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RTOP
Vishay Sfernice
Power Resistor for Mounting onto a Heatsink
Thick Film Technology
FEATURES
• 1 % tolerance available
• High power rating = 200 W
• Wide ohmic value range = 0.046 to 1 MΩ
• Non inductive
• Easy mounting
• Low thermal radiation of the case
• Standard Isotop case (SOT 227 B)
This series of thick film power resistors include modules which can incorporate up to 2 different resistor values in the same
SOT 227B package. Two types of terminations are available along with a 4 terminal device for measurement applications in the
case of the single resistor version. This product range benefits from Vishay Sfernice’s experience in thick film power resistor
technology i.e. high power: volume ratio, low tolerance or individual resistors and excellent overload capabilities (due to the
trimming technique).
RoHS
COMPLIANT
DIMENSIONS in millimeters
RTOP
• Tolerances unless otherwise specified: ± 0.3 mm
MECHANICAL SPECIFICATIONS
Mechanical Protection
Substrate
Alumina on insulated base
Resistive Element
End Connections
Tightening Torque Connections
Tightening Torque Heatsink
Weight
Insulated case
Cermet
V connections: screw M4 x 6
1 Nm
2 Nm
30 g max.
The user must choose the heatsink according to the working
conditions of the component (power, room temperature).
Maximum working temperature must not exceed 125 °C.
The dissipated power is simply calculated by the following
ratio:
resistive layer and outer side of the resistor. It is
the thermal resistance of the component (see
Table Special Features).
R
: Thermal resistance value measured between
TH (c - a)
outer side of the resistor and room temperature.
It is the thermal resistance of the heatsink
depending on the heatsink itself (type, shape)
and the quality of the fastening device.
Example:
R
TH (c - a)
: For RTOP 200 power rating 130 W at ambient
temperature + 30 °C.
Thermal resistance (see table 1) R
ΔT 125 °C - 30 °C - 95 °C≤≤
R
TH (j - c)RTH (c - a)
R
TH (j - c)
R
TH (c - a)
0.5 °C/W≤
0.73 °C/W - 0.5 °C/W 0.23 °C/W≤≤
ΔT
+[]
TH j c–()RTH c a–()
ΔT
95
-------
----------
P
130
TH (j - c)
0.73 °C/W== =+
1()=
: 0.5 °C/W
OVERLOADS
The applied power is 2.5 x rated power for 5 s with a max.
voltage of 2 x nominal voltage.
Accidental overload: The values indicated in the graph
below are applicable to resistors in air or mounted onto a
heatsink.
In case of multi-resistor devices, (DRTOP, TROP and
QROP) the results apply to each resistor value in the device.
RECOMMENDATIONS FOR MOUNTING
ONTO A HEATSINK
Surfaces in contact must be carefully cleaned.
The heatsink must have an acceptable flatness:
from 0.05 mm to 0.1 mm/100 mm.
Roughness of the heater must be around 6.3 µm.
In order to improve thermal conductivity, surfaces in contact
(alumina, heatsink) are laid on with a silicone grease (type SI
340 from Rhône-Poulenc or Dow 340 from Dow Corning).
Tightening torque on heater: 2 Nm
For the electrical connections, it is recommended to use
M4 x 6 screws and if necessary a washer of 1mm thickness.
The recommended screw tightening torque is 1 Nm.
The temperature of the heater should be maintained in the limit specified. To improve the thermal conductivity, surfaces in
contact should be laid on with a silicon grease and the torque applied on the screw for tightening should be around 2 Nm.
MARKING
Series, style, ohmic value (in), tolerance (in %), manufacturing date, VISHAY trade mark.
If RTOP: The first three
digits are significant figures
and the last digit specifies
the number of zeros to
follow.
R designates decimal point.
48R7 = 48.7 Ω
4871 = 4870 Ω
1002 = 10 000 Ω
R010 = 0.01 Ω
R680 = 0.68 Ω
2700 = 2700 Ω = 2K7 Ω
Blank if RTOP.
If DRTOP: The first two
digits are significant figures
and the last digit specifies
the number of zeros to
follow.
R designates decimal point.
48R = 48 Ω
487 = 487 Ω
F = 1 %
G = 2 %
J = 5 %
K = 10 %
B = Box
10 pieces
As applicable
Ex = UA1
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therein, which apply to these products.
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