DRV8874-Q1: DRV8874-Q1 thermal dissipate problem

Part Number: DRV8874-Q1

Hello

I`ve bought some pre-released DRV8874-Q1 for testing, according to the evaluation board of it, it can bear continuous current of 3.3A as suggested on datasheet,

but on my designed board in PWM mode, as I tested it in 12V/3A, it can only run for about 7 sec;

for 12V/3.3A it can only run for 3 sec then the fault LED started to blink, current will drop,

is this problem of heat dissipate problem of my board or some other issue, can you me some advice??

Thank you