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BQ25895: BQ25895 Query

Bino Mani
Prodigy 90 points
Part Number: BQ25895

Tool/software:

Hello Ti Support Team,


I have a query related to BQ25895. I am designing a battery operated medical device and I want to know how should be the D+ & D- pin connected if we plan to charge the battery with 5V, 2.4A?
Looking forward for a quick response.

Regards,
Bino Mani

  • 0
    TI__Mastermind 25805 points

    Hi Bino, 

    Do you expect to use the device with the same input adapter at all times or do you plan to use the device with various input adapters which may have different current ratings? 

    If I assume you wish to always set the input current limit to 2.4A you have a couple options.

    -Option 1 is to force both D+ & D- pins to 2.7V to allow D+/D- detection to result in non-standard adapter divider 4, which automatically sets input current limit to 2.4A.

    -Option 2 is simply short D+ & D- pins together then set input current limit to desired value via I2C. With D+/D- pins shorted the detection result is USB DCP (1.5A current limit), but as I mentioned the 1.5A limit can be overridden by an I2C write to REG00. 

    Best Regards,

    Garrett

  • 0 in reply to Garrett Kreger
    Prodigy 90 points

    Hello Garrett,


    If we consider option-2, then what should be REG00 value to set 2.4A? and same case with option-2, what should resistor (value) on pin ILIM?

  • 0 in reply to Bino Mani
    TI__Mastermind 25805 points

    Hi Bino, 

    Please see my comments below. 

    REG00 = 0x6E hex will set input current limit to 2.4A. The relevant information for configuring IINLIM is located in Table 8-8 on page 32 of the datasheet. 

    The actual input current limit will be the lower value between the register setting and the input current limit set by external resistor at ILIM pin. The ILIM section in the pin functions table provides the equation to calculate RILIM given your desired input current limit. 

    For example, if you wish to set input current limit to 3A RILIM should be 118 ohms. 

    Best Regards,

    Garrett 

  • 0 in reply to Garrett Kreger
    Prodigy 90 points

    Hello Garrett,

    Could you help me how you calculated the RILIM?

  • 0 in reply to Bino Mani
    TI__Mastermind 25805 points

    Hi Bino, 

    As I mentioned in my last response the simple equation for calculating RILIM is listed in the pin functions table in the ILIM pin row on page 4. The 'KILIM' value required for the equation can be found on page 9. All you need to do is divide KILIM by your desired maximum input current. 

    Please refer to the datasheet for relevant information to make this component selection. 

    Best Regards,

    Garrett