If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
ESD Tolerance (Note 2)
Human Body Model
Machine Model
V
IN
Differential
Supply Voltages
Voltage at Input Pins
Storage Temperature Range
2KV
200V
30V
30V or
±
15V
−0.3V to 30V
−65˚C to +150˚C
Junction Temperature (Note 3)
Soldering Information
Infrared or Convection (20 sec.)
Wave Soldering (10 sec.)
+150˚C
235˚C
260˚C
Operating Ratings
(Note 1)
Supply Voltage, V
S
Temperature Range (Note 3)
Package Thermal Resistance (Note 3)
5-Pin SOT23
168˚C/W
5V to 30V
−40˚C to +85˚C
Electrical Characteristics
0V, V
CM
Symbol
V
OS
I
OS
I
B
I
S
I
O
I
LEAKAGE
V
OL
V
CM
A
V
t
PHL
Parameter
Input Offset Voltage
Input Offset Current
Input Bias Current
Supply Current
Output Sink Current
Output Leakage Current
Output Voltage Low
Unless otherwise specified, all limits are guaranteed for T
A
= 25˚C, V
S
= 5V, V
−
=
= V
+
/2 = V
O
.
Boldface
limits apply at the temperature extremes.
Conditions
V
S
= 5V to 30V,
V
O
= 1.4V, V
CM
= 0V
V
O
= 1.4V, V
CM
= 0V
V
O
= 1.4V, V
CM
= 0V
R
L
= Open, V
S
= 5V
R
L
= Open, V
S
= 30V
V
IN+
= 1V,V
IN−
= 0V, V
O
= 1.5V
V
IN+
= 1V,V
IN−
= 0V, V
O
= 5V
V
IN+
= 1V,V
IN−
= 0V, V
O
= 30V
I
O
= −4mA, V
IN+
= 0V,V
IN−
= 1V
0
0
120
900
250
940
440
ns
6
Min
(Note 5)
Typ
(Note 4)
2
1.6
10
0.25
0.30
13
0.1
1
180
400
700
V
S
- 1.5V
V
S
- 2V
Max
(Note 5)
7
10
50
250
250
400
0.7
2
Units
mV
nA
nA
mA
mA
nA
µA
mV
Common-Mode Input Voltage V
S
= 5V to 30V (Note 6)
Range
Voltage Gain
Propagation Delay
(High to Low)
V
S
= 15V, V
O
= 1.4V to 11.4V,
R
L
>
= 15kΩ connected to V
S
Input Overdrive = 5mV
R
L
= 5.1kΩ connected to 5V, C
L
= 15pF
Input Overdrive = 50mV
R
L
= 5.1kΩ connected to 5V, C
L
= 15pF
V
V/mV
t
PLH
Propagation Delay
(Low to High)
Input Overdrive = 5mV
R
L
= 5.1kΩ connected to 5V, C
L
= 15pF
Input Overdrive = 50mV
R
L
= 5.1kΩ connected to 5V, C
L
= 15pF
µs
ns
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, applicable std. MIL-STD-883, Method 3015.7. Machine Model, applicable std. JESD22-A115-A (ESD MM std. of JEDEC)
. The maximum allowable power dissipation at any ambient temperature is
P
D
= (T
J(MAX)
- T
A
)/
θ
JA
. All numbers apply for packages soldered directly onto a PC board.
Note 4:
Typical values represent the most likely parametric norm as determined at the time of characterization. Actual typical values may vary over time and will
also depend on the application and configuration. The typical values are not tested and are not guaranteed on shipped production material.
Note 5:
All limits are guaranteed by testing or statistical analysis.
Note 6:
The input common-mode voltage of either input should not be permitted to go below the negative rail by more than 0.3V. The upper end of the
common-mode voltage range is V
S
- 1.5V at 25˚C.
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2
LM397
Typical Performance Characteristics
Supply Current vs. Supply Voltage
T
A
= 25˚C. Unless otherwise specified.
Input Bias Current vs. Supply Current
20022103
20022101
Output Saturation Voltage vs. Output Sink Current
Input Offset Voltage vs. Supply Voltage
20022104
20022102
Response Time for Various Input Overdrives – t
PHL
Response Time for Various Input Overdrives – t
PLH
20022105
20022106
3
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LM397
Application Notes
Basic Comparators
A comparator is quite often used to convert an analog signal
to a digital signal. The comparator compares an input volt-
age (V
IN
) at the non-inverting pin to the reference voltage
(V
REF
) at the inverting pin. If V
IN
is less than V
REF
the output
(V
O
) is low (V
OL
). However, if V
IN
is greater than V
REF
, the
output voltage (V
O
) is high (V
OH
). Refer to
Figure 2.
When input voltage (V
IN
) at the inverting node is less than
non-inverting node (V
T
), the output is high. The equivalent
circuit for the three resistor network is R
1
in parallel with R
3
and in series with R
2
. The lower threshold voltage V
T1
is
calculated by:
V
T1
= ((V
S
R
2
) / (((R
1
R
3
) / (R
1
+ R
3
)) + R
2
))
When V
IN
is greater than V
T
, the output voltage is low. The
equivalent circuit for the three resistor network is R
2
in
parallel with R
3
and in series with R
1
. The upper threshold
voltage V
T2
is calculated by:
V
T2
= V
S
((R
2
R
3
) / (R
2
+ R
3
)) / (R
1
+ ((R
2
R
3
) / (R
2
+
R
3
)))
The hysteresis is defined as
∆V
IN
= V
T1
– V
T2
20022110
20022112
20022111
FIGURE 2. Basic Comparator
Hysteresis
The basic comparator configuration may oscillate or produce
a noisy output if the applied differential input is near the
comparator’s input offset voltage. This tends to occur when
the voltage on the input is equal or very close to the other
input voltage. Adding hysteresis can prevent this problem.
Hysteresis creates two switching thresholds (one for the
rising input voltage and the other for the falling input volt-
age). Hysteresis is the voltage difference between the two
switching thresholds. When both inputs are nearly equal,
hysteresis causes one input to effectively move quickly pass
the other. Thus, effectively moving the input out of region that
oscillation may occur.
For an inverting configured comparator, hysteresis can be
added with a three resistor network and positive feedback.
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