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Very Low Power - Typical Supply Current 7microA at 5V

High Input Common-Mode Range Beyond V- and V+

Optional Open-Drain Output Optimizes Mixed-Voltage System Design

Sep 26, 1995

SANTA CLARA, CA., Sept. 26, 1995 -- The industry's best-in-class combination of size and performance highlights the first of a new series of voltage comparators from National Semiconductor. Approximately the size of the letter "m" on this page, National's micro- power CMOS comparators offer true rail-to-rail input in space-saving TinyPak SOT23-5 packages, making them ideal for portable designs with critical space and weight requirements.

"In designing these comparators, our goal was to offer best-in-class performance in the smallest possible outline," noted Jim Chase, National's marketing manager. "The process has resulted in a part that packs the performance advantages of rail-to-rail input into a TinyPak at no additional cost."

National's new signal-shaping devices include the LMC7221, the only product in its class with open-drain output, and the LMC7211, with push-pull output. With low supply currents and a high common-mode input range beyond the rails, both parts are ideal for power supervisory and other signal-shaping analog circuits found in small portable battery- powered devices such as cellular phones, pagers, notebook computers, personal digital assistants (PDAs) and PCMCIA cards. Rail-to-rail input voltage is desirable for sensor interfacing, such as light-detector circuits, optical and magnetic sensors, and alarm and status circuits.

The LMC7221, with its open-drain output, can accommodate Wired-OR configurations. Used to multiplex analog signals into a single digital input, this open drain feature simplifies integrating mixed-voltage systems by allowing the output to be pulled to any voltage rail up to 15 volts, regardless of the supply voltage supplied to the part itself.

National's TinyPak comparators also simplify board layout in several ways. First, long printed circuit traces can be avoided by placing a comparator where it is needed rather than routing signals to a dual or quad device. In addition, by using multiple TinyPak comparators rather than duals or quads, complex signal routing and crosstalk can be reduced.

The LMC7211/7221 are characterized at +15V, +5V and +2.7V for multiple supply voltages or low-voltage. At +2.7V, National guarantees a common-mode voltage range extending 200mV below the negative supply.