SLVAF84 September   2021 DRV8311 , DRV8312 , DRV8313 , DRV8316 , DRV8332 , MCT8316Z

 

  1.   Trademarks
  2. 1Introduction
  3. 2Direction of Current Into or Out of the Phase
    1. 2.1 INHx Rising, INLx Falling, Current is Going Out of the Phase
    2. 2.2 INHx Falling, INLx Rising, Current is Going Out of the Phase
    3. 2.3 INHx Rising, INLx Falling, Current is Going Into the Phase
    4. 2.4 INHx Falling, INLx Rising, Current is Going Into the Phase
  4. 3Additional Dead Time From the MCU PWM Inputs
  5. 4Summary of Delay Times in Integrated MOSFET Drivers
  6. 5Delay Compensation to Minimize Duty Cycle Distortion

2.2 INHx Falling, INLx Rising, Current is Going Out of the Phase

In Figure 2-5, when INHx goes low (green), current is again momentarily pulled through the body diode (purple) of the LS FET to continue sourcing current out of OUTx (red). After a short body diode conduction period, the LS FET begins to conduct (blue).

GUID-20210822-SS0I-1VJL-Z3SC-N2PKXBD9QH9K-low.gif Figure 2-5 Current Switching With INHx Falling, INLx Rising, and Current Out of OUTx

Note how the current direction is the same internally between the body diode of the LS FET and the conduction path of the LS FET. The device can turn on the LS FET instead of allowing the body diode to fully conduct because the current direction is the same. This results in a shortened propagation delay and dead time.

The example waveform in Figure 2-6 shows INHx falling and INLx rising and current is going out of the phase (positive current in green) for the DRV8316 with a slew rate of 200 V/µs and sinusoidal commutation. The dead time and propagation delay minimum values in the DRV8316 data sheet specifications are not specified because of this condition due to the internal VGS handshaking feature of the device to avoid any shoot-through conditions.

GUID-20210822-SS0I-CJPW-HFCR-DWHSDMMJP1VQ-low.gif Figure 2-6 Waveforms of Dead Time and Propagation Delay When INHx is Falling, INLx is Rising, and Current Flows Out of OUTx