Data Converter ICs: ADC, DAC & Sigma-Delta Converters

Every embedded system I’ve worked on eventually needs to bridge the gap between the analog world and digital processing. Temperature sensors, audio signals, motor controls—they all require some form of data converter IC to make the translation. Whether you’re digitizing a sensor output or generating an analog waveform from a microcontroller, understanding ADC DAC IC technology is fundamental to successful electronic design.

This guide covers the essential concepts, architectures, and practical considerations for selecting and implementing data converters in your PCB projects. We’ll look at the major ADC and DAC types, dive deep into sigma-delta converters, and provide the specifications and selection guidance you need for real-world applications.

What is a Data Converter IC?

A data converter IC is an integrated circuit that translates signals between analog and digital domains. This category includes two fundamental types:

Analog-to-Digital Converters (ADCs) sample continuous analog signals (like voltage from a sensor) and convert them into discrete digital values that microcontrollers and processors can work with.

Digital-to-Analog Converters (DACs) perform the reverse operation, taking digital data and producing corresponding analog outputs—essential for audio playback, motor control, and any application requiring analog output from a digital system.

These converters form the critical interface between the physical world and digital processing systems. Without them, your microcontroller can’t measure real-world signals, and your digital audio file can’t drive a speaker.

ADC Architectures and Types

Several ADC architectures have emerged to address different application requirements. Each offers distinct trade-offs between speed, resolution, power consumption, and cost.

Successive Approximation Register (SAR) ADC

The SAR ADC is probably the most common architecture you’ll encounter in general-purpose applications. It uses a binary search algorithm to determine the digital output, comparing the input against progressively refined reference voltages from an internal DAC.

How it works: The converter starts by comparing the input to half of the reference voltage (the MSB decision). Depending on whether the input is higher or lower, it then compares against 3/4 or 1/4 of the reference, and so on through each bit position.

Key characteristics:

• Resolution: Typically 8 to 18 bits
• Sample rates: Up to several MSPS
• Good balance of speed, accuracy, and power consumption
• No pipeline delay—results are available after each conversion

Flash (Parallel) ADC

Flash ADCs are the speed demons of the converter world. They use a bank of comparators—one for each possible output level—to perform the conversion in a single clock cycle.

For an n-bit flash ADC, you need 2^n – 1 comparators. This means an 8-bit flash ADC requires 255 comparators, making it expensive and power-hungry at higher resolutions.

Key characteristics:

• Resolution: Typically 4 to 8 bits (practical limit)
• Sample rates: Up to several GSPS
• Highest speed of any ADC architecture
• High power consumption and chip area

Pipeline ADC

Pipeline ADCs break the conversion into multiple stages, each resolving a few bits. The residue from each stage passes to the next, allowing conversions to overlap in a pipelined fashion.

Key characteristics:

• Resolution: 8 to 16 bits typical
• Sample rates: 10 MSPS to hundreds of MSPS
• Combines flash ADC speed with higher resolution
• Inherent latency (pipeline delay) of several clock cycles

Sigma-Delta (ΔΣ) ADC

We’ll cover sigma-delta converters in detail later, but briefly: they use oversampling and noise shaping to achieve very high resolution from a simple 1-bit converter core.

Key characteristics:

• Resolution: 16 to 24 bits typical
• Sample rates: Lower (suitable for DC to audio bandwidth)
• Excellent noise performance and accuracy
• Built-in digital filtering

ADC Architecture Comparison Table

DAC Architectures and Types

Digital-to-analog converters also come in several flavors, each suited to different applications.

Binary Weighted Resistor DAC

The simplest DAC concept uses resistors with binary-weighted values (R, 2R, 4R, 8R…) connected to an op-amp summing junction. Each bit switches its corresponding resistor to either the reference voltage or ground.

The problem? High-resolution DACs require extreme resistor ratios. A 12-bit converter needs resistors ranging from R to 2048R, making precision matching extremely difficult.

R-2R Ladder DAC

The R-2R ladder overcomes the binary-weighted DAC’s limitations by using only two resistor values arranged in a ladder network. This architecture is much easier to manufacture with good precision and scales well to higher resolutions.

Advantages of R-2R:

• Only two resistor values needed
• Easier to achieve precision matching
• Constant output impedance regardless of bit value
• Scalable to any number of bits

Current Steering DAC

Current steering DACs switch binary-weighted current sources to the output rather than voltages through resistors. They’re commonly used in high-speed applications because they can switch very quickly.

Key characteristics:

• Very high speed capability
• Common in video and RF applications
• Requires precision current sources

Delta-Sigma DAC

Like their ADC counterparts, sigma-delta DACs use oversampling and noise shaping to achieve high resolution with simple analog circuits. They dominate the audio DAC market.

Key characteristics:

• Excellent linearity
• Very high resolution possible
• Digital filtering handles most signal processing
• Preferred for audio applications

DAC Architecture Comparison Table

Understanding Sigma-Delta Converters

Sigma-delta (or delta-sigma) converters deserve special attention because they dominate precision measurement and audio applications. Their operation is fundamentally different from Nyquist-rate converters like SAR and flash ADCs.

The Sigma-Delta Principle

At its core, a sigma-delta modulator is remarkably simple: an integrator, a 1-bit quantizer (comparator), and a 1-bit DAC in a feedback loop. This simple analog circuit runs at a very high “oversampled” rate—often 64x to 256x faster than the output data rate.

The magic happens through two mechanisms:

Oversampling spreads quantization noise across a much wider frequency band. If you sample 64 times faster than needed, the noise in your frequency band of interest drops significantly.

Noise shaping uses the feedback loop to push quantization noise out of the signal band and into higher frequencies. The modulator effectively acts as a low-pass filter for the signal but a high-pass filter for quantization noise.

Digital Filtering and Decimation

The sigma-delta modulator outputs a high-speed 1-bit stream where the density of 1s represents the input signal level. A digital filter then:

1. Low-pass filters this bitstream to extract the signal
2. Removes the out-of-band noise pushed there by noise shaping
3. Decimates (reduces) the sample rate to a useful value

The result is a high-resolution output at a practical data rate. A 24-bit sigma-delta ADC might run its modulator at 6.144 MHz but output 24-bit data at 48 kHz for audio applications.

Sigma-Delta Modulator Orders

Higher-order modulators (using multiple integrators) shape noise more aggressively:

Higher orders improve resolution but require careful design to ensure stability. Many practical sigma-delta ADCs use second or third-order modulators with multi-stage noise shaping (MASH) architectures for stability.

When to Choose Sigma-Delta

Sigma-delta converters excel when you need high resolution and can tolerate lower sample rates:

• Precision measurement (temperature, pressure, strain, load cells)
• Audio conversion (both ADC and DAC)
• Industrial sensors and process control
• Battery monitoring and power metering

They’re less suitable for high-bandwidth applications or systems requiring fast multiplexed inputs (the digital filter needs settling time after each channel change).

Key Data Converter Specifications

Understanding these specifications helps you select the right data converter IC for your application.

Resolution

Resolution defines the number of discrete output levels. An n-bit converter divides the input range into 2^n steps. However, stated resolution and actual performance often differ.

Effective Number of Bits (ENOB)

ENOB represents the actual resolution achieved considering noise and distortion. A 16-bit ADC might only achieve 14 ENOB due to internal noise. ENOB is calculated from signal-to-noise-and-distortion ratio (SINAD):

ENOB = (SINAD – 1.76) / 6.02

Sample Rate and Bandwidth

The sample rate must exceed twice the highest signal frequency (Nyquist criterion). In practice, you want at least 5-10x the signal bandwidth for accurate representation. Anti-aliasing filters before the ADC remove frequencies above Nyquist/2.

DNL and INL

Differential Non-Linearity (DNL) measures how much each step deviates from ideal. DNL greater than 1 LSB causes missing codes.

Integral Non-Linearity (INL) measures the maximum deviation of the actual transfer function from an ideal straight line.

Signal-to-Noise Ratio (SNR)

SNR compares signal power to noise power, typically expressed in dB. Higher is better. Theoretical maximum SNR for an ideal n-bit converter is approximately 6.02n + 1.76 dB.

Read more IC types:

ADC vs DAC: Analog-to-Digital and Digital-to-Analog Converters Guide

ASIC Design Guide: Application-Specific Integrated Circuits

Audio Amplifier ICs: Types, Selection Guide & Applications

BGA (Ball Grid Array) Package: Guide to High-Density ICs

Codec ICs Explained: Audio & Video Encoding/Decoding

Comparator IC: Working Principle, Types & Applications

CSP & WLCSP: Chip Scale Packaging for Miniaturization

Data Converter ICs: ADC, DAC & Sigma-Delta Converters

Digital Logic ICs: AND, OR, NOT Gates & Flip-Flops Guide

Digital PCB & IC Design: Logic Circuit Board Layout Guide

DIP (Dual In-Line Package): Classic IC Package Explained

DSP (Digital Signal Processor) IC Guide for Beginners

ECL (Emitter-Coupled Logic): High-Speed IC Technology

FPGA vs ASIC: Complete Comparison Guide [2025]

GaAs & SiGe: High-Frequency Semiconductor Technologies

IC Fabrication Technologies: CMOS, BiCMOS, TTL & More

IC Package Types: Complete Guide (DIP, SMD, QFP, BGA)

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Voltage Regulator ICs Explained: LDO, Linear, and Switching Types

What is a Microcontroller? Beginner’s Complete Guide

Popular Data Converter ICs

Here’s a selection of commonly used ADC DAC IC parts across different categories:

Popular ADC ICs

Popular DAC ICs

Data Converter Selection Guide

Choosing the right converter involves matching your requirements to available architectures:

For High Resolution, Low Speed (Sensors, Measurement)

Choose sigma-delta ADCs. They offer 16-24 bit resolution, excellent noise rejection, and often include integrated features like PGAs and multiplexers. Look at parts like ADS1256, AD7175, or MAX11270.

For Medium Resolution, Medium Speed (General Data Acquisition)

SAR ADCs are typically your best choice. They offer a good balance of speed, resolution, and power. Consider parts like AD7606, ADS8688, or LTC2378.

For High Speed (Video, Communications, RF)

Pipeline ADCs handle the speed requirements. For lower resolutions (8-bit video), flash converters work too. Look at AD9268, LTC2387, or ADS54J series.

For Audio Applications

Delta-sigma dominates here. PCM512x series, ES9038, and CS43xx families are popular choices. They provide the resolution and distortion performance audio demands.

For interfacing with complex programmable logic, Altera FPGA devices often include hardware support for high-speed ADC interfaces like JESD204B.

Design Considerations for Data Converters

Reference Voltage

The reference voltage directly impacts accuracy. External precision references (like REF5050 or ADR4550) outperform internal references when accuracy matters. Keep reference bypassing tight and layout clean.

Power Supply

Separate analog and digital supplies when possible. Use low-noise LDOs rather than switching regulators for sensitive converters. Adequate decoupling (0.1µF ceramic plus bulk capacitance) is essential.

PCB Layout Guidelines

• Keep analog input traces short and shielded
• Separate analog and digital ground planes, joined at a single point near the converter
• Route digital signals away from analog inputs
• Use ground pours under sensitive analog circuitry
• Place decoupling capacitors as close as possible to power pins

Anti-Aliasing and Reconstruction Filters

ADCs need anti-aliasing filters before the input to remove frequencies above Nyquist/2. DACs need reconstruction filters after the output to smooth the stepped waveform. Simple RC filters work for many applications; active filters provide sharper cutoffs when needed.

Useful Resources for Data Converter Design

Design Tools and Calculators

• Analog Devices ADIsimADC: ADC selection and performance simulation
• Texas Instruments WEBENCH: Analog circuit design including data converter support
• Microchip MAPS: Product selection and design resources

Technical References

• Analog Devices Data Conversion Handbook
• TI Precision Labs – ADCs
• Maxim ADC Tutorial Series

Component Sources

• DigiKey Data Converters
• Mouser ADC/DAC Selection
• Arrow Component Search

Frequently Asked Questions

What is the difference between ADC resolution and effective resolution (ENOB)?

Resolution is the number of bits in the converter’s output—a 16-bit ADC produces 16-bit values. Effective Number of Bits (ENOB) represents the actual usable resolution after accounting for noise, distortion, and other non-idealities. A 16-bit ADC might only achieve 13-14 ENOB due to internal noise sources. When selecting converters, check the ENOB specification at your operating frequency, not just the stated resolution.

When should I choose a sigma-delta ADC over a SAR ADC?

Choose sigma-delta when you need very high resolution (20+ bits) for slowly changing signals like temperature, pressure, or weight measurements. The inherent digital filtering provides excellent noise rejection. Choose SAR when you need faster sample rates, need to multiplex multiple inputs quickly (sigma-delta filters need settling time after channel changes), or when low latency matters. For most general-purpose sensor applications up to 16 bits, SAR converters offer a good balance.

How do I determine the required sample rate for my ADC?

At minimum, sample at twice the highest frequency component in your signal (Nyquist criterion). In practice, sample at 5-10x the maximum signal frequency to accurately capture the waveform. For example, audio signals up to 20 kHz need at least 40 kHz sampling—CD audio uses 44.1 kHz. For bandwidth-limited applications, sigma-delta ADCs can provide very high resolution with modest sample rates. Always include an anti-aliasing filter to remove frequencies above half the sample rate.

What causes missing codes in an ADC?

Missing codes occur when an ADC skips certain output values in its transfer function. This happens when Differential Non-Linearity (DNL) exceeds 1 LSB—meaning a step is either too small (code is never output) or too large (skips to the next code). Quality ADCs specify “no missing codes guaranteed” for critical applications. Missing codes are more likely in high-resolution converters where LSB steps are very small. Check DNL specifications and choose monotonic converters for applications like closed-loop control where every code must be represented.

How do I reduce noise in my data converter circuit?

Start with good PCB layout: separate analog and digital grounds, use ground planes, keep analog input traces short and shielded. Use precision external voltage references instead of internal references for critical applications. Power the converter from low-noise LDOs rather than switching regulators—or at minimum, filter switcher outputs with ferrite beads and additional capacitance. Add appropriate input filtering to reject noise outside your signal band. For sigma-delta converters, take advantage of the built-in digital filtering by selecting the lowest sample rate that meets your needs—lower rates mean more averaging and lower noise.

Conclusion

Data converter ICs bridge the essential gap between analog signals and digital processing. Understanding the trade-offs between ADC architectures—from the versatile SAR to the precision sigma-delta to the blazing-fast flash—helps you select the right converter for each application.

Key takeaways for selecting ADC DAC IC solutions:

• Match architecture to requirements: SAR for general purpose, sigma-delta for precision, pipeline for speed
• Look beyond resolution to ENOB, SNR, and linearity specifications
• Consider interface requirements (SPI, I2C, parallel) and available microcontroller resources
• Pay attention to reference voltage, power supply, and PCB layout—they often limit real-world performance more than the converter itself
• Use anti-aliasing and reconstruction filters to maintain signal integrity

With the right converter selected and properly implemented, you’ll have a solid foundation for interfacing your digital systems with the analog world.