SLVSD29 October 2015 DRV8704
PRODUCTION DATA.
IDRIVE is selected based on the gate charge of the FETs. The IDRIVEx and TDRIVEx registers need to be configured so that the FET gates are charged completely during TDRIVE. If IDRIVE is chosen to be too low for a given FET, or if TDRIVE is less than the intended rise time, then the FET may not turn on completely. TI suggests to adjust these values in-system with the required external FETs and motor to determine the best possible setting for any application.
For FETs with a known gate-to-drain charge Qgd and desired rise time RT, IDRIVE and TDRIVE can be selected based on:
Example:
If the gate-to-drain charge is 5.9 nC, and the desired rise time is around 20 to 100 ns:
IDRIVE1 = 6.7 nC / 20 ns = 335 mA
IDRIVE2 = 6.7 nC / 100 ns = 67 mA
Select IDRIVE between 67 and 335 mA.
We select IDRIVEP as 200-mA source and IDRIVEP as 400-mA sink.
We select TDRIVEN and TDRIVEP as 525 ns.