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LM20
SNIS106Q – DECEMBER 1999 – REVISED JANUARY 2015
LM20 2.4-V, 10-µA, SC70, DSBGA Temperature Sensor
1 Features
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1
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3 Description
Rated for −55°C to 130°C Range
Available in SC70 and DSBGA Package
Predictable Curvature Error
Suitable for Remote Applications
Accuracy at 30°C ±1.5 to ±4°C (Maximum)
Accuracy at 130°C and −55°C ±2.5 to ±5°C
(Maximum)
Power Supply Voltage Range 2.4 V to 5.5 V
Current Drain 10 μA (Maximum)
Nonlinearity ±0.4% (Typical)
Output Impedance 160 Ω (Maximum)
Load Regulation
0 μA < IL< 16 μA −2.5 mV (Maximum)
2 Applications
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Cellular Phones
Computers
Power Supply Modules
Battery Management
FAX Machines
Printers
HVAC
Disk Drives
Appliances
Simplified Schematic
The LM20 is a precision analog output CMOS
integrated-circuit temperature sensor that operates
over −55°C to 130°C. The power supply operating
range is 2.4 V to 5.5 V. The transfer function of LM20
is predominately linear, yet has a slight predictable
parabolic curvature. The accuracy of the LM20 when
specified to a parabolic transfer function is ±1.5°C at
an ambient temperature of 30°C. The temperature
error increases linearly and reaches a maximum of
±2.5°C at the temperature range extremes. The
temperature range is affected by the power supply
voltage. At a power supply voltage of 2.7 V to 5.5 V,
the temperature range extremes are 130°C and
−55°C. Decreasing the power supply voltage to 2.4 V
changes the negative extreme to −30°C, while the
positive extreme remains at 130°C.
The LM20 quiescent current is less than 10 μA.
Therefore, self-heating is less than 0.02°C in still air.
Shutdown capability for the LM20 is intrinsic because
its inherent low power consumption allows it to be
powered directly from the output of many logic gates
or does not necessitate shutdown.
Device Information(1)
PART NUMBER
LM20
PACKAGE
BODY SIZE (NOM)
SC70 (5)
2.00 mm × 1.25 mm
DSBGA (4)
0.96 mm × 0.96 mm
(1) For all available packages, see the orderable addendum at
the end of the data sheet.
Output Voltage vs Temperature
1
An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications,
intellectual property matters and other important disclaimers. PRODUCTION DATA.
LM20
SNIS106Q – DECEMBER 1999 – REVISED JANUARY 2015
www.ti.com
Table of Contents
1
2
3
4
5
6
7
Features ..................................................................
Applications ...........................................................
Description .............................................................
Revision History.....................................................
Pin Configuration and Functions .........................
Specifications.........................................................
1
1
1
2
3
3
6.1
6.2
6.3
6.4
6.5
6.6
6.7
6.8
3
4
4
4
4
5
6
7
Absolute Maximum Ratings ......................................
ESD Ratings ............................................................
Recommended Operating Conditions.......................
Thermal Information ..................................................
Electrical Characteristics: LM20B ............................
Electrical Characteristics: LM20C ............................
Electrical Characteristics: LM20S ............................
Typical Characteristics .............................................
7.3 Feature Description................................................... 8
7.4 Device Functional Modes.......................................... 9
8
Application and Implementation ........................ 10
8.1 Application Information............................................ 10
8.2 Typical Applications ................................................ 11
8.3 System Examples ................................................... 14
9 Power Supply Recommendations...................... 15
10 Layout................................................................... 15
10.1 Layout Guidelines ................................................. 15
10.2 Layout Examples................................................... 15
10.3 Thermal Considerations ........................................ 15
11 Device and Documentation Support ................. 17
Detailed Description .............................................. 8
11.1 Trademarks ........................................................... 17
11.2 Electrostatic Discharge Caution ............................ 17
11.3 Glossary ................................................................ 17
7.1 Overview ................................................................... 8
7.2 Functional Block Diagram ......................................... 8
12 Mechanical, Packaging, and Orderable
Information ........................................................... 17
4 Revision History
Changes from Revision P (Feburary 2013) to Revision Q
•
Added Pin Configuration and Functions section, ESD Ratings table, Feature Description section, Device Functional
Modes, Application and Implementation section, Power Supply Recommendations section, Layout section, Device
and Documentation Support section, and Mechanical, Packaging, and Orderable Information section .............................. 1
Changes from Revision O (February 2013) to Revision P
•
2
Page
Page
Changed layout of National Data Sheet to TI Format .......................................................................................................... 14
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SNIS106Q – DECEMBER 1999 – REVISED JANUARY 2015
5 Pin Configuration and Functions
DCK Package
5-Pin SC70
(Top View)
YZR Package
4-Pin DSBGA
(Top View)
Pin Functions
PIN
TYPE
DESCRIPTION
2
GND
Device substrate and die attach paddle, connect to power supply negative
terminal. For optimum thermal conductivity to the PC board ground plane, pin
2 must be grounded. This pin may also be left floating.
A2
5
GND
Device ground pin, connect to power supply negative terminal.
NC
A1
1
—
VO
B1
3
Analog
Output
Temperature sensor analog output
+
B2
4
Power
Positive power supply pin
NAME
DSBGA
SC70
GND
—
GND
V
NC (pin 1) must be left floating or grounded. Other signal traces must not be
connected to this pin.
6 Specifications
6.1 Absolute Maximum Ratings
over operating free-air temperature range (unless otherwise noted) (1) (2)
MIN
MAX
UNIT
Supply Voltage
−0.2
6.5
V
Output Voltage
−0.6
(V+ + 0.6 )
V
Output Current
10
mA
Input Current at any pin (3)
5
mA
150
°C
150
°C
Maximum Junction Temperature (TJMAX)
−65
Storage temperature, Tstg
(1)
(2)
(3)
Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings
only, which do not imply functional operation of the device at these or any other conditions beyond those indicated under Recommended
Operating Conditions. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
Soldering process must comply with TI's Reflow Temperature Profile specifications. Refer to http://www.ti.com/packaging.
When the input voltage (VI) at any pin exceeds power supplies (VI < GND or VI > V+), the current at that pin should be limited to 5 mA.
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6.2 ESD Ratings
VALUE
V(ESD)
(1)
(2)
Electrostatic discharge
Human-body model (HBM), per ANSI/ESDA/JEDEC JS-001 (1)
±2500
Charged-device model (CDM), per JEDEC specification JESD22-C101 (2)
±250
UNIT
V
JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process.
JEDEC document JEP157 states that 250-V CDM allows safe manufacturing with a standard ESD control process.
6.3 Recommended Operating Conditions
over operating free-air temperature range (unless otherwise noted) (1)
MIN
MAX
UNIT
+
LM20B, LM20C with
2.4 V ≤ V ≤ 2.7 V
−30
130
°C
LM20B, LM20C with
2.7 V ≤ V+≤ 5.5 V
−55
130
°C
LM20S with
2.4 V ≤ V+≤ 5.5 V
−30
125
°C
LM20S with
2.7 V ≤ V+≤ 5.5 V
−40
125
°C
2.4
5.5
V
+
Supply Voltage Range (V )
(1)
Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings
only, which do not imply functional operation of the device at these or any other conditions beyond those indicated under Recommended
Operating Conditions. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
6.4 Thermal Information
LM20
THERMAL METRIC
(1)
DCK (SC70)
YZR (DSBGA)
5 PINS
4 PINS
197
RθJA
Junction-to-ambient thermal resistance
282
RθJC(top)
Junction-to-case (top) thermal resistance
93
2
RθJB
Junction-to-board thermal resistance
62
40
ψJT
Junction-to-top characterization parameter
1.6
11
ψJB
Junction-to-board characterization parameter
62
40
RθJC(bot)
Junction-to-case (bottom) thermal resistance
—
—
(1)
UNIT
°C/W
For more information about traditional and new thermal metrics, see the IC Package Thermal Metrics application report, SPRA953.
6.5 Electrical Characteristics: LM20B
Unless otherwise noted, these specifications apply for V+ = 2.7 VDC. All limits TA = TJ = TMIN to TMAX, unless otherwise noted.
PARAMETER
Temperature to Voltage Error
VO = (−3.88×10−6× T 2) + (−1.15×10−2×
T) + 1.8639 V (3)
TEST CONDITIONS
MAX (1)
UNIT
–1.5
1.5
°C
TA = 130°C
–2.5
2.5
°C
TA = 125°C
–2.5
2.5
°C
TA = 100°C
–2.2
2.2
°C
TA = 85°C
–2.1
2.1
°C
TA = 80°C
–2.0
2.0
°C
TA = 0°C
–1.9
1.9
°C
TA = –30°C
–2.2
2.2
°C
TA = –40°C
–2.3
2.3
°C
TA = –55°C
–2.5
2.5
°C
Variance from Curve
4
TYP (2)
TA = 25°C to 30°C
Output Voltage at 0°C
(1)
(2)
(3)
MIN (1)
1.8639
V
±1.0
°C
Limits are ensured to TI's AOQL (Average Outgoing Quality Level).
Typicals are at TJ = TA = 25°C and represent most likely parametric norm.
Accuracy is defined as the error between the measured and calculated output voltage at the specified conditions of voltage, current, and
temperature (expressed in °C).
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Electrical Characteristics: LM20B (continued)
Unless otherwise noted, these specifications apply for V+ = 2.7 VDC. All limits TA = TJ = TMIN to TMAX, unless otherwise noted.
PARAMETER
Non-linearity
(4)
TEST CONDITIONS
MIN (1)
–20°C ≤ TA ≤ 80°C
TYP (2)
MAX (1)
UNIT
–11.4
mV/°C
±0.4%
Sensor Gain (Temperature Sensitivity or
Average Slope) to equation:
–30°C ≤ TA ≤ 100°C
VO=−11.77 mV / °C×T+1.860 V
–12.2
–11.77
Output Impedance
Sourcing IL 0 μA to 16 μA (5) (6)
160
Ω
(7)
Sourcing IL 0 μA to 16 μA (3) (6)
–2.5
mV
2.4 V ≤ V+ ≤ 5.0 V
3.3
mV/V
5.0 V ≤ V+ ≤ 5.5 V
11
mV
Load Regulation
Line Regulation (8)
Quiescent Current
2.4 V ≤ V+ ≤ 5.0 V; TA = 25°C
4.5
7
μA
5.0 V ≤ V+ ≤ 5.5 V; TA = 25°C
4.5
9
μA
2.4 V ≤ V ≤ 5.0 V
4.5
10
μA
2.4 V ≤ V+ ≤ 5.5 V
0.7
μA
–11
nA/°C
0.02
μA
+
Change of Quiescent Current
Temperature Coefficient of Quiescent
Current
Shutdown Current
(4)
(5)
(6)
(7)
(8)
+
V ≤ 0.8 V
Non-linearity is defined as the deviation of the calculated output-voltage-versus-temperature curve from the best-fit straight line, over the
temperature range specified.
The LM20 can at most sink 1 μA and source 16 μA.
Load regulation or output impedance specifications apply over the supply voltage range of 2.4 V to 5.5 V.
Regulation is measured at constant junction temperature, using pulse testing with a low duty cycle. Changes in output due to heating
effects can be computed by multiplying the internal dissipation by the thermal resistance.
Line regulation is calculated by subtracting the output voltage at the highest supply input voltage from the output voltage at the lowest
supply input voltage.
6.6 Electrical Characteristics: LM20C
Unless otherwise noted, these specifications apply for V+ = 2.7 VDC. All limits TA = TJ = TMIN to TMAX, unless otherwise noted.
PARAMETER
Temperature to Voltage Error
VO = (−3.88×10−6× T 2) + (−1.15×10−2×
T) + 1.8639 V (3)
TEST CONDITIONS
MIN (1)
5
°C
TA = 130°C
–5
5
°C
TA = 125°C
–5
5
°C
TA = 100°C
–4.7
4.7
°C
TA = 85°C
–4.6
4.6
°C
TA = 80°C
–4.5
4.5
°C
TA = 0°C
–4.4
4.4
°C
TA = –30°C
–4.7
4.7
°C
TA = –40°C
–4.8
4.8
°C
TA = –55°C
–5.0
5.0
°C
–20°C ≤ TA ≤ 80°C
(1)
(2)
(3)
(4)
(5)
(6)
Sourcing IL 0 μA to 16 μA
1.8639
V
±1.0
°C
±0.4%
Sensor Gain (Temperature Sensitivity or
Average Slope) to equation:
–30°C ≤ TA ≤ 100°C
VO=−11.77 mV / °C×T+1.860 V
Output Impedance
UNIT
–4
Variance from Curve
(4)
MAX (1)
TA = 25°C to 30°C
Output Voltage at 0°C
Non-Linearity
TYP (2)
–12.6
(5) (6)
–11.77
–11.0
mV/°C
160
Ω
Limits are ensured to TI's AOQL (Average Outgoing Quality Level).
Typicals are at TJ = TA = 25°C and represent most likely parametric norm.
Accuracy is defined as the error between the measured and calculated output voltage at the specified conditions of voltage, current, and
temperature (expressed in °C).
Non-linearity is defined as the deviation of the calculated output-voltage-versus-temperature curve from the best-fit straight line, over the
temperature range specified.
The LM20 can at most sink 1 μA and source 16 μA.
Load regulation or output impedance specifications apply over the supply voltage range of 2.4 V to 5.5 V.
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Electrical Characteristics: LM20C (continued)
Unless otherwise noted, these specifications apply for V+ = 2.7 VDC. All limits TA = TJ = TMIN to TMAX, unless otherwise noted.
PARAMETER
Load Regulation
(7)
Line Regulation (8)
TEST CONDITIONS
Sourcing IL 0 μA to 16 μA
MIN (1)
Change of Quiescent Current
(7)
(8)
UNIT
–2.5
mV
3.7
mV/V
5.0 V ≤ V+ ≤ 5.5 V
11
mV
2.4 V ≤ V ≤ 5.0 V; TA = 25°C
4.5
7
μA
5.0 V ≤ V+ ≤ 5.5 V; TA = 25°C
4.5
9
μA
2.4 V ≤ V+ ≤ 5.0 V
4.5
10
μA
2.4 V ≤ V+ ≤ 5.5 V
0.7
μA
–11
nA/°C
0.02
μA
Temperature Coefficient of Quiescent
Current
Shutdown Current
MAX (1)
2.4 V ≤ V+ ≤ 5.0 V
+
Quiescent Current
TYP (2)
(5) (6)
+
V ≤ 0.8 V
Regulation is measured at constant junction temperature, using pulse testing with a low duty cycle. Changes in output due to heating
effects can be computed by multiplying the internal dissipation by the thermal resistance.
Line regulation is calculated by subtracting the output voltage at the highest supply input voltage from the output voltage at the lowest
supply input voltage.
6.7 Electrical Characteristics: LM20S
Unless otherwise noted, these specifications apply for V+ = 2.7 VDC. All limits TA = TJ = TMIN to TMAX, unless otherwise noted.
MIN (1)
TYP (2)
MAX (1)
TA = 25°C to 30°C
–2.5
±1.5
2.5
°C
TA = 125°C
–3.5
3.5
°C
TA = 100°C
–3.2
3.2
°C
TA = 85°C
–3.1
3.1
°C
TA = 80°C
–3.0
3.0
°C
TA = 0°C
–2.9
2.9
°C
TA = –30°C
–3.3
3.3
°C
TA = –40°C
–3.5
3.5
°C
PARAMETER
Temperature to Voltage Error
VO = (−3.88×10−6×T 2) + (−1.15×10−2×
T) + 1.8639 V (3)
TEST CONDITIONS
Output Voltage at 0°C
Variance from Curve
Non-Linearity
(4)
–20°C ≤ TA ≤ 80°C
Sensor Gain (Temperature Sensitivity or
Average Slope) to equation:
–30°C ≤ TA ≤ 100°C
VO= −11.77 mV/ °C × T + 1.860 V
UNIT
1.8639
V
±1.0
°C
±0.4%
–12.6
–11.77
–11.0
mV/°C
Output Impedance
Sourcing IL 0 μA to 16 μA (5) (6)
160
Ω
(7)
Sourcing IL 0 μA to 16 μA (5) (6)
–2.5
mV
2.4 V ≤ V+ ≤ 5.0 V
3.7
mV/V
5.0 V ≤ V+ ≤ 5.5 V
11
mV
Load Regulation
Line Regulation (8)
+
Quiescent Current
(1)
(2)
(3)
(4)
(5)
(6)
(7)
(8)
6
2.4 V ≤ V ≤ 5.0 V; TA = 25°C
4.5
7
μA
5.0 V ≤ V+ ≤ 5.5 V; TA = 25°C
4.5
9
μA
2.4 V ≤ V+ ≤ 5.0 V
4.5
10
μA
Limits are ensured to TI's AOQL (Average Outgoing Quality Level).
Typicals are at TJ = TA = 25°C and represent most likely parametric norm.
Accuracy is defined as the error between the measured and calculated output voltage at the specified conditions of voltage, current, and
temperature (expressed in °C).
Non-linearity is defined as the deviation of the calculated output-voltage-versus-temperature curve from the best-fit straight line, over the
temperature range specified.
The LM20 can at most sink 1 μA and source 16 μA.
Load regulation or output impedance specifications apply over the supply voltage range of 2.4 V to 5.5 V.
Regulation is measured at constant junction temperature, using pulse testing with a low duty cycle. Changes in output due to heating
effects can be computed by multiplying the internal dissipation by the thermal resistance.
Line regulation is calculated by subtracting the output voltage at the highest supply input voltage from the output voltage at the lowest
supply input voltage.
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Electrical Characteristics: LM20S (continued)
Unless otherwise noted, these specifications apply for V+ = 2.7 VDC. All limits TA = TJ = TMIN to TMAX, unless otherwise noted.
PARAMETER
Change of Quiescent Current
TEST CONDITIONS
+
2.4 V ≤ V ≤ 5.5 V
Temperature Coefficient of Quiescent
Current
Shutdown Current
V+ ≤ 0.8 V
MIN (1)
TYP (2)
MAX (1)
UNIT
0.7
μA
–11
nA/°C
0.02
μA
6.8 Typical Characteristics
Figure 1. Temperature Error vs Temperature
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7 Detailed Description
7.1 Overview
The LM20 device is a precision analog output CMOS integrated-circuit temperature sensor that operates over a
temperature range of −55°C to 130°C. The power supply operating range is 2.4 V to 5.5 V. The transfer function
of LM20 is predominately linear, yet has a slight predictable parabolic curvature. The accuracy of the LM20 when
specified to a parabolic transfer function is typically ±1.5°C at an ambient temperature of 30°C. The temperature
error increases linearly and reaches a maximum of ±2.5°C at the temperature range extremes for the LM20. The
temperature range is affected by the power supply voltage. At a power supply voltage of 2.7 V to 5.5 V, the
temperature range extremes are 130°C and −55°C. Decreasing the power supply voltage to 2.4 V changes the
negative extreme to −30°C, while the positive remains at 130°C.
The LM20 quiescent current is less than 10 μA. Therefore, self-heating is less than 0.02°C in still air. Shutdown
capability for the LM20 is intrinsic because its inherent low power consumption allows it to be powered directly
from the output of many logic gates or, does not necessitate shutdown at all.
The temperature sensing element is comprised of a simple base emitter junction that is forward biased by a
current source. The temperature sensing element is then buffered by an amplifier and provided to the OUT pin.
The amplifier has a simple class A output stage thus providing a low impedance output that can source 16 µA
and sink 1 µA.
7.2 Functional Block Diagram
V+
VO
Thermal Diodes
GND
7.3 Feature Description
7.3.1 LM20 Transfer Function
The LM20 transfer function can be described in different ways with varying levels of precision. A simple linear
transfer function with good accuracy near 25°C is:
VO = −11.69 mV/°C × T + 1.8663 V
(1)
Over the full operating temperature range of −55°C to 130°C, best accuracy can be obtained by using the
parabolic transfer function.
VO = (−3.88×10−6×T2) + (−1.15×10−2×T) + 1.8639
(2)
Using Equation 2, the following temperature to voltage output characteristic table can be generated.
Table 1. Temperature to Voltage Output Characteristic Table
8
TEMP
(°C)
VOUT
(V)
TEMP
(°C)
VOUT
(V)
TEMP
(°C)
VOUT
(V)
TEMP
(°C)
VOUT
(V)
TEMP
(°C)
VOUT
(V)
TEMP
(°C)
VOUT
(V)
TEMP
(°C)
VOUT
(V)
-55
2.4847
-28
2.1829
-1
1.8754
26
1.5623
53
1.2435
80
0.9191
107
0.5890
-54
2.4736
-27
2.1716
0
1.8639
27
1.5506
54
1.2316
81
0.9069
108
0.5766
-53
2.4625
-26
2.1603
1
1.8524
28
1.5389
55
1.2197
82
0.8948
109
0.5643
-52
2.4514
-25
2.1490
2
1.8409
29
1.5271
56
1.2077
83
0.8827
110
0.5520
-51
2.4403
-24
2.1377
3
1.8294
30
1.5154
57
1.1958
84
0.8705
111
0.5396
-50
2.4292
-23
2.1263
4
1.8178
31
1.5037
58
1.1838
85
0.8584
112
0.5272
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Feature Description (continued)
Table 1. Temperature to Voltage Output Characteristic Table (continued)
TEMP
(°C)
VOUT
(V)
TEMP
(°C)
VOUT
(V)
TEMP
(°C)
VOUT
(V)
TEMP
(°C)
VOUT
(V)
TEMP
(°C)
VOUT
(V)
TEMP
(°C)
VOUT
(V)
TEMP
(°C)
VOUT
(V)
-49
2.4181
-22
2.1150
5
1.8063
32
1.4919
59
1.1719
86
0.8462
113
0.5149
-48
2.4070
-21
2.1037
6
1.7948
33
1.4802
60
1.1599
87
0.8340
114
0.5025
-47
2.3958
-20
2.0923
7
1.7832
34
1.4684
61
1.1480
88
0.8219
115
0.4901
-46
2.3847
-19
2.0810
8
1.7717
35
1.4566
62
1.1360
89
0.8097
116
0.4777
-45
2.3735
-18
2.0696
9
1.7601
36
1.4449
63
1.1240
90
0.7975
117
0.4653
-44
2.3624
-17
2.0583
10
1.7485
37
1.4331
64
1.1120
91
0.7853
118
0.4529
-43
2.3512
-16
2.0469
11
1.7369
38
1.4213
65
1.1000
92
0.7731
119
0.4405
-42
2.3401
-15
2.0355
12
1.7253
39
1.4095
66
1.0880
93
0.7608
120
0.4280
-41
2.3289
-14
2.0241
13
1.7137
40
1.3977
67
1.0760
94
0.7486
121
0.4156
-40
2.3177
-13
2.0127
14
1.7021
41
1.3859
68
1.0640
95
0.7364
122
0.4032
-39
2.3065
-12
2.0013
15
1.6905
42
1.3741
69
1.0519
96
0.7241
123
0.3907
-38
2.2953
-11
1.9899
16
1.6789
43
1.3622
70
1.0399
97
0.7119
124
0.3782
-37
2.2841
-10
1.9785
17
1.6673
44
1.3504
71
1.0278
98
0.6996
125
0.3658
-36
2.2729
-9
1.9671
18
1.6556
45
1.3385
72
1.0158
99
0.6874
126
0.3533
-35
2.2616
-8
1.9557
19
1.6440
46
1.3267
73
1.0037
100
0.6751
127
0.3408
-34
2.2504
-7
1.9442
20
1.6323
47
1.3148
74
0.9917
101
0.6628
128
0.3283
-33
2.2392
-6
1.9328
21
1.6207
48
1.3030
75
0.9796
102
0.6505
129
0.3158
-32
2.2279
-5
1.9213
22
1.6090
49
1.2911
76
0.9675
103
0.6382
130
0.3033
-31
2.2167
-4
1.9098
23
1.5973
50
1.2792
77
0.9554
104
0.6259
—
—
-30
2.2054
-3
1.8984
24
1.5857
51
1.2673
78
0.9433
105
0.6136
—
—
-29
2.1941
-2
1.8869
25
1.5740
52
1.2554
79
0.9312
106
0.6013
—
—
Solving Equation 2 for T:
(3)
7.4 Device Functional Modes
The only functional mode of the LM20 is that it has an analog output inversely proportional to temperature.
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8 Application and Implementation
NOTE
Information in the following applications sections is not part of the TI component
specification, and TI does not warrant its accuracy or completeness. TI’s customers are
responsible for determining suitability of components for their purposes. Customers should
validate and test their design implementation to confirm system functionality.
8.1 Application Information
The LM20 features make it suitable for many general temperature sensing applications. Multiple package options
expand on its, flexibility.
8.1.1 Capacitive Loads
The LM20 handles capacitive loading well. Without any precautions, the LM20 can drive any capacitive load less
than 300 pF as shown in Figure 2. Over the specified temperature range the LM20 has a maximum output
impedance of 160 Ω. In an extremely noisy environment, it may be necessary to add some filtering to minimize
noise pickup. It is recommended that 0.1 μF be added from V+ to GND to bypass the power supply voltage, as
shown in Figure 4. In a noisy environment, it may even be necessary to add a capacitor from the output to
ground with a series resistor as shown in Figure 4. A 1-μF output capacitor with the 160-Ω maximum output
impedance and a 200-Ω series resistor will form a 442-Hz lowpass filter. Because the thermal time constant of
the LM20 is much slower, the overall response time of the LM20 will not be significantly affected.
In situations where a transient load current is placed on the circuit output the series resistance value may be
increased to compensate for any ringing that may be observed.
Figure 2. LM20 No Decoupling Required for Capacitive Loads Less Than 300 pF
Table 2. Capacitive Loading Isolation
Minimum R (Ω)
C (µF)
200
1
470
0.1
680
0.01
1k
0.001
Figure 3. LM20 With Compensation for Capacitive Loading Greater Than 300 pF
10
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Figure 4. LM20 With Filter for Noisy Environment and Capacitive Loading Greater Than 300 pF
NOTE
Either placement of resistor, as shown in Figure 3 and Figure 4, is just as effective.
8.1.2 LM20 DSBGA Light Sensitivity
Exposing the LM20 DSBGA package to bright sunlight may cause the output reading of the LM20 to drop by
1.5 V. In a normal office environment of fluorescent lighting the output voltage is minimally affected (less than a
millivolt drop). In either case, TI recommends that the LM20 DSBGA be placed inside an enclosure of some type
that minimizes its light exposure. Most chassis provide more than ample protection. The LM20 does not sustain
permanent damage from light exposure. Removing the light source will cause the output voltage of the LM20 to
recover to the proper value.
8.2 Typical Applications
8.2.1 Full-Range Celsius (Centigrade) Temperature Sensor (−55°C to 130°C) Operating from a Single LiIon Battery Cell
The LM20 has a very low supply current and a wide supply range; therefore, it can easily be driven by a battery
as shown in Figure 5.
Figure 5. Full-Range Celsius (Centigrade) Temperature Sensor (−55°C To 130°C) Operating from a Single
Li-Ion Battery Cell
8.2.1.1 Design Requirements
Because the LM20 is a simple temperature sensor that provides an analog output, design requirements related
to layout are more important than electrical requirements. Refer to the Layout section for a detailed description.
8.2.1.2 Detailed Design Procedure
The LM20 transfer function can be described in different ways with varying levels of precision. A simple linear
transfer function with good accuracy near 25°C is:
VO = −11.69 mV/°C × T + 1.8663 V
(4)
Over the full operating temperature range of −55°C to 130°C, best accuracy can be obtained by using the
parabolic transfer function.
VO = (−3.88×10−6×T2) + (−1.15×10−2×T) + 1.8639
(5)
Solving Equation 5 for T:
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Typical Applications (continued)
(6)
An alternative to the quadratic equation a second order transfer function can be determined using the leastsquares method:
T = (−2.3654×VO 2) + (−78.154×VO ) + 153.857
where
•
T is temperature express in °C and VO is the output voltage expressed in volts.
(7)
A linear transfer function can be used over a limited temperature range by calculating a slope and offset that give
best results over that range. A linear transfer function can be calculated from the parabolic transfer function of
the LM20. The slope of the linear transfer function can be calculated using the Equation 8 equation:
m = −7.76 × 10−6× T − 0.0115,
where
•
T is the middle of the temperature range of interest and m is in V/°C.
(8)
For example for the temperature range of TMIN = −30 to TMAX = 100°C:
T = 35°C
(9)
and
m = −11.77 mV/°C
(10)
The offset of the linear transfer function can be calculated using the Equation 11 equation:
b = (VOP(TMAX) + VOP(T) − m × (TMAX+T))/2
where
•
•
VOP(TMAX) is the calculated output voltage at TMAX using the parabolic transfer function for VO
VOP(T) is the calculated output voltage at T using the parabolic transfer function for VO.
(11)
The best fit linear transfer function for many popular temperature ranges was calculated in Table 3. As shown in
Table 3, the error introduced by the linear transfer function increases with wider temperature ranges.
Table 3. First Order Equations Optimized for Different Temperature Ranges
Temperature Range
12
Linear Equation
Maximum Deviation of Linear
Equation from Parabolic Equation (°C)
Tmin (°C)
Tmax (°C)
−55
130
VO = −11.79 mV/°C × T + 1.8528 V
±1.41
−40
110
VO = −11.77 mV/°C × T + 1.8577 V
±0.93
−30
100
VO = −11.77 mV/°C × T + 1.8605 V
±0.70
±0.65
-40
85
VO = −11.67 mV/°C × T + 1.8583 V
−10
65
VO = −11.71 mV/°C × T + 1.8641 V
±0.23
35
45
VO = −11.81 mV/°C × T + 1.8701 V
±0.004
20
30
VO = –11.69 mV/°C × T + 1.8663 V
±0.004
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Table 4. Output Voltage vs Temperature
Temperature (T)
Typical VO
130°C
303 mV
100°C
675 mV
80°C
919 mV
30°C
1515 mV
25°C
1574 mV
0°C
1863.9 mV
–30°C
2205 mV
−40°C
2318 mV
−55°C
2485 mV
8.2.1.3 Application Curve
Figure 6. Output Voltage vs Temperature
8.2.2 Centigrade Thermostat
V+
R3
R4
LM4040
V+
VT
R1
4.1V
U3
0.1 PF
LM20
R2
(High = overtemp alarm)
+
U1
-
VOUT
LM7211
VTemp
U2
Figure 7. Centigrade Thermostat
8.2.2.1 Design Requirements
A simple thermostat can be created by using a reference (LM4040) and a comparator (LM7211) as shown in
Figure 7.
8.2.2.2 Detailed Design Procedure
The threshold values can be calculated using Equation 12 and Equation 13.
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(4.1)R2
R2 + R1||R3
(12)
(4.1)R2||R3
VT2 =
R1 + R2||R3
(13)
VT1 =
8.2.2.3 Application Curve
VTEMP
VT1
VT2
VOUT
Figure 8. Thermostat Output Waveform
8.3 System Examples
8.3.1 Conserving Power Dissipation With Shutdown
The LM20 draws very little power; therefore, it can simply be shutdown by driving its supply pin with the output of
an logic gate as shown in Figure 9.
Figure 9. Conserving Power Dissipation With Shutdown
8.3.2 Analog-to-Digital Converter Input Stage
Most CMOS ADCs found in ASICs have a sampled data comparator input structure that is notorious for causing
grief to analog output devices such as the LM20 and many operational amplifiers. The cause of this grief is the
requirement of instantaneous charge of the input sampling capacitor in the ADC. This requirement is easily
accommodated by the addition of a capacitor. Because not all ADCsFigure 10 have identical input stages, the
charge requirements will vary necessitating a different value of compensating capacitor. This ADC is shown as
an example only. If a digital output temperature is required, refer to devices such as the LM74.
Figure 10. Suggested Connection to a Sampling Analog to Digital Converter Input Stage
14
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9 Power Supply Recommendations
The LM20 has a very wide 2.4-V to 5.5-V power supply voltage range that makes ideal for many applications. In
noisy environments, TI recommends adding at minimum 0.1 μF from V+ to GND to bypass the power supply
voltage. Larger capacitances maybe required and are dependent on the power-supply noise.
10 Layout
10.1 Layout Guidelines
The LM20 can be easily applied in the same way as other integrated-circuit temperature sensors. It can be glued
or cemented to a surface. The temperature that the LM20 is sensing is within approximately 0.02°C of the
surface temperature to which the leads of the LM20 are attached.
Implementing the integrated-circuit temperature sensors presumes that the ambient air temperature is almost the
same as the surface temperature; if the air temperature were much higher or lower than the surface temperature,
the actual temperature measured would be at an intermediate temperature between the surface temperature and
the air temperature.
To ensure good thermal conductivity, the backside of the LM20 die is directly attached to the pin 2 GND. The
temperatures of the lands and traces to the other leads of the LM20 will also affect the temperature that is
sensed.
Alternatively, the LM20 can be mounted inside a sealed-end metal tube, and can then be dipped into a bath or
screwed into a threaded hole in a tank. As with any IC, the LM20 and accompanying wiring and circuits must be
kept insulated and dry, to avoid leakage and corrosion. This is especially true if the circuit may operate at cold
temperatures where condensation can occur. Printed-circuit coatings and varnishes such as a conformal coating
and epoxy paints or dips are often used to ensure that moisture cannot corrode the LM20 or its connections.
10.2 Layout Examples
NC
GND
GND
Vo
V+
Figure 11. Layout Used for No Heat Sink Measurements
NC
GND
GND
NC
Vo
V+
Figure 12. Layout Used for Measurements With Small Heat Sink
10.3 Thermal Considerations
The thermal resistance junction to ambient (RθJA) is the parameter used to calculate the rise of a device junction
temperature due to its power dissipation. For the LM20, the equation used to calculate the rise in the die
temperature is as follows:
TJ = TA + RθJA [(V+ IQ) + (V+ − VO) IL]
where
•
IQ is the quiescent current and ILis the load current on the output. Because the junction temperature of LM20 is
the actual temperature being measured, take care to minimize the load current that the LM20 is required to
drive.
(14)
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Thermal Considerations (continued)
Table 5 summarizes the rise in die temperature of the LM20 without any loading and the thermal resistance for
different conditions.
Table 5. Temperature Rise of LM20 Due to Self-Heating and Thermal Resistance (RΘJA)
See more Layout Examples
SC70-5
SC70-5
No Heat Sink
Small Heat Sink
RθJA
TJ − TA
RθJA
TJ − TA
(°C/W)
(°C)
(°C/W)
(°C)
Still air
412
0.2
350
0.19
Moving air
312
0.17
266
0.15
DSBGA
No Heat Sink
Still air
16
RθJA
TJ − TA
(°C/W)
(°C)
340
0.18
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11 Device and Documentation Support
11.1 Trademarks
All trademarks are the property of their respective owners.
11.2 Electrostatic Discharge Caution
These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam
during storage or handling to prevent electrostatic damage to the MOS gates.
11.3 Glossary
SLYZ022 — TI Glossary.
This glossary lists and explains terms, acronyms, and definitions.
12 Mechanical, Packaging, and Orderable Information
The following pages include mechanical, packaging, and orderable information. This information is the most
current data available for the designated devices. This data is subject to change without notice and revision of
this document. For browser-based versions of this data sheet, refer to the left-hand navigation.
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PACKAGE OPTION ADDENDUM
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22-Oct-2022
PACKAGING INFORMATION
Orderable Device
Status
(1)
Package Type Package Pins Package
Drawing
Qty
Eco Plan
(2)
Lead finish/
Ball material
MSL Peak Temp
Op Temp (°C)
Device Marking
(3)
Samples
(4/5)
(6)
LM20BIM7
NRND
SC70
DCK
5
1000
Non-RoHS
& Green
Call TI
Level-1-260C-UNLIM
-55 to 130
T2B
LM20BIM7/NOPB
ACTIVE
SC70
DCK
5
1000
RoHS & Green
SN
Level-1-260C-UNLIM
-55 to 130
T2B
LM20BIM7X
NRND
SC70
DCK
5
3000
Non-RoHS
& Green
Call TI
Level-1-260C-UNLIM
-55 to 130
T2B
LM20BIM7X/NOPB
ACTIVE
SC70
DCK
5
3000
RoHS & Green
SN
Level-1-260C-UNLIM
-55 to 130
T2B
Samples
LM20CIM7/NOPB
ACTIVE
SC70
DCK
5
1000
RoHS & Green
SN
Level-1-260C-UNLIM
-55 to 130
T2C
Samples
LM20CIM7X
NRND
SC70
DCK
5
3000
Non-RoHS
& Green
Call TI
Level-1-260C-UNLIM
-55 to 130
T2C
LM20CIM7X/NOPB
ACTIVE
SC70
DCK
5
3000
RoHS & Green
SN
Level-1-260C-UNLIM
-55 to 130
T2C
LM20SITL/NOPB
ACTIVE
DSBGA
YZR
4
250
RoHS & Green
SNAGCU
Level-1-260C-UNLIM
-40 to 125
Samples
LM20SITLX/NOPB
ACTIVE
DSBGA
YZR
4
3000
RoHS & Green
SNAGCU
Level-1-260C-UNLIM
-40 to 125
Samples
(1)
The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2)
RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substance
do not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI may
reference these types of products as "Pb-Free".
RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS exemption.
Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of
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