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B57238 (EPCOS) : Total 6 Pages

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NTC thermistors for
inrush current limiting
Leaded and coated disks
www.DataSheet4U.com
Series/Type:
Date:
B57238
March 2006
© EPCOS AG 2006. Reproduction, publication and dissemination of this publication, enclosures hereto and the
information contained therein without EPCOS' prior express consent is prohibited.



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Inrush current limiters
ICLs
B57238
S238
Applications
Switch-mode power supplies
Soft-start motors, e.g. in vacuum cleaners
Dimensional drawing
Features
Useable in series connections up to 265 Vrms
Coated thermistor disk for line applications
Kinked leads of tinned copper wire
Wide resistance range
UL approval (E69802)
Options
Resistance tolerance <20% and alternative
lead configurations available on request
Delivery mode
Bulk (standard),
cardboard tape, reeled or in Ammo pack
General technical data
Dimensions in mm
Approx. weight 3 g
Climatic category
Max. power
Resistance tolerance
Rated temperature
B value tolerance
Dissipation factor
Thermal cooling time constant
Heat capacity
(IEC 60068-1)
(at 25 °C)
(in air)
(in air)
Pmax
RR/RR
TR
B/B
δth
τc
Cth
55/170/21
3.9
±20
25
±3
approx. 20
approx. 80
approx. 1600
W
%
°C
%
mW/K
s
mJ/K
Electrical specification and ordering codes
R25 Imax
No. of
B25/100
(0...65 °C) R/T char-
A
acteristic K
2.5 8.4
1202 2800
3 7.4
1203 2900
4.7 6.6
1207 2965
5 6.4
1207 2965
7 6.0
1207 2965
8 5.5
1208 3065
10 5.0
1208 3065
15 4.4
1209 3165
16 4.0
1209 3165
C 1)
test
230 V
µF
700
700
700
700
700
700
700
700
700
C 1)
test
110 V
µF
2800
2800
2800
2800
2800
2800
2800
2800
2800
Param.
for R(I)1)
k
0.984
1.04
1.20
1.23
1.34
1.40
1.50
1.67
1.69
Param.
for R(I)1)
n
1.36
1.36
1.37
1.37
1.38
1.39
1.39
1.40
1.39
Ordering code
B57238S0259M000
B57238S0309M000
B57238S0479M000
B57238S0509M000
B57238S0709M000
B57238S0809M000
B57238S0100M000
B57238S0150M000
B57238S0160M000
1) For details on the capacitance Ctest as well as on the parameters k and n refer to "Application Notes", chapters 2.6 and 2.7.
Please read Important notes and
Cautions and warnings at the end of this document.
Page 2 of 6



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Inrush current limiters
ICLs
B57238
S238
R25 Imax
No. of
B25/100
(0...65 °C) R/T char-
A
acteristic K
22 4.0
1210 3265
25 3.4
1210 3265
C 1)
test
230 V
µF
700
700
C 1)
test
110 V
µF
2800
2800
Param.
for R(I)1)
k
1.84
1.88
Param.
for R(I)1)
n
1.42
1.40
Ordering code
B57238S0220M000
B57238S0250M000
Reliability data
Test Standard Test conditions
Storage in
dry heat
Storage in damp
heat, steady state
Rapid temperature
cycling
Endurance
Cyclic
endurance
Transient
load
IEC
60068-2-2
IEC
60068-2-78
IEC
60068-2-14
Storage at upper
category temperature
T: 170 °C
t: 1000 h
Temperature of air: 40 °C
Relative humidity of air: 93%
Duration: 21 days
Lower test temperature: 55 °C
Upper test temperature: 170 °C
Number of cycles: 10
I = Imax
t: 1000 h
I = Imax, 1000 cycles
On-time = 1 min
Cooling time = 6 min
Capacitance = Ctest
Number of cycles: 1000
R25/R25
(typical)
< 10%
< 5%
< 10%
< 10%
< 10%
< 5%
Remarks
No visible
damage
No visible
damage
No visible
damage
No visible
damage
No visible
damage
No visible
damage
Cautions and warnings for ICLs
The self-heating of a thermistor during operation depends on the load applied and the applicable
dissipation factor.
When loaded with maximum allowable current/power and the specified dissipation factor is taken
as a basis, the NTC thermistor may reach a mean temperature of up to 250 °C.
The heat developed during operation will also be dissipated through the lead wires. So the
contact areas, too, may become quite hot at maximum load.
When mounting NTC thermistors you have to ensure that there is an adequate distance between
the thermistor and all parts which are sensitive to heat or combustible.
1) For details on the capacitance Ctest as well as on the parameters k and n refer to "Application Notes", chapters 2.6 and 2.7.
Please read Important notes and
Cautions and warnings at the end of this document.
Page 3 of 6



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Inrush current limiters
ICLs
B57238
S238
Cautions and warnings
General
See "Important notes" at the end of this document.
Storage
Store thermistors only in original packaging. Do not open the package before storage.
Storage conditions in original packaging: storage temperature 25 °C ... +45 °C, relative
humidity 75% annual mean, maximum 95%, dew precipitation is inadmissible.
Do not store SMDs where they are exposed to heat or direct sunlight. Otherwise, the packing
material may be deformed or SMDs may stick together, causing problems during mounting.
Avoid contamination of thermistors surface during storage, handling and processing.
Avoid storage of thermistor in harmful environments like corrosive gases (SOx, Cl etc).
After opening the factory seals, such as polyvinyl-sealed packages, use the SMDs as soon as
possible.
Solder thermistors after shipment from EPCOS within the time specified:
SMDs: 12 months
Leaded components: 24 months
Handling
NTC thermistors must not be dropped. Chip-offs must not be caused during handling of NTCs.
Components must not be touched with bare hands. Gloves are recommended.
Avoid contamination of thermistor surface during handling.
Soldering
Use resin-type flux or non-activated flux.
Insufficient preheating may cause ceramic cracks.
Rapid cooling by dipping in solvent is not recommended.
Complete removal of flux is recommended.
Mounting
When NTC thermistors are encapsulated with sealing material or overmolded with plastic
material, the precautions given in chapter “Mounting instructions”, “Sealing, potting and
overmolding” must be observed.
Electrode must not be scratched before/during/after the mounting process.
Contacts and housings used for assembly with thermistor have to be clean before mounting.
During operation, the thermistor’s surface temperature can be very high (ICL). Ensure that
adjacent components are placed at a sufficient distance from the thermistor to allow for proper
cooling ot the thermistors.
Ensure that adjacent materials are designed for operation at temperatures comparable to the
surface temperature of the thermistor. Be sure that surrounding parts and materials can
withstand this temperature.
Make sure that thermistors (ICLs) are adequately ventilated to avoid overheating.
Avoid contamination of thermistor surface during processing.
Please read Important notes and
Cautions and warnings at the end of this document.
Page 4 of 6





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