原来是CPU对电压的要求。
VIN must not exceed OVDD by more than 0.3V at any time including(requirement 1)during power-on reset.
OVDD must not exceed VDD/AVDD by more than 1.2V at any time including(requirement 2)during power-on reset.
VDD/AVDD must not exceed OVDD by more than 0.4V at any time including(requirement 3)during power-on reset.