1. What is an ADC chip? ADC stands for Analog to Digital Converter. Its function is to convert the "continuously changing" analog signals in the real world (such as temperature, voltage, sound, light, etc.) into "discrete digital signals" (such as binary codes like 010101) that can be understood by computers or digital chips. It can be simply understood as:
🧠 The real world speaks "human language" (analog signals)
💻 Digital chips only understand "code" (digital signals)
ADC is the "translator" between these two worlds. 2. Why is ADC chip important? Almost all physical signals around us are analog, such as ECG signals, sounds collected by microphones, pressure or temperature read by sensors, etc. However, we hope to use digital systems (such as MCU, DSP, FPGA) for processing, calculation, analysis, storage, etc.Therefore, ADC is a necessary link in the process. Without it, the digital system is like a deaf person who can't hear anything. Its importance can be summarized in two points: Interface bridge: connecting the analog world and the digital world; Data starting point: It is the first link in the digital signal processing link, which determines how "clearly" the back-end system can see and how "timely" it can respond. 3. The core principle of ADC: How to "translate" analog signals into digital? Analog-to-digital conversion is essentially mapping a continuous analog voltage to a discrete digital code. The working process of ADC can be divided into three steps: Sampling
The continuous-time analog signal is "captured" at a certain frequency to capture a set of values ​​(similar to a camera shutter, capturing one frame each time). This frequency is the "sampling rate". Hold
Keep the signal unchanged after the sampling moment so that the subsequent circuit can process it slowly (avoid signal fluctuations during the processing). Quantization and encoding
Map the voltage value into a specific binary digital code, such as 3.1V mapped to a code like "101011". ⚠️ Note: This process will inevitably lose some accuracy, which is the so-called "quantization error". 4. Common ADC architecture types There are many types of ADCs, each suitable for different scenarios and accuracy requirements. The following are the most common types in engineering:1. SAR type (Successive Approximation Register) Features: Medium rate, medium to high precision, low power consumption. Principle: Compare the input signal with the voltage generated by the internal DAC bit by bit, and gradually approach the true value. Application: MCU integration, industrial instruments, meters, audio control, etc. 2. Σ-Δ type (Sigma-Delta ADC) Features: High precision, low rate, strong anti-noise ability. Principle: Oversampling + noise shaping + digital filter processing. Application: Audio processing, medical instruments (such as electrocardiogram), precision measurement, etc. 3. Flash type (Flash memory ADC) Features: Ultra-high speed, ultra-high bandwidth, high power consumption. Principle: Use a large number of comparators in parallel for simultaneous comparison, and convert almost instantly. Application: High-frequency communication, radar system, high-speed video acquisition.4. Pipeline ADC Features: Medium-high speed, medium precision. Principle: Split the conversion task into multiple stages (Pipeline), each stage processes a portion of the bits. Application: Communication base stations, high-speed data acquisition cards, image systems, etc. V. Key performance indicators: How to evaluate an ADC? Resolution (Resolution) Unit: Bit (bit) indicates how many different voltage levels can be distinguished. For example, a 12-bit ADC has 2¹² = 4096 levels. Sampling Rate (Sampling Rate) Unit: SPS (Sample per Second) indicates how many samples can be collected per second. High-speed systems such as communications and video require high sampling rates.The signal-to-noise ratio (SNR) quantifies the inevitable noise that affects the result during the conversion. The higher the SNR, the cleaner the signal. The total harmonic distortion plus noise (THD+N) measures the fidelity of the ADC to the input signal. The effective number of bits (ENOB) takes into account the actual useful resolution bits after noise and error, which is usually lower than the theoretical resolution. Power consumption is particularly important for portable devices.Input voltage range, reference voltage, interface type (SPI/I²C/parallel port), etc. 6. Manufacturing process and packaging characteristics of ADC chips Analog signals are very sensitive to noise, power supply interference, circuit matching, etc. Therefore, ADC prefers to use mature and stable process nodes, such as 0.18um, 0.13um, and even older 0.35um, rather than pursuing advanced processes. Some high-performance ADCs also use 28nm CMOS+ mixed signal design, but it mainly depends on application requirements. In terms of packaging, traditional small packages such as QFN, TSSOP, DIP, etc. are generally used, and some high-end ADCs use BGA packaging to enhance performance.7. Engineering Challenges of ADC Chip Design Difficulty in Noise Control The analog part is extremely sensitive to power supply, layout, and electromagnetic interference, and requires strict design. The trade-off between power consumption and accuracy. Improving accuracy usually requires more circuits and more power consumption, and a balance needs to be struck between target specifications and battery life. Clock jitter has a significant impact on high-speed ADCs. The testing cost is high, especially for high-resolution ADCs, which require an extremely clean environment and expensive equipment. Analog design relies heavily on experience. Many details cannot be automatically completed through EDA tools, and require years of experience from experienced engineers to adjust parameters and match components.8. Typical application fields of ADC chips Application direction Use scenarios Audio acquisition, capacitive screen touch, sensor interface in consumer electronics mobile phones Industrial control PLC collects temperature, voltage, current, and pressure signals and transmits them to the control system Medical equipment ECG and EEG acquisition systems require extremely high precision and low noise Communication system Collects RF signals in base stations for signal processing, requiring high speed and high precision Signal processing in sensor systems such as automotive electronics radar, camera, TPMS, etc. Aerospace high-reliability analog acquisition system for telemetry and monitoring 9. Future development trend Fusion SoC
More and more ADCs are integrated into MCU, FPGA, DSP and other systems. Low power optimization
For IoT and wearable devices, continue to optimize power consumption below mW. High speed and high precision
New architecture development such as hybrid SAR-Flash attempts to meet bandwidth and precision requirements at the same time. Smart ADC development
Add basic processing units (such as filters, triggers, etc.) to perform simple processing at the front end to reduce the burden on the back end. Summary. ADC chip is a bridge connecting the real world and the digital world, and it is indispensable in almost all electronic systems. Although it may not be as dazzling as CPU and GPU, its stability and accuracy directly affect the data quality of the entire system.The engineering challenges in the ADC field are concentrated on the accumulation of analog design experience, circuit noise control, and system integration complexity, which is why an excellent ADC designer often spends ten years honing his skills. If you are a novice engineer, it is recommended to start with SAR ADC to understand the most basic working mechanism; if you are a system developer, mastering the ADC parameter selection and application scenario matching will help you improve the systematicity and robustness of the overall design.