IR CLass-D solution

[ponymxy]

I'm designing 2*150W and 2*250W Class-D with IR solution based on IRS20955, we design the Class-D schematic and PCB according to IRAUDAMP4 reference design and have completed the primary version PCB and are debugging the PCB. during the course of debugging, I happen to the following problem:
1) if the mosfet is irf4019B and all parameters is same to the attachment, the CSD of the IRS20955 is always charging and discharging and there is no PWM output, that is to say, altrough i have no load, the IC is always OCP.
Please give you advice how to solve the problem.

2) if I want use mosfet FDP3682, how i set the relevent parameters about IRS20955 and can make the class-d work.

Hope to your reply as soon as possible.

Thanks a lot!

The attachment is the schemetic.