFET

  • 0 in reply to Tiger Zhou
    Guru 21930 points

    Hi Tiger,

    Thank you for you explanation.
    >BATFET_ENZ:Turn off BATFET under battery only mode.
    >If charger is not in battery only mode this bit is not allowed to be written to 1. Under battery only OTG mode, this bit is forced to be 0b.
    I understand this.

    Let me check, just in case.
    １．Is it correct to understand that BATFET_ENZ is a function aimed at reducing current consumption?
           Could you give me some advice on how to use it?

    ２．Based on the background of replacement from BQ25731, are there any precautions or risks when using BATFET_ENZ?

    Best regards,
    Yusuke

  • 0 in reply to Tsukui Yusuke
    TI__Mastermind 18685 points

    Since you have so many concerns and questions, it may be of value to refer to this FAQ. 

    e2e.ti.com/.../faq-bq25731-could-i-replace-bq25731-with-bq25730-in-non-power-path-applications

  • 0 in reply to Tiger Zhou
    Guru 21930 points

    Hi Tiger,

    Thank you for your support.
    I refer to the advice you gave me in the past FAQs.

    By the way, in the case of normal usage,
    When is the situation to forcibly turn off BATFET using BATFET_ENZ?
    Could you tell me how TI expects to use it?
    I would like to compare this case with the normal usage.

    Best regards,
    Yusuke

  • +1 in reply to Tsukui Yusuke
    TI__Mastermind 18685 points

    In normal situation, TI does not suggest using the BATFET_ENZ. It is reserved for other uses, for example, when you have two BATFETs connected in parallel.