tFs series
Surge Capable
Thick Film Non Inductive
F e at u r e s
• Appropriate for medical surge protec-
tion applications
• Ideal to replace standard carbon com-
position resistors
• Custom dimensions, values, toler-
ances and characteristics available
The TFS Series has been specifically developed to absorb large
amounts of energy by efficient use of its compact mass. Ideal
for medical surge protection applications, these thick film resis-
tors offer non-inductive performance in an axial package.
Uses include power supply conversion, electron microscopes,
X-ray systems, high-resolution CRT displays, and geophysical
instrument related products.
s e r i e s s p e c i F i c at i o n s
*Published energy rating is for 10ms pulse. For shorter pulses energy rat-
ing has to be derated according to Max. Individual Pulse Rating chart and
Single Pulse Energy Rating considerations.
Type
TFSA
TFSB
TFSC
TFSD
TFSE
TFSF
U (KV)
3
3.5
4
7
7
11
Energy* (J)
6
9
11
33
44
55
Power (W)
0.5
0.5
0.75
1
1.5
2
characteristics
Resistive Element
Thick Film
Encapsulation
Screen Printed Glass
Resistance Value
100Ω up to 100KΩ
Temperature Coefficient
100ppm/°C
Tolerance
1%, 2%, 5%, 10%
Operating Temperature
-55°C to +200°C
Test
VDE 0750 (Pulse Duration 10 msec)
Notes
• Momentary overload capability is 5 times rated power for 1 second or 2 times
rated power for 5 seconds. Always verify designs with pulse and surge condi-
tions through thorough testing of the design at maximum operating tempera-
ture and maximum pulse loading (or some margin above maximum pulse
loading).
• Damage to the resistor by excessive pulse loading is generally indicated by an
increasing resistance of the resistor.
• Energy ratings are based on single pulses (at least 1 minute between pulses).
• For multiple pulse applications the energy pulse rating should be reduced and
the average power should not exceed the nominal power rating of the selected
model.
• See Single Pulse Energy section for more information
dimensions
mm
C
A
B
Type
TFSA
TFSB
Watts
0.5
0.5
1
A
11
9
B
5.5
5.5
8
C
10
10
H
0.7
0.7
E
1.1
1.1
0.50mm
TFSC
TFSE
TFSF
H
E
TFSD
0.75
1.5
2
13
21
5.5
10
21
0.25mm
26
10.5
10
0.7
10.5
10
0.9
1.1
10
0.9
1.3
0.9
1.3
1.3
(continued)
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57
tFs series
Surge Capable
Thick Film Non Inductive
s i n g l e p u l s e e n e r g y r at i n g
Although Ohmite’s TFS Series resistors have been specially designed
and developed to absorb much more energy than standard resistors,
pulses and transients require special consideration since they cause an
instantaneous temperature rise in the resistor film. This application note
can guide you through these considerations.
For applications with transients, pulses
or surges the following must be consid-
V
2
t
ered:
V E = –––
R
1. Do not exceed the normal rated oper-
ating voltage of the device.
t
2. Using the figure at right, estimate the
E=1
2
–CV
energy (E
a
) and the pulse duration
V
2
(t
a
) for a single pulse in your applica-
t = RC
tion.
t
3. Calculate the energy ratio in percent
(E
r
) between the nominal energy rat-
ing of the model you have chosen
V
2
t
V E = –––
3R
(see table) and the single pulse
energy in your application (E
a
from
t
step 2) using the formula:
E
a
E
r
= –––––––– x 100
V
2
t
V E = –––
E
nominal
3R
4. Refer to the Pulse Chart. On this
t
chart find the point where the energy
E = Energy
(joules)
ratio (E
r
), found at step 3, and time
t = Time
(seconds)
(t
a
) coincide. Qualify that this point
V = Voltage
(volts)
falls below the maximum pulse
R = Resistance (ohms)
energy curve. If the point is above
C = Capacitance (farads)
the curve a bigger model should be
chosen.
Example
A 1µF capacitor is charged to
3.5kV and model TFSC, 1KOhm
has been selected. Model TFSC
is rated for 4kV, so the peak volt-
age of 3.5kV is acceptable.
1
E
a
= –– CV
2
= 6.1J
2
t
a
= R C = 1 ms
6.1J
E
r
= ––– x 100 = 55%
11J
width of 1ms falls well above the
energy curve. The limit is actually
located around 25-30%. Model
TFSC cannot be used for this
application.
A bigger model should be chosen,
for example TFSD. Model TFSD,
1KOhm, can be used for this
application because we have an
energy ratio E
r
of 18%, which is
below the energy curve.
6.1J
E
r
= ––– x 100 = 18%
33J
According to the pulse chart, an
energy ratio of 55% for a pulse
Maximum Individual Pulse Rating
1000
Energy Rating %
100
10
1
0.1
1µs
10µs
100µs
1 ms
Pulse Width
10 ms
100 ms
o r d e r i n g i n F o r m at i o n
RoHS Compliant
Standard Part Numbers for TFS Series
Ohms
100
100
220
270
470
Tol.
1%
5%
1%
5%
1%
6 Joules
0.5 Watts
TFSA100RFE
TFSA220RFE
TFSA270RJE
TFSA470RFE
TFSA680RJE
TFSA1K00FE
TFSA1K00JE
9 Joules
0.5 Watts
TFSB100RJE
11 Joules
0.75 Watts
33 Joules
1 Watts
TFSD100RJE
TFSC270RJE TFSD270RJE
TFSB470RJE
TFSB750RJE
TFSB1K00JE
TFSB2K70JE
TFSC4K70JE
TFSB6K80JE
TFSB10K0JE
TFSB20K0JE
TFSC27K0JE
TFSB51K0JE
TFSB100KJE
TFSC51K0JE
TFSC100KJE
TFSD51K0JE
TFSD100KJE
TFSC10K0JE
TFSD10K0JE
TFSD20K0JE
TFSE27K0JE
TFSF51K0JE
TFSE75K0JE
TFSF100KJE
TFSD4K70JE
TFSE6K80JE
TFSF16K0JE
TFSF20K0JE
TFSF10K0JE
TFSC680RJE
TFSC1K00JE
TFSE470RJE
TFSE680RJE
TFSE1K00JE
TFSE2K70JE
44 Joules
1.5 Watts
55 Joules
2 Watts
TFSF100RJE
TFSF270RJE
TFSF680RJE
TFSF750RJE
TFSF1K50JE
TFSF1K00JE
TFSA100KJE
Series Energy Rating
joules
A =
6
D = 33
B =
9 E =
44
C =
11
F = 55
Ohm Value
Example:
100R = 100Ω
2K40 = 2400Ω
Tolerance
F = 1%
G = 2%
J = 5%
K = 10%
100,000 1%
100,000 5%
47,000
50,000
51,000
75,000
16,000
20,000
20,000
22,000
27,000
4,990
5,000
6,800
10,000
10,000
1,500
2,200
2,700
4,700
4,700
470
680
750
1,000
1,000
1%
5%
5%
5%
5%
1%
5%
1%
5%
1%
5%
5%
1%
5%
5%
1%
5%
1%
5%
5%
5%
5%
1%
5%
TFSD750RJE
TFSD1K50JE
TFSD1K00JE
TFSA1K50JE
TFSA2K20FE
TFSA4K70FE
TFSA4K70JE
TFSC1K50JE
TFSA4K99FE
TFSA75K0JE
TFSA10K0FE
TFSA10K0JE
TFSA20K0FE
TFSA22K0FE
TFSA27K0JE
TFSA47K0FE
TFSA50K0JE
TFSA100KFE
58
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