Page 1
TL/H/11058
LM612 Dual-Channel Comparator and Reference
February 1995
LM612
Dual-Channel Comparator and Reference
General Description
The dual-channel comparator consists of two individual
comparators, having an input voltage range that extends
down to the negative supply voltage V
b
. The common
open-collector output can be driven low by either half of the
LM612. This configuration makes the LM612 ideal for use
as a window comparator. The input stages of the comparator have lateral PNP input transistors which maintain low
input currents for large differential input voltages and swings
above V
a
.
The 1.2V voltage reference, referred to the Vbterminal, is a
two-terminal shunt-type band-gap similar to the LM185-1.2
series, with voltage accuracy of
g
0.6% available. The reference features operation over a shunt current range of 17 mA
to 20 mA, low dynamic impedance, and broad capacitive
load range.
As a member of National’s Super-Block
TM
family, the
LM612 is a space-saving monolithic alternative to a multichip solution, offering a high level of integration without sacrificing performance.
Features
COMPARATORS
Y
Low operating current 300 mA
Y
Wide supply voltage range 4V to 36V
Y
Open-collector outputs
Y
Input common-mode range Vbto (V
a
b
1.8V)
Y
Wide differential input voltage
g
36V
REFERENCE
Y
Fixed output voltage 1.24V
Y
Tight initial tolerance available
g
0.6% (25§C)
Y
Wide operating current range 17 mAto20mA
Y
Tolerant of load capacitance
Applications
Y
Voltage window comparator
Y
Power supply voltage monitor
Y
Dual-channel fault monitor
Connection Diagram
TL/H/11058– 1
Top View
Ordering Information
For information about surface-mount packaging of this device, please contact the Analog Product Marketing group at
National Semiconductor Corporation headquarters.
Tolerances
Reference
Temperature Range
Package Package
Number
NSC
Military Industrial
b
55§CsT
J
s
a
125§C
b
40§CsT
J
a
85§C
g
0.6% at 25§C,
LM612AMN LM612AIN
8-Pin
N08E
80 ppm/
§
C Max Molded DIP
LM612AMJ/883 8-Pin
J08A
(Note 13) Ceramic DIP
g
2.0% at 25§C,
LM612MN LM612IN
8-Pin
N08E
150 ppm/
§
C Max Molded DIP
LM612IM
8-Pin Narrow
M08A
Surface Mount
Super-BlockTMis a trademark of National Semiconductor Corporation.
C
1995 National Semiconductor Corporation RRD-B30M115/Printed in U. S. A.
Page 2
Absolute Maximum Ratings (Note 1)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales
Office/Distributors for availability and specifications.
Voltage on Any Pin Except V
R
(referred to Vbpin)
(Note 2) 36V (Max)
(Note 3)
b
0.3V (Min)
Current through Any Input Pin and VRPin
g
20 mA
Differential Input Voltage
g
36V
Output Short-Circuit Duration (Note 4)
Storage Temperature Range
b
65§CsT
J
s
a
150§C
Maximum Junction Temperature 150§C
Thermal Resistance, Junction-to-Ambient (Note 5)
N Package 100
§
C/W
Soldering Information
N Package
Soldering (10 seconds) 260
§
C
ESD Tolerance (Note 6)
g
1kV
Operating Temperature Range
LM612AI, LM612I
b
40§CsT
J
s
a
85§C
LM612AM, LM612M
b
55§CsT
J
s
a
125§C
Electrical Characteristics These specifications apply for V
b
e
GNDe0V, V
a
e
5V, V
CM
e
V
OUT
e
Va/2,
I
R
e
100 mA, unless otherwise specified. Limits in standard typeface are for T
J
e
25§C; limits in boldface type apply over the
Operating Temperature Range.
Symbol Parameter Conditions
(Note 7)
Typical
LM612AM LM612M
Units
LM612AI LM612I
Limits Limits
(Note 8) (Note 8)
COMPARATORS
I
S
Total Supply Current VaCurrent, R
LOAD
e %
, 150 250 250 mA Max
3V
s
V
a
s
36V 170 300 300 mA Max
V
OS
Offset Voltage over 4VsV
a
s
36V, R
L
e
15 kX 1.0 3.0 5.0 mV Max
V
a
Range 2.0 6.0 7.0 mV Max
V
OS
Offset Voltage over 0VsV
CM
s
(V
a
b
1.8V) 1.0 3.0 5.0 mV Max
V
CM
Range V
a
e
30V, R
L
e
15 kX 1.5 6.0 7.0 mV Max
DV
OS
DT
Average Offset Voltage
15 mV/
§
C
Drift
I
B
Input Bias Current 5 25 35 nA Max
83040nA Max
I
OS
Input Offset Current 0.2 4 4 nA Max
0.3 5 5 nA Max
A
V
Voltage Gain R
L
e
10 kX to 36V, 500 50 50 V/mV Min
2V
s
V
OUT
s
27V 100 V/mV
t
R
Large Signal Response V
a
IN
e
1.4V, V
b
IN
e
TTL 1.5 ms
Time Swing, R
L
e
5.1 kX 2.0 ms
I
SINK
Output Sink Current V
a
IN
e
0V, V
b
IN
e
1V, 20 10 10 mA Min
V
OUT
e
1.5V 13 8 8 mA Min
V
OUT
e
0.4V 2.8 1.0 0.8 mA Min
2.4 0.5 0.5 mA Min
I
L
Output Leakage Current V
a
IN
e
1V, V
b
IN
e
0V, 0.1 10 10 mA Max
V
OUT
e
36V 0.2 mA
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Electrical Characteristics These specifications apply for V
b
e
GNDe0V, V
a
e
5V, V
CM
e
V
OUT
e
Va/2,
I
R
e
100 mA, unless otherwise specified. Limits in standard typeface are for T
J
e
25§C; limits in boldface type apply over the
Operating Temperature Range. (Continued)
Symbol Parameter Conditions
(Note 7)
Typical
LM612AM LM612M
Units
LM612AI LM612I
Limits Limits
(Note 8) (Note 8)
VOLTAGE REFERENCE (Note 9)
V
R
Reference Voltage 1.244 1.2365 1.2191 V Min
1.2515 1.2689 V Max
(
g
0.6%) (g2%)
DV
R
DT
Average Drift with (Note 10)
18 80 150
ppm/
§
C
Temperature Max
DV
R
kH
Average Drift with T
J
e
40§C 400 ppm/kH
Time T
J
e
150§C 1000 ppm/kH
DV
R
DT
J
Hysteresis (Note 11)
3.2 mV/
§
C
DV
R
DI
R
VRChange with V
R[100 mA
]
b
V
R[17 mA
]
0.05 1 1 mV Max
Current 0.1 1.1 1.1 mV Max
V
R[10 mA
]
b
V
R[100 mA
]
1.5 5 5 mV Max
(Note 12) 2.0 5.5 5.5 mV Max
R Resistance DV
R[10 mA to 0.1 mA
]
/9.9 mA 0.2 0.56 0.56 X Max
DV
R[100 mAto17mA
]
/83 mA 0.6 13 13 X Max
DV
R
DV
a
VRChange with V
R[Vae5V
]
b
V
R[Vae36V
]
0.1 1.2 1.2 mV Max
V
a
Change 0.1 1.3 1.3 mV Max
V
R[Vae5V
]
b
V
R[Vae3V
]
0.01 1 1 mV Max
0.01 1.5 1.5 mV Max
e
n
Voltage Noise BWe10 Hz to 10 kHz 30 mV
RMS
Note 1: Absolute maximum ratings indicate limits beyond which damage to the component may occur. Electrical specifications do not apply when operating the
device beyond its rated operating conditions.
Note 2: Input voltage above V
a
is not allowed. As long as one input pin voltage remains inside the common-mode range, the comparator will deliver the correct
output.
Note 3: More accurately, it is excessive current flow, with resulting excess heating, that limits the voltages on all pins. When any pin is pulled a diode drop below
V
b
, a parasitic NPN transistor turns ON. No latch-up will occur as long as the current through that pin remains below the Maximum Rating. Operation is undefined
and unpredictable when any parasitic diode or transistor is conducting.
Note 4: Shorting the Output to V
b
will not cause power dissipation, so it may be continuous. However, shorting the Output to any more positive voltage (including
V
a
), will cause 80 mA (typ.) to be drawn through the output transistor. This current multiplied by the applied voltage is the power dissipation in the output transistor.
If this total power causes the junction temperature to exceed 150
§
C, degraded reliability or destruction of the device may occur. To determine junction temperature,
see Note 5.
Note 5: Junction temperature may be calculated using T
J
e
T
A
a
PDiJA. The given thermal resistance is worst-case for packages in sockets in still air. For
packages soldered to copper-clad board with dissipation from one comparator or reference output transistor, nominal i
JA
is 90§C/W for the N package.
Note 6: Human body model, 100 pF discharged through a 1.5 kX resistor.
Note 7: Typical values in standard typeface are for T
J
e
25§C; values in boldface type apply for the full operating temperature range. These values represent the
most likely parametric norm.
Note 8: All limits are guaranteed for T
J
e
25§C (standard type face) or over the full operating temperature range (bold type face).
Note 9: V
R
is the reference output voltage, nominally 1.24V.
Note 10: Average reference drift is calculated from the measurement of the reference voltage at 25
§
C and at the temperature extremes. The drift, in ppm/§C, is
10
6
#
DVR/V
R[25§C
]
#
DTJ, where DVRis the lowest value subtracted from the highest, V
R[25§C
]
is the value at 25§C, and DTJis the temperature range. This
parameter is guaranteed by design and sample testing.
Note 11: Hysteresis is the change in V
R
caused by a change in TJ, after the reference has been ‘‘dehysterized’’. To dehysterize the reference; that is minimize the
hysteresis to the typical value, its junction temperature should be cycled in the following pattern, spiralling in toward 25
§
C: 25§C, 85§C,b40§C, 70§C, 0§C, 25§C.
Note 12: Low contact resistance is required for accurate measurement.
Note 13: A military RETS 612AMX electrical test specification is available on request. The military screened parts can also be procured as a Standard Military
Drawing.
3
Page 4
Simplified Schematic Diagrams
Comparator
TL/H/11058– 2
Reference Bias
TL/H/11058– 3
4
Page 5
Typical Performance Characteristics (Reference)
T
J
e
25§C, V
b
e
0V, unless otherwise noted
Reference Voltage vs Temp. Drift vs Time
Reference Voltage
Voltage Drift vs Time
Accelerated Reference
Current and Temperature
Reference Voltage vs
Reference Current
Reference Voltage vs
with Supply Voltage Step
Reference Voltage Change
Stability Range
Reference AC
vs Frequency
Reference Noise Voltage
Impedance vs Frequency
Reference Small-Signal
Reference Power-Up Time 100E12 mA Current Step
Reference Voltage with
Current Step
for 100 mAE10 mA
Reference Step Response
TL/H/11058– 4
5
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Typical Performance Characteristics (Comparators)
T
J
e
25§C, V
a
e
5V, V
b
e
0V
vs Supply Voltage
Supply Current
Common-Mode Voltage
Input Bias Current vs
Differential Input Voltage
Input Current vs
Voltage vs Sink Current
Output Saturation
Negative Transition
TimesÐInverting Input,
Small-Signal Response
Positive Transition
TimesÐInverting Input,
Small-Signal Response
Positive Transition
TimesÐNon-Inverting Input,
Small-Signal Response
Negative Transition
TimesÐNon-Inverting Input,
Small-Signal Response
Positive Transition
TimesÐInverting Input,
Large-Signal Response
Negative Transition
TimesÐInverting Input,
Large-Signal Response
Positive Transition
TimesÐNon-Inverting Input,
Large-Signal Response
Negative Transition
TimesÐNon-Inverting Input,
Large-Signal Response
TL/H/11058– 6
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Application Information
VOLTAGE REFERENCE
Reference Biasing
The voltage reference is of a shunt regulator topology that
models as a simple zener diode. With current I
R
flowing in
the ‘‘forward’’ direction there is the familiar diode transfer
function. I
R
flowing in the reverse direction forces the refer-
ence voltage to be developed from cathode to anode.
TL/H/11058– 8
FIGURE 1. 1.24V Reference is Developed between
Cathode and Anode; Current Source I
R
is External
The reference equivalent circuit reveals how VRis held at
the constant 1.2V by feedback for a wide range of reverse
current.
TL/H/11058– 9
FIGURE 2. Reference Equivalent Circuit
To generate the required reverse current, typically a resistor
is connected from a supply voltage higher than the reference voltage to the Reference Output pin. Varying that voltage, and so varying I
R
, has small effect with the equivalent
series resistance of less than an ohm at the higher currents.
Alternatively, an active current source, such as the LM134
series, may generate I
R
.
TL/H/11058– 10
FIGURE 3. 1.2V Reference
Capacitors in parallel with the reference are allowed. See
the Reference AC Stability Range typical curve for capacitance valuesÐfrom 20 mA to 3 mA the reference is stable
for any value of capacitance. With the reference’s wide stability range with resistive and capacitive loads, a wide range
of RC filter values will perform noise filtering when necessary.
Reference Hysteresis
The reference voltage depends, slightly, on the thermal history of the die. Competitive micro-power products varyÐalways check the datasheet for any given device. Do not assume that no specification means no hysteresis.
COMPARATORS
Either comparator or the reference may be biased in any
way with no effect on the other sections of the LM612, except when a substrate diode conducts (see Electrical Characteristics Note 3). For example, one or both inputs of one
comparator may be outside the input voltage range limits,
the reference may be unpowered, and the other comparator
will still operate correctly. The inverting input of an unused
comparator should be tied to V
b
and the non-inverting tied
to V
a
.
Hysteresis
Any comparator may oscillate or produce a noisy output if
the applied differential input voltage is near the comparator’s offset voltage. This usually happens when the input
signal is moving very slowly across the comparator’s switching threshold. This problem can be prevented by the addition of hysteresis, or positive feedback, as shown in
Figure
4
.
TL/H/11058– 11
FIGURE 4. RSand RFAdd Hysteresis to Comparator
The amount of hysteresis added in
Figure 4
is
V
H
e
V
a
c
R
S
(R
F
a
RS)
&
V
a
c
R
S
R
F
for R
F
ll
R
S
A good rule of thumb is to add hysteresis of at least the
maximum specified offset voltage. More than about 50 mV
7
Page 8
Application Information (Continued)
of hysteresis can substantially reduce the accuracy of the
comparator, since the offset voltage is effectively being increased by the hysteresis when the comparator output is
high.
It is often a good idea to decrease the amount of hysteresis
until oscillations are observed, then use three times that
minimum hysteresis in the final circuit. Note that the amount
of hysteresis needed is greatly affected by layout. The
amount of hysteresis should be rechecked each time the
layout is changed, such as changing from a breadboard to a
P.C. board.
Input Stage
The input stage uses lateral PNP input transistors which,
unlike those of many op amps, have breakdown voltage
BV
EBO
equal to the absolute maximum supply voltage. Also,
they have no diode clamps to the positive supply nor across
the inputs. These features make the inputs look like high
impedances to input sources producing large differential
and common-mode voltages.
The guaranteed common-mode input voltage range for an
LM612 is V
b
s
V
CM
s
(V
a
b
1.8V), over temperature.
This is the voltage range in which the comparisons must be
made. If both inputs are within this range, the output will be
at the correct state. If one input is within this range, and the
other input is less than (V
b
a
32V), even if this is greater
than V
a
, the output will be at the correct state. If, however,
either or both inputs are driven below V
b
, and either input
current exceeds 10 mA, the output state is not guaranteed
to be correct. If both inputs are above (V
a
b
1.8V), the
output state is also not guaranteed to be correct.
Output Stage
The comparators have a common open-collector output
stage which requires a pull-up resistor to a positive supply
voltage for the output to switch properly. When the internal
output transistor is off, the output (HIGH) voltage will be
pulled up to this external positive voltage.
To ensure that the LOW output voltage is under the TTL-low
threshold, the output transistor’s load current must be less
than 0.8 mA (over temperature) when it turns on. This impacts the minimum value of the pull-up resistor.
Typical Applications
TL/H/11058– 12
Power Supply Monitor with Indicator
8
Page 9
Physical Dimensions inches (millimeters)
8-Pin Ceramic Dual-In-Line Package (J)
Order Number LM612AMJ/883
NS Package Number J08A
8-Pin Surface Mount Package (M)
Order Number LM612IM
NS Package Number M08A
9
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LM612 Dual-Channel Comparator and Reference
Physical Dimensions inches (millimeters) (Continued)
8-Pin Molded Dual-In-Line Package (N)
Order Number LM612AMJ/883, LM612AMN, LM612AIN, LM612MN or LM612IN
NS Package Number N08E
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into the body, or (b) support or sustain life, and whose be reasonably expected to cause the failure of the life
failure to perform, when properly used in accordance support device or system, or to affect its safety or
with instructions for use provided in the labeling, can effectiveness.
be reasonably expected to result in a significant injury
to the user.
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a
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