ZHCSOY8B September 2021 – February 2022 DRV8311
PRODUCTION DATA
The propagation delay is defined as the time taken for changing input logic edges INHx and INLx (whichever changes first if MCU dead time is added) to change the half-bridge output voltage (OUTx). Driver propagation delay (tPD) and dead time (tdead) is specified with a typical and maximum value, but not with a minimum value. This is because the propagation delay can be smaller than typical depending on the direction of current at the OUTx pin during synchronous switching. Driver propagation delay and dead time can be more than typical values due to slower internal turn-ons of the high-side or low-side internal MOSFETs to avoid internal dV/dt coupling.
For more information and examples of how propagation delay and dead time differs for input PWM and output configurations, refer Delay and Dead Time in Integrated MOSFET Drivers.
The dead time from the microcontroller’s PWM outputs can be used as an extra precaution in addition to the DRV8311 internal shoot-through protection. The DRV8311 uses an internal logic prioritizes the MCU dead time or driver dead time based on their durations.
If the MCU dead time is less than the DRV8311 driver dead time, the driver will compensate and make the true output dead time with the value specified by the DRV8311. If the MCU inserted dead time is larger than the driver dead time, then the DRV8311 will adjust timing as per the MCU dead time.
A summary of the DRV8311 delay times with respect to synchronous inputs INHx and INLx, OUTx current direction, and MCU dead time are listed in Table 10-2.
| OUTx Current Direction | INHx | INLx | Propagation Delay (tPD) | Dead Time (tdead) | Inserted MCU Dead Time (tdead(MCU)) | |
|---|---|---|---|---|---|---|
| tdead(MCU) < tdead | tdead(MCU) > tdead | |||||
| Out of OUTx | Rising | Falling | Typical | Typical | Output dead time = tdead | Output dead time = tdead(MCU) |
| Falling | Rising | Smaller than typical | Smaller than typical | Output dead time < tdead | Output dead time < tdead(MCU) | |
| Into OUTx | Rising | Falling | Smaller than typical | Smaller than typical | Output dead time < tdead | Output dead time < tdead(MCU) |
| Falling | Rising | Typical | Typical | Output dead time = tdead | Output dead time = tdead(MCU) | |