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BOOSTXL-DRV8323RS: TDRIVE Testing and Dead Time

Jerome Villapando
Intellectual 290 points
Part Number: BOOSTXL-DRV8323RS
Other Parts Discussed in Thread: DRV8323

Hello,

I am evaluating the BOOSTXL-DRV8323RS andI wanted to ask about TDRIVE and dead time specifics. Take a look at this scope shot:

CH1: Motor Phase A Current, CH2: nFAULT, CH3: GHA, CH4: GLA

I set the IDRIVE settings to the lowest and TDRIVE to the lowest (500ns) to see if I can trigger gate drive faults. In the above scope shot it takes 1.1us to properly go LOW which should trigger the fault. However, upon rereading the TDRIVE section of the DRV8323 datasheet again, it seems that the t_drive is measured between some unknown pair of Vgs thresholds.

Where can I find these thresholds?

These unknown thresholds could also explain why there is overlap between GHA and GLA in the above scope shot, despite there being a supposed dead time insertion.

Jerome

  • 0
    TI__Mastermind 26046 points

    Hi Jerome,

    The thresholds are VGS = 2V. If VGS > 2V, the FET is considered to be "on". If VGS < 2V, the FET is considered to be "off". This may not hit TDRIVE = 500ns because the input capacitance Ciss is too low at the lowest dead time. 

    The time between the FETs being "on" is when dead time is inserted. 

    Try shorting a GHA/GLA pin to GND to see a GDF fault occur. 

    Thanks,
    Aaron