SM72480 [NSC]
SolarMagic 1.6V, LLP-6 Factory Preset Temperature Switch and Temperature Sensor; 的SolarMagic 1.6V ， LLP- 6出厂预设温度开关和温度传感器
| 型号： | SM72480 |
| 厂家： | 
National Semiconductor |
| 描述： | SolarMagic 1.6V, LLP-6 Factory Preset Temperature Switch and Temperature Sensor |
| 文件： | 总18页 (文件大小：462K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
May 11, 2011
SM72480
SolarMagic 1.6V, LLP-6 Factory Preset Temperature Switch
and Temperature Sensor
General Description
Features
The SM72480 is a low-voltage, precision, dual-output, low-
power temperature switch and temperature sensor. The tem-
perature trip point (TTRIP) is set at the factory to be 120°C.
Built-in temperature hysteresis (THYST) keeps the output sta-
ble in an environment of temperature instability.
Renewable Energy Grade
■
■
■
Low 1.6V operation
Latching function: device can latch the Over Temperature
condition
Push-pull and open-drain temperature switch outputs
■
■
■
■
In normal operation the SM72480 temperature switch outputs
assert when the die temperature exceeds TTRIP. The temper-
ature switch outputs will reset when the temperature falls
Very linear analog VTEMP temperature sensor output
VTEMP output short-circuit protected
below
a temperature equal to (TTRIP − THYST). The
2.2 mm by 2.5 mm (typ) LLP-6 package
OVERTEMP digital output, is active-high with a push-pull
structure, while the OVERTEMP digital output, is active-low
with an open-drain structure.
Excellent power supply noise rejection
■
Key Specifications
The analog output, VTEMP, delivers an analog output voltage
with Negative Temperature Coefficient — NTC.
1.6V to 5.5V
■ Supply Voltage
■ Supply Current
■ Accuracy, Trip Point
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 VTEMP output pin, which
could be used to verify the temperature trip point.
8 μA (typ)
0°C to 150°C
0°C to 150°C
±2.2°C
The SM72480'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.
±2.3°C
■ Accuracy, VTEMP
■ VTEMP Output Drive
■ Operating Temperature
■ Hysteresis Temperature
±100 μA
−50°C to 150°C
4.5°C to 5.5°C
Applications
PV Power Optimizers
■
■
■
■
Wireless Transceivers
Battery Management
Automotive
Disk Drives
■
Connection Diagram
Typical Transfer Characteristic
LLP-6
VTEMP Analog Voltage vs Die Temperature
30142001
Top View
See NS Package Number SDB06A
30142024
© 2011 National Semiconductor Corporation
301420
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Block Diagram
30142003
Pin Descriptions
Pin
No.
Name
Type
Equivalent Circuit
Description
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.
TRIP
TEST
Digital
Input
1
Over Temperature Switch output
Active High, Push-Pull
Asserted when the measured temperature exceeds the Trip Point
Temperature or if TRIP TEST = 1
Digital
Output
5
3
OVERTEMP
OVERTEMP
This pin may be left open if not used.
Over Temperature Switch output
Active Low, Open-drain (See Section 2.1 regarding required pull-up
resistor.)
Asserted when the measured temperature exceeds the Trip Point
Temperature or if TRIP TEST = 1
Digital
Output
This pin may be left open if not used.
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2
Pin
No.
Name
Type
Equivalent Circuit
Description
VTEMP Analog Voltage Output
If TRIP TEST = 0 then
VTEMP = VTS, Temperature Sensor Output Voltage
If TRIP TEST = 1 then
Analog
Output
VTEMP
6
VTEMP = VTRIP, Temperature Trip Voltage
This pin may be left open if not used.
VDD
Positive Supply Voltage
Power Supply Ground
4
2
Power
GND
Ground
The best thermal conductivity between the device and the PCB is
achieved by soldering the DAP of the package to the thermal pad on the
PCB. The thermal pad can be a floating node. However, for improved
noise immunity the thermal pad should be connected to the circuit GND
node, preferably directly to pin 2 (GND) of the device.
DAP Die Attach Pad
Typical Application
30142002
3
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Ordering Information
Temperature
Trip Point, °C
NS Package
Number
Package
Marking
Order Number
Description
Transport Media
SM72480SD-125
125°C
6–pin LLP
SDB06A
SDB06A
SDB06A
SDB06A
SDB06A
SDB06A
SDB06A
SDB06A
SDB06A
299
299
299
S80
S80
S80
701
701
701
1000 Units on Tape and
Reel
SM72480SDE-125
SM72480SDX-125
SM72480SD-120
SM72480SDE-120
SM72480SDX-120
SM72480SD-105
SM72480SDE-105
SM72480SDX-105
125°C
125°C
120°C
120°C
120°C
105°C
105°C
105°C
6–pin LLP
6–pin LLP
6–pin LLP
6–pin LLP
6–pin LLP
6–pin LLP
6–pin LLP
6–pin LLP
250 Units on Tape and
Reel
4500 Units on Tape and
Reel
1000 Units on Tape and
Reel
250 Units on Tape and
Reel
4500 Units on Tape and
Reel
1000 Units on Tape and
Reel
250 Units on Tape and
Reel
4500 Units on Tape and
Reel
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4
Absolute Maximum Ratings (Note 1)
Operating Ratings (Note 1)
Specified Temperature Range:
SM72480
ꢀTMIN ≤ TA ≤ TMAX
−50°C ≤ TA ≤ +150°C
Supply Voltage
Voltage at OVERTEMP pin
−0.3V to +6.0V
−0.3V to +6.0V
Voltage at OVERTEMP and
VTEMP pins
Supply Voltage Range (VDD
)
+1.6 V to +5.5 V
−0.3V to (VDD + 0.5V)
−0.3V to (VDD + 0.5V)
±7 mA
Thermal Resistance (θJA) (Note 4)
TRIP TEST Input Voltage
Output Current, any output pin
Input Current at any pin (Note 2)
Storage Temperature
LLP-6 (Package SDB06A)
152 °C/W
5 mA
−65°C to +150°C
Maximum Junction Temperature
TJ(MAX)
+155°C
ESD Susceptibility (Note 3) :
Human Body Model
Machine Model
4500V
300V
Charged Device Model
1000V
For soldering specifications: see product folder at
www.national.com and www.national.com/ms/MS/MS-
SOLDERING.pdf
Accuracy Characteristics
Trip Point Accuracy
Parameter
Limits
(Note 6)
Units
(Limit)
Conditions
VDD = 5.0 V
Trip Point Accuracy (Note 7)
0°C − 150°C
±2.2
°C (max)
VTEMP Analog Temperature Sensor Output Accuracy
The limits do not include DC load regulation. The stated accuracy limits are with reference to the values in the SM72480 Conversion
Table.
Limits
(Note 6)
Units
(Limit)
Parameter
Conditions
TA = 20°C to 40°C
TA = 0°C to 70°C
TA = 0°C to 90°C
TA = 0°C to 120°C
TA = 0°C to 150°C
TA = –50°C to 0°C
TA = 20°C to 40°C
TA = 0°C to 70°C
TA = 0°C to 90°C
TA = 0°C to 120°C
TA = 0°C to 150°C
TA = −50°C to 0°C
VDD = 2.3 to 5.5 V
VDD = 2.5 to 5.5 V
VDD = 2.5 to 5.5 V
VDD = 2.5 to 5.5 V
VDD = 2.5 to 5.5 V
VDD = 3.0 to 5.5 V
VDD = 1.8 to 5.5 V
VDD = 1.9 to 5.5 V
VDD = 1.9 to 5.5 V
VDD = 1.9 to 5.5 V
VDD = 1.9 to 5.5 V
VDD = 2.3 to 5.5 V
±1.8
±2.0
±2.1
±2.2
±2.3
±1.7
±1.8
±2.0
±2.1
±2.2
±2.3
±1.7
VTEMP Temperature
Accuracy
(Note 7)
Trip Point
125°C or 120°C
°C (max)
(Note 7)
VTEMP Temperature
Accuracy
Trip Point
105°C
°C (max)
5
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Electrical Characteristics
Unless otherwise noted, these specifications apply for +VDD = +1.6V to +5.5V. Boldface limits apply for TA = TJ = TMIN to
T
MAX ; all other limits TA = TJ = 25°C.
Symbol Parameter
GENERAL SPECIFICATIONS
Typical
(Note 5)
Limits
(Note 6)
Units
(Limit)
Conditions
IS
Quiescent Power Supply
Current
8
5
16
μA (max)
5.5
4.5
°C (max)
°C (Min)
Hysteresis
OVERTEMP DIGITAL OUTPUT
ACTIVE HIGH, PUSH-PULL
VDD ≥ 1.6V
VDD ≥ 2.0V
VDD ≥ 3.3V
VDD ≥ 1.6V
VDD ≥ 2.0V
VDD ≥ 3.3V
Source ≤ 340 μA
VDD − 0.2V
V (min)
V (min)
Source ≤ 498 μA
Source ≤ 780 μA
Source ≤ 600 μA
Source ≤ 980 μA
Source ≤ 1.6 mA
VOH
Logic "1" Output Voltage
VDD − 0.45V
BOTH OVERTEMP and OVERTEMP DIGITAL OUTPUTS
VDD ≥ 1.6V
VDD ≥ 2.0V
VDD ≥ 3.3V
Sink ≤ 385 μA
Sink ≤ 500 μA
Sink ≤ 730 μA
Sink ≤ 690 μA
Sink ≤ 1.05 mA
Sink ≤ 1.62 mA
0.2
VOL
Logic "0" Output Voltage
V (max)
VDD ≥ 1.6V
VDD ≥ 2.0V
VDD ≥ 3.3V
0.45
OVERTEMP DIGITAL OUTPUT
ACTIVE LOW, OPEN DRAIN
TA = 30 °C
0.001
0.025
Logic "1" Output Leakage
IOH
1
μA (max)
Current (Note 10)
TA = 150 °C
VTEMP ANALOG TEMPERATURE SENSOR OUTPUT
VTEMP Sensor Gain
Trip Point = 105°C
-7.7
mV/°C
mV/°C
Trip Point = 125°C or 120°C
−10.3
Source ≤ 90 μA
(VDD − VTEMP) ≥ 200 mV
−0.1
0.1
−1
1
mV (max)
mV (max)
mV (max)
mV (max)
1.6V ≤ VDD < 1.8V
Sink ≤ 100 μA
VTEMP ≥ 260 mV
VTEMP Load Regulation
Source ≤ 120 μA
(VDD − VTEMP) ≥ 200 mV
(Note 9)
−0.1
0.1
−1
1
VDD ≥ 1.8V
Sink ≤ 200 μA
VTEMP ≥ 260 mV
1
Ohm
mV
Source or Sink = 100 μA
0.29
74
VDD Supply- to-VTEMP
DC Line Regulation
(Note 11)
VDD = +1.6V to +5.5V
μV/V
dB
−82
VTEMP Output Load
Capacitance
CL
Without series resistor. See Section 4.2
1100
pF (max)
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6
Electrical Characteristics
Unless otherwise noted, these specifications apply for +VDD = +1.6V to +5.5V. Boldface limits apply for TA = TJ = TMIN to
T
MAX ; all other limits TA = TJ = 25°C.
Symbol Parameter
TRIP TEST DIGITAL INPUT
Typical
(Note 5)
Limits
(Note 6)
Units
(Limit)
Conditions
VIH
VIL
IIH
VDD− 0.5
0.5
Logic "1" Threshold Voltage
Logic "0" Threshold Voltage
Logic "1" Input Current
V (min)
V (max)
μA (max)
1.5
2.5
Logic "0" Input Current
(Note 10)
IIL
0.001
1
μA (max)
TIMING
Time from Power On to Digital
Output Enabled. See
definition below.
tEN
1.1
1.0
2.3
2.9
ms (max)
ms (max)
Time from Power On to
Analog Temperature Valid.
See definition below.
VTEMP CL = 0 pF to 1100 pF
t
VTEMP
Definitions of tEN and tV
TEMP
30142051
30142050
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: The junction to ambient temperature resistance (θJA) is specified without a heat sink in still air.
Note 5: Typicals are at TJ = TA = 25°C and represent most likely parametric norm.
Note 6: Limits are guaranteed to National's AOQL (Average Outgoing Quality Level).
Note 7: 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 8: Changes in output due to self heating can be computed by multiplying the internal dissipation by the temperature resistance.
Note 9: Source currents are flowing out of the SM72480. Sink currents are flowing into the SM72480.
Note 10: 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 11: 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 12: The curves shown represent typical performance under worst-case conditions. Performance improves with larger overhead (VDD − VTEMP), larger VDD
,
and lower temperatures.
Note 13: The curves shown represent typical performance under worst-case conditions. Performance improves with larger VTEMP, larger VDD and lower
temperatures.
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Typical Performance Characteristics
VTEMP Output Temperature Error vs. Temperature
Minimum Operating Temperature vs. Supply Voltage
30142007
30142006
Supply Current vs. Temperature
Supply Current vs. Supply Voltage
30142004
30142005
VTEMP Supply-Noise Rejection vs. Frequency
Line Regulation
VTEMP vs. Supply Voltage
Trip Points
120°C
30142043
30142036
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VTEMP, Analog Output Voltage, mV
1.0 SM72480 VTEMP vs Die
Temperature Conversion Table
Die Temp.,
°C
TTRIP
=
TTRIP = 105°C
125 or 120°C
2252
2242
2232
2222
2212
2202
2192
2182
2171
2161
2151
2141
2131
2121
2111
2101
2090
2080
2070
2060
2050
2040
2029
2019
2009
1999
1989
1978
1968
1958
1948
1938
1927
1917
1907
1897
1886
1876
1866
1856
1845
1835
1825
1815
1804
1794
1784
1774
The SM72480 has a factory-set gain, which is dependent on
the Temperature Trip Point. The VTEMP temperature sensor
voltage, in millivolts, at each discrete die temperature over the
complete operating range is shown in the conversion table
below.
−13
−12
−11
−10
−9
−8
−7
−6
−5
−4
−3
−2
−1
0
1690
1682
1674
1667
1659
1652
1644
1637
1629
1621
1614
1606
1599
1591
1583
1576
1568
1561
1553
1545
1538
1530
1522
1515
1507
1499
1492
1484
1477
1469
1461
1454
1446
1438
1431
1423
1415
1407
1400
1392
1384
1377
1369
1361
1354
1346
1338
1331
VTEMP Temperature Sensor Output Voltage vs Die
Temperature Conversion Table
The VTEMP temperature sensor output voltage, in mV, vs Die
Temperature, in °C for the gain corresponding to the temper-
ature trip point. VDD = 5.0V.
VTEMP, Analog Output Voltage, mV
Die Temp.,
TTRIP
=
TTRIP = 105°C
°C
125 or 120°C
2623
2613
2603
2593
2583
2573
2563
2553
2543
2533
2523
2513
2503
2493
2483
2473
2463
2453
2443
2433
2423
2413
2403
2393
2383
2373
2363
2353
2343
2333
2323
2313
2303
2293
2283
2272
2262
−50
−49
−48
−47
−46
−45
−44
−43
−42
−41
−40
−39
−38
−37
−36
−35
−34
−33
−32
−31
−30
−29
−28
−27
−26
−25
−24
−23
−22
−21
−20
−19
−18
−17
−16
−15
−14
1967
1960
1952
1945
1937
1930
1922
1915
1908
1900
1893
1885
1878
1870
1863
1855
1848
1840
1833
1825
1818
1810
1803
1795
1788
1780
1773
1765
1757
1750
1742
1735
1727
1720
1712
1705
1697
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
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VTEMP, Analog Output Voltage, mV
VTEMP, Analog Output Voltage, mV
Die Temp.,
°C
Die Temp.,
°C
TTRIP
=
TTRIP = 105°C
TTRIP
=
TTRIP = 105°C
125 or 120°C
1763
1753
1743
1732
1722
1712
1701
1691
1681
1670
1660
1650
1639
1629
1619
1608
1598
1588
1577
1567
1557
1546
1536
1525
1515
1505
1494
1484
1473
1463
1453
1442
1432
1421
1411
1400
1390
1380
1369
1359
1348
1338
1327
1317
1306
1296
1285
1275
125 or 120°C
1264
1254
1243
1233
1222
1212
1201
1191
1180
1170
1159
1149
1138
1128
1117
1106
1096
1085
1075
1064
1054
1043
1032
1022
1011
1001
990
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
1323
1315
1307
1300
1292
1284
1276
1269
1261
1253
1245
1238
1230
1222
1214
1207
1199
1191
1183
1176
1168
1160
1152
1144
1137
1129
1121
1113
1105
1098
1090
1082
1074
1066
1059
1051
1043
1035
1027
1019
1012
1004
996
83
84
949
941
933
925
917
909
901
894
886
878
870
862
854
846
838
830
822
814
807
799
791
783
775
767
759
751
743
735
727
719
711
703
695
687
679
671
663
655
647
639
631
623
615
607
599
591
583
575
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
979
969
958
948
937
926
916
905
894
884
873
862
852
841
831
820
988
809
980
798
972
788
964
777
957
766
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10
VTEMP, Analog Output Voltage, mV
Die Temp.,
°C
TTRIP
=
TTRIP = 105°C
125 or 120°C
756
1.1.2 The First-Order Approximation (Linear)
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
567
559
551
543
535
527
519
511
503
495
487
479
471
463
455
447
438
430
422
414
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
constant and slope in the following set of equations, the best-
fit VTEMP vs Die Temperature performance can be calculated
with an approximation error less than 18 mV. VTEMP is in mV.
745
734
724
713
702
691
681
670
659
1.1.3 First-Order Approximation (Linear) over Small
Temperature Range
649
For a linear approximation, a line can easily be calculated
over the desired temperature range from the Conversion Ta-
ble using the two-point equation:
638
627
616
606
595
584
573
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.
562
552
1.1 VTEMP vs DIE TEMPERATURE APPROXIMATIONS
The SM72480's VTEMP 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
VTEMP voltage output vs Temperature.
Using this method of linear approximation, the transfer func-
tion can be approximated for one or more temperature ranges
of interest.
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.
VTEMP is in mV.
11
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(1) We see that for VOL of 0.2 V the electrical specification for
OVERTEMP shows a maximim isink of 385 µA.
2.0 OVERTEMP and OVERTEMP
Digital Outputs
(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
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 si-
multaneously 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 dig-
ital outputs enable the user the flexibility to choose the type
of output that is most suitable for his design.
(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 re-
sistor 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.
Either the OVERTEMP or the OVERTEMP Digital Output pins
can be left open if not used.
2.2 NOISE IMMUNITY
The SM72480 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 re-
sistor 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 exam-
ple, driving dynamic loads like an input stage on an analog-
to-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 discus-
sion of this topic. The SM72480 is ideal for this and other
applications which require strong source or sink current.
30142052
The Pull-up resistor value is calculated at the condition of
maximum total current, iT, through the resistor. The total cur-
rent is:
where,
4.1 NOISE CONSIDERATIONS
iT
iT is the maximum total current through the Pull-up
Resistor at VOL
The SM72480's supply-noise rejection (the ratio of the AC
signal on VTEMP to the AC signal on VDD) was measured dur-
ing 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.
.
iL
iL is the load current, which is very low for typical
digital inputs.
VOUT
VOUT is the Voltage at the OVERTEMP pin. Use
VOL for calculating the Pull-up resistor.
For operation in very noisy environments, some bypass ca-
pacitance should be present on the supply within approxi-
mately 2 inches of the SM72480.
VDD(Max) 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 ex-
tremely noisy environment, or when driving a switched sam-
pling 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 VDD of 3.3 V ± 0.3V, a
CMOS digital input as a load, a VOL of 0.2 V.
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12
5.0 Mounting and Temperature
Conductivity
The SM72480 can be applied easily in the same way as other
integrated-circuit temperature sensors. It can be glued or ce-
mented to a surface.
The best thermal conductivity between the device and the
PCB is achieved by soldering the DAP of the package to the
thermal pad on the PCB. The temperatures of the lands and
traces to the other leads of the SM72480 will also affect the
temperature reading.
30142015
FIGURE 1. SM72480 No Decoupling Required for
Capacitive Loads Less than 1100 pF.
Alternatively, the SM72480 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 SM72480
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 con-
densation can occur. If moisture creates a short circuit from
the VTEMP output to ground or VDD, the VTEMP output from the
SM72480 will not be correct. Printed-circuit coatings are often
used to ensure that moisture cannot corrode the leads or cir-
cuit traces.
30142033
CLOAD
1.1 nF to 99 nF
100 nF to 999 nF
1 μF
Minimum RS
3 kΩ
The thermal resistance junction-to-ambient (θJA) is the pa-
rameter used to calculate the rise of a device junction tem-
perature due to its power dissipation. The equation used to
calculate the rise in the SM72480's die temperature is
1.5 kΩ
800 Ω
FIGURE 2. SM72480 with series resistor for capacitive
loading greater than 1100 pF.
where TA is the ambient temperature, IQ is the quiescent cur-
rent, 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, show-
ing a self-heating error of only 0.021°C. Since the SM72480's
junction temperature is the actual temperature being mea-
sured, care should be taken to minimize the load current that
the VTEMP output is required to drive. If The OVERTEMP out-
put is used with a 100 k pull-up resistor, and this output is
asserted (low), then for this example the additional contribu-
tion is [(152° C/W)x(5V)2/100k] = 0.038°C for a total self-
heating error of 0.059°C. Figure 3 shows the thermal
resistance of the SM72480.
4.3 VOLTAGE SHIFT
The SM72480 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 specifica-
tions in the Electrical Characteristics table already includes
this possible shift.
NS Package
Number
Thermal
Device Number
Resistance (θJA
)
SM72480SD
SDB06A
152° C/W
FIGURE 3. SM72480 Thermal Resistance
13
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6.0 Applications Circuits
30142061
FIGURE 4. Temperature Switch Using Push-Pull Output
30142062
FIGURE 5. Temperature Switch Using Open-Drain Output
30142028
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 SM72480 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
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14
30142018
FIGURE 7. Celsius Temperature Switch
30142060
FIGURE 8. TRIP TEST Digital Output Test Circuit
30142065
The TRIP TEST pin, normally used to check the operation of the OVERTEMP and OVERTEMP pins, may be used to latch the
outputs whenever the temperature exceeds the programmed limit and causes the digital outputs to assert. As shown in the figure,
when OVERTEMP goes high the TRIP TEST input is also pulled high and causes OVERTEMP output to latch high and the
OVERTEMP output to latch low. The latch can be released by either momentarily pulling the TRIP TEST pin low (GND), or by
toggling the power supply to the device. The resistor limits the current out of the OVERTEMP output pin.
FIGURE 9. Latch Circuit using OVERTEMP Output
15
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Physical Dimensions inches (millimeters) unless otherwise noted
6-Lead LLP-6 Package
NS Package Number SDB06A
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16
Notes
17
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