Simplifying Signal Chain Data Acquisition Design with Standardized, Customizable Solutions

Signal chains are integral to numerous electronic systems for communications, biomedical devices, industrial automation, instrumentation and sensors, and many other applications. System architects and hardware designers face numerous logistical and technical challenges in balancing specific requirements against the need to shrink footprints, minimize design iterations, and accelerate time to market. Those challenges make the case for more standardized, integrated solutions that can still be highly customized to meet application needs.

Signal chains typically include digital and analog components, such as analog-to-digital converters (ADCs), operational amplifiers, digital isolators, and application-specific components. Engineers and product designers seeking to create optimal solutions must navigate multiple trade-offs in component selection, including noise, power consumption, bandwidth, and cost.

Many designers create data acquisition signal chains for applications such as automated test equipment, aviation, machine automation, and, in healthcare, monitoring, diagnostics, and imaging systems. Hardware trends favor advanced precision data conversion performance and increased robustness for complex designs, often stressing thermal and printed circuit board (PCB) density limitations.

Achieving higher throughput, minimizing system power, and protecting and driving ADC inputs can create design conflicts over using highly integrated customer-specific integrated circuits (ICs) or discrete standard components that are more cost-effective. Either approach drives up research and development costs in developing high-performance, precision signal chain blocks for end applications. The customer-specific approach is usually more costly, but discrete devices are likely to degrade in their performance across the operating temperature and lifetime of the circuit.

Analog Devices, Inc. (ADI) addresses major data acquisition signal chain design issues by leveraging heterogeneous integration via system-in-package (SiP) technology to achieve higher density, increased functionality, enhanced performance, and longer mean-time-to-failure. ADI's precision signal chain μModule ® solutions provide a compact, customizable, and integrated solution that simplifies design, improves performance, and saves development time.

Improving density without performance falloff

A key goal of advanced precision signal chains is to improve the density of the signal chain without negatively impacting performance, as designers attempt to fit more channels into the same form factor or adopt an ADC-per-channel approach.

Data acquisition signal chains must often interface with multiple sensors with different common-mode voltages and input signals. Common problems include circuit imbalance or a mismatch in feedback and gain resisters that may result in undesirable signal-to-noise ratio (SNR), distortion, gain error, and input rejection ratios.

ADI's precision signal chain μModule solutions integrate multiple analog and digital components into a single module, utilizing the company's integrated passives technology—iPassives—with ADI signal conditioning ICs and SiPs. iPassives was developed at ADI several years ago to overcome past limitations and complexities of adopting discrete passive components manufactured separately and connected on a PCB. This provides developers with a flexible design tool to create robust system solutions with best-in-class performance and short development cycle times.

With μModule solutions, designers can create what appears to be a single device to deliver functionality that previously required multiple discrete components in board-level solutions. This approach eliminates mismatches and enables smaller footprints.

Faster time to market

System designers can achieve higher levels of integration and faster time to market while ensuring improved speed performance and reduced power consumption at an affordable price. The μModule approach enables complete solutions packaged in spatially efficient footprints and optimizes the signal chain's performance and reliability.

ADI’s precision signal chain μModule solutions aim to enhance density in a smaller form factor by combining top-notch devices and advanced 2.5D/3D assembly processes while maintaining intelligent and efficient management of the system components. Combining functions such as amplification, filtering, and ADC in a single module eliminates the need to craft a complex data acquisition signal chain solution with individual components. This approach significantly reduces interconnectivity parasitics such as inductance, capacitance, and resistance.

With predesigned, fabricated, characterized, and tested cores, ADI precision signal chain μModules can significantly reduce design time. They also come with preconfigured signal chains and ADI support resources, including evaluation boards and software development kits.

Designers can tailor the parameters and characteristics of the signal chain to specific application requirements through intelligent partitioning of components. Adjustable gain, bandwidth, filtering options, and other customizable features result in a versatile platform that addresses various design challenges.

Instead of struggling over intricate circuit-level implementation, with μModules, system designers can focus on system-level design and functionality, providing for more rapid prototyping and system validation and enabling faster time to market for innovative applications by promoting more aggressive scheduling of processes from system definition to parts delivery.

Passive components that impact performance and yield during manufacturing are integrated into the μModule device, which results in lower secondary costs, such as assembly pick and place, system PCB yield losses, field return support, and signal chain calibration. Integrating passive components into the PCB substrate reduces temperature-dependent error sources while minimizing the number of discrete components and interconnects on a PCB, ultimately reducing solder joints and improving reliability.

ADI's ADAQ7980 (Figure 1) and ADAQ7988 μModules are 16-bit ADC data acquisition systems that integrate four signal processing and conditioning blocks into a 5 mm x 4 mm LGA package. These systems support various applications, including automated test equipment, battery-powered instrumentation, communications, process control, and medical instruments. The devices incorporate the most critical passive components, eliminating many design challenges associated with traditional signal chains that use successive approximation register (SAR) ADCs. Additionally, multiple devices can be daisy-chained on a single, 3-wire bus with a compatible serial peripheral interface (SPI). All active components in the SiP are designed by ADI, including:

• High-accuracy, low-power 16-bit SAR ADC
• Low-power, high-bandwidth, high-input impedance ADC driver
• Low-power stable reference buffer
• An efficient power management block

Figure 1: ADI's ADAQ7980 μModule (Source: Analog Devices, Inc.)

Applying precision signal chain μModules

ADI's portfolio of precision signal chain data acquisition μModules supports a wide array of applications in different industries, such as the following:

Communications. The ADAQ8092 is a 14-bit, 105 MSPS, high-speed, dual-channel data acquisition μModule for various demodulator and data acquisition applications, such as transceivers, cellular base stations, and network infrastructure. The device incorporates signal conditioning, an ADC driver, a voltage reference, and an ADC in a single package. Separating RF and digital circuits effectively mitigates electromagnetic interference provided by digital counterparts of noise-sensitive RF electronics.

The device forms a complete signal chain that integrates all active and iPassives components in a footprint six times smaller than a comparable discrete solution. Built-in power supply decoupling capacitors enhance power supply rejection performance. The ADAQ8092 operates on 3.3 V to 5 V analog and 1.8 V digital supplies.

Industrial automation. The ADAQ7768-1 is a 24-bit precision data acquisition μModule that encapsulates signal conditioning, conversion, and processing blocks. The device supports various input types, including IEPE sensors, resistive bridges, voltage, and current inputs, for condition-based monitoring (CbM) applications that utilize sensors to establish trends, predict failures, calculate asset lifetimes, and ensure human safety.

Users can configure the ADAQ7768-1 to operate under two device-configuration methods by altering the registers through its serial peripheral interface (SPI), or a simple hardware pin strapping method. Seven pin-configurable gain settings offer additional system dynamic range and improved signal chain noise performance with input signals of lower amplitude.

Automotive testing. The ADAQ23878 is suitable for Hardware in the Loop (HiL)—a digital twin technique that is used for testing complex real-time systems, such as electronic control units (ECUs), power steering systems, suspension systems, battery management systems, or any other vehicle subsystems. It can also be used for automatic test equipment and nondestructive acoustic emissions testing applications, among others.

The ADAQ23878 combines multiple signal processing and conditioning blocks in a single device, including a low noise FDA, a stable reference buffer, and a high speed, 18-bit, 15 MSPS SAR ADC. Its small footprint, 9 mm × 9 mm, 0.8 mm pitch, 100-ball chip scale package ball grid array (CSP_BGA) enables more compact form factor instruments without sacrificing performance. A serial low voltage differential signaling (LVDS) digital interface with one-lane or two-lane output modes allows users to optimize the interface data rate for each application.

Conclusion

Digital transformation and automation are driving demand for signal chain data acquisition solutions optimized for demanding applications in electrification, automotive, digital health, instrumentation, smart industry, energy, and sustainability. ADI precision signal chain μModules offer designers an optimum balance of integration and flexibility without compromising signal chain performance. Eliminating many discrete components reduces the risk of system redesign, simplifies the system bill of materials, and can result in a shorter time to market and reduced development cost.