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Pipeline ADC

Jul 13, 2024

Pipeline ADC

Introduction

  • Focus on Pipeline ADC
  • Input voltage to be digitized using Pipeline ADC
  • Comparison with Subranging Converters

Key Components

  • Sample and Hold Circuit: First step in digitizing the input signal
  • Coarse ADC: Converts input to digital initially
  • Fine ADC: Completes conversion, providing full digital output
  • Residue Amplifier: Amplifies the difference between DAC output and original input

Process Overview

  1. Time (t1): Input voltage sampled and held
  2. Coarse ADC Operation: Initial digitization and residue generation
  3. Residue Amplification: Amplifies the difference for Fine ADC
  4. Fine ADC Operation: Final digitization after residue amplification

Conversion Timing

  • Coarse ADC must wait for Fine ADC to finish before starting next input
  • Causes inefficiency: prolonged conversion time
  • Affects throughput: fewer samples in given time span

Pipeline ADC Advantages

  • Minimizes idle time for Coarse ADC
  • Increases overall throughput
  • Allows multiple samples within the same timeframe

Working Stages

  • Multiple stages: Sample and Hold, k-bit ADC, DAC, Residue Amplifier
  • Operations occur in sequence across stages
  • Isolation between stages allows concurrent processing

Workflow in Pipeline ADC

  1. Stage 1: Initial sample and digitize
  2. Stage 2 onwards: Process residue from Stage 1 and accept new sample
  3. Each stage operates on current input while previous stages work on residues

Pipeline Efficiency

  • Enables acceptance of new input as soon as previous stage completes
  • Reduces overall conversion time significantly
  • More samples processed concurrently

Example Workflow

  1. First Stage: Accepts input at time (t1), starts digitization
  2. Second Stage: Processes residue from first stage by time (t2)
  3. Each subsequent stage continues processing residues from previous stage
  4. Pipeline allows efficient and continuous sampling/digital conversion

Practical Example

  • Consider a 10-bit ADC implementation
  • Possible configuration: First stage with 1 bit, subsequent stages with 3 bits each
  • Digital output available after several clock pulses

Conclusion

  • Pipeline ADC optimizes conversion time and throughput significantly
  • Efficiently handles multiple samples in a continuous and streamlined process

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