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BQ25792: BQ25792 , Setting the charging current ?

eso18
Prodigy 150 points
Part Number: BQ25792

Hi,

I will design a 4s2p Li-ion battery charger with BQ24792. According to my design criteria, the charge current is 0.5C, which should be about 3A.

When I examine the datasheet, there is a 1A setting for the 4S cell. Can I set the current to 3A directly with I2C (REG 0X03) ? Do we have to use the PROG pin?

Thank you for your supports, 

  • +1
    TI__Guru**** 165986 points

    Hi eso18,

    Yes, you can change the charge current by writing to REG0x03-04.  The PROG pin value is only used at initial power up.  Keep in mind that if the watchdog timer (REG0x10[2:0]) is not disabled and expires because the host is not writing to the watchdog timer bit (REGx10[3]), the charge current resets to the PROG pin defaults.  Also if the input current limit is too low per input current limit register (REG0x06-07) or clamped by the ILIM_HIZ resistor divider because EN_LIM bit is 1 (REG0x14[1]), then the converter isn't getting enough input power and may not be able to provide the desired charge current.  Also, if the VINDPM threshold is too high in REG0x05 and there is a resistive drop from your input power source to the VACx pins, then input power is also clamped to prevent the input voltage from dropping further.

    Regards,

    Jeff 

  • 0 in reply to Jeff F
    Prodigy 150 points

    Thank you Jeff

  • 0 in reply to Jeff F
    Prodigy 150 points

    Hello Jeff,

    I also have one more question. Are voltage divider resistors connected to the ILIM_HIZ pin for initial current limiting?  as a result we can set it from I2C  REG06_Input_Current_Limit Register).

  • +1 in reply to eso18
    TI__Guru**** 165986 points

    Hi eso18,

    If the EN_ILIM register bit (REGx014[1]) is set, the ILIM_HIZ resistors set the maximum input current limit in REG0x06 at each power up even if the D+/D- resets in negotiating a higher input current limit.

    Regards,

    Jeff