38.5.10.1 Input-Output Transfer Functions

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

Single-ended—ADC_CCR.DIFFx = 0. This is the default mode after a reset.
Differential—ADC_CCR.DIFFx = 1 (see the figure Analog Full Scale Ranges in Single-ended/Differential Applications). In Differential mode, the ADC requires differential input signals with a VDD/2 common mode voltage (refer to the section “Electrical Characteristics”).

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

In the formulae below, REFP = VREFP, REFN = GND.

Single-ended mode:

ADC_LCDR.LDATA = \frac{ADx - REFN}{REFP - REFN} \times 2^{12}

Differential mode:

ADC_LCDR.LDATA = (1 + \frac{ADx - ADx+1}{REFP - REFN}) \times 2^{11}

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_CCR are applied to all channels.

The following table gives the internal positive and negative ADC inputs assignment with respect to the programmed mode (ADC_CCR.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.

Figure 38-7. Analog Full Scale Ranges in Single-ended/Differential Applications

Table 38-1. Input Pins and Channel Numbers in Single-ended and Differential Modes
Internal ADC Inputs (VIN+, VIN-)		Channel Numbers
Single-ended Mode	Differential Mode	Single-ended Mode	Differential Mode
AD0, GND	AD0, AD1	CH0	CH0
AD1, GND	–	CH1	CH0
AD2, GND	AD2, AD3	CH2	CH2
AD3, GND	–	CH3	CH2
AD4, GND	–	CH4	–
VBAT, GND	–	CH5	–
VREFTEMP, GND	–	CH6	–
VTEMP, GND	–	CH7	–