LM94021
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SNIS138E – FEBRUARY 2005 – REVISED JUNE 2013
LM94021/LM94021Q Multi-Gain Analog Temperature Sensor
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FEATURES
DESCRIPTION
•
The LM94021 is a precision analog output CMOS
integrated-circuit temperature sensor that operates at
a supply voltage as low as 1.5V. While operating over
the wide temperature range of −50°C to +150°C, the
LM94021 delivers an output voltage that is inversely
proportional
to
measured
temperature.
The
LM94021's low supply current makes it ideal for
battery-powered systems as well as general
temperature sensing applications.
1
2
•
•
•
•
•
•
•
•
LM94021Q is AEC-Q100 Grade 0 Qualified and
is Manufactured on an Automotive Grade Flow
Low 1.5V Operation
Four Selectable Gains
Very Accurate Over Wide Temperature Range
of −50°C to +150°C
Low Quiescent Current
Output is Short-Circuit Protected
Extremely Small SC70 Package
Footprint Compatible with the IndustryStandard LM20 Temperature Sensor
UL Recognized Component
APPLICATIONS
•
•
•
•
•
•
•
Cell Phones
Wireless Transceivers
Battery Management
Automotive
Disk Drives
Games
Appliances
Two logic inputs, Gain Select 1 (GS1) and Gain
Select 0 (GS0), select the gain of the temperature-tovoltage output transfer function. Four slopes are
selectable: −5.5 mV/°C, −8.2 mV/°C, −10.9 mV/°C,
and −13.6 mV/°C. In the lowest gain configuration
(GS1 and GS0 both tied low), the LM94021 can
operate with a 1.5V supply while measuring
temperature over the full −50°C to +150°C operating
range. Tying both inputs high causes the transfer
function to have the largest gain of −13.6 mV/°C for
maximum temperature sensitivity. The gain-select
inputs can be tied directly to VDD or Ground without
any pull-up or pull-down resistors, reducing
component count and board area. These inputs can
also be driven by logic signals allowing the system to
optimize the gain during operation or system
diagnostics.
Table 1. KEY SPECIFICATIONS
Supply Voltage
1.5V to 5.5V
9 μA (typ)
Supply Current
Temperature Accuracy
20°C to 40°C
−50°C to 70°C
−50°C to 90°C
−50°C to 150°C
Operating Temperature
±1.5°C
±1.8°C
±2.1°C
±2.7°C
–50°C to 150°C
1
2
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
All trademarks are the property of their respective owners.
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
Copyright © 2005–2013, Texas Instruments Incorporated
LM94021
SNIS138E – FEBRUARY 2005 – REVISED JUNE 2013
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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.
CONNECTION DIAGRAM
1
5
GS0
GS1
2
GND
LM94021
3
4
OUT
VDD
Figure 1. 5-Pin SC70 - Top View
TYPICAL TRANSFER CHARACTERISTIC
Output Voltage vs Temperature
TYPICAL APPLICATION
Full-Range Celsius Temperature Sensor (−50°C to +150°C) operating from a Single Battery Cell
VDD (+1.5V to +5.5V)
VDD
Single Battery
Cell
LM94021
GS1
OUT
GS0
GND
2
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PIN DESCRIPTIONS
LABEL
PIN NUMBER
TYPE
GS1
5
Logic Input
GS0
1
Logic Input
EQUIVALENT CIRCUIT
VDD
ESD
CLAMP
FUNCTION
Gain Select 1 - One of two inputs for
selecting the slope of the output
response
Gain Select 0 - One of two inputs for
selecting the slope of the output
response
GND
VDD
OUT
3
Outputs a voltage which is inversely
proportional to temperature
Analog Output
GND
VDD
4
Power
Positive Supply Voltage
GND
2
Ground
Power Supply Ground
ABSOLUTE MAXIMUM RATINGS
(1)
VALUES
−0.3V to +6.0V
Supply Voltage
−0.3V to (VDD + 0.5V)
Voltage at Output Pin
Output Current
±7 mA
−0.3V to +6.0V
Voltage at GS0 and GS1 Input Pins
Input Current at any pin
(2)
5 mA
−65°C to +150°C
Storage Temperature
Maximum Junction Temperature (TJMAX)
ESD Susceptibility
(3)
+150°C
Human Body Model
2500V
Machine Model
250V
Soldering process must comply with Reflow Temperature Profile specifications. Refer to http://www.ti.com/packaging. (4)
(1)
(2)
(3)
(4)
Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for
which the device is functional, but do not ensure specific performance limits. For ensured specifications and test conditions, see the
Electrical Characteristics. The ensured specifications apply only for the test conditions listed. Some performance characteristics may
degrade when the device is not operated under the listed test conditions.
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.
The human body model is a 100 pF capacitor discharged through a 1.5 kΩ resistor into each pin. The machine model is a 200 pF
capacitor discharged directly into each pin.
Reflow temperature profiles are different for lead-free and non-lead-free packages.
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LM94021
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OPERATING RATINGS
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(1)
TMIN ≤ TA ≤ TMAX
Specified Temperature Range
−50°C ≤ TA ≤ +150°C
LM94021
Supply Voltage Range (VDD)
Thermal Resistance (θJA)
5-Pin SC70
(1)
(2)
(3)
+1.5 V to +5.5 V
(2) (3)
415°C/W
Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for
which the device is functional, but do not ensure specific performance limits. For ensured specifications and test conditions, see the
Electrical Characteristics. The ensured specifications apply only for the test conditions listed. Some performance characteristics may
degrade when the device is not operated under the listed test conditions.
The junction to ambient thermal resistance (θJA) is specified without a heat sink in still air.
Changes in output due to self heating can be computed by multiplying the internal dissipation by the thermal resistance.
ACCURACY CHARACTERISTICS
These limits do not include DC load regulation. These stated accuracy limits are with reference to the values in the LM94021
Transfer Table.
PARAMETER
CONDITIONS
GS1 = 0
GS0 = 0
GS1 = 0
GS0 = 1
Temperature Error
(2)
GS1 = 1
GS0 = 0
GS1 = 1
GS0 = 1
(1)
(2)
4
LIMITS
(1)
UNITS
(LIMIT)
TA = +20°C to +40°C; VDD = 1.5V to 5.5V
±1.5
°C (max)
TA = +0°C to +70°C; VDD = 1.5V to 5.5V
±1.8
°C (max)
TA = +0°C to +90°C; VDD = 1.5V to 5.5V
±2.1
°C (max)
TA = +0°C to +120°C; VDD = 1.5V to 5.5V
±2.4
°C (max)
TA = +0°C to +150°C; VDD = 1.5V to 5.5V
±2.7
°C (max)
TA = −50°C to +0°C; VDD = 1.6V to 5.5V
±1.8
°C (max)
TA = +20°C to +40°C; VDD = 1.8V to 5.5V
±1.5
°C (max)
TA = +0°C to +70°C; VDD = 1.9V to 5.5V
±1.8
°C (max)
TA = +0°C to +90°C; VDD = 1.9V to 5.5V
±2.1
°C (max)
TA = +0°C to +120°C; VDD = 1.9V to 5.5V
±2.4
°C (max)
TA = +0°C to +150°C; VDD = 1.9V to 5.5V
±2.7
°C (max)
TA = −50°C to +0°C; VDD = 2.3V to 5.5V
±1.8
°C (max)
TA = +20°C to +40°C; VDD = 2.2V to 5.5V
±1.5
°C (max)
TA = +0°C to +70°C; VDD = 2.4V to 5.5V
±1.8
°C (max)
TA = +0°C to +90°C; VDD = 2.4V to 5.5V
±2.1
°C (max)
TA = +0°C to +120°C; VDD = 2.4V to 5.5V
±2.4
°C (max)
TA = +0°C to +150°C; VDD = 2.4V to 5.5V
±2.7
°C (max)
TA = −50°C to +0°C; VDD = 3.0V to 5.5V
±1.8
°C (max)
TA = +20°C to +40°C; VDD = 2.7V to 5.5V
±1.5
°C (max)
TA = +0°C to +70°C; VDD = 3.0V to 5.5V
±1.8
°C (max)
TA = +0°C to +90°C; VDD = 3.0V to 5.5V
±2.1
°C (max)
TA = +0°C to +120°C; VDD = 3.0V to 5.5V
±2.4
°C (max)
TA = 0°C to +150°C; VDD = 3.0V to 5.5V
±2.7
°C (max)
TA = −50°C to +0°C; VDD = 3.6V to 5.5V
±1.8
°C (max)
Limits are ensured to TI's AOQL (Average Outgoing Quality Level).
Accuracy is defined as the error between the measured and reference output voltages, tabulated in the Transfer Table at the specified
conditions of supply gain setting, voltage, and temperature (expressed in °C). Accuracy limits include line regulation within the specified
conditions. Accuracy limits do not include load regulation; they assume no DC load.
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ELECTRICAL CHARACTERISTICS
Unless otherwise noted, these specifications apply for +VDD = +1.5V to +5.5V . Boldface limits apply for TA = TJ = TMIN to
TMAX ; all other limits TA = TJ = 25°C.
PARAMETER
GS1
GS1
GS1
GS1
Sensor Gain
Load Regulation
Line Regulation
= 0, GS0
= 0, GS1
= 1, GS0
= 1, GS0
=0
=1
=0
=1
Source ≤ 2.0 μA
Sink ≤ 100 μA
Sink = 50 μA
(3)
(5)
IS
Supply Current
CL
Output Load Capacitance
Power-on Time
CONDITIONS
(1)
LIMITS
(2)
−5.5
−8.2
−10.9
−13.6
(4)
UNITS
(LIMIT)
mV/°C
mV/°C
mV/°C
mV/°C
−1
1.6
0.4
mV (max)
mV (max)
mV
(VDD - VOUT) ≥ 200 mV
200
μV/V
TA = +30°C to +150°C
TA = −50°C to +150°C
9
12
13
1100
CL= 0 pF
CL=1100 pF
(6)
TYPICAL
0.7
0.8
μA (max)
μA (max)
pF (max)
1.6
2.4
ms (max)
ms (max)
VIH
GS1 and GS0 Input Logic "1" Threshold
Voltage
VDD- 0.5V
V (min)
VIL
GS1 and GS0 Input Logic "0" Threshold
Voltage
0.5
V (max)
IIH
Logic "1" Input Current
(7)
IIL
Logic "0" Input Current
(7)
(1)
(2)
(3)
(4)
(5)
(6)
(7)
0.001
1
μA (max)
0.001
1
μA (max)
Typicals are at TJ = TA = 25°C and represent most likely parametric norm.
Limits are ensured to TI's AOQL (Average Outgoing Quality Level).
Source currents are flowing out of the LM94021. Sink currents are flowing into the LM94021.
Assumes (VDD - VOUT) ≥ 200 mV.
Line regulation is calculated by subtracting the output voltage at the highest supply voltage from the output voltage at the lowest supply
voltage. The typical line regulation specification does not include the output voltage shift discussed in Section 5.0.
Specified by design.
The input current is leakage only and is highest at high temperature. It is typically only 0.001 µA. The 1 µA limit is solely based on a
testing limitation and does not reflect the actual performance of the part.
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LM94021
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TYPICAL PERFORMANCE CHARACTERISTICS
Temperature Error vs. Temperature
Minimum Operating Temperature vs. Supply Voltage
4
MAX Limit
TEMPERATURE ERROR (ºC)
3
2
1
0
MIN Limit
-1
-2
-3
-4
-50
-25
0
25
50
75
100 125 150
TEMPERATURE (ºC)
6
Figure 2.
Figure 3.
Supply Current vs. Temperature
Supply Current vs. Supply Voltage
Figure 4.
Figure 5.
Load Regulation, Sourcing Current
Load Regulation, Sinking Current
Figure 6.
Figure 7.
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TYPICAL PERFORMANCE CHARACTERISTICS (continued)
Change in VOUT vs. Overhead Voltage
Supply Noise Gain vs. Frequency
0
-10
VDD = 5.0V
TEMP = 25°C
CLOAD = 0 pF
GAIN (dB)
-20
-30
CLOAD = 100 pF
-40
-50
CLOAD = 1 nF
-60
-70
100
1k
10k
100k
1M
10M
FREQUENCY (Hz)
Figure 8.
Figure 9.
Line Regulation: Output Voltage vs. Supply Voltage
Gain Select = 00
Line Regulation: Output Voltage vs. Supply Voltage
Gain Select = 01
Figure 10.
Figure 11.
Line Regulation: Output Voltage vs. Supply Voltage
Gain Select = 10
Line Regulation: Output Voltage vs. Supply Voltage
Gain Select = 11
Figure 12.
Figure 13.
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LM94021
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APPLICATION INFORMATION
LM94021 TRANSFER FUNCTION
The LM94021 has four selectable gains, each of which can be selected by the GS1 and GS0 input pins. The
output voltage for each gain, across the complete operating temperature range is shown in Table 2, below. This
table is the reference from which the LM94021 accuracy specifications (listed in the ELECTRICAL
CHARACTERISTICS section) are determined. This table can be used, for example, in a host processor look-up
table.
A
file
containing
this
data
is
available
for
download
at
http://www.ti.com/lsds/ti/analog/temperature_sensor.page.
Table 2. LM94021 Transfer Table
8
TEMPERATURE
(°C)
GS = 00
(mV)
GS = 01
(mV)
GS = 10
(mV)
GS = 11
(mV)
−50
1299
1955
2616
3277
−49
1294
1949
2607
3266
−48
1289
1942
2598
3254
−47
1284
1935
2589
3243
−46
1278
1928
2580
3232
−45
1273
1921
2571
3221
−44
1268
1915
2562
3210
−43
1263
1908
2553
3199
−42
1257
1900
2543
3186
−41
1252
1892
2533
3173
−40
1247
1885
2522
3160
−39
1242
1877
2512
3147
−38
1236
1869
2501
3134
−37
1231
1861
2491
3121
−36
1226
1853
2481
3108
-35
1221
1845
2470
3095
−34
1215
1838
2460
3082
−33
1210
1830
2449
3069
−32
1205
1822
2439
3056
−31
1200
1814
2429
3043
−30
1194
1806
2418
3030
−29
1189
1798
2408
3017
−28
1184
1790
2397
3004
−27
1178
1783
2387
2991
−26
1173
1775
2376
2978
−25
1168
1767
2366
2965
−24
1162
1759
2355
2952
−23
1157
1751
2345
2938
−22
1152
1743
2334
2925
−21
1146
1735
2324
2912
−20
1141
1727
2313
2899
−19
1136
1719
2302
2886
−18
1130
1711
2292
2873
−17
1125
1703
2281
2859
−16
1120
1695
2271
2846
−15
1114
1687
2260
2833
−14
1109
1679
2250
2820
−13
1104
1671
2239
2807
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Table 2. LM94021 Transfer Table (continued)
TEMPERATURE
(°C)
GS = 00
(mV)
GS = 01
(mV)
GS = 10
(mV)
GS = 11
(mV)
−12
1098
1663
2228
2793
−11
1093
1656
2218
2780
−10
1088
1648
2207
2767
−9
1082
1639
2197
2754
−8
1077
1631
2186
2740
−7
1072
1623
2175
2727
−6
1066
1615
2164
2714
−5
1061
1607
2154
2700
−4
1055
1599
2143
2687
−3
1050
1591
2132
2674
−2
1044
1583
2122
2660
−1
1039
1575
2111
2647
0
1034
1567
2100
2633
1
1028
1559
2089
2620
2
1023
1551
2079
2607
3
1017
1543
2068
2593
4
1012
1535
2057
2580
5
1007
1527
2047
2567
6
1001
1519
2036
2553
7
996
1511
2025
2540
8
990
1502
2014
2527
9
985
1494
2004
2513
10
980
1486
1993
2500
11
974
1478
1982
2486
12
969
1470
1971
2473
13
963
1462
1961
2459
14
958
1454
1950
2446
15
952
1446
1939
2433
16
947
1438
1928
2419
17
941
1430
1918
2406
18
936
1421
1907
2392
19
931
1413
1896
2379
20
925
1405
1885
2365
21
920
1397
1874
2352
22
914
1389
1864
2338
23
909
1381
1853
2325
24
903
1373
1842
2311
25
898
1365
1831
2298
26
892
1356
1820
2285
27
887
1348
1810
2271
28
882
1340
1799
2258
29
876
1332
1788
2244
30
871
1324
1777
2231
31
865
1316
1766
2217
32
860
1308
1756
2204
33
854
1299
1745
2190
34
849
1291
1734
2176
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Table 2. LM94021 Transfer Table (continued)
10
TEMPERATURE
(°C)
GS = 00
(mV)
GS = 01
(mV)
GS = 10
(mV)
GS = 11
(mV)
35
843
1283
1723
2163
36
838
1275
1712
2149
37
832
1267
1701
2136
38
827
1258
1690
2122
39
821
1250
1679
2108
40
816
1242
1668
2095
41
810
1234
1657
2081
42
804
1225
1646
2067
43
799
1217
1635
2054
44
793
1209
1624
2040
45
788
1201
1613
2026
46
782
1192
1602
2012
47
777
1184
1591
1999
48
771
1176
1580
1985
49
766
1167
1569
1971
50
760
1159
1558
1958
51
754
1151
1547
1944
52
749
1143
1536
1930
53
743
1134
1525
1916
54
738
1126
1514
1902
55
732
1118
1503
1888
56
726
1109
1492
1875
57
721
1101
1481
1861
58
715
1093
1470
1847
59
710
1084
1459
1833
60
704
1076
1448
1819
61
698
1067
1436
1805
62
693
1059
1425
1791
63
687
1051
1414
1777
64
681
1042
1403
1763
65
676
1034
1391
1749
66
670
1025
1380
1735
67
664
1017
1369
1721
68
659
1008
1358
1707
69
653
1000
1346
1693
70
647
991
1335
1679
71
642
983
1324
1665
72
636
974
1313
1651
73
630
966
1301
1637
74
625
957
1290
1623
75
619
949
1279
1609
76
613
941
1268
1595
77
608
932
1257
1581
78
602
924
1245
1567
79
596
915
1234
1553
80
591
907
1223
1539
81
585
898
1212
1525
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Table 2. LM94021 Transfer Table (continued)
TEMPERATURE
(°C)
GS = 00
(mV)
GS = 01
(mV)
GS = 10
(mV)
GS = 11
(mV)
82
579
890
1201
1511
83
574
881
1189
1497
84
568
873
1178
1483
85
562
865
1167
1469
86
557
856
1155
1455
87
551
848
1144
1441
88
545
839
1133
1427
89
539
831
1122
1413
90
534
822
1110
1399
91
528
814
1099
1385
92
522
805
1088
1371
93
517
797
1076
1356
94
511
788
1065
1342
95
505
779
1054
1328
96
499
771
1042
1314
97
494
762
1031
1300
98
488
754
1020
1286
99
482
745
1008
1272
100
476
737
997
1257
101
471
728
986
1243
102
465
720
974
1229
103
459
711
963
1215
104
453
702
951
1201
105
448
694
940
1186
106
442
685
929
1172
107
436
677
917
1158
108
430
668
906
1144
109
425
660
895
1130
110
419
651
883
1115
111
413
642
872
1101
112
407
634
860
1087
113
401
625
849
1073
114
396
617
837
1058
115
390
608
826
1044
116
384
599
814
1030
117
378
591
803
1015
118
372
582
791
1001
119
367
573
780
987
120
361
565
769
973
121
355
556
757
958
122
349
547
745
944
123
343
539
734
929
124
337
530
722
915
125
332
521
711
901
126
326
513
699
886
127
320
504
688
872
128
314
495
676
858
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LM94021
SNIS138E – FEBRUARY 2005 – REVISED JUNE 2013
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Table 2. LM94021 Transfer Table (continued)
TEMPERATURE
(°C)
GS = 00
(mV)
GS = 01
(mV)
GS = 10
(mV)
GS = 11
(mV)
129
308
487
665
843
130
302
478
653
829
131
296
469
642
814
132
291
460
630
800
133
285
452
618
786
134
279
443
607
771
135
273
434
595
757
136
267
425
584
742
137
261
416
572
728
138
255
408
560
713
139
249
399
549
699
140
243
390
537
684
141
237
381
525
670
142
231
372
514
655
143
225
363
502
640
144
219
354
490
626
145
213
346
479
611
146
207
337
467
597
147
201
328
455
582
148
195
319
443
568
149
189
310
432
553
150
183
301
420
538
Although the LM94021 is very linear, its response does have a slight umbrella's parabolic shape. This shape is
very accurately reflected in the LM94021 Transfer Table. The Transfer Table can be calculated by using the
parabolic equation.
mV
mV
2
J2,G00 : VTEMP mV = 870.6mV - 5.506
T - 30°C - 0.00176 2 T - 30°C
°C
°C
mV
mV
2
J3,G01 : VTEMP mV = 1324.0mV - 8.194
T - 30°C - 0.00262 2 T - 30°C
°C
°C
mV
mV
2
J4,G10 : VTEMP mV = 1777.3mV - 10.888
T - 30°C - 0.00347 2 T - 30°C
°C
°C
mV
mV
2
T - 30°C - 0.00433 2 T - 30°C
J5,G11 : VTEMP mV = 2230.8mV - 13.582
°C
°C
(1)
For a linear approximation, a line can easily be calculated over the desired temperature range from the Table
using the two-point equation:
·
¹
V - V1 =
V2 - V1
T2 - T1
· u (T - T1)
¹
(2)
Where V is in mV, T is in °C, T1 and V1 are the coordinates of the lowest temperature, T2 and V2 are the
coordinates of the highest temperature.
For example, if we want to determine the equation of a line with the Gain Setting at GS1 = 0 and GS0 = 0, over a
temperature range of 20°C to 50°C, we would proceed as follows:
760 mV - 925 mV ·
u (T - 20oC)
50oC - 20oC ¹
·
¹
V - 925 mV =
(3)
o
12
o
V - 925 mV = (-5.50 mV / C) u (T - 20 C)
(4)
o
V = (-5.50 mV / C) u T + 1035 mV
(5)
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Using this method of linear approximation, the transfer function can be approximated for one or more
temperature ranges of interest.
MOUNTING AND THERMAL CONDUCTIVITY
The LM94021 can be applied easily in the same way as other integrated-circuit temperature sensors. It can be
glued or cemented to a surface.
To ensure good thermal conductivity, the backside of the LM94021 die is directly attached to the GND pin (Pin
2). The temperatures of the lands and traces to the other leads of the LM94021 will also affect the temperature
reading.
Alternatively, the LM94021 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 LM94021 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. If moisture creates a short circuit from the output to ground
or VDD, the output from the LM94021 will not be correct. Printed-circuit coatings are often used to ensure that
moisture cannot corrode the leads or circuit traces.
The thermal resistance junction to ambient (θJA) is the parameter used to calculate the rise of a device junction
temperature due to its power dissipation. The equation used to calculate the rise in the LM94021's die
temperature is
[
TJ = TA + TJA (VDDIQ) + (VDD - VO) IL
]
(6)
where TA is the ambient temperature, IQ is the quiescent current, IL is the load current on the output, and VO is
the output voltage. For example, in an application where TA = 30°C, VDD = 5 V, IDD = 9 μA, Gain Select = 11,
VOUT = 2.231 mV, and IL = 2 μA, the junction temperature would be 30.021°C, showing a self-heating error of
only 0.021°C. Since the LM94021's junction temperature is the actual temperature being measured, care should
be taken to minimize the load current that the LM94021 is required to drive. Table 3 shows the thermal
resistance of the LM94021.
Table 3. LM94021 Thermal Resistance
DEVICE NUMBER
PACKAGE NUMBER
THERMAL RESISTANCE (θJA)
LM94021BIMG
DCK0005A
415°C/W
NOISE CONSIDERATIONS
The LM94021 has excellent noise rejection (the ratio of the AC signal on VOUT to the AC signal on VDD). During
bench tests, sine wave rejection of −54 dB or better was observed over 200 Hz to 10 kHz; Also, −28 dB or better
was observed from 10 kHz to 1 MHz. A load capacitor on the output can help filter noise; for example, a 1 nF
load capacitor resulted in −51 dB or better from 200 Hz to 1 MHz.
There is no specific requirement for the use of a bypass capacitor close to the LM94021 because it does not
draw transient currents. For operation in very noisy environments, some bypass capacitance may be required.
The capacitance does not need to be in close proximity to the LM94021. The LM94021 has been bench tested
successfully with a bypass capacitor as far as 6 inches away. In fact, it can be powered by a properly-bypassed
logic gate.
CAPACITIVE LOADS
The LM94021 handles capacitive loading well. In an extremely noisy environment, or when driving a switched
sampling input on an ADC, it may be necessary to add some filtering to minimize noise coupling. Without any
precautions, the LM94021 can drive a capacitive load less than or equal to 1100 pF as shown in Figure 14. For
capacitive loads greater than 1100 pF, a series resistor may be required on the output, as shown in Figure 15.
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LM94021
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VDD
LM94021
OPTIONAL
BYPASS
CAPACITANCE
OUT
GND
CLOAD < 1100 pF
Figure 14. LM94021 No Decoupling Required for Capacitive Loads Less than 1100 pF
VDD
RS
LM94021
OPTIONAL
BYPASS
CAPACITANCE
OUT
GND
CLOAD > 1100 pF
Figure 15. LM94021 with Series Resistor for Capacitive Loading greater than 1100 pF
OUTPUT VOLTAGE SHIFT
The LM94021 is very linear over temperature and supply voltage range. Due to the intrinsic behavior of an
NMOS/PMOS rail-to-rail buffer, a slight shift in the output can occur when the supply voltage is ramped over the
operating range of the device. The location of the shift is determined by the relative levels of VDD and VOUT. The
shift typically occurs when VDD- VOUT = 1.0V.
This slight shift (a few millivolts) takes place over a wide change (approximately 200 mV) in VDD or VOUT. Since
the shift takes place over a wide temperature change of 5°C to 20°C, VOUT is always monotonic. The accuracy
specifications in the ELECTRICAL CHARACTERISTICS table already include this possible shift.
SELECTABLE GAIN FOR OPTIMIZATION AND IN SITU TESTING
The Gain Select digital inputs can be tied to the rails or can be driven from digital outputs such as microcontroller
GPIO pins. In low-supply voltage applications, the ability to reduce the gain to −5.5 mV/°C allows the LM94021 to
operate over the full −50°C to 150°C range. When a larger supply voltage is present, the gain can be increased
as high as −13.6 mV/°C. The larger gain is optimal for reducing the effects of noise (for example, noise coupling
on the output line or quantization noise induced by an analog-to-digital converter which may be sampling the
LM94021 output).
Another application advantage of the digitally selectable gain is the ability to perform dynamic testing of the
LM94021 while it is running in a system. By toggling the logic levels of the gain select pins and monitoring the
resultant change in the output voltage level, the host system can verify the functionality of the LM94021.
14
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SNIS138E – FEBRUARY 2005 – REVISED JUNE 2013
APPLICATION CIRCUITS
V+
VTEMP
R3
VT1
R4
VT2
LM4040
VDD
VT
R1
4.1V
U3
0.1 PF
LM94021
R2
(High = overtemp alarm)
+
U1
-
VOUT
VOUT
VTemp
U2
VT1 =
(4.1)R2
R2 + R1||R3
VT2 =
(4.1)R2||R3
R1 + R2||R3
Figure 16. Celsius Thermostat
VDD
SHUTDOWN
VOUT
LM94021
Any logic
device output
Figure 17. Conserving Power Dissipation with Shutdown
SAR Analog-to-Digital Converter
Reset
+1.5V to +5.5V
Input
Pin
LM94021
4
VDD
OUT
3
CBP
GND
5
GS1
GS0
2
Sample
RIN
CFILTER
CIN
CSAMPLE
1
Most CMOS ADCs found in microcontrollers and ASICs have a sampled data comparator input structure. When the
ADC charges the sampling cap, it requires instantaneous charge from the output of the analog source such as the
LM94021 temperature sensor and many op amps. This requirement is easily accommodated by the addition of a
capacitor (CFILTER). The size of CFILTER depends on the size of the sampling capacitor and the sampling frequency.
Since not all ADCs have identical input stages, the charge requirements will vary. This general ADC application is
shown as an example only.
Figure 18. Suggested Connection to a Sampling Analog-to-Digital Converter Input Stage
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LM94021
SNIS138E – FEBRUARY 2005 – REVISED JUNE 2013
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REVISION HISTORY
Changes from Revision C (February 2013) to Revision D
•
16
Page
Changed layout of National Data Sheet to TI format .......................................................................................................... 15
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PACKAGE OPTION ADDENDUM
www.ti.com
9-Jun-2018
PACKAGING INFORMATION
Orderable Device
Status
(1)
Package Type Package Pins Package
Drawing
Qty
Eco Plan
Lead/Ball Finish
MSL Peak Temp
(2)
(6)
(3)
Op Temp (°C)
Device Marking
(4/5)
LM94021 MDA
OBSOLETE
DIESALE
Y
0
TBD
Call TI
Call TI
-40 to 85
LM94021BIMG
NRND
SC70
DCK
5
1000
TBD
Call TI
Call TI
-50 to 150
21B
LM94021BIMG/NOPB
ACTIVE
SC70
DCK
5
1000
Green (RoHS
& no Sb/Br)
CU SN
Level-1-260C-UNLIM
-50 to 150
21B
LM94021BIMGX/NOPB
ACTIVE
SC70
DCK
5
3000
Green (RoHS
& no Sb/Br)
CU SN
Level-1-260C-UNLIM
-50 to 150
21B
LM94021QBIMG/NOPB
ACTIVE
SC70
DCK
5
1000
Green (RoHS
& no Sb/Br)
CU SN
Level-1-260C-UNLIM
-50 to 150
21Q
LM94021QBIMGX/NOPB
ACTIVE
SC70
DCK
5
3000
Green (RoHS
& no Sb/Br)
CU SN
Level-1-260C-UNLIM
-50 to 150
21Q
(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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