DRV8874-Q1: What can trigger nFAULT driven LOW?

Hi Experts,

When DRV8874-Q1 is working as direct drive forward-rotating. High side OUT1 short to GND. The nFAULT was driven LOW. What can trigger nFAULT LOW?

According to the fault condition, 

• The current mirror is on low side, so it can't be trigger by OCP or Itrip.
• The test Vm is close VBATT, far above UVLO, so it can't be trigger by UV.
• The nFault can be trigger as soon as short, so it can't be trigger by TSD.

What else reason can trigger this?

BR

Frank