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

A mixed-signal integrated circuit is any

cell phones, telecommunications, portable electronics, and automobiles with electronics and digital sensors
.

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

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

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

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

Further information:
Digital telephony

The

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

rapid scaling and miniaturization of MOS technology.[14][10]

RF CMOS circuits

Main article: RF CMOS

While working at

bipolar transistors and towards CMOS integrated circuits.[15]

Abidi was researching analog

radio transceivers in all wireless networking devices and modern mobile phones are mass-produced as RF CMOS devices.[15]

The

mobile communication devices.[19]

Commercial examples

See also

Notes

  1. 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.

References

  1. ^
    ISBN 978-0071825719
    and 0071825711.
  2. ^ "Mixed-Signal IC Design". quote: "mixed-signal (IC's with mixed analog and digital circuits on a single chip)"
  3. ^ Mark Burns and Gordon W. Roberts, "An Introduction to Mixed-Signal IC Test and Measurement", 2001.
  4. ^ "ESS Mixed Signal Circuits" Archived 2010-10-11 at the Wayback Machine
  5. S2CID 206955680
    .
  6. ISBN 0-85296-695-4
    .
  7. ^ "Mixed-Signal IC Merges 14-Bit ADC With DSP In 0.18-μm CMOS"
  8. ^ "Microsemi Fusion mixed-signal FPGA"
  9. ISBN 9788793609860
    .
  10. ^
    ISBN 9788793609860
    .
  11. U.S. Government Printing Office
    . 1974. p. 46.
  12. ^
    ISBN 9781420041163
    .
  13. S2CID 27580722
    .
  14. S2CID 25112828
    .
  15. ^
    ISSN 1098-4232
    .
  16. ISBN 9781420005967
    .
  17. ISBN 9781461400370
    .
  18. ISBN 9783319475974
    .
  19. ^ "Infineon Hits Bulk-CMOS RF Switch Milestone". EE Times. 20 November 2018. Retrieved 26 October 2019.

Further reading

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