RTO 20

Power Resistors Thick Film Technology

Vishay Sfernice

Document Number: 50005

For technical questions, contact: sfer@vishay.com

www.vishay.com

Revision: 05-Jun-07

15

Note: For very low ohmic values, TCR for information

CHOICE OF THE HEATSINK

The user must choose according to the working conditions of the component (power, room temperature).

Maximum working temperature must not exceed 155 °C. The dissipated power is simply calculated by the following ratio:

P:

expressed in W

ΔT:

difference between maximum working temperature and room temperature

(j-c): thermal resistance value measured between resistive layer and outer side of the resistor. It is the thermal

resistance of the component: (Special Features Table)

(c-a): thermal resistance value measured between outer side of the resistor and room temperature. It is the thermal

resistance of the heatsink itself (type, shape) and the quality of the fastening device.

Example:

Considering equation (1) we have:

PERFORMANCE

TESTS

CONDITIONS

TYPICAL DRIFTS

Momentary Overload

EN 60115-1

2 Pr for R < 2

Ω

1.6 Pr for R

≥ 2 Ω

Us < 1.5 UL

± (0.25 % + 0.005

Ω)

Rapid Temperature Change

EN 60115-1/60068-2-14

5 cycles

- 55 °C to + 155 °C

± (0.5 % + 0.005

Ω)

Load Life

EN 60115-1

1000 h Pr at + 25 °C

± (1 % + 0.005

Ω)

Humidity (Steady State)

EN 60115-1

56 days R.H. 95 %

± (0.5 % + 0.005

Ω)

High Temperature Exposure

NF EN 140 000

1000 h - 40 % Pr at + 100 °C

± (0.5 % + 0.005

Ω)

Vibration

MIL STD 202, Method 204 C Test D

± (0.2 % + 0.005

Ω)

Terminal Strength

MIL STD 202, Method 211 Test A1

± (0.2 % + 0.005

Ω)

Shock

IEC 60115-1

IEC 60068-2-27

Saw tooth: 100 g/6 ms

± (0.5 % + 0.005

Ω)

SPECIAL FEATURES

Resistance Values

≥ 0.01

≥ 0.015

≥ 0.1

≥ 0.5

Tolerances

± 1 % at ± 10 %

Typical Temperature

Coefficient Range

(- 55 °C/+ 155 °C)

± 900 ppm/°C

± 700 ppm/°C

± 250 ppm/°C

± 150 ppm/°C

P =

ΔT

R

[]

-------------------------------------------------------------

1

()

ΔT

155 °C - 25 °C

130 °C

==

R

ΔT

P

------- =

130

10

---------- = 13 °C/W

R