Page 1
July 2002
LMC7221
Tiny CMOS Comparator with Rail-To-Rail Input and Open
Drain Output
General Description
The LM7221 is a micropower CMOS comparator available in
the space saving SOT23-5 package. This makes this comparator ideal for space and weight critical designs. The
LMC7221 is also available in the SO-8 package. The
LMC7221 is supplied in two offset voltage grades, 5 mV and
15 mV.
The open drain output can be pulled up with a resistor to a
voltage which can be higher or lower than the supply
voltage —this makes the part useful for mixed voltage systems.
For a tiny comparator with a push-pull output, please see the
LMC7211 datasheet.
Features
n Tiny SOT 23-5 package saves space
n Package is less than 1.43 mm thick
n Guaranteed specs at 2.7V, 5V, 15V supplies
n Typical supply current 7 µA at 5V
n Response time of 4 µs at 5V
n LMC7221 — open drain output
n Input common-mode range beyond V− and V+
n Low input current
Applications
n Mixed voltage battery powered products
n Notebooks and PDAs
n PCMCIA cards
n Mobile communications
n Alarm and security circuits
n Driving low current LEDs
n Direct sensor interface
LMC7221 Tiny CMOS Comparator with Rail-To-Rail Input and Open Drain Output
Connection Diagrams
8–Pin SO-8
Top View
Ordering Information
Package Ordering NSC Drawing Package Transport Media
Information Number Marking
LMC7221AIM M08A LMC7221AIM Rails
8-Pin SO-8
5-Pin SOT 23-5
LMC7221AIMX M08A LMC7221AIM 2.5k Units Tape and Reel
LMC7221BIM M08A LMC7221BIM Rails
LMC7221BIMX M08A LMC7221BIM 2.5k Units Tape and Reel
LMC7221AIM5 MA05A C01A 1k Units Tape and Reel
LMC7221AIM5X MA05A C01A 3k Units Tape and Reel
LMC7221BIM5 MA05A C01B 1k Units Tape and Reel
LMC7221BIM5X MA05A C01B 3k Units Tape and Reel
01234601
5-Pin SOT23-5
01234602
Top View
© 2004 National Semiconductor Corporation DS012346 www.national.com
Page 2
Absolute Maximum Ratings (Note 1)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
LMC7221
Distributors for availability and specifications.
(soldering, 10 sec.) 260˚C
Storage Temperature Range −65˚C to +150˚C
Junction Temperature
(Note 4) 150˚C
ESD Tolerance (Note 2) 2 kV
Differential Input Voltage (V
Voltage at Input (V
Voltage at Output Pin 15V
Supply Voltage (V
+–V−
) 16V
Current at Input Pin
(Note 7)
Current at Output Pin
(Notes 3, 8)
Current at Power Supply Pin 40 mA
) +0.3V to
CC
(−V
CC
) + 0.3V to
CC
(−V
CC
±
)−0.3V
)−0.3V
±
5mA
30 mA
Operating Ratings (Note 1)
Supply Voltage 2.7 ≤ V
Junction Temperature Range
LMC7221AI, LMC7221BI −40˚C ≤ T
Thermal Resistance (θ
SO-8 Package,
8-Pin Surface Mount 180˚C/W
M05A Package,
5-Pin Surface Mount 325˚C/W
)
JA
Lead Temperature
2.7V Electrical Characteristics
Unless otherwise specified, all limits guaranteed for TJ= 25˚C, V+= 2.7V, V−= 0V, VCM=VO= V+/2. Boldface limits apply at
the temperature extremes
Typ LMC7221AI LMC7221BI
Symbol Parameter Conditions (Note 5) Limit Limit Units
(Note 6) (Note 6)
V
OS
TCV
OS
I
B
I
OS
CMRR Common Mode 0V ≤ V
PSRR Power Supply 2.7V ≤ V
A
V
CMVR Input Common-Mode CMRR
V
OL
I
S
Input Offset Voltage 3 5 15 mV
818max
Input Offset Voltage 1.0 µV/˚C
Temperature Drift
Input Offset Voltage (Note 10) 3.3 µV/Month
Average Drift
Input Current 0.04 pA
Input Offset Current 0.02 pA
≤ 2.7V 75 dB
CM
Rejection Ratio
+
≤ 15V 80 dB
Rejection Ratio
Voltage Gain 100 dB
>
55 dB 3.0 2.9 2.9 V
Voltage Range 2.7 2.7 min
>
CMRR
55 dB −0.3 −0.2 −0.2 V
0.0 0.0 max
Output Voltage Low I
= 2.5 mA 0.2 0.3 0.3 V
load
0.4 0.4 max
Supply Current V
= low 7 12 12 µA
OUT
14 14 max
CC
≤ 15V
J
+85˚C
≤
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Page 3
5.0V and 15.0V Electrical Characteristics
Unless otherwise specified, all limits guaranteed for TJ= 25˚C, V+= 5.0V and 15V, V−= 0V, VCM=VO=V+/2. Boldface limits
apply at the temperature extremes
Typ LMC7221AI LMC7221BI
Symbol Parameter Conditions (Note 5) Limit Limit Units
(Note 6) (Note 6)
V
OS
TCV
OS
I
B
I
OS
CMRR Common Mode V+ = 5.0V 75 dB
PSRR Power Supply 5V ≤ V
A
V
CMVR Input Common-Mode V+ = 5.0V 5.3 5.2 5.2 V
V
OL
I
S
I
SC
Input Offset Voltage 3 5 15 mV
818max
Input Offset Voltage V+= 5V 1.0 µV/˚C
Temperature Drift V
Input Offset Voltage V
Average Drift V
+
= 15V 4.0
+
= 5V (Note 10) 3.3 µV/Month
+
= 15V (Note 10) 4.0
Input Current 0.04 pA
Input Offset Current 0.02 pA
Rejection Ration V+ = 15.0V 82 dB
+
≤ 10V 80 dB
Rejection Ratio
Voltage Gain 100 dB
Voltage Range CMRR
>
55 dB 5.0 5.0 min
V+ = 5.0V −0.3 −0.2 −0.2 V
>
CMRR
55 dB 0.0 0.0 max
V+ = 15.0V 15.3 15.2 15.2 V
>
CMRR
55 dB 15.0 15.0 min
V+ = 15.0V −0.3 −0.2 −0.2 V
>
CMRR
55 dB 0.0 0.0 max
Output Voltage Low V+ = 5V 0.2 0.40 0.40 mV
I
=5mA 0.55 0.55 max
load
V+ = 15V 0.2 0.40 0.40 mV
I
=5mA 0.55 0.55 max
load
Supply Current V
= Low 7 14 14 µA
OUT
18 18 max
Short Circuit Current Sinking (Note 8) 45 mA
LMC7221
Leakage Characteristics
TJ= 25˚C
Typ LMC7221AI LMC7221BI
Symbol Parameter Conditions (Note 5) Limit Limit Units
(Note 6) (Note 6)
I
LEAKAGE
Output Leakage V+ = 2.7V
Current V
(+) = 0.5V 0.1 500 500 nA
IN
V
(−)=0V
IN
V
= 15V
OUT
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Page 4
AC Electrical Characteristics
Unless otherwise specified, all limits guaranteed for TJ= 25˚C, V+= 5V, V−= 0V, VCM=VO=V+/2. Boldface limits apply at
the temperature extreme
LMC7221
Typ LMC7221AI LMC7221BI
Symbol Parameter Conditions (Note 5) Limit Limit Units
(Note 6) (Note 6)
t
rise
t
fall
t
PHL
t
PLH
Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is
intended to be functional, but specific performance is not guaranteed. For guaranteed specifications and the test conditions, see the Electrical Characteristics.
Note 2: Human body model, 1.5 kΩ in series with 100 pF.
Note 3: Applies to both single-supply and split-supply operation. Continuous short circuit operation at elevated ambient temperature can result in exceeding the
maximum allowed junction temperature of 150˚C. Output currents in excess of
Note 4: The maximum power dissipation is a function of T
Note 5: P
Note 6: Typical values represent the most likely parametric norm.
Note 7: All limits are guaranteed by testing or statistical analysis.
Note 8: Limiting input pin current is only necessary for input voltages which exceed the absolute maximum input voltage rating.
Note 9: Do not short circuit the output to V+ when V+ is greater than 12V or reliability will be adversely affected.
Note 10: C
Note 11: Input offset voltage average drift is calculated by dividing the accelerated operating life V
case input conditions and includes the first 30 days of drift.
Note 12: Input step voltage for propagation delay measurement is 2V.
Rise Time f = 10 kHz, CL= 50 pF, (Note 9) 0.3 µs
Overdrive = 10 mV, 5 kΩ Pullup
Fall Time f = 10 kHz, CL= 50 pF, (Note 9) 0.3 µs
Overdrive = 10 mV, 5 kΩ Pullup
Propagation Delay f = 10 kHz, 10 mV 10 µs
(High to Low) C
= 50 pF, 100 mV 4
L
(Note 11) 5 kΩ Pullup
(Note 9)
V+ = 2.7V, 10 mV 10 µs
f = 10 kHz,
C
= 50 pF, 100 mV 4
L
5kΩ Pullup
(Note 9)
Propagation Delay f = 10 kHz, 10 mV 6 µs
(Low to High) C
= 50 pF, 100 mV 4
L
(Note 11) 5 kΩ Pullup
(Note 9)
V+ = 2.7V, 10 mV 7 µs
f = 10 kHz,
C
= 50 pF, 100 mV 4
L
5kΩ Pullup
(Note 9)
±
30 mA may adversely affect reliability.
, θJA, and TA. The maximum allowable power dissipation at any ambient temperature is
=(T
D
J(max)−TA
includes the probe and test jig capacitance.
L
)/θJA. All numbers apply for packages soldered directly into a PC board.
J(max)
drift by the equivalent operational time. This represents worst
OS
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Page 5
Typical Performance Characteristics
LMC7221
Supply Current vs
Supply Voltage
Output Sinking Current vs
Supply Voltage
Supply Current vs
Temperature while Sinking
01234603 01234604
Output Sinking Current vs
@
Output Voltage
5V
Output Sinking Current vs
@
Output Voltage
15V
01234605
01234607
Response Time for Various
Input Overdrives −t
PHL
01234606
01234608
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Page 6
Typical Performance Characteristics (Continued)
LMC7221
Response Time vs Various
Input Overdrives −t
PHL
Input Bias Current vs
Common Mode Voltage
01234609
Response Time vs Various
Input Overdrives −t
PHL
Input Bias Current vs
Common Mode Voltage
01234610
Input Bias Current vs
Common Mode Voltage
01234611
01234613
01234612
Input Bias Current vs
Temperature
01234614
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Page 7
Typical Performance Characteristics (Continued)
Leakage Current vs
Supply Voltage
01234615
LMC7221
Application Information
1.0 BENEFITS OF THE LMC7221 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
Comparator 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
reduced.
Low Supply Current. The typical 7 µA supply current of the
LMC7221 extends battery life in portable applications, and
may allow the reduction of the size of batteries in some
applications.
Wide Voltage Range. The LMC7221 is characterized at
15V, 5V and 2.7V. Performance data is provided at these
popular voltages. This wide voltage range makes the
LMC7221 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
useful for interfacing analog signals to microprocessors and
other digital circuits. The LMC7221 can be thought of as a
one-bit a/d converter.
Open Drain Output. The open drain output is like the open
collector output of a logic gate. This makes the LMC7221
very useful for mixed voltage systems.
Driving LEDs (Light Emitting Diodes). With a 5 volt power
supply, the LMC7221’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 LMC7221 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 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 supply, 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 LMC7221’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 LMC7221 to be used to sense high
impedance signals from sensors. They also make it possible
to use the LMC7221 in timing circuits built with large value
resistors. This can reduce the power dissipation of timing
circuits. 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 LMC7221 may make it possible
to directly 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 LMC7221
can compare the sensor signal with an appropriately small
reference voltage. 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 signals interface with digital circuits. The LMC7221 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 (guaranteed) below the negative supply.
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Page 8
Application Information (Continued)
3.0 OPEN DRAIN OUTPUT
This feature, in addition to the comparator being able to
LMC7221
sense signals near the positive rail, is extremely useful in low
voltage applications.
FIGURE 1. Even at Low-Supply Voltage of 2.7V, an
Input Signal which Exceeds the Supply Voltages
Produces No Phase Inversion at the Output
+
= 2.7V propagation delays are t
At V
=4µsandt
PLH
4 µs with overdrives of 100 mV.
Please refer to the performance curves for more extensive
characterization.
01234616
PHL
Output Stage
01234617
=
01234621
FIGURE 2.
Figure 2 shows the difference between push-pull output and
open drain output.
Push pull outputs will have a conventional high or low digital
output, the same as a logic gate. Low will be the negative
supply rail (usually ground) and high will be the positive
supply rail.
This is useful if the chips you are interfacing to run on the
same supply voltage as the comparator. An example would
be an all +5V system.
Open drain outputs will only pull low — for the high output
they depend on an external pull-up resistor. This can pull up
to a voltage higher or lower than the comparator supply
voltage. This voltage can be as high as 15V. This makes the
open drain parts useful in mixed voltage systems. An example would be where the comparator runs at 5V and the
logic circuits are at 3.3V. The pull-up resistor would go to the
3.3V supply.
Open drain outputs are the CMOS equivalent of open col-
lector outputs.
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Page 9
Application Information (Continued)
4.0 OUTPUT SHORT CIRCUIT CURRENT
The LMC7221 has short circuit protection of 40 mA. However, it is not designed to withstand continuous short circuits,
transient voltage or current spikes, or shorts to any voltage
beyond the supplies. A resistor in series with the output
should reduce the effect of shorts. For outputs which send
signals off PC boards additional protection devices, such as
diodes to the supply rails, and varistors may be used.
5.0 INPUT PROTECTION
If input signals are likely to exceed the common mode range
of the LMC7221, or it is likely that signals may be present
when power is off, damage to the LMC7221 may occur.
Large value (100 kΩ to MΩ) input resistors may reduce the
likelihood of damage by limiting the input currents. Since the
LMC7221 has very low input leakage currents, the effect on
accuracy will be small. Additional protection may require the
use of diodes, as shown in Figure 3. Note that diode leakage
current may affect accuracy during normal operation.
The R-C time constant of R
also slow response time.
6.0 LAYOUT CONSIDERATIONS
The LMC7221 is not an especially fast comparator, so high
speed design practices are not required. The LMC7221 is
capable of operating with very high impedance inputs, so
precautions should be taken to reduce noise pickup with
high impedance (∼ 100 kΩ and greater) designs and in
electrically noisy environments.
Keeping high value resistors close to the LMC7221 and
minimizing the size of the input nodes is a good practice.
With multilayer designs, try to avoid long loops which could
act as inductors (coils). Sensors which are not close to the
comparator may need twisted pair or shielded connections
to reduce noise.
and the diode capacitance may
IN
01234618
FIGURE 3.
7.0 PUSH-PULL OUTPUTS, DUAL VERSIONS
The LMC7211 is a comparator similar to the LMC7221, but
with push-pull outputs which can source current.
The performance of the LMC7221 is available in a dual
device. Please see the LMC6772 datasheet. For a dual
device with push-pull outputs, please see the LMC6762
datasheet.
Rail-to-Rail Input Low Power Comparators —
Push-Pull Output
LMC7221 SOT23-5, SO-8 Single
LMC6762 SO-8 Dual
Open Drain Output
LMC7221 SOT23-5, SO-8 Single
LMC6772 SO-8, Dual
8.0 ADDITIONAL SOT23-5 TINY DEVICES
National Semiconductor has additional parts available in the
space saving SOT23 Tiny package, including amplifiers,
voltage references, and voltage regulators. These devices
include —
LMC7101 1 MHz gain-bandwidth rail-to-rail input and output
amplifier —high input impedance and high gain
700 µA typical current 2.7V, 3V, 5V and 15V
specifications.
LMC7111 Low power 50 kHz gain-bandwidth rail-to-rail in-
put and output amplifier with 25 µA typical current
specified at 2.7V, 3.0V, 3.3V, 5V and 10V.
LM7131 Tiny Video amp with 70 MHz gain bandwidth 3V,
5V and
LP2980 Micropower SOT 50 mA Ultra Low-Dropout
Regulator.
LM4040 Precision micropower shunt voltage reference.
Fixed voltages of 2.500V, 4.096V, 5.000V, 8.192V
and 10.000V.
LM4041 Precision micropower shut voltage reference
1.225V and adjustable.
LM385 Low current voltage reference. Fixed Voltages of
1.2V and 2.5V.
Contact your National Semiconductor representative for the
latest information.
9.0 SPICE MACROMODEL
A Spice Macromodel is available for the LMC7221 comparator on the National Semiconductor Amplifier Macromodel
disk. Contact your National Semiconductor representative to
obtain the latest version.
±
5V specifications.
LMC7221
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Page 10
Application Information (Continued)
LMC7221
REEL DIMENSIONS
8 mm 7.00 0.059 0.512 0.795 2.165 0.331 + 0.059/−0.000 0.567 W1+ 0.078/−0.039
330.00 1.50 13.00 20.20 55.00 8.40 + 1.50/−0.00 14.40 W1 + 2.00/−1.00
Tape Size A B C D N W1 W2 W3
SOT-23-5 Tape and Reel Specification
TAPE FORMAT
Tape Section # Cavities Cavity Status Cover Tape Status
Leader 0 (min) Empty Sealed
(Start End) 75 (min) Empty Sealed
Carrier 3000 Filled Sealed
1000 Filled Sealed
Trailer 125 (min) Empty Sealed
(Hub End) 0 (min) Empty Sealed
01234619
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Page 11
SOT-23-5 Tape and Reel Specification (Continued)
Tape Dimensions
LMC7221
8 mm 0.130 0.124 0.130 0.126 0.138±0.002 0.055±0.004 0.157 0.315±0.012
(3.3) (3.15) (3.3) (3.2) (3.5
Tape Size DIM A DIM Ao DIM B DIM Bo DIM F DIM Ko DIM P1 DIM W
±
0.05) (1.4±0.11) (4) (8±0.3)
01234620
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Page 12
Physical Dimensions inches (millimeters)
unless otherwise noted
LMC7221
5-Pin SOT Package
Order Number LMC7221AIM5, LMC7221AIM5X, LMC7221BIM5, or LMC7221BIMX
NS Package Number MA05A
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Page 13
Physical Dimensions inches (millimeters) unless otherwise noted (Continued)
LMC7221 Tiny CMOS Comparator with Rail-To-Rail Input and Open Drain Output
8-Pin Small Outline Package
Order Number LMC7221AIM, LMC7221AIMX, LMC7221BIM, or LMC7221BIMX
NS Package Number M08A
National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves
the right at any time without notice to change said circuitry and specifications.
For the most current product information visit us at www.national.com.
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CORPORATION. As used herein:
1. Life support devices or systems are devices or systems
which, (a) are intended for surgical implant into the body, or
(b) support or sustain life, and whose failure to perform when
properly used in accordance with instructions for use
2. A critical component is any component of a life support
device or system whose failure to perform can be reasonably
expected to cause the failure of the life support device or
system, or to affect its safety or effectiveness.
provided in the labeling, can be reasonably expected to result
in a significant injury to the user.
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Specification (CSP-9-111C2) and the Banned Substances and Materials of Interest Specification (CSP-9-111S2) and contain no ‘‘Banned
Substances’’ as defined in CSP-9-111S2.
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