LMC6772_15 Datasheet, PDF (12/25 Pages) Texas Instruments – Dual Micropower Rail-To-Rail Input CMOS Comparator with Open Drain Output

LMC6772
SNOS749F – SEPTEMBER 1995 – REVISED MARCH 2013
APPLICATION INFORMATION
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INPUT COMMON-MODE VOLTAGE RANGE
At supply voltages of 2.7V, 5V and 15V, the LMC6772 has an input common-mode voltage range which exceeds
both supplies. As in the case of operational amplifiers, CMVR is defined by the V_OS shift of the comparator over
the common-mode range of the device. A CMRR (ΔV_OS/ΔV_CM) of 75 dB (typical) implies a shift of < 1 mV over
the entire common-mode range of the device. The absolute maximum input voltage at V⁺ = 5V is 200 mV beyond
either supply rail at room temperature.
Figure 29. An Input Signal Exceeds the LMC6772 Power Supply Voltages with No Output Phase
Inversion
A wide input voltage range means that the comparator can be used to sense signals close to ground and also to
the power supplies. This is an extremely useful feature in power supply monitoring circuits.
An input common-mode voltage range that exceeds the supplies, 20 fA input currents (typical), and a high input
impedance makes the LMC6772 ideal for sensor applications. The LMC6772 can directly interface to sensors
without the use of amplifiers or bias circuits. In circuits with sensors which produce outputs in the tens to
hundreds of millivolts, the LMC6772 can compare the sensor signal with an appropriately small reference
voltage. This reference voltage can be close to ground or the positive supply rail.
LOW VOLTAGE OPERATION
Comparators are the common devices by which analog signals interface with digital circuits. The LMC6772 has
been designed to operate at supply voltages of 2.7V, without sacrificing performance, to meet the demands of 3V
digital systems.
At supply voltages of 2.7V, the common-mode voltage range extends 200 mV (ensured) below the negative
supply. This feature, in addition to the comparator being able to sense signals near the positive rail, is extremely
useful in low voltage applications.
Figure 30. Even at Low-Supply Voltage of 2.7V, an Input Signal which Exceeds the Supply Voltages
Produces No Phase Inversion at the Output
At V⁺ = 2.7V, propagation delays are t_PLH = 4 μs and t_PHL = 4 μs with overdrives of 100 mV. Please refer to the
performance curves for more extensive characterization.
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