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Passive slew rate of PROFET™+2 devices

Passive slew rate of PROFET™+2 devices

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What is the meaning of the Passive Slew Rate specification for PROFET™+2 devices?


PROFET™+2 "Passive Slew Rate" parameter

The PROFET™+2 specification introduced a new parameter called "Passive Slew Rate" (for bridge configurations).  The max value given for this parameter is +/-10V/usec.

This specification is relevant for half bridge/full bridge motor drive applications where the PROFET™+2 device is used as the high side for the bridge application and a MOSFET/HITFET is used as the low side for the bridge application.


Importance of the passive slew rate in an application

Typically, if the application uses PWM to control motor speed/torque the high side PROFET™ is left ON statically and the low side MOSFET/HITFET is PWM'd at the appropriate frequency/duty cycle (in full H-bridge configuration opposite corner HS/LS are driven together to activate the motor in a certain direction).

In such an application the low side switch in PWM application is impressing its slew rate to the OUTPUT of the PROFET™ hi side switch that is in OFF state.  This dV/dt is seen at the source of the internal DMOS of the PROFET™ in OFF state.  If this dV/dt becomes too fast it can begin to start to charge the PROFET internal Gate-Source capacitance (Igs=Cgs*dVgs/dt).  This charging of the internal Cgs may at some point start to turn on the DMOS of the PROFET even though it is commanded for OFF state, and this can cause cross currents within the H-bridge application which must be avoided.