Hot!MIC5021 High -Side Fet driver without Current Sensing

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RobinCCN
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2019/02/15 03:51:22 (permalink)
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MIC5021 High -Side Fet driver without Current Sensing

I am using a MIC5021 and have disabled Current Sensing (datasheet chapter 6.8) by connecting the sense inputs to power supply. I have also disabled retries by connecting Ct to ground (chapter 5.4). I notice the driver sometimes doesn't respond to the input, a power down is necessary to get the driver functioning again. I expect the driver comes in an overcurrent fault.

But how can it detect an overcurrent if the sense inputs are connected together to supply? Does someone recognize this issue?
post edited by RobinCCN - 2019/02/18 02:44:18
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    RobinCCN
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    Re: MIC5021 High -Side Fet driver without Current Sensing 2019/04/17 01:00:08 (permalink)
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    The problem has been found and expected to be solved. Due to a high inductive load the FET source becomes negative for some time (even with a schottky diode present). This negative pulse travels through the (large) gate-source capacitance and introduces a negative spike on the gate output of the MIC5021. Somehow this negative voltage on the gate triggers the overcurrent. Disconnecting the Ct resets the overcurrent and the MIC5021 works again. Placing a small signal diode between the gate en ground limits the gate negative level and the MIC5021 doesn't come in overcurrent anymore.
     
    post edited by RobinCCN - 2019/04/17 02:29:28
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