DRV8320R: Deadtime characteristics between GHx and GLx

yeonsu kim said:

If I add 1us software deadtime from MCU between Vinhx and VinLx like below picture.

and DRV8320's hardware deadtime is 100ns.

then What is the total deadtime between GLx and GHx pin?

1100ns? or just 1000ns?

I agree with you that the datasheet is not clear about the total dead-time. Below is how dead-time is defined: It says an additional digital dead time can be inserted (tDead) and so this sounds like 100ns dead-time for the H/W device is an optional, but it is not as there is no way to select or not select to have this 100ns additional deadtime. So assuming you are using the non-spi driver, then the total dead time in your example is 1100ns.

TI engineer: can you revise the datasheet to make it clearer for the users that the digital dead-time can be selected from 40ns to 400ns for the SPI device, and 100ns for the non-spi driver, as the minimum dead-time and the device might add more deadtime automatically if needed.

Question: if the driver uses VGS voltage monitors to determine the correct time to switch the output, then why it needs to provide the additional 100ns (or 40 to 400ns for the spi version) deadtime? Too confusing.

Brian

"The DRV832x family of devices uses VGS voltage monitors to measure the MOSFET gate-to-source voltage and determine the correct time to switch instead of relying on a fixed time value. This feature lets the dead time of the gate driver adjust for variation in the system such as temperature drift and variation in the MOns SFET parameters. An additional digital dead time (tDEAD) can be inserted and is adjustable through the registers on SPI devices."

Dear sir.

Thank you for quick reply.

Please confirm that my understanding(below 3cases) is correct.

 ※ we are using DRV8320RH(H/W device) 

case1) applied input deadtime is enough longer than

            deadtime setting by DRV8320RH(100ns) and falling, rising time of mosfet :

for example, If the deadtime from MCU between Vinhx and VinLx is 1us like the image I attached,

falling-time of mosfet is 20ns and rising time of mosfet is 40ns,

then deadtime between GLx and GHx is 1us.

case2) applied input deadtime is shorter than deadtime setting by DRV8320RH(100ns)

            and falling, rising time of mosfet is shorter than deadtime setting by DRV8320RH  :

If the deadtime from MCU between Vinhx and VinLx is zero,

but falling-time of mosfet is 20ns and rising time of mosfet is 40ns.

then deadtime between GLx and GHx is 100ns by DRV8320RH.

case3) applied input deadtime is shorter than deadtime setting by DRV8320RH(100ns)

            but falling, rising time of mosfet is longer than deadtime setting by DRV8320RH  :

If the deadtime from MCU between Vinhx and VinLx is zero,

but falling-time of mosfet is 200ns and rising time of mosfet is 400ns.

then deadtime over 100ns is added automatically by DRV8320RH between GLx and GHx until Vds-low is off.