Mixed-signal integrated circuit

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Mixed signal integrated circuit: the metal areas on the right-hand side are capacitors, on top of which are large output transistors; the left-hand side is occupied by the digital logic Mixed signal IC.jpg
Mixed signal integrated circuit: the metal areas on the right-hand side are capacitors, on top of which are large output transistors; the left-hand side is occupied by the digital logic

A mixed-signal integrated circuit is any integrated circuit that has both analog circuits and digital circuits on a single semiconductor die. [1] [2] [3] [4] Their usage has grown dramatically with the increased use of cell phones, telecommunications, portable electronics, and automobiles with electronics and digital sensors.

Contents

Overview

Integrated circuits (ICs) are generally classified as digital (e.g. a microprocessor) or analog (e.g. an operational amplifier). Mixed-signal ICs contain both digital and analog circuitry on the same chip, and sometimes embedded software. Mixed-signal ICs process both analog and digital signals together. For example, an analog-to-digital converter (ADC) is a typical mixed-signal circuit.

Mixed-signal ICs are often used to convert analog signals to digital signals so that digital devices can process them. For example, mixed-signal ICs are essential components for FM tuners in digital products such as media players, which have digital amplifiers. Any analog signal can be digitized using a very basic ADC, and the smallest and most energy efficient of these are mixed-signal ICs.

Mixed-signal ICs are more difficult to design and manufacture than analog-only or digital-only integrated circuits. For example, an efficient mixed-signal IC may have its digital and analog components share a common power supply. However, analog and digital components have very different power needs and consumption characteristics, which makes this a non-trivial goal in chip design.

Mixed-signal functionality involves both traditional active elements (like transistors) and well-performing passive elements (like coils, capacitors, and resistors) on the same chip. This requires additional modelling understanding and options from manufacturing technologies. High voltage transistors might be needed in the power management functions on a chip with digital functionality, possibly with a low-power CMOS processor system. Some advanced mixed-signal technologies may enable combining analog sensor elements (like pressure sensors or imaging diodes) on the same chip with an ADC.

Typically, mixed-signal ICs do not necessarily need the fastest digital performance. Instead, they need more mature models of active and passive elements for more accurate simulations and verification, such as for testability planning and reliability estimations. Therefore, mixed-signal circuits are typically realized with larger line widths than the highest speed and densest digital logic, and the implementation technologies can be two to four generations behind the latest digital-only implementation technologies. Additionally, mixed signal processing may need passive elements like resistors, capacitors, and coils, which may require specialized metal, dielectric layers, or similar adaptations of standard fabrication processes. Because of these specific requirements, mixed-signal ICs and digital ICs can have different manufacturers (known as foundries).

Applications

There are numerous applications of mixed-signal integrated circuits, such as in mobile phones, modern radio and telecommunication systems, sensor systems with on-chip standardized digital interfaces (including I2C, UART, SPI, or CAN), voice-related signal processing, aerospace and space electronics, the Internet of things (IoT), unmanned aerial vehicles (UAVs), and automotive and other electrical vehicles. Mixed-signal circuits or systems are typically cost-effective solutions, such as for building modern consumer electronics and in industrial, medical, measurement, and space applications.

Examples of mixed-signal integrated circuits include data converters using delta-sigma modulation, analog-to-digital converters and digital-to-analog converters using error detection and correction, and digital radio chips. Digitally controlled sound chips are also mixed-signal circuits. With the advent of cellular and network technology, this category now includes cellular telephone, software radio, and LAN and WAN router integrated circuits.

Design and development

Typically, mixed-signal chips perform some whole function or sub-function in a larger assembly, such as the radio subsystem of a cell phone, or the read data path and laser SLED control logic of a DVD player. Mixed-signal ICs often contain an entire system-on-a-chip. They may also contain on-chip memory blocks (like OTP), which complicates the manufacturing compared to analog ICs. A mixed-signal IC minimizes off-chip interconnects between digital and analog functionality in the system—typically reducing size and weight due to minimized packaging and a smaller module substrate—and therefore increases the reliability of the system.

Because of the use of both digital signal processing and analog circuitry, mixed-signal ICs are usually designed for a very specific purpose. Their design requires a high level of expertise and careful use of computer aided design (CAD) tools. There also exists specific design tools (like mixed-signal simulators) or description languages (like VHDL-AMS). Automated testing of the finished chips can also be challenging. Teradyne, Keysight, and Advantest are the major suppliers of the test equipment for mixed-signal chips.

There are several particular challenges of mixed-signal circuit manufacturing:

Variations

Mixed-signal devices are available as standard parts, but sometimes custom-designed application-specific integrated circuits (ASICs) are necessary. ASICs are designed for new applications, when new standards emerge, or when new energy source(s)[ clarification needed ] are implemented in the system. Due to their specialization, ASICs are usually only developed when production volumes are estimated to be high. The availability of ready-and-tested analog- and mixed-signal IP blocks from foundries or dedicated design houses has lowered the gap to realize mixed-signal ASICs.

There also exist mixed-signal field-programmable gate arrays (FPGAs) and microcontrollers. [note 1] In these, the same chip that handles digital logic may contain mixed-signal structures like analog-to-digital and digital-to-analog converter(s), operational amplifiers, or wireless connectivity blocks. [8] These mixed-signal FPGAs and microcontrollers are bridging the gap between standard mixed-signal devices, full-custom ASICs, and embedded software; they offer a solution during product development or when product volume is too low to justify an ASIC. However, they can have performance limitations, such as the resolution of the analog-to-digital converters, the speed of digital-to-analog conversion, or a limited number of inputs and outputs. Nevertheless, they can speed up the system architecture design, prototyping, and even production (at small and medium scales). Their usage also can be supported with development boards, development community, and possibly software support.

History

MOS switched-capacitor circuits

The metal–oxide–semiconductor field-effect transistor (MOSFET, or MOS transistor) was invented by Mohamed M. Atalla and Dawon Kahng at Bell Telephone Laboratories in 1959, and the MOS integrated circuit (MOS IC) chip was proposed soon after. However, MOS technology was initially overlooked by Bell because they did not find it practical for analog telephone applications, before it was commercialized by Fairchild and RCA for digital electronics such as computers. [9] [10] MOS technology eventually became practical for telephony applications with the MOS mixed-signal integrated circuit, which combines analog and digital signal processing on a single chip, developed by former Bell engineer David A. Hodges with Paul R. Gray at UC Berkeley in the early 1970s. [10] In 1974, Hodges and Gray worked with R.E. Suarez to develop MOS switched capacitor (SC) circuit technology, which they used to develop a digital-to-analog converter (DAC) chip, using MOS capacitors and MOSFET switches for data conversion. [10] MOS analog-to-digital converter (ADC) and DAC chips were commercialized by 1974. [11]

MOS SC circuits led to the development of pulse-code modulation (PCM) codec-filter chips in the late 1970s. [10] [12] The silicon-gate CMOS (complementary MOS) PCM codec-filter chip, developed by Hodges and W.C. Black in 1980, [10] has since been the industry standard for digital telephony. [10] [12] By the 1990s, telecommunication networks such as the public switched telephone network (PSTN) had been largely digitized with very-large-scale integration (VLSI) CMOS PCM codec-filters, widely used in electronic switching systems for telephone exchanges, private branch exchanges (PBX), and key telephone systems (KTS); user-end modems; data transmission applications such as digital loop carriers, pair gain multiplexers, telephone loop extenders, integrated services digital network (ISDN) terminals, digital cordless telephones, and digital cell phones; and applications such as speech recognition equipment, voice data storage, voice mail, and digital tapeless answering machines. [12] The bandwidth of digital telecommunication networks has been rapidly increasing at an exponential rate, as observed by Edholm's law, [13] largely driven by the rapid scaling and miniaturization of MOS technology. [14] [10]

RF CMOS circuits

While working at Bell Labs in the early 1980s, Pakistani engineer Asad Abidi worked on the development of sub-micron MOSFET (metal–oxide–semiconductor field-effect transistor) VLSI (very large-scale integration) technology at the Advanced LSI Development Lab, along with Marty Lepselter, George E. Smith, and Harry Bol. As one of the few circuit designers at the lab, Abidi demonstrated the potential of sub-micron NMOS integrated circuit technology in high-speed communication circuits, and developed the first MOS amplifiers for Gb/s data rates in optical fiber receivers. Abidi's work was initially met with skepticism from proponents of gallium arsenide and bipolar junction transistors, the dominant technologies for high-speed circuits at the time. In 1985, he joined UCLA, where he pioneered RF CMOS technology in the late 1980s. His work changed the way in which radio-frequency (RF) circuits would be designed, away from discrete bipolar transistors and towards CMOS integrated circuits. [15]

Abidi was researching analog CMOS circuits for signal processing and communications during the late 1980s to early 1990s. In the mid-1990s, the RF CMOS technology that he pioneered was widely adopted in wireless networking, as mobile phones began entering widespread use. As of 2008, the radio transceivers in all wireless networking devices and modern mobile phones are mass-produced as RF CMOS devices. [15]

The baseband processors [16] [17] and radio transceivers in all modern wireless networking devices and mobile phones are mass-produced using RF CMOS devices. [15] RF CMOS circuits are widely used to transmit and receive wireless signals in a variety of applications, such as satellite technology (such as GPS), Bluetooth, Wi-Fi, near-field communication (NFC), mobile networks (such as 3G, 4G, and 5G), terrestrial broadcast, and automotive radar applications, among other uses. [18] RF CMOS technology is crucial to modern wireless communications, including wireless networks and mobile communication devices. [19]

Commercial examples

See also

Notes

  1. Mixed-signal FPGAs are an extension of field-programmable analog arrays.
  2. Some foundries may also have design service or list of partners capable for mixed signal design services for their technologies.

Related Research Articles

<span class="mw-page-title-main">Electronics</span> Branch of physics and electrical engineering

Electronics is a scientific and engineering discipline that studies and applies the principles of physics to design, create, and operate devices that manipulate electrons and other charged particles. Electronics is a subfield of electrical engineering, but it differs from it in that it focuses on using active devices such as transistors, diodes, and integrated circuits to control and amplify the flow of electric current and to convert it from one form to another, such as from alternating current (AC) to direct current (DC) or from analog to digital. Electronics also encompasses the fields of microelectronics, nanoelectronics, optoelectronics, and quantum electronics, which deal with the fabrication and application of electronic devices at microscopic, nanoscopic, optical, and quantum scales.

<span class="mw-page-title-main">Integrated circuit</span> Electronic circuit formed on a small, flat piece of semiconductor material

An integrated circuit or monolithic integrated circuit is a set of electronic circuits on one small flat piece of semiconductor material, usually silicon. Large numbers of miniaturized transistors and other electronic components are integrated together on the chip. This results in circuits that are orders of magnitude smaller, faster, and less expensive than those constructed of discrete components, allowing a large transistor count. The IC's mass production capability, reliability, and building-block approach to integrated circuit design have ensured the rapid adoption of standardized ICs in place of designs using discrete transistors. ICs are now used in virtually all electronic equipment and have revolutionized the world of electronics. Computers, mobile phones and other home appliances are now inextricable parts of the structure of modern societies, made possible by the small size and low cost of ICs such as modern computer processors and microcontrollers.

<span class="mw-page-title-main">MOSFET</span> Type of field-effect transistor

The metal-oxide-semiconductor field-effect transistor is a type of field-effect transistor (FET), most commonly fabricated by the controlled oxidation of silicon. It has an insulated gate, the voltage of which determines the conductivity of the device. This ability to change conductivity with the amount of applied voltage can be used for amplifying or switching electronic signals. A metal-insulator-semiconductor field-effect transistor (MISFET) is a term almost synonymous with MOSFET. Another synonym is IGFET for insulated-gate field-effect transistor.

<span class="mw-page-title-main">CMOS</span> Technology for constructing integrated circuits

Complementary metal–oxide–semiconductor is a type of metal–oxide–semiconductor field-effect transistor (MOSFET) fabrication process that uses complementary and symmetrical pairs of p-type and n-type MOSFETs for logic functions. CMOS technology is used for constructing integrated circuit (IC) chips, including microprocessors, microcontrollers, memory chips, and other digital logic circuits. CMOS technology is also used for analog circuits such as image sensors, data converters, RF circuits, and highly integrated transceivers for many types of communication.

<span class="mw-page-title-main">Application-specific integrated circuit</span> Integrated circuit customized for a specific task

An application-specific integrated circuit is an integrated circuit (IC) chip customized for a particular use, rather than intended for general-purpose use, such as a chip designed to run in a digital voice recorder or a high-efficiency video codec. Application-specific standard product chips are intermediate between ASICs and industry standard integrated circuits like the 7400 series or the 4000 series. ASIC chips are typically fabricated using metal–oxide–semiconductor (MOS) technology, as MOS integrated circuit chips.

Bipolar CMOS (BiCMOS) is a semiconductor technology that integrates two semiconductor technologies, those of the bipolar junction transistor and the CMOS logic gate, into a single integrated circuit. In more recent times the bipolar processes have been extended to include high mobility devices using silicon–germanium junctions.

<span class="mw-page-title-main">Gate array</span> Type of integrated circuit

A gate array is an approach to the design and manufacture of application-specific integrated circuits (ASICs) using a prefabricated chip with components that are later interconnected into logic devices according to custom order by adding metal interconnect layers in the factory. It was popular during the upheaval in the semiconductor industry in the 1980s, and its usage declined by the end of the 1990s.

<span class="mw-page-title-main">Analog Devices</span> American semiconductor manufacturer

Analog Devices, Inc. (ADI), also known simply as Analog, is an American multinational semiconductor company specializing in data conversion, signal processing, and power management technology, headquartered in Wilmington, Massachusetts.

In computer engineering, a logic family is one of two related concepts:

<span class="mw-page-title-main">IC power-supply pin</span> Power supply connections for integrated circuits

IC power-supply pins denote a voltage and current supply terminals in electric, electronics engineering, and in Integrated circuit design. Integrated circuits (ICs) have at least two pins that connect to the power rails of the circuit in which they are installed. These are known as the power-supply pins. However, the labeling of the pins varies by IC family and manufacturer. The double subscript notation usually corresponds to a first letter in a given IC family (transistors) notation of the terminals.

<span class="mw-page-title-main">Integrated circuit design</span> Engineering process for electronic hardware

Integrated circuit design, or IC design, is a sub-field of electronics engineering, encompassing the particular logic and circuit design techniques required to design integrated circuits, or ICs. ICs consist of miniaturized electronic components built into an electrical network on a monolithic semiconductor substrate by photolithography.

A linear integrated circuit or analog chip is a set of miniature electronic analog circuits formed on a single piece of semiconductor material.

Maxim Integrated, a subsidiary of Analog Devices, designs, manufactures, and sells analog and mixed-signal integrated circuits for the automotive, industrial, communications, consumer, and computing markets. Maxim's product portfolio includes power and battery management ICs, sensors, analog ICs, interface ICs, communications solutions, digital ICs, embedded security, and microcontrollers. The company is headquartered in San Jose, California, and has design centers, manufacturing facilities, and sales offices worldwide.

A field-programmable analog array (FPAA) is an integrated circuit device containing computational analog blocks (CAB) and interconnects between these blocks offering field-programmability. Unlike their digital cousin, the FPGA, the devices tend to be more application driven than general purpose as they may be current mode or voltage mode devices. For voltage mode devices, each block usually contains an operational amplifier in combination with programmable configuration of passive components. The blocks can, for example, act as summers or integrators.

<span class="mw-page-title-main">Electronic circuit</span> Electrical circuit with active components

An electronic circuit is composed of individual electronic components, such as resistors, transistors, capacitors, inductors and diodes, connected by conductive wires or traces through which electric current can flow. It is a type of electrical circuit and to be referred to as electronic, rather than electrical, generally at least one active component must be present. The combination of components and wires allows various simple and complex operations to be performed: signals can be amplified, computations can be performed, and data can be moved from one place to another.

Precision Monolithics, Inc. also known as PMI, was an American company based in Santa Clara, California, that developed and produced mixed signal and linear integrated circuits (ICs). It was a pioneer in the fields of digital-to-analog converters and operational amplifiers.

<span class="mw-page-title-main">Asad Abidi</span> Pakistani-American electrical engineer

Asad Ali Abidi is a Pakistani-American electrical engineer. He serves as a tenured professor at University of California, Los Angeles, and is the inaugural holder of the Abdus Salam Chair at the Lahore University of Management Sciences (LUMS). He is best known for pioneering RF CMOS technology during the late 1980s to early 1990s. As of 2008, the radio transceivers in all wireless networking devices and modern mobile phones are mass-produced as RF CMOS devices.

The following outline is provided as an overview of and topical guide to electronics:

RF CMOS is a metal–oxide–semiconductor (MOS) integrated circuit (IC) technology that integrates radio-frequency (RF), analog and digital electronics on a mixed-signal CMOS RF circuit chip. It is widely used in modern wireless telecommunications, such as cellular networks, Bluetooth, Wi-Fi, GPS receivers, broadcasting, vehicular communication systems, and the radio transceivers in all modern mobile phones and wireless networking devices. RF CMOS technology was pioneered by Pakistani engineer Asad Ali Abidi at UCLA during the late 1980s to early 1990s, and helped bring about the wireless revolution with the introduction of digital signal processing in wireless communications. The development and design of RF CMOS devices was enabled by van der Ziel's FET RF noise model, which was published in the early 1960s and remained largely forgotten until the 1990s.

<span class="mw-page-title-main">MOSFET applications</span> BILLIE JO BLAKE © 1969 SOURCE CODE

The metal–oxide–semiconductor field-effect transistor, also known as the metal–oxide–silicon transistor, is a type of insulated-gate field-effect transistor (IGFET) that is fabricated by the controlled oxidation of a semiconductor, typically silicon. The voltage of the covered gate determines the electrical conductivity of the device; this ability to change conductivity with the amount of applied voltage can be used for amplifying or switching electronic signals.

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Further reading