LMC6772
Dual Micropower Rail-To-Rail Input CMOS Comparator
with Open Drain Output
General Description
The LMC6772 is an ultra low power dual comparator with a
maximum 10 A/comparator power supply current. It is de-
signed to operate over a wide range of supply voltages, with
a minimum supply voltage of 2.7V.
The common mode voltage range of the LMC6772 exceeds
both the positive and negative supply rails, a significant ad-
vantage in single supply applications. The open drain output
of the LMC6772 allows for wired-OR configurations. The
open drain output also offers the advantage of allowing the
output to be pulled to any voltage rail up to 15V, regardless
of the supply voltage of the LMC6772.
The LMC6772 is targeted for systems where low power con-
sumption is the critical parameter. Guaranteed operation at
supply voltages of 2.7V and rail-to-rail performance makes
this comparator ideal for battery-powered applications.
Refer to the LMC6762 datasheet for a push-pull output stage
version of this device.
Features
(Typical unless otherwise noted)
n
Low power consumption (max):
I
S
= 10 A/comp
n
Wide range of supply voltages:
2.7V to 15V
n
Rail-to-Rail Input Common Mode Voltage Range
n
Open drain output
n
Short circuit protection:
40 mA
n
Propagation delay (
@
V
S
= 5V, 100 mV overdrive): 5 s
Applications
n
Laptop computers
n
Mobile phones
n
Metering systems
n
Hand-held electronics
n
RC timers
n
Alarm and monitoring circuits
n
Window comparators, multivibrators
Connection Diagram
Ordering Information
Package
Temperature Range
NSC Drawing
Transport
-40C to +85C
Media
8-Pin Molded DIP
LMC6772AIN, LMC6772BIN
N08E
Rails
8-Pin Small Outline
LMC6772AIM, LMC6772BIM
M08A
Rails
LMC6772AIMX, LMC6772BIMX
M08A
Tape and Reel
8-Pin DIP/SO
DS012347-1
Top View
September 1995
LMC6772
Dual
Micropower
Rail-T
o-Rail
Input
CMOS
Comparator
with
Open
Drain
Output
1999 National Semiconductor Corporation
DS012347
www.national.com
Absolute Maximum Ratings
(Note 1)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
ESD Tolerance (Note 2)
1.5 kV
Differential Input Voltage
(V
+
)+0.3V to (V
-
)-0.3V
Voltage at Input/Output Pin
(V
+
)+0.3V to (V
-
)-0.3V
Supply Voltage (V
+
V
-
)
16V
Current at Input Pin (Note 8)
5 mA
Current at Output Pin (Notes 3, 7)
30 mA
Current at Power Supply Pin, LMC6772
40 mA
Lead Temperature (Soldering, 10 seconds)
260C
Storage Temperature Range
-65C to +150C
Junction Temperature (Note 4)
150C
Operating Ratings
(Note 1)
Supply Voltage
2.7
V
S
15V
Junction Temperature Range
LMC6772AI, LMC6772BI
40C
T
J
+85C
Thermal Resistance (
JA
)
N Package, 8-Pin Molded DIP
100C/W
M Package, 8-Pin Surface Mount
172C/W
2.7V Electrical Characteristics
Unless otherwise specified, all limits guaranteed for T
J
= 25C, V
+
= 2.7V, V
-
= 0V, V
CM
= V
+
/2. Boldface limits apply at the
temperature extremes.
Symbol
Parameter
Conditions
Typ
(Note 5)
LMC6772AI
LMC6772BI
Units
Limit
Limit
(Note 6)
(Note 6)
V
OS
Input Offset Voltage
3
5
15
mV
8
18
max
TCV
OS
Input Offset Voltage
2.0
V/C
Temperature Drift
Input Offset Voltage
(Note 10)
3.3
V/Month
Average Drift
I
B
Input Current
0.02
pA
I
OS
Input Offset Current
0.01
pA
CMRR
Common Mode Rejection Ratio
75
dB
PSRR
Power Supply Rejection Ratio
1.35V
<
V
S
<
7.5V
80
dB
A
V
Voltage Gain
(By Design)
100
dB
V
CM
Input Common-Mode
CMRR
>
55 dB
3.0
2.9
2.9
V
Voltage Range
2.7
2.7
min
-0.3
-0.2
-0.2
V
0.0
0.0
max
V
OL
Output Voltage Low
I
LOAD
= 2.5 mA
0.2
0.3
0.3
V
0.4
0.4
max
I
S
Supply Current
For Both Comparators
12
20
20
A
(Output Low)
25
25
max
I
Leakage
Output Leakage Current
V
IN
(+) = 0.5V,
0.1
500
500
nA
V
IN
(-) = 0V, V
O
= 15V
5.0V and 15.0V Electrical Characteristics
Unless otherwise specified, all limits guaranteed for T
J
= 25C, V
+
= 5.0V and 15.0V, V
-
= 0V, V
CM
= V
+
/2. Boldface limits
apply at the temperature extremes.
Symbol
Parameter
Conditions
Typ
(Note 5)
LMC6772AI
LMC6772BI
Units
Limit
Limit
(Note 6)
(Note 6)
V
OS
Input Offset Voltage
3
5
15
mV
8
18
max
TCV
OS
Input Offset Voltage
V
+
= 5V
2.0
V/C
Temperature Drift
V
+
= 15V
4.0
Input Offset Voltage
V
+
= 5V (Note 10)
3.3
V/Month
Average Drift
V
+
= 15V (Note 10)
4.0
www.national.com
2
5.0V and 15.0V Electrical Characteristics
(Continued)
Unless otherwise specified, all limits guaranteed for T
J
= 25C, V
+
= 5.0V and 15.0V, V
-
= 0V, V
CM
= V
+
/2. Boldface limits
apply at the temperature extremes.
Symbol
Parameter
Conditions
Typ
(Note 5)
LMC6772AI
LMC6772BI
Units
Limit
Limit
(Note 6)
(Note 6)
I
B
Input Current
V = 5V
0.04
pA
I
OS
Input Offset Current
V
+
= 5V
0.02
pA
CMRR
Common Mode
V
+
= 5V
75
dB
Rejection Ratio
V
+
= 15V
82
dB
PSRR
Power Supply Rejection Ratio
2.5V
<
V
S
<
5V
80
dB
A
V
Voltage Gain
(By Design)
100
dB
V
CM
Input Common-Mode
V
+
= 5.0V
5.3
5.2
5.2
V
Voltage Range
CMRR
>
55 dB
5.0
5.0
min
-0.3
-0.2
-0.2
V
0.0
0.0
max
V
+
= 15.0V
15.3
15.2
15.2
V
CMRR
>
55 dB
15.0
15.0
min
-0.3
-0.2
-0.2
V
0.0
0.0
max
V
OL
Output Voltage Low
V
+
= 5V
0.2
0.4
0.4
V
I
LOAD
= 5 mA
0.55
0.55
max
V
+
= 15V
0.2
0.4
0.4
V
I
LOAD
= 5 mA
0.55
0.55
max
I
S
Supply Current
For Both Comparators
12
20
20
A
(Output Low)
25
25
max
I
SC
Short Circuit Current
V
+
= 15V, Sinking, V
O
= 12V
45
mA
(Note 7)
AC Electrical Characteristics
Unless otherwise specified, all limits guaranteed for T
J
= 25C, V
+
= 5V, V
-
= 0V, V
CM
= V
O
= V
+
/2. Boldface limits apply at
the temperature extreme.
Symbol
Parameter
Conditions
Typ
(Note 5)
LMC6772AI
LMC6772BI
Units
Limit
Limit
(Note 6)
(Note 6)
t
RISE
Rise Time
f = 10 kHz, C
L
= 50 pF,
0.3
s
Overdrive = 10 mV (Note 9)
t
FALL
Fall Time
f = 10 kHz, C
L
= 50 pF,
0.3
s
Overdrive = 10 mV (Note 9)
t
PHL
Propagation Delay
f = 10 kHz,
10 mV
10
s
(High to Low)
C
L
= 50 pF
100 mV
4
s
(Note 9)
V
+
= 2.7V,
10 mV
10
s
f = 10 kHz,
C
L
= 50 pF
100 mV
4
s
(Note 9)
www.national.com
3
AC Electrical Characteristics
(Continued)
Unless otherwise specified, all limits guaranteed for T
J
= 25C, V
+
= 5V, V
-
= 0V, V
CM
= V
O
= V
+
/2. Boldface limits apply at
the temperature extreme.
Symbol
Parameter
Conditions
Typ
(Note 5)
LMC6772AI
LMC6772BI
Units
Limit
Limit
(Note 6)
(Note 6)
t
PLH
Propagation Delay
f = 10 kHz,
10 mV
10
s
(Low to High)
C
L
= 50 pF
100 mV
4
s
(Note 9)
V
+
= 2.7V,
10 mV
8
s
f = 10 kHz,
C
L
= 50 pF
100 mV
4
s
(Note 9)
Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is in-
tended 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 k
in series with 100 pF. The output pins of the two comparators (pin 1 and pin 7) have an ESD tolerance of 1.5 kV. All other pins
have an ESD tolerance of 2 kV.
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 150C. Output currents in excess of
30 mA over long term may adversely affect reliability.
Note 4: The maximum power dissipation is a function of T
J(max)
,
JA
, and T
A
. The maximum allowable power dissipation at any ambient temperature is P
D
= (T
J(max)
T
A
)/
JA
. All numbers apply for packages soldered directly into a PC board.
Note 5: Typical Values represent the most likely parametric norm.
Note 6: All limits are guaranteed by testing or statistical analysis.
Note 7: Do not short circuit output to V
+
, when V+ is
>
12V or reliability will be adversely affected.
Note 8: Limiting input pin current is only necessary for input voltages that exceed absolute maximum input voltage ratings.
Note 9: C
L
inlcudes the probe and jig capacitance. The rise time, fall time and propagation delays are measured with a 2V input step.
Note 10: Input offset voltage Average Drift is calculated by dividing the accelerated operating life drift average by the equivalent operational time. The input offset
voltage average drift represents the input offset voltage change at worst-case input conditions.
Typical Performance Characteristics
V
+
= 5V, Single Supply, T
A
= 25C unless otherwise specified
Supply Current vs Supply
Voltage (Output High)
DS012347-3
Supply Current vs Supply
Voltage (Output Low)
DS012347-4
Input Current vs
Common-Mode Voltage
DS012347-5
Input Current vs
Common-Mode Voltage
DS012347-6
Input Current vs
Common-Mode Voltage
DS012347-7
Input Current
vs Temperature
DS012347-8
www.national.com
4
Typical Performance Characteristics
V
+
= 5V, Single Supply, T
A
= 25C unless otherwise
specified (Continued)
V
OS
vs
V
CM
V
S
= 2.7V
DS012347-9
V
OS
vs
V
CM
V
S
= 5V
DS012347-10
V
OS
vs
V
CM
V
S
= 15V
DS012347-11
Output Voltage vs
Output Current (Sinking)
DS012347-12
Output Voltage vs
Output Current (Sinking)
DS012347-13
Output Voltage vs
Output Current (Sinking)
DS012347-14
Output Short Circuit
Current (Sinking) vs
Supply Voltage
DS012347-15
Leakage Current
vs Output Voltage
DS012347-16
Response Time for
Overdrive (t
PLH
)
DS012347-17
www.national.com
5
Typical Performance Characteristics
V
+
= 5V, Single Supply, T
A
= 25C unless otherwise
specified (Continued)
Application Hints
1.0 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 sup-
plies. As in the case of operational amplifiers, CMVR is de-
fined by the V
OS
shift of the comparator over the
common-mode range of the device. A CMRR (
V
OS
/
V
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.
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 sup-
plies, 20 fA input currents (typical), and a high input imped-
ance 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 pro-
duce outputs in the tens to hundreds of millivolts, the
Response Time
for Overdrive (t
PHL
)
DS012347-18
Response Time
for Overdrive (t
PLH
)
DS012347-19
Response Time
for Overdrive (t
PHL
)
DS012347-20
Response Time for
Overdrive (t
PLH
)
DS012347-21
Response Time for
Overdrive (t
PHL
)
DS012347-22
Response Time vs
Capacitive Load
DS012347-23
DS012347-24
FIGURE 1. An Input Signal Exceeds the LMC6772
Power Supply Voltages with No Output Phase
Inversion
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6
1.0 Input Common-Mode Voltage
Range
(Continued)
LMC6772 can compare the sensor signal with an appropri-
ately small reference voltage. This reference voltage can be
close to ground or the positive supply rail.
2.0 Low Voltage Operation
Comparators are the common devices by which analog sig-
nals interface with digital circuits. The LMC6772 has been
designed to operate at supply voltages of 2.7V, without sac-
rificing 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.
At V
+
= 2.7V, propagation delays are t
PLH
= 4 s and t
PHL
=
4 s with overdrives of 100 mV. Please refer to the perfor-
mance curves for more extensive characterization.
3.0 Output Short Circuit Current
The LMC6772 has short circuit protection of 40 mA. How-
ever, it is not designed to withstand continuous short circuits,
transient voltage or current spikes, or shorts to any voltage
beyond the supplies. A resistor is 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.
4.0 Hysteresis
If the input signal is very noisy, the comparator output might
trip several times as the input signal repeatedly passes
through the threshold. This problem can be addressed by
making use of hysteresis as shown below.
The capacitor added across the feedback resistor increases
the switching speed and provides more short term hyster-
esis. This can result in greater noise immunity for the circuit.
5.0 Spice Macromodel
A Spice Macromodel is available for the LMC6772. The
model includes a simulation of:
Input common-mode voltage range
Quiescent and dynamic supply current
Input overdrive characteristics
and many more characteristics as listed on the macromodel
disk.
Contact the National Semiconductor Customer Response
Center at 1-800-272-9959 to obtain an operational amplifier
spice model library disk.
Typical Applications
Universal Logic Level Shifter
The output of the LMC6772 is the uncommitted drain of the
output NMOS transistor. Many drains can be tied together to
provide an output OR'ing function. An output pullup resistor
can be connected to any available power supply voltage
within the permitted power supply range.
The two 1 k
resistors bias the input to half of the power
supply voltage. The pull-up resistor should go to the output
logic supply. Due to its wide operating range, the LMC6772
is ideal for the logic level shifting applications.
DS012347-25
FIGURE 2. Even at Low-Supply Voltage of 2.7V, an
Input Signal which Exceeds the Supply Voltages
Produces No Phase Inversion at the Output
DS012347-26
FIGURE 3. Canceling the Effect of Input Capacitance
DS012347-27
FIGURE 4. Universal Logic Level Shifter
www.national.com
7
Typical Applications
(Continued)
One-Shot Multivibrator
A monostable multivibrator has one stable state in which it
can remain indefinitely. It can be triggered externally to an-
other quasi-stable state. A monostable multivibrator can thus
be used to generate a pulse of desired width.
The desired pulse width is set by adjusting the values of C
2
and R
4
. The resistor divider of R
1
and R
2
can be used to de-
termine the magnitude of the input trigger pulse. The
LMC6772 will change state when V
1
<
V
2
. Diode D
2
pro-
vides a rapid discharge path for capacitor C
2
to reset at the
end of the pulse. The diode also prevents the non-inverting
input from being driven below ground.
Bi-Stable Multivibrator
A bi-stable multivibrator has two stable states. The reference
voltage is set up by the voltage divider of R
2
and R
3
. A pulse
applied to the SET terminal will switch the output of the com-
parator high. The resistor divider of R
1
, R
4
, and R
5
now
clamps the non-inverting input to a voltage greater than the
reference voltage. A pulse applied to RESET will now toggle
the output low.
Zero Crossing Detector
A voltage divider of R
4
and R
5
establishes a reference volt-
age V
1
at the non-inverting input. By making the series resis-
tance of R
1
and R
2
equal to R
5
, the comparator will switch
when V
IN
= 0. Diode D
1
insures that V
3
never drops below
-0.7V. The voltage divider of R
2
and R
3
then prevents V
2
from going below ground. A small amount of hysteresis is
setup to ensure rapid output voltage transitions.
Oscillator
Figure 8 shows the application of the LMC6772 in a square
wave generator circuit. The total hysteresis of the loop is set
by R
1
, R
2
and R
3
. R
4
and R
5
provide separate charge and
discharge paths for the capacitor C. The charge path is set
through R
4
and D
1
. So, the pulse width t
1
is determined by
the RC time constant of R
4
and C. Similarly, the discharge
path for the capacitor is set by R
5
and D
2
. Thus, the time t
2
between the pulses can be changed by varying R
5
, and the
pulse width can be altered by R
4
. The frequency of the out-
put can be changed by varying both R
4
and R
5
.
DS012347-28
FIGURE 5. One-Shot Multivibrator
DS012347-30
FIGURE 6. Bi-Stable Multivibrator
DS012347-29
FIGURE 7. Zero Crossing Detector
DS012347-31
FIGURE 8. Square Wave Generator
www.national.com
8
Typical Applications
(Continued)
The circuit shown above provides output signals at a pre-
scribed time interval from a time reference and automatically
resets the output when the input returns to ground. Consider
the case of V
IN
= 0. The output of comparator 4 is also at
ground. This implies that the outputs of comparators 1, 2,
and 3 are also at ground. When an input signal is applied,
the output of comparator 4 swings high and C charges expo-
nentially through R. This is indicated above. The output volt-
ages of comparators 1, 2, and 3 swtich to the high state
when V
C1
rises above the reference voltages V
A
, V
B
and V
C
.
A small amount of hysteresis has been provided to insure
fast switching when the RC time constant is chosen to give
long delay times.
Time Delay Generator
DS012347-32
FIGURE 9. Time Delay Generator
www.national.com
9
Physical Dimensions
inches (millimeters) unless otherwise noted
8-Pin Small Outline Package
Order Number LMC6772AI or LMC6772BI
NS Package Number M08A
8-Pin Molded Dual-In-Line Package
Order Number LMC6772AI or LMC6772BI
NS Package Number N08E
www.national.com
10
Notes
LIFE SUPPORT POLICY
NATIONAL'S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT
DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT OF NATIONAL
SEMICONDUCTOR 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 provided in the
labeling, can be reasonably expected to result in a
significant injury to the user.
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.
National Semiconductor
Corporation
Americas
Tel: 1-800-272-9959
Fax: 1-800-737-7018
Email: support@nsc.com
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Fax: +49 (0) 1 80-530 85 86
Email: europe.support@nsc.com
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Response Group
Tel: 65-2544466
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Email: sea.support@nsc.com
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Japan Ltd.
Tel: 81-3-5639-7560
Fax: 81-3-5639-7507
www.national.com
LMC6772
Dual
Micropower
Rail-T
o-Rail
Input
CMOS
Comparator
with
Open
Drain
Output
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.
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