PSF

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Vishay Dale

Revision: 13-Jul-12

3

Document Number: 30162

THIS DOCUMENT IS SUBJECT TO CHANGE WITHOUT NOTICE. THE PRODUCTS DESCRIBED HEREIN AND THIS DOCUMENT

TEMPERATURE COEFFICIENT OF RESISTANCE

Temperature coefficient (TC) of resistance is normally stated as the maximum amount of resistance change from the original + 25 °C value

as the ambient temperature increases or decreases. This is most commonly expressed in parts per million per degree centigrade (ppm/°C).

The resistance curve over the operating temperature range is usually a non-linear curve within predictable maximum limits. PSF resistors

have a very uniform resistance temperature characteristic when measured over the operating range of - 20 °C to + 85 °C. The standard

temperature coefficients available are

E = ± 25 ppm/°C, X = ± 15 ppm/°C, Y = ± 10 ppm/°C, and Z = ± 5 ppm/°C.

Some applications of the PSF require operation beyond the specifications of - 20 °C to + 85 °C. The change in temperature coefficient of

resistance is very small (less than ± 0.05 ppm/°C) over the expanded temperature range of - 55 °C to + 150 °C. Therefore, when operating

outside the range of - 20 °C to + 85 °C, the designer can plan for a worst case addition of ± 0.05 ppm/°C for each degree centigrade beyond

either - 20 °C or + 85 °C as indicated in the graph. This applies to all four temperature coefficient codes.

Example:



Assume the operating characteristics demand a temperature range from - 55 °C to + 125 °C. This requires a ± 35 °C

 below - 20 °C and

a ± 40 °C

 above + 85 °C. The extreme  being ± 40 °C means that the worst case addition to the specified TC limit of ± 0.05 ppm/°C

times ± 40 °C or ± 2 ppm/°C. Therefore, a Z which is characterized by a base TC limit of ± 5 ppm/°C over the temperature range of

- 20 °C to + 85 °C will exhibit a maximum temperature coefficient of ± 7 ppm/°C over the expanded portion of the temperature range of

- 55 °C to 125 °C.

PERFORMANCE

TEST

CONDITIONS OF TEST

TEST RESULTS

(TYPICAL TEST LOTS)

Life

MIL-STD-202, method 108, 1000 h rated power at + 85 °C

 ± 0.04 %

Short time overload

MIL-PRF-55342, paragraph 4.8.6

 ± 0.01 %

Thermal shock

MIL-STD-202, method 107, - 65 °C to + 150 °C

 ± 0.02 %

Low temperature operation

MIL-PRF-55342, paragraph 4.8.5

 ± 0.02 %

Resistance to bonding exposure

MIL-STD-202, method 210

 ± 0.02 %

Moisture resistance

MIL-PRF-55342, paragraph 4.8.9

 ± 0.08 %

Solder mounting integrity

MIL-PRF-55342, paragraph 4.8.13, 3 kg for 30 s

No evidence of mechanical damage

Dielectric withstanding voltage

MIL-STD-202, methods 301 and 105

 ± 0.01 %

Solderability

MIL-STD-202, method 208

95 % coverage

- 50

- 30

- 40

- 20

90

150

140

130

120

110

100

E, X, Y, OR Z

EXPANDED

OPERATING RANGE

+ 85 °C to + 150 °C

EXPANDED

OPERATING RANGE

- 55 °C to - 20 °C

- 20 °C to + 85 °C

BASE TC LIMIT

4

3

2

1

0