DRV8245S-Q1LEVM: Why there is a PWM drop during the PWM mode control?

Hi Team, 

When testing the DRV8245S-Q1LEVM in the PWM mode, the input voltage is 12V with no load. There will be  a voltage drop in the OUT1 and OUT2. Please see the pic below. What's the reason for that?

Thanks a lot

Matthew