USR UNR 2-T220 / T220B / T221
USS UNS 2-T220
Precision Foil Resistors
SPECIFICATIONS (continued)
Temperature Coefficient
800
600
400
200
0
+5ppm/K
-5ppm/K
Nominal Spread
±2.3ppm/K
-200
-400
-600
-800
Nominal ∆R/R
Nominal Spread
±2.3ppm/K
100
0
25
50
75
125
-50
-25
Temperature (°C)
Derating
Power Rating Notes -
The U-Series Resistors must be attached to a suitable heatsink.
The maximum internal resistor temperature is 155°C.
To specify an appropriate heatsink use the following formula :
120
100
80
60
40
20
0
RθH = TMAX - ( P x RθR ) - TA
P
Where: RθH = Thermal Resistance of Heatsink ( K/W )
RθR = Thermal Resistance of Resistor ( K/W )
TMAX = Maximum Temperature of Resistor
TA = Ambient Temperature of Heatsink ( °C )
P = Power Through Resistor ( W )
25
50
85 100 115 130 145 155
Temperature of the backplate(°C)
Dimensions
USS 2-T220 / UNS 2-T220
tol.
tol.
Dimension
mm
12.70
10.16
0.76
(±mm)
0.2
0.2
0.1
0.1
0.1
0.1
0.2
0.2
0.2
0.1
0.1
inches
0.50
0.40
0.03
0.20
0.16
0.05
0.57
0.59
0.68
0.02
0.07
(±inches)
Dimension
mm
12.10
11.16
18.33
5.08
inches
0.476
0.439
0.722
0.200
0.069
0.126
A
B
C
D
E
F
G
H
I
0.008
0.008
0.004
0.004
0.004
0.004
0.008
0.008
0.008
0.004
0.004
A
B
C
D
E
F
5.08
4.00
1.76
1.20
3.20
14.60
15.00
17.33
0.40
J
K
1.85
Riedon Inc.
300 Cypress Avenue
Alhambra CA 91801
(626) 284-9901
(626) 284-1704
10/13
www.riedon.com
RIEDON [ RIEDON POWERTRON ]
