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AS1970

8 Detailed Description

The AS1970 - AS1975 are single/dual/quad low-power, comparators. The devices operate with a supply voltage range

between 2.5 and 5.5V while consuming down to 8.5µA per comparator. Their common-mode input voltage range

extends 0.25V beyond each rail.

Internal hysteresis ensures clean output switching, even with slow input signals. Large internal output drivers allow rail-

to-rail output swing with up to 8mA loads.

The output stage design minimizes supply-current surges while switching, virtually eliminating the power supply tran-

sients typical. The AS1970/AS1972/AS1974 push/pull output stage sinks and sources current, wheras the AS1971/

Input Stage

the common-mode voltage range.

Inputs are protected from over-voltage by internal ESD protection diodes connected to the supply rails. As the input

voltage exceeds the supply rails, these diodes become forward biased and begin to conduct and the bias currents

increase exponentially as the input voltage exceeds the supply rails.

Output Stage

The push/pull and open-drain output stages were designed to provide rail-to-rail operation with up to 8mA loads. Even

at loads of up to 8mA, the supply-current change during an output transition is extremely small (see Figure 4 on page

6). Figure 4 shows the minimal supply-current increase as the output switching frequency approaches 1MHz. This

characteristic eliminates the need for power-supply filter capacitors to reduce glitches created by comparator switching

currents.

Because of the unique design of its output stage, the AS1970 - AS1975 can dramatically increase battery life, even in

high-speed applications.