One-gate logic uses and their benefits application note (PDF) from ON Semiconductor.
One–Gate logic devices have been in use for several years, and are nothing more than single–gate derivatives of their multi–gate cousins. Traditional ICs were packaged in 14 and 16 pin Dual–in–line Packages (DIPs), and the goal of the IC manufacturer was to get as much functionality as possible into a single–package device. Double, triple, quadruple, and quintuple versions of simple logic functions became the norm. Often there was not enough room to add an additional logic element on the chip and still keep the board size small. The designer was faced with having to re–design the entire chip or to add additional IC components to the board layout to accomplish the required task. A solution to this dilemma was to use One–Gate designs, initially offered in the SOT–23, 5–pin package, and later in the even smaller SOT–353 (SC88A). The latter package takes up only 4.2 mm 2 of board space, and less than the area of a TSSOP–20 pin device. One–Gate products, now fabricated in a .6µ advanced high–speed CMOS technology, are very fast, with < 4 nsecs gate delays, and enough drive (8 mA) to support most typical applications. The package is so small, that it fits “in–line” with the trace that it is mounted on.