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Circuit Cellar's editorial team comprises professional engineers, technical editors, and digital media specialists. You can reach the Editorial Department at editorial@circuitcellar.com, @circuitcellar, and facebook.com/circuitcellar

The World Is Analog

The world we live in is analog. We are analog. Any inputs we can perceive are analog. For example, sounds are analog signals; they are continuous time and continuous value. Our ears listen to analog signals and we speak with analog signals. Images, pictures, and video are all analog at the source and our eyes are analog sensors. Measuring our heartbeat, tracking our activity, all requires processing analog sensor information.

Computers are digital. Information is represented with discrete time and amplitude quantized signals using digital bits. Such representation lends itself to efficient processing and long-term storage of signals and information. But information and signals come from the physical world and need to move back into the physical world for us to perceive them. No matter how “digital” our electronic devices get, they always require interfaces that translate signals from the physical world into the digital world of electronics.

Even when computers talk to computers, analog interfaces are required. To transmit information over long distances (e.g., over a high-speed bus between the memory and the processor or over a wired network connection), the digital information needs to be moved into an analog format at the transmitter to drive the communication channel. At the receiver, the signals typically picked up from the channel do not look anymore like digital signals and need to be processed in the analog domain before they can be converted back into digital information. This is even more so if we consider wireless communications, where the digital information needs to be modulated on a high-speed radio-frequency (RF) carrier in the transmitter and demodulated at the receiver. RF electronics are also analog in nature.

The semiconductor industry has lived through tremendous advances fueled by what is known as Moore’s law: about every two years, thanks to increasing device miniaturization, the number of devices on a chip doubles. This exponential scaling has led to unprecedented advances in computing and software and has made the digitization of most information possible. Our literature, music, movies, and pictures are all processed and stored in digital format nowadays. Digital chips make up most of the volume of chips fabricated and it is thus economically desirable to fine-tune CMOS technologies for digital circuits. But electronic systems need analog interfaces to connect the bits to the world and most consumer products now rely on System-on-Chip (SoC) solutions where one integrated circuit contains the whole system function, from interfaces to digital signal processing and memory blocks. SoCs need a lot of analog interfaces, but their area is mainly composed of digital blocks (often over 90%). As technology scales, the performance of the digital core improves and this in turn increases the requirements of the analog interfaces.

Today’s analog designers are thus asked to design more interfaces with higher performance but using circuits that are as compatible with digital circuits as possible. This trend emerged a few decades ago and has grown stronger and stronger driven by the continuing increase of the functional density of SoCs. Not only do SoCs need more interfaces and better interfaces, the analog performance of highly miniaturized devices like nanometer CMOS transistors has steadily degraded.

This essay appears in Circuit Cellar #292 November 2014. 

Making nanoscale transistors is great to increase the functional density, but has its drawbacks when designing analog circuits. Nanoscale transistors can only withstand small supply voltages. For example, circuits designed with the latest CMOS transistors can only work with a supply voltage of up to 1 V or so. Traditionally analog circuits operated from voltages as large as +5 V/–5 V, but steadily their supply voltage was forced to reduce to 5 V, to 3.3 V, to 1.8 V, to 1.2 V and projections for future devices are as low as 0.5 V or even 0.2 V since reducing supply voltages also helps digital designs reduce energy consumption. However, for analog circuits, reducing the supply voltage increases their susceptibility to noise or interference and degrades signal quality. To add to the difficulties, nanoscale transistors also exhibit more mismatches, leading to random offset errors, more flicker (1/f) noise, and have poor gain performance.

But analog designers always like to rise up to a challenge. Research in academic and industrial groups has devised a number of novel analog design techniques to build better analog circuits while relying less and less on the performance of an individual device. In my group, for example, we have developed a set of design techniques to design analog circuits that operate with supplies as low as 0.5 V.

Scaling also offers new avenues for designing analog circuits. In nanoscale processes transistors are not able to handle large voltages, but they can intrinsically switch very fast. That allows us to introduce different signal representations at the transistor level for analog functions. Instead of using the traditional voltages or currents, we can now use time delays to represent analog information. This opens a whole range of opportunities to explore new circuits. Technology scaling is driving a paradigm shift in analog design away from the transistor used as a current source or voltage-controlled current source towards the transistor used as a fast switch even when processing analog information. In fact, analog circuits are being built out of what traditionally are digital blocks like switches or ring oscillators. But with the appropriate signal representation and circuit arrangements, they can process analog information to provide interfaces between the real world and the digital world.

The analog electronics field is going through very exciting times. The digital revolution in electronics has made analog even more necessary. And the future is looking bright. Mobile devices are packed with analog interfaces and a host of analog sensors, whose count increases with each new generation. The Internet of Things is all about massively gathering sensor information in one form of another, under strict power-consumption and cost constraints. All this while the traditional analog design techniques are clearly showing their limitations in the face of aggressive device scaling. This makes for a very challenging but a very interesting time for analog designers with plenty of opportunities to make an impact. Analog is the future!

KingetTTFPeter Kinget is a Professor of Electrical Engineering at Columbia University in New York. He received his engineering and PhD degrees in Electrical Engineering from the Katholieke Universiteit in Leuven (Belgium). His research group focusses on the design of analog and RF integrated circuits in scaled technologies and the novel systems or applications they enable in communications, sensing, and power management. (For more information, visit www.ee.columbia.edu/~kinget.)


WillowTree Apps Named Microchip Design Partner

Microchip Technology recently announced its first App Developer Specialist—WillowTree Apps—the latest company to join its Design Partner Network. WillowTree is an iOS, Android, and Mobile Web app developer that enables Microchip’s customers to focus on Internet of Things (IoT) designs.MicrochipWillowTree

WillowTree wrote the first mobile app for Microchip’s Wi-Fi Client Module Development Kit 1, which is available in the Apple App Store. It enables customers to quickly get up and running with the kit’s cloud-based demo. WillowTree can also modify this cloud-demo app to suit a broad range of customer IoT design requirements.

Source: Microchip Technology

Small High-Current Power Modules


Exar Corp. recently announced the 10-A XR79110 and 15-A XR79115 single-output, synchronous step-down power modules. The modules will be available in mid-November in RoHS-compliant, green/halogen-free, QFN packages.

In a product release, Exar noted that “both devices provide easy to use, fully integrated power converters including MOSFETs, inductors, and internal input and output capacitors.”

The modules come in compact 10 x 10 x 4 mm and 12 x 12 x 4 mm footprints, respectively. The XR79110 and XR79115 offer versatility to convert from common input voltages such as 5, 12, and 19 V.

Both modules feature Exar’s emulated current-mode COT control scheme. The COT control loop enables operation with ceramic output capacitors and eliminates loop compensation components. According to Exar documentation, tthe output voltage can be set from 0.6 to 18 V and with exceptional full range 0.1% line regulation and 1% output accuracy over full temperature range.

The XR79110 and XR79115 are priced at $8.95 and $10.95, respectively, in 1,000-piece quantities.

Source: Exar Corp.

Bluetooth Low Energy (BLE) Module Featuring smartBASIC

Laird Technologies recently announced the BL620 Bluetooth Low Energy (BLE) module, which is the newest edition to its BL600 series. Although it uses the BL600 hardware, the BL620 “has a new firmware load supporting Central mode connectivity,” Laird noted in its product release.”The BL620 makes it easy to add single-mode Bluetooth Low Energy (BLE), or Bluetooth Smart, to small, portable, power-conscious devices, including those powered by AAA or coin cell batteries.”LairdBL620_140px

Key features:

  • Event-driven smartBASIC programming language, which significantly simplifies BLE integration.
  • Reduces the engineering burden and design risk of integrating Bluetooth and BLE to a device.
  • Fully approved programmable
  • Compact footprint, low-power

If you already have a BL600 development kit, you can download the BL620 firmware and test it. You can download the BL620 firmware file from the Laird Bluetooth Firmware Download Center.

Source: Laird Technologies

Single-Board, Arduino Uno Shield-Compatible Dev Kit

Nordic Semiconductor’s new Aruduino Uno shield-compatible nRF51 DK development kit supports Bluetooth Smart, ANT, and 2.4-GHz designs. Nordic also announced the availability of its nRF51 Dongle, which is a 16 mm × 28 mm USB dongle for the testing, analysis, and development of Bluetooth Smart, ANT, and 2.4-GHz applications.Nordic-nRF51 DK_1

The nRF51 DK is based on Nordic’s nRF51 Series SoC, which combines a 2.4-GHz multiprotocol radio, 32-bit ARM Corte M0 processor, flash memory, and 16- or 32-KB RAM. The SoCs can support a wide range of peripherals and are available in quad flat no-lead (QFN) and wafer level chip scale package (WLCSP) options.

Key points about the nRF51 DK and nRF51 Dongle

  • You can use the nRF51 DK with a variety of third-party Arduino shield expansion boards. It also supports ARM mbed for rapid prototyping projects.
  • The nRF51 DK allows access to all device peripherals, interfaces, and I/Os.
  • The nRF51 DK includes four user-programmable buttons and LEDS plus voltage and current pins to measure device power consumption.
  • nRF51 DK and nRF51 Dongle are supported by standard tool-chain options including Keil, IAR, and Gnu Compiler Collection (GCC).
  • The 63 mm × 101 mm nRF51 DK includes a coin-cell battery holder for field testing
  • You can use nRF51 DKhe DK as a programmer for other target boards that use the nRF51 Series SoC.

The nRF51 DK costs $69. The nRF51 Dongle is $49.

Source: Nordic Semiconductor