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Successive Approximation ADC - Coggle Diagram
Successive Approximation ADC
Concept
Meaning
A type of ADC that converts an analog signal into a digital output using a binary search algorithm.
Determines each bit sequentially, starting from the Most Significant Bit (MSB) to the Least Significant Bit (LSB).
Objective
To accurately and quickly convert analog voltages into digital form for processing in embedded systems.
Examples
Used in microcontrollers like the ATmega328P, instrumentation devices, and digital sensors.
Functional Blocks
Comparator
Compares input analog voltage (Vin) with the DAC’s output voltage (Vdac).
Outputs high or low depending on which signal is larger.
Digital-to-Analog Converter (DAC)
Converts trial digital code from SAR into an analog voltage for comparison.
Determines whether to keep or reset bits during conversion.
Successive Approximation Register (SAR)
Controls conversion sequence bit by bit.
Stores intermediate and final binary results.
Control Logic
Synchronizes SAR, DAC, and comparator operation.
Ensures proper timing and output storage.
Sample-and-Hold (S/H) Circuit
Holds the analog voltage steady during conversion.
Prevents signal fluctuation error
Working Principle
Sampling
Analog signal is captured and held by the S/H circuit.
Bit Testing
SAR sets MSB = 1, DAC generates corresponding voltage.
Binary Search
SAR keeps or resets bits based on comparator result.
Process continues for each bit down to the LSB.
Output
Final digital code stored in ADC data register.
Represents closest digital equivalent of the input analog voltage.
Characteristics
Resolution
Determines how finely the input voltage is divided
Speed
Faster than integrating ADCs; slower than Flash ADCs.
Accuracy
High accuracy when using a stable reference and precise DAC.
Conversion Time
Requires one comparison per bit; for n-bit ADC, n cycles are needed.
Advantages & Limitations
Advantages
High accuracy and deterministic conversion time.
Low power consumption compared to Flash ADCs.
Compact design—ideal for embedded applications.
disadvantages
Slower than Flash ADCs due to sequential operation.
Needs stable input during conversion
Applications
Embedded Systems
Microcontrollers (ATmega328P, STM32, etc.) for sensor data acquisition.
Instrumentation
Used in digital multimeters, data loggers, and control systems.
Automation & Robotics
Converts analog sensor readings (temperature, pressure, light, etc.) to digital data.