Glossary Terms and Definitions Beginning with the Letter U

uA Microampere, or microamp: A millionth of an Ampere. Ampere is the basic unit for measuring electrical current.

Often written as uA, but the u is a plain-text substitute for the Greek letter mu.

UART Universal Asynchronous Receiver-Transmitter: An IC that converts parallel data to serial, for transmission; and converts received serial data to parallel data.

See: UART-related application notes

UBM Underbump metal
UHF Filter Ultra High Frequency filter
UI Unit interval (used to describe jitter generation); user information; user interface
Ultra High Frequency Filter See UHF Filter
Ultra-Wideband See UWB
ULTRA160 A SCSI interface label, where 160 refers to the maximum reliable throughput in megabits per second.
UMTS UMTS (Universal Mobile Telecommunications System) is a third-generation cellular standard based on the GSM standard and developed by the 3rd Generation Partnership Project (3GPP).
Uninterruptible Power Supply An uninterruptible power supply (UPS) is a device that maintains power in the event of a failure. A UPS commonly includes a battery that is kept charged and ready. When power fails, the battery supplies power, as long as it lasts. When the battery fails, a UPS may contain circuitry that triggers an orderly shutdown.

An uninterruptible power supply may also provide line regulation, protecting against voltage variations.

UniqueWare A unique identification technique
UniqueWare Serialized A factory-programming service for 1-Wire EPROM chips with customer-specified data. Service provides one serialization file for customers to create identifiers in silicon.
Universal Mobile Telecommunications System See UMTS
Universal Serial Bus See USB
UP Reset See Microprocessor Supervisor
UP Supervisor See Microprocessor Supervisor
Upconverter See Upconverters
Upconverters A device which provides frequency conversion to a higher frequency, e.g., in digital broadcast-satellite applications.
UPS See Uninterruptible Power Supply
Upverter See Upconverters
URL Uniform/universal resource locator — web address, eg
USB Universal Serial Bus (USB): A standard port that enables you to connect external devices (such as digital cameras, scanners, keyboards, and mice) to computers. The USB standard supports data transfer at three rates: low speed (1.5MBps), full speed (12Mbps) and high speed (480 MBps).

Mbps=million bits per second.

UV Ultraviolet
UVLO Undervoltage lockout
UWB Ultra-Wideband (UWB) is a communications technology that employs a wide bandwidth (typically defined as greater than 20% of the center frequency or 500MHz). UWB is usually used in short-range wireless applications but can be sent over wires. Ultra-Wideband advantages are that it can carry high data rates with low power and little interference.

UWB is the modern version of older "impulse" technologies which are generated by very short pulses (impulse waveforms). They were called "carrier-free" or "baseband" because the energy is so widespread in the frequency domain that there is no discernible carrier frequency.

For a crude example, connect a metal file to one terminal of a battery and a wire to the other terminal. Brush the wire across the teeth of the file and note that the electrical noise can be heard on a radio tuned to just about any frequency.

The FCC authorizes UWB between 3.1 and 10.6GHz (but is not likely to approve devices that rely on a file and a wire.)