
Absolute Maximum Ratings
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales
Office/Distributors for availability and specifications.
Supply Current (Externally Set)
Output Collector Voltage, V
aa
10 mA
36V
Feedback Input Voltage Range
0V to
a
7.0V
Output Short Circuit Duration
Indefinite
Operating Temperature Range
b
25
§
C to
a
85
§
C
b
65
§
C to
a
150
§
C
Storage Temperature Range
Lead Temperature (Soldering, 10 seconds)
260
§
C
Electrical Characteristics
(Note 1)
Parameter
Conditions
Min
Typ
Max
Units
SENSOR
Output Voltage
T
A
eb
25
§
C, (Note 2)
T
A
ea
25
§
C, (Note 2)
T
A
ea
85
§
C, (Note 2)
D
T
e
100
§
C
2.36
2.48
2.60
V
Output Voltage
2.88
2.98
3.08
V
Output Voltage
3.46
3.58
3.70
V
Linearity
0.5
2
%
Long-Term Stability
0.3
%
Repeatability
0.3
%
VOLTAGE REFERENCE
Reverse Breakdown Voltage
1 mA
s
I
z
s
5 mA
1 mA
s
I
z
s
5 mA
6.55
6.85
7.25
V
Reverse Breakdown Voltage
Change With Current
10
35
mV
Temperature Stability
20
85
mV
Dynamic Impedance
I
z
e
1 mA
10 Hz
s
f
s
10 kHz
T
A
ea
85
§
C
3.0
X
RMS Noise Voltage
30
m
V
Long Term Stability
6.0
mV
OP AMP
Input Bias Current
T
A
ea
25
§
C
35
150
nA
Input Bias Current
45
250
nA
Voltage Gain
R
L
e
36k, V
aa
e
36V
T
A
e
25
§
C (Note 3)
(Note 3)
2500
15000
V/V
Output Leakage Current
0.2
2
m
A
Output Leakage Current
1.0
8
m
A
Output Source Current
V
OUT
s
3.70
1V
s
V
OUT
s
36V
10
m
A
Output Sink Current
Note 1:
These specifications apply for
b
25
§
C
s
T
A
s
a
85
§
C and 0.9 mA
s
I
SUPPLY
s
1.1 mA unless otherwise specified; C
L
s
50 pF.
Note 2:
The output voltage applies to the basic thermometer configuration with the output and input terminals shorted and a load resistance of
t
1.0 M
X
. This is
the feedback sense voltage and includes errors in both the sensor and op amp. This voltage is specified for the sensor in a rapidly stirred oil bath. The output is
referred to V
a
.
2.0
mA
Note 3:
The output leakage current is specified with
t
100 mV overdrive. Since this voltage changes with temperature, the voltage drive for turn-off changes and is
defined as V
OUT
(with output and input shorted)
b
100 mV. This specification applies for V
OUT
e
36V.
Application Hints
Although the LM3911 is designed to be totally trouble-free,
certain precautions should be taken to insure the best pos-
sible performance.
As with any temperature sensor, internal power dissipation
will raise the sensor’s temperature above ambient. Nominal
suggested operating current for the shunt regulator is 1.0
mA and causes 7.0 mW of power dissipation. In free, still, air
this raises the package temperature by about 1.2
§
K. Al-
though the regulator will operate at higher reverse currents
and the output will drive loads up to 5.0 mA, these higher
currents will raise the sensor temperature to about 19
§
K
above ambient-degrading accuracy. Therefore, the sensor
should be operated at the lowest possible power level.
With moving air, liquid or surface temperature sensing, self-
heating is not as great a problem since the measured
media will conduct the heat from the sensor. Also, there are
many small heat sinks designed for transistors which will
improve heat transfer to the sensor from the surrounding
medium. A small finned clip-on heat sink is quite effective in
free-air. It should be mentioned that the LM3911 die is on
the base of the package and therefore coupling to the base
is preferable.
The internal reference regulator provides a temperature sta-
ble voltage for offsetting the output or setting a comparison
point in temperature controllers. However, since this refer-
ence is at the same temperature as the sensor temperature,
changes will also cause reference drift. For application
where maximum accuracy is needed an external reference
should be used. Of course, for fixed temperature controllers
the internal reference is adequate.
2