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USB-PD-CHG-EVM-01: About input current limit value of BQ25792

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Guru 21045 points
Part Number: USB-PD-CHG-EVM-01
Other Parts Discussed in Thread: BQ25792, , TPS25750

Hi Team,

 

I understand that IINDPM(ILIM_HIZ)=500mA setting on EVM and don’t connect D+ and D- pins.

Currently, our customer can provide output current 2.5A at the following conditions.

So, input current limit is more than 500mA.

 

<Conditions>

VBUS=20V/2.25A (45W)

VSYS=16V

IOUT=2.5A

<EVM>

 

I have two questions.

 

--------

[Q1]

Could you please let us know the input current limit value of BQ25792 on EVM?

 

[Q2]

How long is " IINDPM(ILIM_HIZ)=500mA " applied after startup?

 

By the way, I found “9.3.4.5 Input Source Type Detection” and “9.3.4.5.1 D+/D– Detection Sets Input Current Limit” in datasheet.

D+ and D- pins of are open on EVM so I guess that BQ25792 can’t detect D+ and D-.

Therefore, BQ25792 don't know the timing of " 1. Input Current Limit (IINDPM) register is changed to set current limit".

--------

 

Regards,

Hide

  • 0
    TI__Mastermind 30815 points

    1. Input current limit is 0.5 A by default when using the EVM. The charger charges at 1 or 2 A by default after startup.

    2. (ILIM_HIZ)=500mA is applied immediately after startup because it is programmed by a resistor on the board. Afterwards, the registers may be programmed by I2C or the D+ D- pins. D+ D- pins will program the registers once a USB adapter is plugged in.

    What's the voltage of VBAT for the setup? Also, can you measure the exact input current?

  • 0 in reply to Ethan Galloway
    Guru 21045 points

    Hi Ethan-san,

     

    Thank you for your prompt reply.

    VBAT is 16.4V and they don’t measure the exact input current.

    However.  EVM can supply IOUT=2.5A so current limit is more than 500mA.

    (By the way, if IOUT is 2.6A(increase), current also flows from the battery.)

     

    D+ and D- pins of BQ25792 on EVM don’t connect.

    Nevertheless, does BQ25792 behave as follows?

    > D+ D- pins will program the registers once a USB adapter is plugged in.

     

    If yes, could you please let us know the current limit value at this time?

     

    Regards,

    Hide

  • 0 in reply to Hide
    TI__Mastermind 40325 points

    Hello Hide,

    For the USB-PD-CHG-EVM-01 the input current limit is set by the TPS25750 firmware according to the negotiated contract.

    If your load cannot be supported by just the input current then the battery will decrease and may enter supplement mode to provide the necessary power.

    Regards,

    Mike Emanuel

  • 0 in reply to Michael Emanuel35
    Guru 21045 points

    Hi Mike-san,

     

    I understand your comment.

    > For the USB-PD-CHG-EVM-01 the input current limit is set by the TPS25750 firmware according to the negotiated contract.

     

    I have one more question.

    D+ and D- pins of BQ25792 on EVM don’t connect.

    Then, is the input current limit of BQ25792 “3A”?

    (I guess that “D+ and D- pins open”=” Unknown Adapter” so input current limit is 3A. )

    Is my understanding correct?

    If no, could you please let us know value?

     

    <BQ25792 datasheet>

     

     

    Regards,

    Hide

  • 0 in reply to Hide
    TI__Mastermind 40325 points

    Hi Hide,

    As explained previously, the input current limit will be set by the TP25750 according to the current rating of the attached PD source in Register 0x06. D+/D- is not connected so as to facilitate this programming.

    Regards,

    Mike Emanuel

  • 0 in reply to Michael Emanuel35
    Guru 21045 points

    Hi Mike-san,

     

    Thank you for always kind support.

    I have one more question.

     

    I understand that “the input current limit will be set by the TP25750 according to the current rating of the attached PD source in Register 0x06”.

    Then, is EN_EXTILIM of BQ25792 also set(From “1h” to “0h”)?

     

    <Background>

    “1h” of EN_EXTILIM is default.

    If “1h”, input current limit of BQ25792 is 500mA(ILIM_HIZ pin setting value).

    Therefore, I understand that EN_EXTILIM must be "0h".

     

    Regards,

    Hide

  • +1 in reply to Hide
    TI__Mastermind 40325 points

    Hide,

    The EN_EXTILIM should be set to 0h disable by the TPS25750.

    Regards,

    Mike Emanuel

  • 0 in reply to Michael Emanuel35
    Guru 21045 points

    Hi Mike-san,

    Thank you for the information.

    Regards,

    Hide