你要看数据手册，里面讲得很清楚。
12.2.6 ADC Reference Voltage
The positive reference voltage for analog-to-digital conversions is selectable as either an internally
generated voltage, the AVDD5 pin, an external voltage applied to the AIN7 input pin, or a differential
voltage applied to the AIN6–AIN7 inputs.
The accuracy of the conversion results depend on the stability and noise properties of the reference
voltage. Offset from the wanted voltage introduces a gain error in the ADC proportional to the ratio of the
wanted voltage and the actual voltage. Noise on the reference must be lower than quantization noise of
the ADC to ensure the specified SNR is achieved.
你要看数据手册，里面讲得很清楚。
12.2.6 ADC Reference Voltage
The positive reference voltage for analog-to-digital conversions is selectable as either an internally
generated voltage, the AVDD5 pin, an external voltage applied to the AIN7 input pin, or a differential
voltage applied to the AIN6–AIN7 inputs.
The accuracy of the conversion results depend on the stability and noise properties of the reference
voltage. Offset from the wanted voltage introduces a gain error in the ADC proportional to the ratio of the
wanted voltage and the actual voltage. Noise on the reference must be lower than quantization noise of
the ADC to ensure the specified SNR is achieved.
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