65.6.10.1 Input-output Transfer Functions

The ADC can be configured to operate in the following input voltage modes:

  • Single-ended—ADC_COR.DIFFx = 0. This is the default mode after a reset.
  • Differential—ADC_COR.DIFFx = 1 (see the figure below). In Differential mode, the ADC requires differential input signals having a VDD/2 common mode voltage (refer to section “Electrical Characteristics”).

The following equations give the unsigned ADC input-output transfer function in each mode(1). With signed conversions (see field ADC_EMR.SIGNMODE), subtract 2047 from the ADC_LCDR.DATA value given below.

In the formula, REFP = VREFP, REFN = VREFN.

Single-ended mode:

ADC_LCDR.LDATA=ADx−REFNREFP−REFN×212

Differential mode:

ADC_LCDR.LDATA=1+ADx−ADx+1REFP−REFN×211
Note: Equations assume ADC_EMR.OSR = 1

If ADC_MR.ANACH is set, the ADC can manage both differential channels and single-ended channels. If ADC_MR.ANACH is cleared, the parameters defined in ADC_COR are applied to all channels.

The following table give s the internal positive and negative ADC inputs assignment with respect to the programmed mode (ADC_COR.DIFFx).

For example, if Differential mode is required on channel 0, input pins AD0 and AD1 are used. In this case, only channel 0 must be enabled by writing a 1 to ADC_CHER.CH0.

Table 65-2. Input Pins and Channel Numbers
Input PinChannel Number
Single-ended ModeDifferential Mode
AD0CH0CH0
AD1CH1
AD2CH2CH2
AD3CH3
AD4CH4CH4
AD5CH5
AD6CH6CH6
AD7CH7
AD8CH8CH8
AD9CH9
AD10CH10CH10
AD11CH11
Figure 65-7. Analog Full Scale Ranges in Single-Ended/Differential Applications