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What is an A/D converter?

A/D Converter Configuration 3 (Successive Approximation Type)


This method compares the sampled analog input with the converter's output in succession, starting with the MSB.

  • The analog input signal is sampled (S&H)
  • A successive approximation register (SAR), which is designed to supply an approximate digital code to the internal DAC, is initialized so that the most significant bit (MSB) is set to '1'.
  • The digital values from the SAR are converted into equivalent analog values by the internal DAC.
  • The sampled input voltage is compared with the DAC output voltage.
    • If the sampled voltage > DAC output voltage → MSB = 1
    • If the sampled voltage < DAC output voltage → MSB = 0

The digital conversion is completed by repeating the operation up to LSB.

Basic configuration of a successive approximation type converter Successive comparison (large/small)
  • High resolution conversion possible (up to 18bit)
  • Since a clock cycle is required (resolution + α), conversion speed is moderate (10MHz max. sampling frequency)
  • Good response. Connecting a multiplexer to the the input makes it easy to switch analog signals.
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