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Temperature Compensation Devices

Surface Mount
Thermistors


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SMD
(CHIP STYLE)
Features
  • Wide Ohmic Value Range
  • Accurate & Stable
  • Fast Thermal Response Time
  • Standard Sizes
  • High Sensitivity
 NTC Thermistors

Negative Temperature Coefficient (NTC) thermistors are thermally sensitive semiconductor resistors which exhibit a decrease in resistance as absolute temperature increases. Change in the resistance of the NTC thermistor can be brought about either by a change in the ambient temperature or internally by self-heating resulting from current flowing through the device. Most of the practical applications of NTC thermistors are based on these material characteristics.

Surface Mount Thermistors

RTI manufactures precision resistance-temperature SMD thermistors. Standard values from 250 ohms to 150,000 ohms are available. As with RTI's disc and chip thermistors, SMD thermistors are suitable for temperature sensing applications over a wide range of resistance values and temperature coefficients. SMD's operating temperature range is from -55°C to +150°C. Dissipation constant is 2mW/°C, with a maximum power rating of 250mW @ 25°C.

Thermistor Terminology for SMD Temperature Measurement
  • D.C. - The dissipation constant is the ratio, normally expressed in milliwatts per degree C (mw/°C), at a specified ambient temperature, of a change in power dissipated in a thermistor to the resultant change in body temperature.
  • T.C. - The thermal time constant is the time required for a thermistor to change 63.2% of the total difference between its initial and final body temperature when subjected to a step function change in temperature under zero-power conditions and is normally expressed in seconds (S).
  • Alpha () or Temperature Coefficient of Resistance - The temperature coefficient of resistance is the ratio at a specified temperature, T, of the rate of change of zero-power resistance with temperature to the zero-power resistance of the thermistor. The temperature coefficient is commonly expressed in percent per degree C (%/°C).

SMD
on Considerations
  • Select Req'd. Resistance Value & Temperature Coefficient
  • Calculate DEV for R @ T
  • Determine Accuracy Req'd.
  • Review Power Dissipation
  • Review Thermal Time Constant
 Applications

Most semiconductors and the circuits comprised of them exhibit a positive temperature coefficient. NTC thermistors are well suited for compensating these responses to temperature changes. It is important to match the temperature of the compensating NTC thermistor to that of the component responsible for the temperature response.

RTI's SMD temperature measurement NTC sensors can operate over a wide temperature range (-55 to +150°C). They are stable throughout a long lifetime, and are small and comparatively inexpensive. Typically, they have negative temperature coefficients between -3.3 and -4.7%/°C at 25°C. RTI's SMD style thermistors are used in many applications that require a high degree of accuracy and reliability.

Some of the most popular applications of NTC thermistors include:

  • Temperature Compensation
  • Temperature Measurement & Control
  • LCD Controls
  • Power Transistor Stabilization

Selection Considerations for SMD NTC Devices

To determine the nominal resistance value of a thermistor at a specified temperature, multiply its RT/R25 value for the desired temperature and R-T curve from the table on NTC Resistance/Temperature Conversion Tables by its nominal resistance value at 25°C. As an example, the nominal resistance value at 80°C for a thermistor with the part number KR0805B103K is 10,000 times 0.157, the RT/R25 value in the R-T Curve "B" in the table under NTC Resistance/Temperature Conversion Tables.

Standard resistance tolerances at 25°C for RTI's SMD thermistors is ±10% and is indicated in its part number by the addition of the suffix K. To determine the resistance value at other than 25°C, add the appropriate DEV value from the NTC resistance/Temperature Conversion Tables to its resistance tolerance at 25°C. For example, the resistance tolerance at 80°C for a thermistor with part number KR0805B103K is ±10% ±3.0%, the DEV value from the R-T Curve "B" Table.

Although standard sizes, resistance values and tolerances are listed on SMD Standard Products and Sizes, custom sizes, resistance values and tolerances are available depending on the application and volume requirements.


 
 
SMD
Configuration
Options
  • Standard EIA Sizes Available
  • Bulk or Tape and Reel Packaging
  • Two Sided & Wrap Around Terminations
  • Silver Palladium Terminations

KR Series

Size 0805 1206
Units Inches Millimeters Inches Millimeters
W 0.049
±0.008		 1.240
±0.200		 0.063
±0.008		 1.600
±0.200
H 0.051
Maximum		 1.300
Maximum		 0.059
Maximum		 1.500
Maximum
L 0.079
±0.008		 2.000
±0.200		 0.126
±0.008		 3.200
±0.200
B 0.008
Minimum		 0.200
Minimum		 0.008
Minimum		 0.200
Minimum

STANDARD PRODUCTS

Part Number
Size 0805

Part Number
Size 1206

Resistance @ 25°C
±10% (Ohms)

Temperature
Coefficient (@25°C)

KR0805A251K KR1206A251K 250 -3.3%/°C
KR0805A501K KR1206A501K 500 -3.3%/°C
KR0805J102K KR1206J102K 1.0K -3.5%/°C
KR0805J252K KR1206J252K 2.5K -3.5%/°C
KR0805B502K KR1206B502K 5.0K -3.9%/°C
KR0805B103K KR1206B103K 10K -3.9%/°C
KR0805C203K KR1206C203K 20K -4.4%/°C
KR0805C253K KR1206C253K 25K -4.4%/°C
KR0805C503K KR1206C503K 50K -4.4%/°C
KR0805W104K KR1206W104K 100K -4.7%/°C
KR0805W154K KR1206W154K 150K -4.7%/°C

Ordering Information

KR
|
Model

0805
|
Size

A
|
R-T Curve

251
|
Resistance*

K
|
Tolerance**

X
|
Termination***

* Resistance value: First two digits are resistance value, third is the number of zeroes. Example: 251 = 250 ohms.
** Tolerances available: K = ±10% and J= ±5%.
***Terminations: No letter = Palladium Silver (Consult factory for optional terminations)
 
 
SMD
Configuration
Options
  • Standard EIA Sizes Available 
  • Bulk or Tape and Reel Packaging 
  • Two Sided & Wrap Around Terminations 
  • Nickel barrier Terminations

TR Series


Size

0603

0805

Units

Inches

Millimeters

Inches

Millimeters

Length

0.063 
±0.006

1.60 
±0.150

0.080 
±0.008

2.00 
±0.20

Width

0.0315 
±0.006

0.80 
±0.15

0.050 
±0.004

1.25 
±0.10

Height

0.020 
±0.004

0.50 
±0.10

0.020 
±0.004

0.50 
±0.10

Termination

0.0012 
±0.0079

0.30 
±0.2

0.0016 
±0.008

0.40 
±0.20


STANDARD PRODUCTS

Part Number 
Size 0603 		 Part Number 
Size 0805 		 Resistance @ 25°C 
±10% (Ohms) 		 Temperature 
Coefficient (@25°C) 
TR0603A251K TR0805A251K 250 -3.3%/°C
TR0603A501K TR0805A501K 500 -3.3%/°C
TR0603J102K TR0805J102K 1.0K -3.5%/°C
TR0603J252K TR0805J252K 2.5K -3.5%/°C
TR0603B502K TR0805B502K 5.0K -3.9%/°C
TR0603B103K TR0805B103K 10K -3.9%/°C
TR0603C203K TR0805C203K 20K -4.4%/°C
TR0603C253K TR0805C253K 25K -4.4%/°C
TR0603C503K TR0805C503K 50K -4.4%/°C
TR0603W104K TR0805W104K 100K -4.7%/°C
TR0603W154K TR0805W154K 150K -4.7%/°C

Ordering Information

TR
|
Model

0805 
| 
Size 

A 
| 
R-T Curve 

251 
| 
Resistance* 

K 
| 
Tolerance** 

X 
| 
Termination*** 

Resistance value: First two digits are resistance value, third is the number of zeroes. Example: 251 = 250 ohms. 
** Tolerances available: K =±;10% and J=±;5%. 
***Terminations: No letter = Nickel Barrier (Consult factory for optional terminations)
For tape and reel add suffix -T/R
 

NTC Resistance/Temperature Conversion Tables

Temperature °C R-T
Curve A		 R-T
Curve B		 R-T
Curve C		 R-T
Curve J		 R-T
Curve W
RT/R25 DEV RT/R25 DEV RT/R25 DEV RT/R25 DEV RT/R25 DEV
-60 43.0   75.0 6.6 140.5 6.6 52.5      
-55 31.9   54.1 6.1 96.4 6.1 39.0      
-50 24.3   39.7 5.6 67.0 5.6 29.2 18.5    
-45 18.6   29.2 5.2 47.2 5.2 22.1 17.0    
-40 14.4 7.6 21.7 4.7 33.7 4.7 16.9 15.4 40.2 7.6
-35 11.3 6.9 16.4 4.3 24.3 4.3 13.0 14.0 28.6 6.9
-30 8.93 6.2 12.5 3.8 17.7 3.8 10.1 12.5 20.6 6.2
-25 7.10 5.6 9.58 3.4 13.0 3.4 7.90 11.2 15.0 5.6
-20 5.69 5.0 7.42 3.0 9.71 3.0 6.24 9.9 11.0 5.0
-15 4.56 4.4 5.75 2.6 7.30 2.6 4.96 8.7 8.18 4.4
-10 3.68 3.7 4.50 2.2 5.53 2.2 3.97 7.4 6.12 3.7
-5 2.99 3.1 3.55 1.9 4.23 1.9 3.20 6.2 4.62 3.1
0 2.45 2.5 2.82 1.5 3.27 1.5 2.60 5.0 3.51 2.5
5 2.02 2.0 2.26 1.2 2.54 1.2 2.12 3.9 2.69 2.0
10 1.68 1.6 1.83 0.8 1.99 0.8 1.74 2.7 2.08 1.6
15 1.42 1.1 1.48 0.5 1.57 0.5 1.44 1.6 1.62 1.1
20 1.18 0.6 1.22 0.2 1.25 0.2 1.20 0.5 1.27 0.6
25 1.00 0.0 1.00 0.0 1.00 0.0 1.00 0.0 1.00 0.0
30 0.854 0.6 0.828 0.4 0.806 0.4 0.841 1.4 0.794 0.6
35 0.732 1.1 0.689 0.7 0.653 0.7 0.710 2.3 0.635 1.1
40 0.628 1.6 0.576 1.0 0.533 1.0 0.602 3.2 0.510 1.6
45 0.537 2.0 0.482 1.3 0.437 1.3 0.513 4.3 0.413 2.0
50 0.464 2.5 0.406 1.5 0.360 1.5 0.439 5.0 0.336 2.5
55 0.403 3.0 0.343 1.8 0.299 1.8 0.377 5.9 0.275 3.0
60 0.350 3.4 0.292 2.0 0.249 2.0 0.326 6.7 0.226 3.4
65 0.305 3.8 0.247 2.3 0.208 2.3 0.282 7.5 0.187 3.8
70 0.267 4.2 0.212 2.5 0.175 2.5 0.245 8.2 0.155 4.2
75 0.236 4.6 0.182 2.8 0.148 2.8 0.214 9.0 0.129 4.6
80 0.208 4.9 0.157 3.0 0.126 3.0 0.188 9.8 0.108 4.9
85 0.183 5.3 0.137 3.2 0.107 3.2 0.165 10.5 0.0912 5.3
90 0.163 5.6 0.120 3.4 0.0916 3.4 0.146 11.2 0.0771 5.6
95 0.145 6.0 0.105 3.6 0.0787 3.6 0.129 11.9 0.0654 6.0
100 0.130 6.3 0.0920 3.8 0.0679 3.8 0.114 12.6 0.0557 6.3
105 0.117 6.7 0.0812 4.0 0.0588 4.0 0.102 13.3 0.0476 6.7
110 0.105 7.0 0.0723 4.2 0.0511 4.2 0.0908 13.9 0.0408 7.0
115 0.0943 7.3 0.0641 4.4 0.0445 4.4 0.0813 14.4 0.0351 7.3
120 0.0852 7.6 0.0569 4.6 0.0389 4.6 0.0730 14.9 0.0303 7.6
125 0.0771 7.9 0.0508 4.8 0.0342 4.8 0.0657 15.6 0.0263 7.9
130 0.0700 8.2 0.0455 4.9 0.0301 4.9 0.0593 16.3 0.0228 8.2
135 0.0636 8.4 0.0408 5.1 0.0265 5.1 0.0536 17.0 0.0199 8.4
140 0.0579 8.6 0.0368 5.3 0.0235 5.3 0.0486 17.6 0.0173 8.6
145 0.0529 9.0 0.0332 5.4 0.0208 5.4 0.0442 18.0 0.0152 9.0
150 0.0483 9.3 0.0300 5.5 0.0185 5.5 0.0402 18.4 0.0133 9.3

NTC Resistance/Temperature Curve Characteristics

R-T Curve A B C J W
Temperature Coefficient @ 25°C -3.3%/°C -3.9%/°C -4.4%/°C -3.5%/°C -4.7%/°C
Beta, ß 3000°K 3530°K 3965°K 3200°K 4250°K
R0°C/R50°C 5.3±5% 6.9±3% 9.1±3% 5.9±5% 10.45±5%
R25°C/R125°C 13.0 19.8 29.4 15.2 38.0