adc design basics

**ADC (Analog-to-Digital Converter)** — a circuit that converts continuous analog signals into discrete digital numbers, the essential bridge between the physical and digital worlds. **Key Specifications** - **Resolution**: Number of bits (8, 10, 12, 14, 16, 24-bit). $2^N$ quantization levels - **Sampling Rate**: Samples per second (kS/s to GS/s) - **ENOB**: Effective Number of Bits (actual resolution including noise) - **SNR/SNDR**: Signal-to-noise ratio — fundamental performance metric **ADC Architectures** | Architecture | Speed | Resolution | Power | Use Case | |---|---|---|---|---| | Flash | Fastest (GS/s) | Low (6-8 bit) | High | RF, high-speed SerDes | | SAR | Fast (MS/s) | Medium (10-16 bit) | Low | IoT, sensor, SoC | | Pipeline | Fast (100MS/s+) | Medium (10-14 bit) | Medium | Comm, video | | Sigma-Delta (ΣΔ) | Slow (kS/s) | High (16-24 bit) | Low | Audio, precision measurement | | Time-Interleaved | Fastest (10+ GS/s) | Medium | High | 5G, radar, oscilloscopes | **SAR ADC (Most Common on SoCs)** - Binary search algorithm: Compare input to successively refined DAC output - N comparisons for N bits (e.g., 12 comparisons for 12-bit) - Excellent power efficiency — dominant in IoT, MCUs, and SoC peripherals **ADCs** are in every system that processes real-world signals — from smartphone microphones to autonomous vehicle sensors to scientific instruments.