Mixed-signal integrated circuit

Mixed-signal integrated circuit

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A mixed-signal integrated circuit
Integrated circuit
An integrated circuit or monolithic integrated circuit is an electronic circuit manufactured by the patterned diffusion of trace elements into the surface of a thin substrate of semiconductor material...

is any integrated circuit that has both analog circuits and digital circuit
Digital circuit
Digital electronics represent signals by discrete bands of analog levels, rather than by a continuous range. All levels within a band represent the same signal state...

s on a single semiconductor die.

Examples


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
Control logic
Control logic is a key part of a software program that controls the operations of the program. The control logic responds to commands from the user, and it also acts on its own to perform automated tasks that have been structured into the program....

 of a DVD
DVD
A DVD is an optical disc storage media format, invented and developed by Philips, Sony, Toshiba, and Panasonic in 1995. DVDs offer higher storage capacity than Compact Discs while having the same dimensions....

 player. They often contain an entire system-on-a-chip
System-on-a-chip
A system on a chip or system on chip is an integrated circuit that integrates all components of a computer or other electronic system into a single chip. It may contain digital, analog, mixed-signal, and often radio-frequency functions—all on a single chip substrate...

.

Examples of mixed-signal integrated circuits include data converters using delta-sigma modulation
Delta-sigma modulation
Delta-sigma modulation is a method for encoding high-resolution or analog signals into lower-resolution digital signals. The conversion is done using error feedback, where the difference between the two signals is measured and used to improve the conversion...

, analog-to-digital converter
Analog-to-digital converter
An analog-to-digital converter is a device that converts a continuous quantity to a discrete time digital representation. An ADC may also provide an isolated measurement...

/digital-to-analog converter
Digital-to-analog converter
In electronics, a digital-to-analog converter is a device that converts a digital code to an analog signal . An analog-to-digital converter performs the reverse operation...

 using error detection and correction
Error detection and correction
In information theory and coding theory with applications in computer science and telecommunication, error detection and correction or error control are techniques that enable reliable delivery of digital data over unreliable communication channels...

, and digital radio
Digital radio
Digital radio has several meanings:1. Today the most common meaning is digital radio broadcasting technologies, such as the digital audio broadcasting system, also known as Eureka 147. In these systems, the analog audio signal is digitized into zeros and ones, compressed using formats such as...

 chips. Digitally controlled sound chip
Sound chip
A sound chip is an integrated circuit designed to produce sound . It might be doing this through digital, analog or mixed-mode electronics...

s are also mixed-signal circuits. With the advent of cellular technology and network technology this category now includes cellular telephone, software radio, LAN
Local area network
A local area network is a computer network that interconnects computers in a limited area such as a home, school, computer laboratory, or office building...

 and WAN
Wide area network
A wide area network is a telecommunication network that covers a broad area . Business and government entities utilize WANs to relay data among employees, clients, buyers, and suppliers from various geographical locations...

 router integrated circuits.

Because of the use of both digital signal processing and analog circuitry, mixed-signal ICs are usually designed for a very specific purpose and their design requires a high level of expertise and careful use of computer aided design (CAD) tools. Automated testing of the finished chips can also be challenging. Teradyne
Teradyne
Teradyne , a US company, is a supplier of automatic test equipment . The company's divisions Semiconductor Test and Systems Test Group, are organized by the products they develop and deliver.-History:...

, Agilent, and Texas Instruments
Texas Instruments
Texas Instruments Inc. , widely known as TI, is an American company based in Dallas, Texas, United States, which develops and commercializes semiconductor and computer technology...

 are the major suppliers of the test equipment for mixed-signal chips.

The particular challenges of mixed signal include:
  • CMOS
    CMOS
    Complementary metal–oxide–semiconductor is a technology for constructing integrated circuits. CMOS technology is used in microprocessors, microcontrollers, static RAM, and other digital logic circuits...

     technology is usually optimal for digital performance and scaling while bipolar transistors are usually optimal for analog performance, yet until the last decade it has been difficult to either combine these cost-effectively or to design both analog and digital in a single technology without serious performance compromises. The advent of technologies like high performance CMOS
    CMOS
    Complementary metal–oxide–semiconductor is a technology for constructing integrated circuits. CMOS technology is used in microprocessors, microcontrollers, static RAM, and other digital logic circuits...

    , BiCMOS
    BiCMOS
    BiCMOS is an evolved semiconductor technology that integrates two formerly separate semiconductor technologies - those of the analog bipolar junction transistor and the digital CMOS transistor - in a single integrated circuit device....

    , CMOS SOI
    Silicon on insulator
    Silicon on insulator technology refers to the use of a layered silicon-insulator-silicon substrate in place of conventional silicon substrates in semiconductor manufacturing, especially microelectronics, to reduce parasitic device capacitance and thereby improving performance...

     and SiGe
    SiGe
    SiGe , or silicon-germanium, is a general term for the alloy Si1−xGex which consists of any molar ratio of silicon and germanium. It is commonly used as a semiconductor material in integrated circuits for heterojunction bipolar transistors or as a strain-inducing layer for CMOS transistors...

     have removed many of the compromises that previously had to be made.

  • Testing functional operation of mixed-signal ICs remains complex, expensive and often a "one-off" implementation task.

  • Systematic design methodologies comparable to digital design methods are far more primitive in the analog and mixed-signal arena. Analog circuit design can not generally be automated to nearly the extent that digital circuit design can. Combining the two technologies multiplies this complication.

  • Fast-changing digital signals send noise to sensitive analog inputs. One path for this noise is substrate coupling
    Substrate coupling
    In an integrated circuit, a signal can couple from one node to another via the substrate. This phenomenon is referred to as substrate coupling or substrate noise coupling....

    . A variety of techniques are used to attempt to block or cancel this noise coupling, such as fully differential amplifier
    Fully differential amplifier
    A fully differential amplifier, usually referred to as an FDA for brevity, is a DC-coupled high-gain electronic voltage amplifier with differential inputs and differential outputs...

    s, P+ guard-rings, differential topology, on-chip decoupling, and triple-well isolation.

Commercial examples

  • PSoC
    PSoC
    PSoC is a family of integrated circuits made by Cypress Semiconductor. These chips include a CPU and mixed-signal arrays of configurable integrated analog and digital peripherals.- History :...

     - Cypress PSoC Programmable System on Chip
  • Atari POKEY
    Atari POKEY
    The Pot Keyboard Integrated Circuit is a digital I/O chip found in the Atari 8-bit family of home computers and many arcade games in the 1980s. It was commonly used to sample potentiometers and scan matrices of switches...

  • MOS Technology SID
    MOS Technology SID
    The MOS Technology 6581/8580 SID is the built-in Programmable Sound Generator chip of Commodore's CBM-II, Commodore 64, Commodore 128 and Commodore MAX Machine home computers...

  • Texas Instruments
    Texas Instruments
    Texas Instruments Inc. , widely known as TI, is an American company based in Dallas, Texas, United States, which develops and commercializes semiconductor and computer technology...

    ' MSP430
    TI MSP430
    The MSP430 is a mixed-signal microcontroller family from Texas Instruments. Built around a 16-bit CPU, the MSP430 is designed for low cost, and specifically, low power consumption embedded applications. The architecture dates from the 1990s and is reminiscent of the DEC PDP-11.-Applications:The...

  • Triad Semiconductor - Configurable Mixed Signal ASICs

Most modern radio and communications use mixed signal circuits.