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MCT8316Z-Q1: MCT8316Z-Q1 cycle by cycle current limit

Tom Li53
Prodigy 290 points
Part Number: MCT8316Z-Q1

Hello,

From datasheet of MCT8316Z-Q1, the maximum current limit is 8A with AVDD/2-0.4V on ILIM pin. Does this happened only with GAIN = 0.15V/A? And what will happen if the voltage on ILIM pin less than AVDD/2-0.4V? Thanks!

Tom Li

  • 0
    TI__Intellectual 1240 points

    Hi Tom,

    I am looking into this and will get an answer to you by the end of this week.

    Regards,

    Hong

  • 0
    TI__Intellectual 1240 points

    Hi Tom,

    Referring to section 8.3.12 of the datasheet, the measured voltage, which involves the current sense amplifier, is calculated with the following equation:

    The current limit is activated when Vmeas is less than VILIM. This measured voltage is how the device sees its own output current, and as expected, it is dependent on all of the phase currents (dividing by 3 averages them) and CSA_GAIN.

    Vmeas = (3.3/2) - ((0 + 0 + 0) * 0.15/3) = 1.65V = AVDD/2,

    Vmeas = (3.3/2) - ((0 + 8 + 0) * 0.15/3) = 1.25V = AVDD/2 - 0.4V

    when CSA_GAIN = 0.15 V/A.

    However, on this device, there is a datasheet error, and CSA_GAIN is not configurable even for the SPI device. The fixed value for both the SPI and HW version is 0.15 V/A.

    To answer your second question, the voltage on ILIM sets the current limit. If ILIM's voltage is less than AVDD/2 - 0.4, this sets the current limit beyond 8A, which means the current limit will not act as the current sense amplifiers may saturate.

    Regards,

    Hong