The number of voltage regulators currently available makes the introduction of another regulator seem almost unnecessary. However， a new device， the LT?1005， offers auxiliary functions which help solve problems often associated with voltage regulation in circuits.

　　The LT1005 （Figure 1） consists of a 5V， 1A1 regulator， which is controlled by a positive logic enable pin， and a 5V auxiliary regulator. The auxiliary regulator’s output is unaffected by the state of the main regulator. Thermal overload protection and current limiting round out the device. The enable pin is a high impedance input which floats in a high state. 10μA1 of current pulled from the pin will force it below its 1.6V turn-off threshold， shutting down the main output. Figure 2a shows a simple but useful application. Here， the regulator’s enable pin is controlled by the state of a toggling flip-flop which is triggered by a pushbutton on a computer keyboard. The auxiliary 5V output powers

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