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dsPIC33A 12-bit 40MSPS Analog-to-Digital Converter (ADC) Deep Dive

Analog-to-Digital Converter (ADC) Input and Data Format

Last modified by Microchip on 2026/03/31 13:08
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The dsPIC33A Analog-to-Digital Converter (ADC) supports two distinct types of analog input signals:

Single-Ended Mode

When DIFF = 0, the ADC operates in Single-ended mode. The conversion result is measured relative to the ADC’s ground pin. VINN serves as the ground reference, and VINP is the signal input. The maximum input voltage is limited by AVDD - AVSS, with the usable range being (VREF – AVSS). The data channel output is unsigned data.

  • Signal input single-ended mode (DIFF= 0)
  • Data channel output, unsigned data
  • VSR = input signal range (AVDD max)
  • VINP = positive Input
  • VINN = negative input  (0VDC)

Single-Ended Mode

Differential Mode

When DIFF = 1, the ADC is in differential mode. It measures the voltage delta between VINP and VINN.  The maximum allowed differential voltage between VINP and VINN is ±VREF/4. For a typical VREF of 3.3V, this means the maximum differential input is ±0.825V centered around the Common mode voltage. If the voltage difference exceeds ±VREF/4, the ADC output will be clamped to its minimum or maximum value. In differential mode, the common mode voltage should be within AVDD – (VREF/4) to AVSS + (VREF/4) to allow the full differential range. Data channel output is signed data (two’s compliment)

  • Signal input differential mode (DIFF= 1)
  • Data channel output, signed data (two’s compliment)
  • VSR/2 = input signal range (AVDD max /2)
  • VINP = positive input
  • VINN = negative input

Differential Mode