Data converters are electronic circuits that interface between analog and digital signals.

8.1 Principles of Data Conversion

• Resolution: The minimum change in analog input voltage required to produce a change in the digital output. It is dependent on the number of bits (N) in the digital word. It can be expressed as: Resolution=\frac{V_{FS}}{2^{N}-1}, where V_{FS} is the full-scale voltage.
• Conversion Time: The time required for a converter to perform its conversion.

8.2 Digital-to-Analog Converters (DACs)

DACs convert a digital binary input into an equivalent analog output signal.

• Weighted Resistor DAC: Uses binary-weighted resistors in an inverting adder circuit. Its main disadvantage is the wide range of resistor values required, which becomes difficult to fabricate accurately for high-bit converters.
• R-2R Ladder DAC: Uses a repeating ladder network of only two resistor values (R and 2R). This design is easier to fabricate accurately and is scalable, making it preferable to the weighted resistor type.

8.3 Analog-to-Digital Converters (ADCs)

ADCs convert an analog input signal into an equivalent digital binary code.

8.3.1 Direct Type ADCs

These converters perform the conversion directly by comparing the analog input to an internally generated reference.

• Counter Type ADC: Uses a counter to increment a digital value, which is converted to an analog signal via a DAC and compared to the input. The process stops when the internal signal exceeds the input.
• Successive Approximation ADC: A more efficient method that uses a Successive Approximation Register (SAR) to perform a binary search for the correct digital value, converging much faster than the counter type.
• Flash Type ADC: The fastest type of ADC. It uses a bank of comparators and a priority encoder to determine the digital output simultaneously. A 3-bit flash ADC requires 7 comparators.

8.3.2 Indirect Type ADCs

These converters first transform the analog signal into a time or frequency representation before converting to a digital value.

• Dual Slope ADC: Known for high accuracy. It first integrates the analog input voltage for a fixed period, then integrates a reference voltage of opposite polarity until the integrator output returns to zero. The time taken for the second phase is proportional to the input voltage, and this time is measured by a counter to produce the digital output.