Integrated circuits that would perform a variety of analog-signal, digital- signal, and power input/output functions have been proposed. Conceived for use as versatile, fault-tolerant interfaces among components and subsystems of spacecraft, these multifunction integrated circuits could also be attractive for similar uses in a variety of terrestrial systems, including ground vehicles, aircraft, industrial facilities, and communication systems.

This Interface Circuit would contain a variety of analog and digital circuitry, all integrated on a single chip, for performing a complete set of signal and power input and output functions for the subsystem to which it would be connected.
Each such multifunction integrated circuit would be fabricated as a single complementary metal oxide semiconductor (CMOS) chip that would contain some or all of the following functional units (see figure):

  • A transceiver for spread-spectrum radio communication with other such integrated circuits;
  • A microprocessor functioning as a central processing unit (CPU) or digital signal processor (DSP);
  • Volatile and/or nonvolatile memory circuits;
  • Analog input circuits, including signalconditioning amplifiers and analog-todigital converters (ADCs);
  • Analog output circuits, including digital- to-analog converters (DACs);
  • Digital input/output (I/O) circuits;
  • Power-switching circuits containing high-power metal oxide semiconductor field-effect transistors (MOSFETs).

The multifunction integrated circuit would serve as both a power and a signal interface for the subsystem or component to which it was connected. If, for example, the subsystem were a motor, then the multifunction integrated circuit could receive motor commands transmitted by radio from a different subsystem, switch the motor power on and off as needed, and possibly transmit data on the operation of the motor (e.g., shaft-angle, speed, voltage, and/or current readings) to another subsystem. Other than wire connections for a radio-communication antenna and for the motor or other subsystem served, the only wire connections between the multifunction integrated circuit and the rest of the system would be those needed to supply power to the circuit and subsystem.

All data and control signals — both digital and analog — would be transmitted via the radio links. By serving as standardized interfaces that would eliminate the need for signal wiring, these multifunction integrated circuits could make it easier to design and construct multinode systems that could be reconfigured in software (and perhaps in hardware). With respect to digital communication among subsystems, each of the multifunction integrated circuits would constitute a node of a wireless communication network. By use of previously developed Ethernet (or equivalent) and spread-spectrum protocols, babbling (uncontrolled transmission) by one of the nodes of the network would be prevented from interfering with communication among the other nodes.

This work was done by James Dillon and Michael Newell of Caltech for NASA’s Jet Propulsion Laboratory.

This Brief includes a Technical Support Package (TSP).
Multifunction Input / Output Integrated Circuits

(reference NPO-30212) is currently available for download from the TSP library.

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This article first appeared in the August, 2002 issue of NASA Tech Briefs Magazine.

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