3.1 Differential Signal Measurement

The ADC peripheral of the PIC16F17146 and PIC16F18146 families of microcontrollers supports a Single-Ended and Differential Measurement mode. The modes are configured using the ADC Input Configuration (IC) bit of the ADCON0 register.

The simple and most widely used analog sensors provide single-ended signals, which occupy only one analog microcontroller input per sensor. There is a large selection of available sensors in case of single-ended measurement. The simplicity and ease of use come with a few challenges, such as the sensors being sensitive to noise along the analog signal path and to common-mode noise on the ground and reference voltage levels of the microcontroller. The signal path between the sensor and the microcontroller should be as short as possible to minimize noise and ground-level differences.

Differential inputs offer the best performance by rejecting DC and dynamic common-mode voltages. In a differential signal system, two lines carry the desired signals, and the signals run in parallel to each other. As a result, an equal amount of noise occurs on both the lines. As the differential ADC measures the difference in voltage between the positive and negative terminals, the common noise is rejected. This results in an improved signal-to-noise ratio while also removing even-order harmonics. Figure 3-1 shows the common mode noise cancellation in Differential mode configuration.

Refer to the Differential and Single-Ended ADCC whitepaper for more details regarding both modes.

Below are the application examples showcasing the usage of the ADC in Differential Measurement mode.