LMC6762
Dual MicroPower Rail-To-Rail Input CMOS Comparator
with Push-Pull Output
General Description
The LMC6762 is an ultra low power dual comparator with a
maximum supply current of 10 A/comparator. It is designed
to operate over a wide range of supply voltages, from 2.7V to
15V. The LMC6762 has guaranteed specs at 2.7V to meet
the demands of 3V digital systems.
The LMC6762 has an input common-mode voltage range
which exceeds both supplies. This is a significant advantage
in low-voltage applications. The LMC6762 also features a
push-pull output that allows direct connections to logic de-
vices without a pull-up resistor.
A quiescent
power
consumption
of
50
W/amplifier
(
@
V
+
= 5V) makes the LMC6762 ideal for applications in
portable phones and hand-held electronics. The ultra-low
supply current is also independent of power supply voltage.
Guaranteed operation at 2.7V and a rail-to-rail performance
makes this device ideal for battery-powered applications.
Refer to the LMC6772 datasheet for an open-drain 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
Rail-to-rail output swing (Within 100 mV of the supplies,
@
V
+
= 2.7V, and I
LOAD
= 2.5 mA)
n
Short circuit protection:
40 mA
n
Propagation delay
(
@
V
+
= 5V, 100 mV
overdrive):
4 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
LMC6762AIN, LMC6762BIN
N08E
Rails
8-Pin Small Outline
LMC6762AIM, LMC6762BIM
M08A
Rails
LMC6762AIMX, LMC6762BIMX
M08A
Tape and Reel
8-Pin DIP/SO
DS012320-1
Top View
July 1997
LMC6762
Dual
MicroPower
Rail-T
o-Rail
Input
CMOS
Comparator
with
Push-Pull
Output
1999 National Semiconductor Corporation
DS012320
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)
2 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
5 mA
Current at Output Pin
(Notes 7, 3)
30 mA
Current at Power Supply Pin,
LMC6762
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
LMC6762AI, LMC6762BI
-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)
LMC6762AI
LMC6762BI
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 8)
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
OH
Output Voltage High
I
LOAD
= 2.5 mA
2.5
2.4
2.4
V
2.3
2.3
min
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
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2
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)
LMC6762AI
LMC6762BI
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 8)
3.3
V/Month
Average Drift
V
+
= 15V (Note 8)
4.0
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
OH
Output Voltage High
V
+
= 5V
4.8
4.6
4.6
V
I
LOAD
= 5mA
4.45
4.45
min
V
+
= 15V
14.8
14.6
14.6
V
I
LOAD
= 5 mA
14.45
14.45
min
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
Sourcing
30
mA
Sinking, V
O
= 12V
45
(Note 7)
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3
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)
LMC6762AI
LMC6762BI
Units
Limit
Limit
(Note 6)
(Note 6)
t
RISE
Rise Time
f = 10 kHz, C
L
= 50 pF,
0.3
s
Overdrive = 10 mV (Notes 9, 10)
t
FALL
Fall Time
f = 10 kHz, C
L
= 50 pF,
0.3
s
Overdrive = 10 mV (Notes 9, 10)
t
PHL
Propagation Delay
f = 10 kHz,
Overdrive = 10 mV
10
s
(High to Low)
C
L
= 50 pF
Overdrive = 100 mV
4
s
(Notes 9, 10)
V
+
= 2.7V,
Overdrive = 10 mV
10
s
f = 10 kHz,
C
L
= 50 pF
Overdrive = 100 mV
4
s
(Notes 9, 10)
t
PLH
Propagation Delay
f = 10 kHz,
Overdrive = 10 mV
6
s
(Low to High)
C
L
= 50 pF
Overdrive = 100 mV
4
s
(Notes 9, 10)
V
+
= 2.7V,
Overdrive = 10 mV
7
s
f = 10 kHz,
C
L
= 50 pF
Overdrive = 100 mV
4
s
(Notes 9, 10)
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.
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 greater than 12V or reliability will be adversely affected.
Note 8: 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.
Note 9: C
L
includes the probe and jig capacitance.
Note 10: The rise and fall times are measured with a 2V input step. The propagation delays are also measured with a 2V input step.
Typical Performance Characteristics
V
+
= 5V, Single Supply, T
A
= 25C unless otherwise specified
Supply Current vs Supply
Voltage (Output High)
DS012320-20
Supply Current vs Supply
Voltage (Output Low)
DS012320-21
Input Current vs
Common-Mode Voltage
DS012320-22
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4
Typical Performance Characteristics
V
+
= 5V, Single Supply, T
A
= 25C unless otherwise
specified (Continued)
Input Current vs
Common-Mode Voltage
DS012320-23
Input Current vs
Common-Mode Voltage
DS012320-24
Input Current
vs Temperature
DS012320-25
V
OS
vs
V
CM
DS012320-26
V
OS
vs
V
CM
DS012320-27
V
OS
vs
V
CM
DS012320-28
Output Voltage vs
Output Current (Sourcing)
DS012320-29
Output Voltage vs
Output Current (Sourcing)
DS012320-30
Output Voltage vs
Output Current (Sourcing)
DS012320-31
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5
Typical Performance Characteristics
V
+
= 5V, Single Supply, T
A
= 25C unless otherwise
specified (Continued)
Output Voltage vs
Output Current (Sinking)
DS012320-32
Output Voltage vs
Output Current (Sinking)
DS012320-33
Output Voltage vs
Output Current (Sinking)
DS012320-34
Output Short Circuit Current
vs Supply Voltage (Sourcing)
DS012320-35
Output Short Circuit Current
vs Supply Voltage (Sinking)
DS012320-36
Response Time for
Overdrive (t
PLH
)
DS012320-37
Response Time for
Overdrive (t
PHL
)
DS012320-38
Response Time for
Overdrive (t
PLH
)
DS012320-39
Response Time for
Overdrive (t
PHL
)
DS012320-40
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6
Typical Performance Characteristics
V
+
= 5V, Single Supply, T
A
= 25C unless otherwise
specified (Continued)
Response Time for
Overdrive (t
PLH
)
DS012320-41
Response Time for
Overdrive (t
PHL
)
DS012320-42
Response Time vs
Capacitive Load
DS012320-43
www.national.com
7
Application Hints
1.0 Input Common-Mode Voltage Range
At supply voltages of 2.7V, 5V and 15V, the LMC6762 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 LMC6762 ideal for sensor applications. The
LMC6762 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
LMC6762 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 LMC6762 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 Shoot-Through Current
The shoot-through current is defined as the current surge,
above the quiescent supply current, between the positive
and negative supplies of a device. The current surge occurs
when the output of the device switches states. This transient
switching current results in glitches in the supply voltage.
Usually, glitches in the supply lines are compensated by by-
pass capacitors. When the switching currents are minimal,
the values of the bypass capacitors can be reduced
considerably.
DS012320-5
FIGURE 1. An Input Signal Exceeds the LMC6762
Power Supply Voltages with No Output Phase
Inversion
DS012320-6
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
DS012320-7
FIGURE 3. LMC6762 Circuit for Measurement
of the Shoot-Through Current
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8
Application Hints
(Continued)
From
Figure 3 and Figure 4 the shoot-through current for the
LMC6762 can be approximated to be 0.2 mA (200 mV/1 k
).
The duration of the transient is measured as 1 s. The val-
ues needed for the local bypass capacitors can be calcu-
lated as follows:
Area of
=
1
/
2
(1 s x 200 A)
= 100 pC
If the local bypass capacitor has to provide this charge of
100 pC, the minimum value of the local capacitor to prevent
local degradation of V
CC
can be calculated. Suppose that the
maximum voltage droop that the system can tolerate is
100mV,
Q = C
*
(
V)
C = (
Q/
V)
= 100 pC/100 mV
= 0.001 F
The low internal feedthrough current of the LMC6762 thus
requires lower values for the local bypass capacitors. In ap-
plications where precision is not critical, this is a significant
advantage, as lower values of capacitors result in savings of
board space, and cost.
It is worth noting here that the delta shift of the power supply
voltage due to the transient currents causes a threshold shift
of the comparator. This threshold shift is reduced by the high
PSRR of the comparator. However, the value of the PSRR
applicable in this instance is the transient PSRR and not the
DC PSRR. The transient PSRR is significantly lower than the
DC PSRR.
Generally, it is a good goal to reduce the delta voltage on the
power supply to a value equal to or less than the hysteresis
of the comparator. For example, if the comparator has 50 mV
of hysteresis, it would be reasonable to increase the value of
the local bypass capacitor to 0.01 F to reduce the voltage
delta to 10 mV.
4.0 Output Short Circuit Current
The LMC6762 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.
5.0 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.
6.0 Spice Macromodel
A Spice Macromodel is available for the LMC6762. 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
One-Shot Multivibrator
DS012320-8
FIGURE 4. Measurement of the Shoot-Through Current
DS012320-9
DS012320-10
FIGURE 5. Canceling the Effect of Input Capacitance
DS012320-14
FIGURE 6. One-Shot Multivibrator
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9
Typical Applications
(Continued)
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
LMC6762 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 9 shows the application of the LMC6762 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
.
DS012320-15
FIGURE 7. Bi-Stable Multivibrator
DS012320-16
FIGURE 8. Zero Crossing Detector
DS012320-19
FIGURE 9. Square Wave Generator
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10
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 voltages of comparators 1, 2, and 3 switch to the
high state when V
C1
rises above the reference voltage 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.
DS012320-18
FIGURE 10. Time Delay Generator
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11
Physical Dimensions
inches (millimeters) unless otherwise noted
8-Pin Small Outline Package
Order Number LMC6762AIM, LMC6762BIM, LMC6762AIMX or LMC6762BIMX
NS Package Number M08A
8-Pin Molded Dual-In-Line Package
Order Number LMC6762AIN or LMC6762BIN
NS Package Number N08E
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12
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
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Tel: 81-3-5639-7560
Fax: 81-3-5639-7507
www.national.com
LMC6762
Dual
MicroPower
Rail-T
o-Rail
Input
CMOS
Comparator
with
Push-Pull
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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