我要用12位的AD测一个±2.5V的峰值的方波
参考电压是差分输入的为AIN6-AIN7，才能测得负的电压值
但是如果要测±2.5V范围的电压，AIN6 和AIN7 两个口应该分别加上多少的电压呢？
下面是datasheet的两端描述：
第一个是讲差分可以在-VREF~+VREF中测量
For differential
configurations, the difference between two pins is converted, and this difference can be negatively signed.
For example, with a decimation rate of 512 using only the 12 MSBs of the digital conversion result
register, the maximum value of 2047 is reached when the analog input (Vconv) is equal to VREF, and
minimum value of –2048 is reached when the analog input is equal to –VREF .
第二个讲参考电压的选择
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.
AIN6和AIN7 应该加+2.5v和-2.5v吗？
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