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BQ25798: SYS pin

Yoshinobu Kagawa
Expert 2030 points
Part Number: BQ25798

Tool/software:

Please provide the following two specifications for the SYS terminal of the BQ25798.

1. What is the maximum discharge current of the SYS terminal of the bq25798?
2. If overcurrent protection specifications for the SYS terminal are specified, please let us know.

Regards,
Kagawa

  • 0
    TI__Guru**** 167356 points

    Hi Kagawa,

    Please see the datasheet table below:

    In summary, converter max output to SYS (including charge current to BAT) is 5A.  Max DC battery discharge current from to SYS is 6A.  Max battery discharge current for 1 sec is 10A.

    Regards,

    Jeff

  • 0 in reply to Jeff F
    Expert 2030 points

    Hi Jeff-san,

    Please explain in detail the following two specifications regarding the SYS terminal of the BQ25798.
    ・Does the 5A maximum discharge current listed in the datasheet indicate the actual value of the current that can flow from the SYS terminal of the bq25798?
    ・Or, does the 5A listed in the datasheet refer to the OCP (Over Current Protection) threshold, which automatically stops the bq25798 if the current exceeds the threshold?
    We are planning to perform a short-circuit test between each terminal of the bq25798 and GND, but the overcurrent protection specifications for the SYS terminal are not listed in the data sheet.
    Therefore, we would like to confirm if the overcurrent limit of the SYS pin is 5A or if another value is specified.

    Regards,
    Kagawa

  • 0 in reply to Yoshinobu Kagawa
    TI__Guru**** 167356 points

    Hi Kagawa,

    Neither. There is no OCP circuit for current flowing from converter to SYS. The max recommended output current through the converter to SYS pin is 5A.    A transient might briefly exceed 5A or reach one of the switch's cycle by cycle current limit shown below. 

     But a dc load of 5A for a long time will likely put the converter into thermal regulation where input current is reduced until the IC die temp drops. 

    There is OCP for battery discharge current from BAT to SYS.  There is a fault flag that reports if the current exceeds 9.3A min.  The max can be closer to 13A.

    If the REG0x14[0]=1, the OCP event turns off the shipFET.

     Regards,

    Jeff