NSC LM26LVCISD-XPE

LM26LV
1.6 V, LLP-6 Factory Preset Temperature Switch and
Temperature Sensor
General Description
The LM26LV is a low-voltage, precision, dual-output, lowpower temperature switch and temperature sensor. The temperature trip point (TTRIP) can be preset at the factory to any
temperature in the range of 0°C to 150°C in 1°C increments.
Built-in temperature hysteresis (THYST) keeps the output stable in an environment of temperature instability.
In normal operation the LM26LV temperature switch outputs
assert when the die temperature exceeds TTRIP. The temperature switch outputs will reset when the temperature falls
below a temperature equal to (TTRIP − THYST). The
OVERTEMP digital output, is active-high with a push-pull
structure, while the OVERTEMP digital output, is active-low
with an open-drain structure.
An analog output, VTEMP, delivers an analog output voltage
which is inversely proportional to the measured temperature.
Driving the TRIP TEST input high: (1) causes the digital outputs to be asserted for in-situ verification and, (2) causes the
threshold voltage to appear at the VTEMP output pin, which
could be used to verify the temperature trip point.
The LM26LV's low minimum supply voltage makes it ideal for
1.8 Volt system designs. Its wide operating range, low supply
current , and excellent accuracy provide a temperature switch
solution for a wide range of commercial and industrial applications.
■
■
■
■
Automotive
Disk Drives
Games
Appliances
Features
■
■
■
■
■
■
■
■
■
Low 1.6V operation
Low quiescent current
Push-pull and open-drain temperature switch outputs
Wide trip point range of 0°C to 150°C
Very linear analog VTEMP temperature sensor output
VTEMP output short-circuit protected
Accurate over −50°C to 150°C temperature range
2.2 mm by 2.5 mm (typ) LLP-6 package
Excellent power supply noise rejection
Key Specifications
■ Supply Voltage
■ Supply Current
■ Accuracy, Trip Point
Cell phones
Wireless Transceivers
Digital Cameras
Personal Digital Assistants (PDA's)
Battery Management
■ Accuracy, VTEMP
■ VTEMP Output Drive
■ Operating Temperature
■ Hysteresis Temperature
Connection Diagram
8 μA (typ)
0°C to 150°C
±2.2°C
0°C to 150°C
0°C to 120°C
−50°C to 0°C
±2.3°C
±2.2°C
±1.7°C
Temperature
Applications
■
■
■
■
■
1.6V to 5.5V
±100 μA
−50°C to 150°C
4.5°C to 5.5°C
Typical Transfer Characteristic
LLP-6
VTEMP Analog Voltage vs Die Temperature
20204701
Top View
See NS Package Number SDB06A
20204724
© 2007 National Semiconductor Corporation
202047
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LM26LV 1.6 V, LLP-6 Factory Preset Temperature Switch and Temperature Sensor
July 2007
LM26LV
Block Diagram
20204703
Pin Descriptions
Pin
No.
1
5
3
6
Name
TRIP
TEST
OVERTEMP
OVERTEMP
VTEMP
Type
Equivalent Circuit
Description
Digital
Input
TRIP TEST pin. Active High input.
If TRIP TEST = 0 (Default) then:
VTEMP = VTS, Temperature Sensor Output Voltage
If TRIP TEST = 1 then:
OVERTEMP and OVERTEMP outputs are asserted and
VTEMP = VTRIP, Temperature Trip Voltage.
This pin may be left open if not used.
Digital
Output
Over Temperature Switch output
Active High, Push-Pull
Asserted when the measured temperature exceeds the Trip
Point Temperature or if TRIP TEST = 1
This pin may be left open if not used.
Digital
Output
Over Temperature Switch output
Active Low, Open-drain (See Section 2.1 regarding required pullup resistor.)
Asserted when the measured temperature exceeds the Trip
Point Temperature or if TRIP TEST = 1
This pin may be left open if not used.
Analog
Output
VTEMP Analog Voltage Output
If TRIP TEST = 0 then
VTEMP = VTS, Temperature Sensor Output Voltage
If TRIP TEST = 1 then
VTEMP = VTRIP, Temperature Trip Voltage
This pin may be left open if not used.
4
VDD
Power
Positive Supply Voltage
2
GND
Ground
Power Supply Ground
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2
LM26LV
Typical Application
20204702
Ordering Information
Order Number
Temperature Trip
Point, °C
NS Package
Number
Top Mark
Transport Media
LM26LVCISD-XPE
105°C
SDB06A
XPE
1000 Units on Tape and Reel
LM26LVCISDX-XPE
105°C
SDB06A
XPE
4500 Units on Tape and Reel
3
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LM26LV
Machine Model
250V
Charged Device Model
1000V
Soldering process must comply with National's
Reflow Temperature Profile specifications. Refer to
www.national.com/packaging. (Note 4)
Absolute Maximum Ratings (Note 1)
Supply Voltage
Voltage at OVERTEMP pin
Voltage at OVERTEMP and
VTEMP pins
TRIP TEST Input Voltage
Output Current, any output pin
Input Current at any pin (Note 2)
Storage Temperature
Maximum Junction Temperature
TJ(MAX)
ESD Susceptibility (Note 3) :
Human Body Model
−0.2V to +6.0V
−0.2V to +6.0V
−0.2V to (VDD + 0.5V)
−0.2V to (VDD + 0.5V)
±7 mA
5 mA
−65°C to +150°C
Operating Ratings
(Note 1)
Specified Temperature Range:
TMIN ≤ TA ≤ TMAX
−50°C ≤ TA ≤ +150°C
LM26LV
Supply Voltage Range (VDD)
+1.6 V to +5.5 V
Thermal Resistance (θJA) (Note 5)
LLP-6 (Package SDB06A)
+155°C
152 °C/W
2500V
Accuracy Characteristics
Trip Point Accuracy
Parameter
Trip Point Accuracy (Note 8)
Conditions
VDD = 5.0 V
0 − 150°C
Limits
(Note 7)
Units
(Limit)
±2.2
°C (max)
VTEMP Analog Temperature Sensor Output Accuracy
There are four gains corresponding to each of the four Temperature Trip Point Ranges. Gain 1 is the sensor gain used for Temperature Trip Point 0 - 69°C. Likewise Gain 2 is for Trip Points 70 - 109 °C; Gain 3 for 110 - 129 °C; and Gain 4 for 130 - 150 °C.
These limits do not include DC load regulation. These stated accuracy limits are with reference to the values in the LM26LV
Conversion Table.
Parameter
Gain 1: for Trip Point
Range 0 - 69°C
Gain 2: for Trip Point
Range 70 - 109°C
VTEMP Temperature
Accuracy
(Note 8)
Gain 3: for Trip Point
Range 110 - 129°C
Gain 4: for Trip Point
Range 130 - 150°C
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Limits
(Note 7)
Conditions
TA = 20°C to 40°C
VDD = 1.6 to 5.5 V
±1.8
TA = 0°C to 70°C
VDD = 1.6 to 5.5 V
±2.0
TA = 0°C to 90°C
VDD = 1.6 to 5.5 V
±2.1
TA = 0°C to 120°C
VDD = 1.6 to 5.5 V
±2.2
TA = 0°C to 150°C
VDD = 1.6 to 5.5 V
±2.3
TA = −50°C to 0°C
VDD = 1.7 to 5.5 V
±1.7
TA = 20°C to 40°C
VDD = 1.8 to 5.5 V
±1.8
TA = 0°C to 70°C
VDD = 1.9 to 5.5 V
±2.0
TA = 0°C to 90°C
VDD = 1.9 to 5.5 V
±2.1
TA = 0°C to 120°C
VDD = 1.9 to 5.5 V
±2.2
TA = 0°C to 150°C
VDD = 1.9 to 5.5 V
±2.3
TA = −50°C to 0°C
VDD = 2.3 to 5.5 V
±1.7
TA = 20°C to 40°C
VDD = 2.3 to 5.5 V
±1.8
TA = 0°C to 70°C
VDD = 2.5 to 5.5 V
±2.0
TA = 0°C to 90°C
VDD = 2.5 to 5.5 V
±2.1
TA = 0°C to 120°C
VDD = 2.5 to 5.5 V
±2.2
TA = 0°C to 150°C
VDD = 2.5 to 5.5 V
±2.3
TA = −50°C to 0°C
VDD = 3.0 to 5.5 V
±1.7
TA = 20°C to 40°C
VDD = 2.7 to 5.5 V
±1.8
TA = 0°C to 70°C
VDD = 3.0 to 5.5 V
±2.0
TA = 0°C to 90°C
VDD = 3.0 to 5.5 V
±2.1
TA = 0°C to 120°C
VDD = 3.0 to 5.5 V
±2.2
TA = 0°C to 150°C
VDD = 3.0 to 5.5 V
±2.3
TA = −50°C to 0°C
VDD = 3.6 to 5.5 V
±1.7
4
Units
(Limit)
°C (max)
°C (max)
°C (max)
°C (max)
Unless otherwise noted, these specifications apply for +VDD = +1.6V to +5.5V. Boldface limits apply for TA = TJ = TMIN to
TMAX ; all other limits TA = TJ = 25°C.
Symbol
Parameter
Conditions
Typical
(Note 6)
Limits
(Note 7)
Units
(Limit)
Quiescent Power Supply
Current
8
16
μA (max)
Hysteresis
5
5.5
°C (max)
4.5
°C (Min)
VDD − 0.2V
V (min)
VDD − 0.45V
V (min)
GENERAL SPECIFICATIONS
IS
OVERTEMP DIGITAL OUTPUT
VOH
Logic "1" Output Voltage
ACTIVE HIGH, PUSH-PULL
VDD ≥ 1.6V
Source ≤ 340 μA
VDD ≥ 2.0V
Source ≤ 498 μA
VDD ≥ 3.3V
Source ≤ 780 μA
VDD ≥ 1.6V
Source ≤ 600 μA
VDD ≥ 2.0V
Source ≤ 980 μA
VDD ≥ 3.3V
Source ≤ 1.6 mA
BOTH OVERTEMP and OVERTEMP DIGITAL OUTPUTS
VOL
Logic "0" Output Voltage
OVERTEMP DIGITAL OUTPUT
IOH
Logic "1" Output Leakage
Current (Note 12)
VDD ≥ 1.6V
Sink ≤ 385 μA
VDD ≥ 2.0V
Sink ≤ 500 μA
VDD ≥ 3.3V
Sink ≤ 730 μA
VDD ≥ 1.6V
Sink ≤ 690 μA
VDD ≥ 2.0V
Sink ≤ 1.05 mA
VDD ≥ 3.3V
Sink ≤ 1.62 mA
0.2
V (max)
0.45
ACTIVE LOW, OPEN DRAIN
TA = 30 °C
0.001
TA = 150 °C
0.025
1
μA (max)
VTEMP ANALOG TEMPERATURE SENSOR OUTPUT
Gain 1: If Trip Point = 0 - 69°C
VTEMP Sensor Gain
VTEMP Load Regulation
(Note 10)
CL
−5.1
mV/°C
Gain 2: If Trip Point = 70 - 109°C
−7.7
mV/°C
Gain 3: If Trip Point = 110 - 129°C
−10.3
mV/°C
Gain 4: If Trip Point = 130 - 150°C
−12.8
mV/°C
Source ≤ 90 μA, (VDD − VTEMP) ≥ 200 mV
−0.1
−1
mV (max)
Sink ≤ 100 μA, VTEMP ≥ 260 mV
0.1
1
mV (max)
Source or Sink = 100 μA
VDD Supply- to-VTEMP
DC Line Regulation
(Note 13)
VDD = +1.6V to +5.5V
VTEMP Output Load
Capacitance
Without series resistor. See Section 4.2
1
Ohm
0.29
mV
74
μV/V
−82
dB
1100
pF (max)
TRIP TEST DIGITAL INPUT
VIH
Logic "1" Threshold Voltage
VDD− 0.5
V (min)
VIL
Logic "0" Threshold Voltage
0.5
V (max)
IIH
Logic "1" Input Current
1.5
2.5
μA (max)
IIL
Logic "0" Input Current
(Note 12)
0.001
1
μA (max)
5
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LM26LV
Electrical Characteristics
LM26LV
Symbol
Parameter
Conditions
Typical
(Note 6)
Limits
(Note 7)
Units
(Limit)
Time from Power On to Digital
Output Enabled. See
definition below.
(Note 11).
1.1
10
ms (max)
Time from Power On to
Analog Temperature Valid.
See definition below.
(Note 11)
0.9
10
ms (max)
TIMING
tEN
tVTEMP
Definitions of tEN and tVTEMP
20204751
20204750
Notes
Note 1: 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 guarantee specific performance limits. For guaranteed specifications and test conditions, see the Electrical Characteristics. The guaranteed
specifications apply only for the test conditions listed. Some performance characteristics may degrade when the device is not operated under the listed test
conditions.
Note 2: When the input voltage (VI) at any pin exceeds power supplies (VI < GND or VI > VDD), the current at that pin should be limited to 5 mA.
Note 3: The Human Body Model (HBM) is a 100 pF capacitor charged to the specified voltage then discharged through a 1.5 kΩ resistor into each pin. The
Machine Model (MM) is a 200 pF capacitor charged to the specified voltage then discharged directly into each pin. The Charged Device Model (CDM) is a specified
circuit characterizing an ESD event that occurs when a device acquires charge through some triboelectric (frictional) or electrostatic induction processes and then
abruptly touches a grounded object or surface.
Note 4: Reflow temperature profiles are different for lead-free and non-lead-free packages.
Note 5: The junction to ambient temperature resistance (θJA) is specified without a heat sink in still air.
Note 6: Typicals are at TJ = TA = 25°C and represent most likely parametric norm.
Note 7: Limits are guaranteed to National's AOQL (Average Outgoing Quality Level).
Note 8: Accuracy is defined as the error between the measured and reference output voltages, tabulated in the Conversion 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.
Note 9: Changes in output due to self heating can be computed by multiplying the internal dissipation by the temperature resistance.
Note 10: Source currents are flowing out of the LM26LV. Sink currents are flowing into the LM26LV.
Note 11: Guaranteed by design.
Note 12: The 1 µA limit is based on a testing limitation and does not reflect the actual performance of the part. Expect to see a doubling of the current for every
15°C increase in temperature. For example, the 1 nA typical current at 25°C would increase to 16 nA at 85°C.
Note 13: Line regulation (DC) is calculated by subtracting the output voltage at the highest supply voltage from the output voltage at the lowest supply voltage.
The typical DC line regulation specification does not include the output voltage shift discussed in Section 4.3.
Note 14: The curves shown represent typical performance under worst-case conditions. Performance improves with larger overhead (VDD − VTEMP), larger VDD,
and lower temperatures.
Note 15: The curves shown represent typical performance under worst-case conditions. Performance improves with larger VTEMP, larger VDD and lower
temperatures.
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6
VTEMP Output Temperature Error vs. Temperature
Minimum Operating Temperature vs. Supply Voltage
20204706
20204707
Supply Current vs. Temperature
Supply Current vs. Supply Voltage
20204704
20204705
Load Regulation, 100 mV Overhead
T = 80°C Sourcing Current (Note 14)
Load Regulation, 200 mV Overhead
T = 80°C Sourcing Current (Note 14)
20204740
20204746
7
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LM26LV
Typical Performance Characteristics
LM26LV
Load Regulation, 400 mV Overhead
T = 80°C Sourcing Current (Note 14)
Load Regulation, 1.72V Overhead
T = 150°C, VDD = 2.4V
Sourcing Current (Note 14)
20204747
20204748
Load Regulation, VDD = 1.6V
Sinking Current (Note 15)
Load Regulation, VDD = 1.8V
Sinking Current (Note 15)
20204741
20204744
Load Regulation, VDD = 2.4V
Sinking Current (Note 15)
Change in VTEMP vs. Overhead Voltage
20204742
20204745
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8
LM26LV
VTEMP Supply-Noise Gain vs. Frequency
VTEMP vs. Supply Voltage
Gain 1: For Trip Points
0 - 69°C
20204743
20204734
VTEMP vs. Supply Voltage
Gain 2: For Trip Points
70 - 109°C
VTEMP vs. Supply Voltage
Gain 3: For Trip Points
110 - 129°C
20204735
20204736
VTEMP vs. Supply Voltage
Gain 4: For Trip Points
130 - 150°C
20204737
9
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LM26LV
1.0 LM26LV VTEMP vs Die
Temperature Conversion Table
−22
1172
1757
2343
2929
−21
1167
1750
2333
2916
−20
1162
1742
2323
2903
−19
1157
1735
2313
2891
−18
1152
1727
2303
2878
−17
1147
1720
2293
2866
−16
1142
1712
2283
2853
−15
1137
1705
2272
2841
−14
1132
1697
2262
2828
−13
1127
1690
2252
2815
−12
1122
1682
2242
2803
−11
1116
1674
2232
2790
−10
1111
1667
2222
2777
−9
1106
1659
2212
2765
−8
1101
1652
2202
2752
−7
1096
1644
2192
2740
−6
1091
1637
2182
2727
−5
1086
1629
2171
2714
−4
1081
1621
2161
2702
−3
1076
1614
2151
2689
−2
1071
1606
2141
2676
−1
1066
1599
2131
2664
0
1061
1591
2121
2651
3278
1
1056
1583
2111
2638
3266
2
1051
1576
2101
2626
3253
3
1046
1568
2090
2613
1041
1561
2080
2600
The LM26LV has one out of four possible factory-set gains,
Gain 1 through Gain 4, depending on the range of the Temperature Trip Point. The VTEMP temperature sensor voltage,
in millivolts, at each discrete die temperature over the complete operating temperature range, and for each of the four
Temperature Trip Point ranges, is shown in the Conversion
Table below. This table is the reference from which the
LM26LV accuracy specifications (listed in the Electrical Characteristics section) are determined. This table can be used,
for example, in a host processor look-up table. See Section
1.1.1 for the parabolic equation used in the Conversion Table.
VTEMP Temperature Sensor Output Voltage vs Die
Temperature Conversion Table
The VTEMP temperature sensor output voltage, in mV, vs Die
Temperature, in °C, for each of the four gains corresponding
to each of the four Temperature Trip Point Ranges. Gain 1 is
the sensor gain used for Temperature Trip Point 0 - 69°C.
Likewise Gain 2 is for Trip Points 70 - 109 °C; Gain 3 for 110
- 129 °C; and Gain 4 for 130 - 150 °C. VDD = 5.0V. The values
in bold font are for the Trip Point range.
VTEMP, Analog Output Voltage, mV
Die
Temp.,
°C
−50
−49
−48
Gain 1:
for
TTRIP =
0-69°C
1312
1307
1302
Gain 2:
Gain 3:
Gain 4:
for
for
for
TTRIP =
TTRIP =
TTRIP =
70-109°C 110-129°C 130-150°C
1967
1960
1952
2623
2613
2603
−47
1297
1945
2593
3241
4
−46
1292
1937
2583
3229
5
1035
1553
2070
2587
3216
6
1030
1545
2060
2575
1025
1538
2050
2562
−45
1287
1930
2573
−44
1282
1922
2563
3204
7
−43
1277
1915
2553
3191
8
1020
1530
2040
2549
3179
9
1015
1522
2029
2537
1010
1515
2019
2524
−42
1272
1908
2543
−41
1267
1900
2533
3166
10
−40
1262
1893
2523
3154
11
1005
1507
2009
2511
3141
12
1000
1499
1999
2498
995
1492
1989
2486
−39
1257
1885
2513
−38
1252
1878
2503
3129
13
−37
1247
1870
2493
3116
14
990
1484
1978
2473
3104
15
985
1477
1968
2460
3091
16
980
1469
1958
2447
974
1461
1948
2435
−36
−35
1242
1237
1863
1855
2483
2473
−34
1232
1848
2463
3079
17
−33
1227
1840
2453
3066
18
969
1454
1938
2422
3054
19
964
1446
1927
2409
959
1438
1917
2396
−32
1222
1833
2443
−31
1217
1825
2433
3041
20
−30
1212
1818
2423
3029
21
954
1431
1907
2383
3016
22
949
1423
1897
2371
944
1415
1886
2358
−29
1207
1810
2413
−28
1202
1803
2403
3004
23
−27
1197
1795
2393
2991
24
939
1407
1876
2345
2979
25
934
1400
1866
2332
2966
26
928
1392
1856
2319
923
1384
1845
2307
918
1377
1835
2294
−26
−25
1192
1187
1788
1780
2383
2373
−24
1182
1773
2363
2954
27
−23
1177
1765
2353
2941
28
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10
913
1369
1825
2281
80
649
972
1296
1620
30
908
1361
1815
2268
81
643
964
1285
1607
31
903
1354
1804
2255
82
638
957
1275
1593
32
898
1346
1794
2242
83
633
949
1264
1580
33
892
1338
1784
2230
84
628
941
1254
1567
34
887
1331
1774
2217
85
622
933
1243
1554
35
882
1323
1763
2204
86
617
925
1233
1541
36
877
1315
1753
2191
87
612
917
1222
1528
37
872
1307
1743
2178
88
607
909
1212
1515
38
867
1300
1732
2165
89
601
901
1201
1501
39
862
1292
1722
2152
90
596
894
1191
1488
40
856
1284
1712
2139
91
591
886
1180
1475
41
851
1276
1701
2127
92
586
878
1170
1462
42
846
1269
1691
2114
93
580
870
1159
1449
43
841
1261
1681
2101
94
575
862
1149
1436
44
836
1253
1670
2088
95
570
854
1138
1422
45
831
1245
1660
2075
96
564
846
1128
1409
46
825
1238
1650
2062
97
559
838
1117
1396
47
820
1230
1639
2049
98
554
830
1106
1383
48
815
1222
1629
2036
99
549
822
1096
1370
49
810
1214
1619
2023
100
543
814
1085
1357
50
805
1207
1608
2010
101
538
807
1075
1343
51
800
1199
1598
1997
102
533
799
1064
1330
52
794
1191
1588
1984
103
527
791
1054
1317
53
789
1183
1577
1971
104
522
783
1043
1304
54
784
1176
1567
1958
105
517
775
1032
1290
55
779
1168
1557
1946
106
512
767
1022
1277
56
774
1160
1546
1933
107
506
759
1011
1264
57
769
1152
1536
1920
108
501
751
1001
1251
58
763
1144
1525
1907
109
496
743
990
1237
59
758
1137
1515
1894
110
490
735
979
1224
60
753
1129
1505
1881
111
485
727
969
1211
61
748
1121
1494
1868
112
480
719
958
1198
62
743
1113
1484
1855
113
474
711
948
1184
63
737
1105
1473
1842
114
469
703
937
1171
64
732
1098
1463
1829
115
464
695
926
1158
65
727
1090
1453
1816
116
459
687
916
1145
66
722
1082
1442
1803
117
453
679
905
1131
67
717
1074
1432
1790
118
448
671
894
1118
68
711
1066
1421
1776
119
443
663
884
1105
69
706
1059
1411
1763
120
437
655
873
1091
70
701
1051
1400
1750
121
432
647
862
1078
71
696
1043
1390
1737
122
427
639
852
1065
72
690
1035
1380
1724
123
421
631
841
1051
73
685
1027
1369
1711
124
416
623
831
1038
74
680
1019
1359
1698
125
411
615
820
1025
75
675
1012
1348
1685
126
405
607
809
1011
76
670
1004
1338
1672
127
400
599
798
998
77
664
996
1327
1659
128
395
591
788
985
78
659
988
1317
1646
129
389
583
777
971
79
654
980
1306
1633
130
384
575
766
958
11
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LM26LV
29
LM26LV
linear formula below can be used. Using this formula, with the
offset and slope in the following table, the best-fit VTEMP vs
Die Temperature performance can be calculated with an approximation error less than 18 mV.
131
379
567
756
945
132
373
559
745
931
133
368
551
734
918
134
362
543
724
904
135
357
535
713
891
136
352
527
702
878
137
346
519
691
864
Sensor Gain
VTEMP(30°C), mV
Slope, mV/°C
1059.9
-5.1751
138
341
511
681
851
GAIN 1
139
336
503
670
837
GAIN 2
1589.9
-7.765
140
330
495
659
824
GAIN 3
2119.0
-10.355
141
325
487
649
811
GAIN 4
2648.6
-12.944
142
320
479
638
797
143
314
471
627
784
144
309
463
616
770
145
303
455
606
757
146
298
447
595
743
147
293
438
584
730
148
287
430
573
716
149
282
422
562
703
150
277
414
552
690
1.1.3 First-Order Approximation (Linear) over Small
Temperature Range
For a linear approximation, a line can easily be calculated
over the desired temperature range from the Conversion Table using the two-point equation:
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 Gain 4, over a temperature range of 20°C to 50°C, we
would proceed as follows:
1.1 VTEMP vs DIE TEMPERATURE APPROXIMATIONS
The LM26LV's VTEMP analog temperature output is very linear. The Conversion Table above and the equation in Section
1.1.1 represent the most accurate typical performance of the
VTEMP voltage output vs Temperature.
1.1.1 The Second-Order Equation (Parabolic)
The data from the Conversion Table, or the equation below,
when plotted, has an umbrella-shaped parabolic curve.
Sensor Gain VTEMP(30°C), mV Slope, mV/°C
Parabola,
mV/°C2
GAIN 1
907.87
-5.1321
-0.001076
GAIN 2
1361.35
-7.7011
-0.001596
GAIN 3
1814.62
-10.2703
-0.002117
GAIN 4
2268.14
-12.8384
-0.002639
Using this method of linear approximation, the transfer function can be approximated for one or more temperature ranges
of interest.
1.1.2 The First-Order Approximation (Linear)
For a quicker approximation, although less accurate than the
second-order, over the full operating temperature range the
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12
The OVERTEMP Active High, Push-Pull Output and the
OVERTEMP Active Low, Open-Drain Output both assert at
the same time whenever the Die Temperature reaches the
factory preset Temperature Trip Point. They also assert simultaneously whenever the TRIP TEST pin is set high. Both
outputs de-assert when the die temperature goes below the
Temperature Trip Point - Hysteresis. These two types of digital outputs enable the user the flexibility to choose the type
of output that is most suitable for his design.
Either the OVERTEMP or the OVERTEMP Digital Output pins
can be left open if not used.
2.2 NOISE IMMUNITY
The LM26LV is virtually immune from false triggers on the
OVERTEMP and OVERTEMP digital outputs due to noise on
the power supply. Test have been conducted showing that,
with the die temperature within 0.5°C of the temperature trip
point, and the severe test of a 3 Vpp square wave "noise"
signal injected on the VDD line, over the VDD range of 2V to
5V, there were no false triggers.
2.1 OVERTEMP OPEN-DRAIN DIGITAL OUTPUT
The OVERTEMP Active Low, Open-Drain Digital Output, if
used, requires a pull-up resistor between this pin and VDD.
The following section shows how to determine the pull-up resistor value.
Determining the Pull-up Resistor Value
3.0 TRIP TEST Digital Input
The TRIP TEST pin simply provides a means to test the
OVERTEMP and OVERTEMP digital outputs electronically
by causing them to assert, at any operating temperature, as
a result of forcing the TRIP TEST pin high.
When the TRIP TEST pin is pulled high the VTEMP pin will be
at the VTRIP voltage.
If not used, the TRIP TEST pin may either be left open or
grounded.
4.0 VTEMP Analog Temperature
Sensor Output
The VTEMP push-pull output provides the ability to sink and
source significant current. This is beneficial when, for example, driving dynamic loads like an input stage on an analogto-digital converter (ADC). In these applications the source
current is required to quickly charge the input capacitor of the
ADC. See the Applications Circuits section for more discussion of this topic. The LM26LV is ideal for this and other
applications which require strong source or sink current.
20204752
The Pull-up resistor value is calculated at the condition of
maximum total current, iT, through the resistor. The total current is:
where,
iT
iL
VOUT
VDD(Max)
4.1 NOISE CONSIDERATIONS
The LM26LV's supply-noise gain (the ratio of the AC signal
on VTEMP to the AC signal on VDD) was measured during
bench tests. It's typical attenuation is shown in the Typical
Performance Characteristics section. A load capacitor on the
output can help to filter noise.
For operation in very noisy environments, some bypass capacitance should be present on the supply within approximately 2 inches of the LM26LV.
iT is the maximum total current through the Pull-up
Resistor at VOL.
iL is the load current, which is very low for typical
digital inputs.
VOUT is the Voltage at the OVERTEMP pin. Use
VOL for calculating the Pull-up resistor.
VDD(Max) is the maximum power supply voltage to be
used in the customer's system.
The pull-up resistor maximum value can be found by using
the following formula:
4.2 CAPACITIVE LOADS
The VTEMP Output 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 VTEMP can drive a capacitive load less than or equal to
1100 pF as shown in Figure 1. For capacitive loads greater
than 1100 pF, a series resistor is required on the output, as
shown in Figure 2, to maintain stable conditions.
EXAMPLE CALCULATION
Suppose we have, for our example, a V DD of 3.3 V ± 0.3V, a
CMOS digital input as a load, a VOL of 0.2 V.
13
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LM26LV
(1) We see that for VOL of 0.2 V the electrical specification for
OVERTEMP shows a maximim isink of 385 µA.
(2) Let iL= 1 µA, then iT is about 386 µA max. If we select
35 µA as the current limit then iT for the calculation becomes
35 µA
(3) We notice that VDD(Max) is 3.3V + 0.3V = 3.6V and then
calculate the pull-up resistor as
RPull-up = (3.6 − 0.2)/35 µA = 97k
(4) Based on this calculated value, we select the closest resistor value in the tolerance family we are using.
In our example, if we are using 5% resistor values, then the
next closest value is 100 kΩ.
2.0 OVERTEMP and OVERTEMP
Digital Outputs
LM26LV
To ensure good temperature conductivity, the backside of the
LM26LV die is directly attached to the GND pin (Pin 2). The
temperatures of the lands and traces to the other leads of the
LM26LV will also affect the temperature reading.
Alternatively, the LM26LV can be mounted inside a sealedend metal tube, and can then be dipped into a bath or screwed
into a threaded hole in a tank. As with any IC, the LM26LV
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 VTEMP output to ground or VDD, the VTEMP output from the
LM26LV 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 LM26LV's die temperature is
20204715
FIGURE 1. LM26LV No Decoupling Required for
Capacitive Loads Less than 1100 pF.
20204733
CLOAD
RS
1.1 nF to 99 nF
3 kΩ
100 nF to 999 nF
1.5 kΩ
1 μF
800 Ω
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 4, VTEMP = 2231 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 LM26LV's
junction temperature is the actual temperature being measured, care should be taken to minimize the load current that
the VTEMP output is required to drive. If The OVERTEMP output is used with a 100 k pull-up resistor, and this output is
asserted (low), then for this example the additional contribution is [(152° C/W)x(5V)2/100k] = 0.038°C for a total selfheating error of 0.059°C. Figure 3 shows the thermal
resistance of the LM26LV.
FIGURE 2. LM26LV with series resistor for capacitive
loading greater than 1100 pF.
4.3 VOLTAGE SHIFT
The LM26LV 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 VTEMP. The shift typically occurs when
VDD − VTEMP = 1.0V.
This slight shift (a few millivolts) takes place over a wide
change (approximately 200 mV) in VDD or VTEMP. Since the
shift takes place over a wide temperature change of 5°C to
20°C, VTEMP is always monotonic. The accuracy specifications in the Electrical Characteristics table already includes
this possible shift.
NS Package
Number
Thermal
Resistance (θJA)
LM26LVCISD
SDB06A
152° C/W
FIGURE 3. LM26LV Thermal Resistance
5.0 Mounting and Temperature
Conductivity
The LM26LV can be applied easily in the same way as other
integrated-circuit temperature sensors. It can be glued or cemented to a surface.
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Device Number
14
LM26LV
6.0 Applications Circuits
20204761
FIGURE 4. Temperature Switch Using Push-Pull Output
20204762
FIGURE 5. Temperature Switch Using Open-Drain Output
20204728
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 LM26LV 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 6. Suggested Connection to a Sampling Analog-to-Digital Converter Input Stage
15
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LM26LV
20204718
FIGURE 7. Celsius Temperature Switch
20204760
FIGURE 8. TRIP TEST Digital Output Test Circuit
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16
LM26LV
Physical Dimensions inches (millimeters) unless otherwise noted
6-Lead LLP-6 Package
Order Number LM26LVCISD, LM26LVCISDX
NS Package Number SDB06A
17
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LM26LV 1.6 V, LLP-6 Factory Preset Temperature Switch and Temperature Sensor
Notes
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