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 www.national.com 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 www.national.com 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 www.national.com 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 www.national.com 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 www.national.com 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. www.national.com 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 www.national.com 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 www.national.com 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 www.national.com 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 www.national.com 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 www.national.com 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 www.national.com 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 www.national.com 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. www.national.com 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 www.national.com LM26LV 20204718 FIGURE 7. Celsius Temperature Switch 20204760 FIGURE 8. TRIP TEST Digital Output Test Circuit www.national.com 16 LM26LV Physical Dimensions inches (millimeters) unless otherwise noted 6-Lead LLP-6 Package Order Number LM26LVCISD, LM26LVCISDX NS Package Number SDB06A 17 www.national.com LM26LV 1.6 V, LLP-6 Factory Preset Temperature Switch and Temperature Sensor Notes THE CONTENTS OF THIS DOCUMENT ARE PROVIDED IN CONNECTION WITH NATIONAL SEMICONDUCTOR CORPORATION (“NATIONAL”) PRODUCTS. NATIONAL MAKES NO REPRESENTATIONS OR WARRANTIES WITH RESPECT TO THE ACCURACY OR COMPLETENESS OF THE CONTENTS OF THIS PUBLICATION AND RESERVES THE RIGHT TO MAKE CHANGES TO SPECIFICATIONS AND PRODUCT DESCRIPTIONS AT ANY TIME WITHOUT NOTICE. NO LICENSE, WHETHER EXPRESS, IMPLIED, ARISING BY ESTOPPEL OR OTHERWISE, TO ANY INTELLECTUAL PROPERTY RIGHTS IS GRANTED BY THIS DOCUMENT. TESTING AND OTHER QUALITY CONTROLS ARE USED TO THE EXTENT NATIONAL DEEMS NECESSARY TO SUPPORT NATIONAL’S PRODUCT WARRANTY. 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