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What is an A/D converter?

A/D Converter Configuration 2 (Pipeline Type)


In the case of a 1.5bit/stage configuration, the following processes are repeated in order from Stage 1 that determines MSB via pipeline operation (VREF: Reference Voltage).

  • Analog input is sampled (using an S&H circuit)
  • At the same time the analog input is converted by ADC into a 3-value digital format (1.5bit). (Here the digital output stage is defined.)
    • Analog input ≦ -VREF/4 → D="00"
    • -VREF/4 < Analog input ≦ +VREF/4 → D="01"
    • +VREF/4 < Analog input →D="10"
  • These digital values are then converted into analog values using a digital to analog converter (DAC).
    • D="00" → DAC output:-VREF/2
    • D="01" → DAC output:0
    • D="10" → DAC output:+VREF/2
  • The negative DAC output voltage is amplified (x2) and output to the next stage.

Once processing of Stage N that determines LSB is completed the delay between each stage is corrected then digital conversion completed by adding the respective digital output.

Basic Bipolar Type A/D Converter Configuration
  • High resolution enabled (up to 16bit)
  • High-speed conversion possible (200MHz max. sampling frequency)
  • There is a necessary wait time until the digital signal is output (based on bipolar operation), making this impractical for applications requiring real-time processing (i.e. control).
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