Analog to Digital Conversion

(Published Dec. 2007, last update Feb. 26 2009)

Analog to digital conversion is one of the most needed functions in mixed signal design. Most sensors provide analog signals (voltage, current) that must be converted into computer readable data.
The history of analog to digital conversion is long. The number of concepts found throughout the last at least four decades is high. This page list some, but surely not all possible implementations.

1. Flash converters

The fastest but also the most expensive implementation. Requires extremely high analog performance of the selected technology.

2. Voltage to Frequency conversion

Simple but needs high precision components and frequent calibration. Was used before the era of high integration.

3. Dual Slope Converters

Slow but very accurate. A good choice for slow high precision measurements.

4. Successive Aproximation Converters

The standard topology implemented on many microcontrollers. A good choice for 8 to 10 bit resolution.

5. Tracking Converters

Simple and acceptably well usable for signals with limited slew rate. Probably the smallest thing you can build on an integrated circuit.

6. Delta Sigma Converters

Currently the optimum for technologies offering poor analog capabilities and high performance digital capabilities. Suggested for 0.35mm and smaller technologies.