Datasheet LM26LV, LM26LVCISD-XPE Datasheet (NSC)

Page 1

July 2007

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 (T

TRIP

) 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 (T

HYST

) keeps the output sta-

ble in an environment of temperature instability. In normal operation the LM26LV temperature switch outputs

assert when the die temperature exceeds T

TRIP

. The temperature switch outputs will reset when the temperature falls below a temperature equal to (T

TRIP

− T

HYST

). 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, V

TEMP

, delivers an analog output voltage

which is inversely proportional to the measured temperature. Driving the TRIP TEST input high: (1) causes the digital out-

puts to be asserted for in-situ verification and, (2) causes the threshold voltage to appear at the V

TEMP

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.

Applications

■

Cell phones

■

Wireless Transceivers

■

Digital Cameras

■

Personal Digital Assistants (PDA's)

■

Battery Management

■

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 V

TEMP

temperature sensor output

■

TEMP

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

1.6V to 5.5V

■ Supply Current

8 μA (typ)

■ Accuracy, Trip Point

Temperature

0°C to 150°C ±2.2°C

■ Accuracy, V

TEMP

0°C to 150°C ±2.3°C

0°C to 120°C ±2.2°C

−50°C to 0°C ±1.7°C

■ V

TEMP

Output Drive

±100 μA

■ Operating Temperature −50°C to 150°C

■ Hysteresis Temperature 4.5°C to 5.5°C

Connection Diagram

LLP-6

20204701

Top View

See NS Package Number SDB06A

Typical Transfer Characteristic

TEMP

Analog Voltage vs Die Temperature

20204724

LM26LV 1.6 V, LLP-6 Factory Preset Temperature Switch and Temperature Sensor

Page 2

Block Diagram

20204703

Pin Descriptions

Pin No.

Name Type Equivalent Circuit Description

TRIP

TEST

Digital

Input

TRIP TEST pin. Active High input. If TRIP TEST = 0 (Default) then: V

TEMP

= VTS, Temperature Sensor Output Voltage If TRIP TEST = 1 then: OVERTEMP and OVERTEMP outputs are asserted and V

TEMP

= V

TRIP

, Temperature Trip Voltage.

This pin may be left open if not used.

5 OVERTEMP

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.

3 OVERTEMP

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.

TEMP

Analog Output

TEMP

Analog Voltage Output If TRIP TEST = 0 then V

TEMP

= VTS, Temperature Sensor Output Voltage If TRIP TEST = 1 then V

TEMP

= V

TRIP

, Temperature Trip Voltage

This pin may be left open if not used.

Power

Positive Supply Voltage

2 GND Ground Power Supply Ground

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LM26LV

Page 3

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

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LM26LV

Page 4

Absolute Maximum Ratings (Note 1)

Supply Voltage −0.2V to +6.0V Voltage at OVERTEMP pin −0.2V to +6.0V Voltage at OVERTEMP and

TEMP

pins −0.2V to (VDD + 0.5V)

TRIP TEST Input Voltage −0.2V to (VDD + 0.5V)

Output Current, any output pin ±7 mA Input Current at any pin (Note 2) 5 mA Storage Temperature −65°C to +150°C Maximum Junction Temperature

J(MAX)

+155°C ESD Susceptibility (Note 3) : Human Body Model 2500V

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)

Operating Ratings (Note 1)

Specified Temperature Range:

MIN

≤ TA ≤ T

MAX

LM26LV

−50°C ≤ TA ≤ +150°C

Supply Voltage Range (VDD)

+1.6 V to +5.5 V

Thermal Resistance (θJA) (Note 5) LLP-6 (Package SDB06A) 152 °C/W

Accuracy Characteristics

Trip Point Accuracy

Parameter Conditions

Limits

(Note 7)

Units

(Limit)

Trip Point Accuracy (Note 8) 0 − 150°C

VDD = 5.0 V

±2.2 °C (max)

TEMP

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 Conditions

Limits

(Note 7)

Units

(Limit)

TEMP

Temperature

Accuracy

(Note 8)

Gain 1: for Trip Point

Range 0 - 69°C

TA = 20°C to 40°C VDD = 1.6 to 5.5 V

±1.8

°C (max)

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

Gain 2: for Trip Point

Range 70 - 109°C

TA = 20°C to 40°C VDD = 1.8 to 5.5 V

±1.8

°C (max)

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

Gain 3: for Trip Point

Range 110 - 129°C

TA = 20°C to 40°C VDD = 2.3 to 5.5 V

±1.8

°C (max)

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

Gain 4: for Trip Point

Range 130 - 150°C

TA = 20°C to 40°C VDD = 2.7 to 5.5 V

±1.8

°C (max)

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

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LM26LV

Page 5

Electrical Characteristics

Unless otherwise noted, these specifications apply for +VDD = +1.6V to +5.5V. Boldface limits apply for TA = TJ = T

MIN

MAX

; all other limits TA = TJ = 25°C.

Symbol Parameter Conditions Typical

(Note 6)

Limits

(Note 7)

Units

(Limit)

GENERAL SPECIFICATIONS

Quiescent Power Supply

Current

8 16

μA (max)

Hysteresis

5.5 °C (max)

4.5 °C (Min)

OVERTEMP DIGITAL OUTPUT ACTIVE HIGH, PUSH-PULL

Logic "1" Output Voltage

VDD ≥ 1.6V Source ≤ 340 μA

VDD − 0.2V

V (min)

VDD ≥ 2.0V Source ≤ 498 μA

VDD ≥ 3.3V Source ≤ 780 μA

VDD ≥ 1.6V Source ≤ 600 μA

VDD − 0.45V

V (min)

VDD ≥ 2.0V Source ≤ 980 μA

VDD ≥ 3.3V Source ≤ 1.6 mA

BOTH OVERTEMP and OVERTEMP DIGITAL OUTPUTS

Logic "0" Output Voltage

VDD ≥ 1.6V Sink ≤ 385 μA

0.2

V (max)

VDD ≥ 2.0V Sink ≤ 500 μA

VDD ≥ 3.3V Sink ≤ 730 μA

VDD ≥ 1.6V Sink ≤ 690 μA

0.45

VDD ≥ 2.0V Sink ≤ 1.05 mA

VDD ≥ 3.3V Sink ≤ 1.62 mA

OVERTEMP DIGITAL OUTPUT ACTIVE LOW, OPEN DRAIN

Logic "1" Output Leakage

Current (Note 12)

TA = 30 °C

0.001 1

μA (max)

TA = 150 °C

0.025

TEMP

ANALOG TEMPERATURE SENSOR OUTPUT

TEMP

Sensor Gain

Gain 1: If Trip Point = 0 - 69°C −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

TEMP

Load Regulation

(Note 10)

Source ≤ 90 μA, (VDD − V

TEMP

) ≥ 200 mV

−0.1 −1 mV (max)

Sink ≤ 100 μA, V

TEMP

≥ 260 mV

0.1 1 mV (max)

Source or Sink = 100 μA

1 Ohm

VDD Supply- to-V

TEMP

DC Line Regulation (Note 13)

VDD = +1.6V to +5.5V

0.29 mV

μV/V

−82 dB

TEMP

Output Load

Capacitance

Without series resistor. See Section 4.2 1100

pF (max)

TRIP TEST DIGITAL INPUT

Logic "1" Threshold Voltage

VDD− 0.5

V (min)

Logic "0" Threshold Voltage

0.5 V (max)

Logic "1" Input Current

1.5 2.5

μA (max)

Logic "0" Input Current (Note 12)

0.001 1

μA (max)

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LM26LV

Page 6

Symbol Parameter Conditions Typical

(Note 6)

Limits

(Note 7)

Units

(Limit)

TIMING

Time from Power On to Digital Output Enabled. See definition below. (Note 11).

1.1 10 ms (max)

TEMP

Time from Power On to Analog Temperature Valid. See definition below. (Note 11)

0.9 10 ms (max)

Definitions of tEN and t

TEMP

20204750

20204751

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 − V

TEMP

), larger VDD,

and lower temperatures.

Note 15: The curves shown represent typical performance under worst-case conditions. Performance improves with larger V

TEMP

, larger VDD and lower

temperatures.

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LM26LV

Page 7

Typical Performance Characteristics

TEMP

Output Temperature Error vs. Temperature

20204707

Minimum Operating Temperature vs. Supply Voltage

20204706

Supply Current vs. Temperature

20204704

Supply Current vs. Supply Voltage

20204705

Load Regulation, 100 mV Overhead

T = 80°C Sourcing Current (Note 14)

20204740

Load Regulation, 200 mV Overhead

T = 80°C Sourcing Current (Note 14)

20204746

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LM26LV

Page 8

Load Regulation, 400 mV Overhead

T = 80°C Sourcing Current (Note 14)

20204747

Load Regulation, 1.72V Overhead

T = 150°C, VDD = 2.4V

Sourcing Current (Note 14)

20204748

Load Regulation, VDD = 1.6V

Sinking Current (Note 15)

20204741

Load Regulation, VDD = 1.8V

Sinking Current (Note 15)

20204744

Load Regulation, VDD = 2.4V

Sinking Current (Note 15)

20204745

Change in V

TEMP

vs. Overhead Voltage

20204742

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LM26LV

Page 9

TEMP

Supply-Noise Gain vs. Frequency

20204743

TEMP

vs. Supply Voltage

Gain 1: For Trip Points

0 - 69°C

20204734

TEMP

vs. Supply Voltage

Gain 2: For Trip Points

70 - 109°C

20204735

TEMP

vs. Supply Voltage

Gain 3: For Trip Points

110 - 129°C

20204736

TEMP

vs. Supply Voltage

Gain 4: For Trip Points

130 - 150°C

20204737

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LM26LV

Page 10

1.0 LM26LV V

TEMP

vs Die

Temperature Conversion Table

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 V

TEMP

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.

TEMP

Temperature Sensor Output Voltage vs Die

Temperature Conversion Table

The V

TEMP

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.

Die

Temp.,

°C

TEMP

, Analog Output Voltage, mV

Gain 1:

for

TRIP

0-69°C

Gain 2:

for

TRIP

70-109°C

Gain 3:

for

TRIP

110-129°C

Gain 4:

for

TRIP

130-150°C

−50 1312 1967 2623 3278

−49 1307 1960 2613 3266

−48 1302 1952 2603 3253

−47 1297 1945 2593 3241

−46 1292 1937 2583 3229

−45 1287 1930 2573 3216

−44 1282 1922 2563 3204

−43 1277 1915 2553 3191

−42 1272 1908 2543 3179

−41 1267 1900 2533 3166

−40 1262 1893 2523 3154

−39 1257 1885 2513 3141

−38 1252 1878 2503 3129

−37 1247 1870 2493 3116

−36 1242 1863 2483 3104

−35 1237 1855 2473 3091

−34 1232 1848 2463 3079

−33 1227 1840 2453 3066

−32 1222 1833 2443 3054

−31 1217 1825 2433 3041

−30 1212 1818 2423 3029

−29 1207 1810 2413 3016

−28 1202 1803 2403 3004

−27 1197 1795 2393 2991

−26 1192 1788 2383 2979

−25 1187 1780 2373 2966

−24 1182 1773 2363 2954

−23 1177 1765 2353 2941

−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

1 1056 1583 2111 2638

2 1051 1576 2101 2626

3 1046 1568 2090 2613

4 1041 1561 2080 2600

5 1035 1553 2070 2587

6 1030 1545 2060 2575

7 1025 1538 2050 2562

8 1020 1530 2040 2549

9 1015 1522 2029 2537

10 1010 1515 2019 2524

11 1005 1507 2009 2511

12 1000 1499 1999 2498

13 995 1492 1989 2486

14 990 1484 1978 2473

15 985 1477 1968 2460

16 980 1469 1958 2447

17 974 1461 1948 2435

18 969 1454 1938 2422

19 964 1446 1927 2409

20 959 1438 1917 2396

21 954 1431 1907 2383

22 949 1423 1897 2371

23 944 1415 1886 2358

24 939 1407 1876 2345

25 934 1400 1866 2332

26 928 1392 1856 2319

27 923 1384 1845 2307

28 918 1377 1835 2294

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LM26LV

Page 11

29 913 1369 1825 2281

30 908 1361 1815 2268

31 903 1354 1804 2255

32 898 1346 1794 2242

33 892 1338 1784 2230

34 887 1331 1774 2217

35 882 1323 1763 2204

36 877 1315 1753 2191

37 872 1307 1743 2178

38 867 1300 1732 2165

39 862 1292 1722 2152

40 856 1284 1712 2139

41 851 1276 1701 2127

42 846 1269 1691 2114

43 841 1261 1681 2101

44 836 1253 1670 2088

45 831 1245 1660 2075

46 825 1238 1650 2062

47 820 1230 1639 2049

48 815 1222 1629 2036

49 810 1214 1619 2023

50 805 1207 1608 2010

51 800 1199 1598 1997

52 794 1191 1588 1984

53 789 1183 1577 1971

54 784 1176 1567 1958

55 779 1168 1557 1946

56 774 1160 1546 1933

57 769 1152 1536 1920

58 763 1144 1525 1907

59 758 1137 1515 1894

60 753 1129 1505 1881

61 748 1121 1494 1868

62 743 1113 1484 1855

63 737 1105 1473 1842

64 732 1098 1463 1829

65 727 1090 1453 1816

66 722 1082 1442 1803

67 717 1074 1432 1790

68 711 1066 1421 1776

69 706 1059 1411 1763

70 701 1051 1400 1750

71 696 1043 1390 1737

72 690 1035 1380 1724

73 685 1027 1369 1711

74 680 1019 1359 1698

75 675 1012 1348 1685

76 670 1004 1338 1672

77 664 996 1327 1659

78 659 988 1317 1646

79 654 980 1306 1633

80 649 972 1296 1620

81 643 964 1285 1607

82 638 957 1275 1593

83 633 949 1264 1580

84 628 941 1254 1567

85 622 933 1243 1554

86 617 925 1233 1541

87 612 917 1222 1528

88 607 909 1212 1515

89 601 901 1201 1501

90 596 894 1191 1488

91 591 886 1180 1475

92 586 878 1170 1462

93 580 870 1159 1449

94 575 862 1149 1436

95 570 854 1138 1422

96 564 846 1128 1409

97 559 838 1117 1396

98 554 830 1106 1383

99 549 822 1096 1370

100 543 814 1085 1357

101 538 807 1075 1343

102 533 799 1064 1330

103 527 791 1054 1317

104 522 783 1043 1304

105 517 775 1032 1290

106 512 767 1022 1277

107 506 759 1011 1264

108 501 751 1001 1251

109 496 743 990 1237

110 490 735 979 1224

111 485 727 969 1211

112 480 719 958 1198

113 474 711 948 1184

114 469 703 937 1171

115 464 695 926 1158

116 459 687 916 1145

117 453 679 905 1131

118 448 671 894 1118

119 443 663 884 1105

120 437 655 873 1091

121 432 647 862 1078

122 427 639 852 1065

123 421 631 841 1051

124 416 623 831 1038

125 411 615 820 1025

126 405 607 809 1011

127 400 599 798 998

128 395 591 788 985

129 389 583 777 971

130 384 575 766 958

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LM26LV

Page 12

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

138 341 511 681 851

139 336 503 670 837

140 330 495 659 824

141 325 487 649 811

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 V

TEMP

vs DIE TEMPERATURE APPROXIMATIONS

The LM26LV's V

TEMP

analog temperature output is very lin-

ear. The Conversion Table above and the equation in Section

1.1.1 represent the most accurate typical performance of the V

TEMP

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

TEMP(30°C)

, mV

Slope, mV/°C

Parabola,

mV/°C

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

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

linear formula below can be used. Using this formula, with the offset and slope in the following table, the best-fit V

TEMP

vs Die Temperature performance can be calculated with an approximation error less than 18 mV.

Sensor Gain

TEMP(30°C)

, mV

Slope, mV/°C

GAIN 1 1059.9 -5.1751

GAIN 2 1589.9 -7.765

GAIN 3 2119.0 -10.355

GAIN 4 2648.6 -12.944

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:

Using this method of linear approximation, the transfer function can be approximated for one or more temperature ranges of interest.

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LM26LV

Page 13

2.0 OVERTEMP and OVERTEMP Digital Outputs

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.

2.1 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

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The Pull-up resistor value is calculated at the condition of maximum total current, iT, through the resistor. The total current is:

where,

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.

OUT

is the Voltage at the OVERTEMP pin. Use

VOL for calculating the Pull-up resistor.

DD(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:

EXAMPLE CALCULATION

Suppose we have, for our example, a VDD of 3.3 V ± 0.3V, a CMOS digital input as a load, a VOL of 0.2 V.

(1) We see that for VOL of 0.2 V the electrical specification for OVERTEMP shows a maximim i

sink

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 V

DD(Max)

is 3.3V + 0.3V = 3.6V and then

calculate the pull-up resistor as R

Pull-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.

2.2 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.

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 V

TEMP

pin will be

at the V

TRIP

voltage.

If not used, the TRIP TEST pin may either be left open or grounded.

4.0 V

TEMP

Analog Temperature

Sensor Output

The V

TEMP

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.

4.1 NOISE CONSIDERATIONS

The LM26LV's supply-noise gain (the ratio of the AC signal on V

TEMP

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.

4.2 CAPACITIVE LOADS

The V

TEMP

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 V

TEMP

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.

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FIGURE 1. LM26LV No Decoupling Required for

Capacitive Loads Less than 1100 pF.

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LOAD

1.1 nF to 99 nF

3 kΩ

100 nF to 999 nF

1.5 kΩ

1 μF

800 Ω

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 V

TEMP

. The shift typically occurs when

VDD − V

TEMP

= 1.0V.

This slight shift (a few millivolts) takes place over a wide change (approximately 200 mV) in VDD or V

TEMP

. Since the shift takes place over a wide temperature change of 5°C to 20°C, V

TEMP

is always monotonic. The accuracy specifications in the Electrical Characteristics table already includes this possible shift.

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.

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 V

TEMP

output to ground or VDD, the V

TEMP

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

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, V

TEMP

= 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 V

TEMP

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.

Device Number

NS Package

Number

Thermal

Resistance (θJA)

LM26LVCISD SDB06A 152° C/W

FIGURE 3. LM26LV Thermal Resistance

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6.0 Applications Circuits

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FIGURE 4. Temperature Switch Using Push-Pull Output

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FIGURE 5. Temperature Switch Using Open-Drain Output

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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 (C

FILTER

). The size of C

FILTER

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

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FIGURE 7. Celsius Temperature Switch

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FIGURE 8. TRIP TEST Digital Output Test Circuit

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LM26LV

Page 17

Physical Dimensions inches (millimeters) unless otherwise noted

6-Lead LLP-6 Package

Order Number LM26LVCISD, LM26LVCISDX

NS Package Number SDB06A

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LM26LV

Page 18

Notes

LM26LV 1.6 V, LLP-6 Factory Preset Temperature Switch and Temperature Sensor

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