LMC7211AIM5/NOPB National Semiconductor, LMC7211AIM5/NOPB Datasheet - Page 8

• Manufacturer Part Number: LMC7211AIM5/NOPB
• Description: IC COMPAR TINY R-R CMOS SOT23-5
• Manufacturer: National Semiconductor
• Type: General Purposer

Specifications of LMC7211AIM5/NOPB

• Number Of Elements: 1
• Output Type: Push-Pull
• Voltage - Supply: 2.7 V ~ 15 V, ±1.35 V ~ 7.5 V
• Mounting Type: Surface Mount
• Package / Case: SC-74A, SOT-753
• Comparator Type: Micropower
• No. Of Comparators: 1
• Response Time: 4µs
• Ic Output Type: Push Pull
• Supply Current: 7µA
• Supply Voltage Range: 2.7V To 15V
• Amplifier Case Style: SOT-23
• No. Of Pins: 5
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: LMC7211AIM5; LMC7211AIM5TR

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Application Information
1.0 Benefits of the LMC7211 Tiny Comparator
Size. The small footprint of the SOT 23-5 packaged Tiny
Comparator, (0.120 x 0.118 inches, 3.05 x 3.00 mm) saves
space on printed circuit boards, and enable the design of
smaller electronic products. Because they are easier to carry,
many customers prefer smaller and lighter products.
Height. The height (0.056 inches, 1.43 mm) of the Tiny Com-
parator makes it possible to use it in PCMCIA type III cards.
Simplified Board Layout. The Tiny Comparator can simplify
board layout in several ways. First, by placing a comparator
where comparators are needed, instead of routing signals to
a dual or quad device, long pc traces may be avoided.
By using multiple Tiny Comparators instead of duals or quads,
complex signal routing and possibly crosstalk can be re-
duced.
Low Supply Current. The typical 7 μA supply current of the
LMC7211 extends battery life in portable applications, and
may allow the reduction of the size of batteries in some ap-
plications.
Wide Voltage Range. The LMC7211 is characterized at 15V,
5V and 2.7V. Performance data is provided at these popular
voltages. This wide voltage range makes the LMC7211 a
good choice for devices where the voltage may vary over the
life of the batteries.
Digital Outputs Representing Signal Level. Comparators
provide a high or low digital output depending on the voltage
levels of the (+) and (−) inputs. This makes comparators use-
ful for interfacing analog signals to microprocessors and other
digital circuits. The LMC7211 can be thought of as a one-bit
a/d converter.
Push-Pull Output. The push-pull output of the LMC7211 is
capable of both sourcing and sinking milliamp level currents
even at a 2.7 volt supply. This can allow the LMC7211 to drive
multiple logic gates.
Driving LEDs (Light Emitting Diodes). With a 5 volt power
supply, the LMC7211's output sinking current can drive small,
high efficiency LEDs for indicator and test point circuits. The
small size of the Tiny package makes it easy to find space to
add this feature to even compact designs.
Input range to Beyond Rail to Rail. The input common
mode range of the LMC7211 is slightly larger than the actual
power supply range. This wide input range means that the
comparator can be used to sense signals close to the power
supply rails. This wide input range can make design easier by
eliminating voltage dividers, amplifiers, and other front end
Input Bias Current vs. Temperature
8
circuits previously used to match signals to the limited input
range of earlier comparators. This is useful to power supply
monitoring circuits which need to sense their own power sup-
ply, and compare it to a reference voltage which is close to
the power supply voltage. The wide input range can also be
useful for sensing the voltage drop across a current sense
resistor for battery chargers.
Zero Crossing Detector. Since the LMC7211's common
mode input range extends below ground even when powered
by a single positive supply, it can be used with large input
resistors as a zero crossing detector.
Low Input Currents and High Input Impedance. These
characteristics allow the LMC7211 to be used to sense high
impedance signals from sensors. They also make it possible
to use the LMC7211 in timing circuits built with large value
resistors. This can reduce the power dissipation of timing cir-
cuits. For very long timing circuits, using high value resistors
can reduce the size and cost of large value capacitors for the
same R-C time constant.
Direct Sensor Interfacing. The wide input voltage range and
high impedance of the LMC7211 may make it possible to di-
rectly interface to a sensor without the use of amplifiers or bias
circuits. In circuits with sensors which can produce outputs in
the tens to hundreds of millivolts, the LMC7211 can compare
the sensor signal with an appropriately small reference volt-
age. This may be done close to ground or the positive supply
rail. Direct sensor interfacing may eliminate the need for an
amplifier for the sensor signal. Eliminating the amplifier can
save cost, space, and design time.
2.0 Low Voltage Operation
Comparators are the common devices by which analog sig-
nals interface with digital circuits. The LMC7211 has been
designed to operate at supply voltages of 2.7V without sacri-
ficing performance to meet the demands of 3V digital sys-
tems.
At supply voltages of 2.7V, the common-mode voltage range
extends 200 mV (guaranteed) 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.
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