36.5.2.2 Selection of Negative Inputs

Negative input selection is determined by the setting of the DIFFx bit of the ADCIMCON1 register. The DIFFx bit allows the inputs to be rail-to-rail and either single-ended or differential. The SIGNx and DIFFx bits in the ADCIMCON1 register scale the internal ADC analog inputs and reference voltages and configure the digital result to align with the expected full-scale output range.

For the shared ADC module, the analog inputs have individual settings for the DIFFx bit. Therefore, the user has the ability to select certain inputs as single-ended and others as differential while being connected to the same shared ADC module. While sampling, the signal changes on-the-fly as single-ended or differential according to its corresponding DIFFx bit setting.

Table 36-2. Negative Input Selection
ADCIMCON1Input ConfigurationInput VoltageOutput
DIFFxSIGNx

1

1

Differential 2’s complement

Minimum input

VINP - VINN = -VREF

-2048

Maximum input

VINP - VINN = VREF

+2047

1

0

Differential unipolar

Minimum input

VINP - VINN = -VREF

0

Maximum input

VINP - VINN = VREF

+4095

0

1

Single-ended 2’s complement

Minimum input

VINP = VREF

-2048

Maximum input

VINP - VINN = VREF

+2047

0

0

Single-ended unipolar

Minimum input

VINP = VREF

0

Maximum input

VINP - VINN = VREF

+4095

Legend:
  • VINP = Positive S&H input
  • VINN = Negative S&H input
  • VREF = VREFH - VREFL
Note: For proper operation and to prevent device damage, input voltage levels must not exceed the limits listed in the Electrical Specifications.