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[原创] They are ubiquitous in modern systems, including IoT devices, medical imaging, industrial control

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发表于 昨天 03:41 | 显示全部楼层 |阅读模式

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[color=var(--md-box-samantha-normal-text-color) !important]Data converters are critical analog-digital interface circuits that bridge continuous-time analog signals (e.g., sensor outputs, audio, RF) and discrete-time digital signals (e.g., microprocessor inputs, digital storage). They are ubiquitous in modern systems, including IoT devices, medical imaging, industrial control, 5G/6G communications, and consumer electronics. The [color=var(--md-box-samantha-deep-text-color) !important]analysis of data converters focuses on evaluating their performance against key metrics, while [color=var(--md-box-samantha-deep-text-color) !important]design involves selecting architectures, circuit topologies, and mitigating non-idealities to meet application-specific requirements.
1. Core Classification of Data Converters[color=var(--md-box-samantha-normal-text-color) !important]Data converters are divided into two primary categories, each with distinct principles and use cases:

[td]
Type
Function
Key Application Scenarios
[color=var(--md-box-samantha-deep-text-color) !important]DAC (Digital-to-Analog Converter)
Converts discrete digital codes (binary/gray) into continuous analog voltages/currents.
Audio amplifiers, display drivers, motor control, signal synthesis.
[color=var(--md-box-samantha-deep-text-color) !important]ADC (Analog-to-Digital Converter)
Converts continuous analog signals into discrete digital codes.md-box-samantha-normal-text-color) !important]tv.sohu.com/v/dXMvMzM1MTQyMTg0LzY2NTI1MzQwNC5zaHRtbA==.html


Sensor readouts, medical imaging (CT/MRI), RF receivers, oscilloscopes.


2. Critical Performance Metrics (For Analysis)[color=var(--md-box-samantha-normal-text-color) !important]Performance metrics define how well a data converter maps between analog and digital domains. They are split into [color=var(--md-box-samantha-deep-text-color) !important]static (DC/low-frequency behavior) and [color=var(--md-box-samantha-deep-text-color) !important]dynamic (AC/high-frequency behavior) categories—both are essential for analysis.
2.1 Static Performance Metrics[color=var(--md-box-samantha-normal-text-color) !important]These metrics quantify deviations from the [color=var(--md-box-samantha-deep-text-color) !important]ideal transfer function (a linear relationship between input and output) at steady state.

[td]
Metric
Definition
Impact
[color=var(--md-box-samantha-deep-text-color) !important]Resolution (N)
Number of bits (N) defining the number of discrete levels: 2^N levels. Higher N = finer signal granularity.
A 12-bit ADC has 4096 levels; a 16-bit ADC has 65536 levels. Critical for precision (e.g., medical sensors).
[color=var(--md-box-samantha-deep-text-color) !important]Full-Scale Range (FSR)
Maximum analog signal range (e.g., 0–5V or ±2.5V).
Determines the largest signal the converter can handle without clipping.
[color=var(--md-box-samantha-deep-text-color) !important]LSB (Least Significant Bit)
Smallest analog step size: LSB = FSR / (2^N - 1) (for unipolar) or FSR / 2^N (for bipolar).
Defines the converter’s minimum detectable signal change.
[color=var(--md-box-samantha-deep-text-color) !important]Offset Error
Deviation of the first transition (e.g., digital code 0001 for ADC) from its ideal analog input.
Causes a constant shift in the transfer curve; corrected via calibration.
[color=var(--md-box-samantha-deep-text-color) !important]Gain Error
Deviation of the last transition (e.g., digital code 1110 for ADC) from its ideal input, relative to FSR.
Introduces a linear scaling error; corrected via gain calibration.
[color=var(--md-box-samantha-deep-text-color) !important]DNL (Differential Non-Linearity)
Deviation of an actual step size (between consecutive codes) from the ideal LSB: DNL = (Actual Step - LSB) / LSB.
A DNL > 1 LSB means a [color=var(--md-box-samantha-deep-text-color) !important]missing code (critical for linearity).
[color=var(--md-box-samantha-deep-text-color) !important]INL (Integral Non-Linearity)
Maximum deviation of the actual transfer curve from the ideal linear line (after offset/gain correction), in LSBs.
Quantifies cumulative linearity errors; critical for precision applications.


2.2 Dynamic Performance Metrics[color=var(--md-box-samantha-normal-text-color) !important]These metrics evaluate how well the converter handles [color=var(--md-box-samantha-deep-text-color) !important]time-varying signals (e.g., high-frequency inputs) and quantifies noise/distortion.

[td]
Metric
Definition
Formula/Interpretation
[color=var(--md-box-samantha-deep-text-color) !important]Sampling Rate (f_s)
Number of samples the converter processes per second (for ADCs) or updates per second (for DACs).
Measured in MSPS (Mega-samples per second) or GSPS (Giga-samples per second).
[color=var(--md-box-samantha-deep-text-color) !important]Nyquist Frequency (f_N)
Half the sampling rate (f_N = f_s / 2). For ADCs, inputs above f_N cause [color=var(--md-box-samantha-deep-text-color) !important]aliasing (must be filtered).
Critical for anti-aliasing filter design.
[color=var(--md-box-samantha-deep-text-color) !important]SNR (Signal-to-Noise Ratio)
Ratio of the fundamental signal power to the total noise power (quantization noise + thermal noise + flicker noise).
Ideal SNR (quantization-only): SNR_ideal = 6.02N + 1.76 dB (for sine-wave inputs).
[color=var(--md-box-samantha-deep-text-color) !important]THD (Total Harmonic Distortion)
Ratio of the fundamental signal power to the sum of powers of all harmonic components (distortion from non-linearities).
Lower THD = less distortion (e.g., < -80 dB for high-fidelity audio).
[color=var(--md-box-samantha-deep-text-color) !important]SNDR (Signal-to-Noise-and-Distortion Ratio)
Ratio of the fundamental signal power to the sum of noise and harmonic distortion power.
More realistic than SNR for real-world converters.
[color=var(--md-box-samantha-deep-text-color) !important]ENOB (Effective Number of Bits)
Converts SNDR into equivalent bits (accounts for both noise and distortion): ENOB = (SNDR - 1.76) / 6.02.
A 12-bit ADC with ENOB = 10.5 bits performs like a ideal 10.5-bit converter.
[color=var(--md-box-samantha-deep-text-color) !important]SFDR (Spurious-Free Dynamic Range)
Ratio of the fundamental signal power to the power of the largest spurious (non-harmonic) component.
Critical for communications (spurs can interfere with adjacent channels).


3. Digital-to-Analog Converters (DACs): Analysis & Design[color=var(--md-box-samantha-normal-text-color) !important]DACs take an N-bit digital code and generate an analog output proportional to the code. Their design focuses on [color=var(--md-box-samantha-deep-text-color) !important]linearity, [color=var(--md-box-samantha-deep-text-color) !important]settling time, and [color=var(--md-box-samantha-deep-text-color) !important]power efficiency.
3.1 Core Operating Principle[color=var(--md-box-samantha-normal-text-color) !important]For an N-bit unipolar DAC, the ideal analog output V_OUT is:
V_OUT = V_REF * (D / 2^N),
where V_REF is the reference voltage, and D is the digital code (0 ≤ D ≤ 2^N - 1).

3.2 Common DAC Architectures[color=var(--md-box-samantha-normal-text-color) !important]Each architecture trades off speed, resolution, linearity, and area.
[color=var(--md-box-samantha-normal-text-color) !important][color=var(--md-box-samantha-normal-text-color) !important]my.tv.sohu.com/us/335142184/665253404.shtml




[td]
Architecture
Working Principle
Key Advantages
Key Disadvantages
Use Cases
[color=var(--md-box-samantha-deep-text-color) !important]R-2R Ladder DAC
Resistor network with values R and 2R, generating binary-weighted currents/voltages.
- Simple design
- Low area (no binary-weighted resistors)
- Good linearity (if resistors match)
- Slow settling time (RC delays)
- Sensitive to resistor mismatch
Low-speed, medium-resolution (8–12 bits): industrial control, audio.
[color=var(--md-box-samantha-deep-text-color) !important]Current-Steering DAC
Binary-weighted or thermometer-coded current sources summed to generate output current.
- High speed (fast settling)
- Good for




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