NTC thermistors for
inrush current limiting
Leaded and coated disks,
insulation voltage 1000 VDC
Series/Type:
B57237
Date:
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.
1) For details on the capacitance C
test
as well as on the parameters k and n refer to "Application Notes", chapters 2.6 and 2.7.
Applications
Switch-mode power supplies
Soft-start motors, e.g. in vacuum cleaners
Features
Improved insulation voltage
Useable in series connections up to 265 V
rms
Coated thermistor disk
Kinked leads of tinned copper wire
Wide resistance range
UL approval (E69802)
Options
Alternative lead configurations available on
request
Delivery mode
Bulk (standard),
cardboard tape, reeled or in Ammo pack
Dimensional drawing
Dimensions in mm
Approx. weight 2 g
General technical data
Climatic category
(IEC 60068-1)
55/170/21
Max. power
(at 25
C)
P
max
3.1
W
Resistance tolerance
R
R
/R
R
15
%
Rated temperature
T
R
25
C
B value tolerance
B/B
3
%
Dissipation factor
(in air)
th
approx. 17
mW/K
Thermal cooling time constant
(in air)
c
approx. 90
s
Heat capacity
C
th
approx. 1530
mJ/K
Test voltage
(t = 1 s)
V
test
1000
VDC
Electrical specification and ordering codes
R
25
I
max
(0...25
C)
A
No. of
R/T char-
acteristic
B
25/100
K
C
test
1)
230 V
F
C
test
1)
110 V
F
Param.
for R(I)
1)
k
Param.
for R(I)
1)
n
Ordering code
1
9.0
1201
2700
700
2800
0.622
1.27
B57237S0109L002
2.2 7.0
1202
2800
700
2800
0.806
1.30
B57237S0229L002
2.5 6.5
1202
2800
700
2800
0.843
1.30
B57237S0259L002
4.7 5.1
1203
2900
700
2800
1.03
1.32
B57237S0479L002
5
5.0
1203
2900
700
2800
1.05
1.32
B57237S0509L002
7
4.2
1302
3000
700
2800
1.16
1.33
B57237S0709L002
10
3.7
1308
3060
700
2800
1.29
1.34
B57237S0100L002
15
3.0
1302
3000
700
2800
1.49
1.33
B57237S0150L002
Inrush current limiters
B57237
ICLs, insulation voltage 1000 VDC for 1 s
S237
Page 2 of 6
Please read Important notes and
Cautions and warnings at the end of this document.
1) For details on the capacitance C
test
as well as on the parameters k and n refer to "Application Notes", chapters 2.6 and 2.7.
R
25
I
max
(0...25
C)
A
No. of
R/T char-
acteristic
B
25/100
K
C
test
1)
230 V
F
C
test
1)
110 V
F
Param.
for R(I)
1)
k
Param.
for R(I)
1)
n
Ordering code
22
2.8
1304
3300
700
2800
1.57
1.37
B57237S0220L002
33
2.5
1304
3300
900
3600
1.78
1.37
B57237S0330L002
Reliability data
Test
Standard
Test conditions
R
25
/R
25
(typical)
Remarks
Storage in
dry heat
IEC
60068-2-2
Storage at upper
category temperature
T: 170
C
t: 1000 h
< 10%
No visible
damage
Storage in damp
heat, steady state
IEC
60068-2-78
Temperature of air: 40
C
Relative humidity of air: 93%
Duration: 21 days
< 5%
No visible
damage
Rapid temperature
cycling
IEC
60068-2-14
Lower test temperature:
55
C
Upper test temperature: 170
C
Number of cycles: 10
< 10%
No visible
damage
Endurance
I = I
max
t: 1000 h
< 10%
No visible
damage
Cyclic
endurance
I = I
max
, 1000 cycles
On-time = 1 min
Cooling time = 6 min
< 10%
No visible
damage
Transient
load
Capacitance = C
test
Number of cycles: 1000
< 5%
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.
Inrush current limiters
B57237
ICLs, insulation voltage 1000 VDC for 1 s
S237
Page 3 of 6
Please read Important notes and
Cautions and warnings at the end of this document.
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.
Inrush current limiters
B57237
ICLs, insulation voltage 1000 VDC for 1 s
S237
Page 4 of 6
Please read Important notes and
Cautions and warnings at the end of this document.
Operation
Use thermistors only within the specified operating temperature range.
Use thermistors only within the specified voltage and current ranges (ICLs).
Environmental conditions must not harm the thermistors. Use thermistors only in normal
atmospheric conditions.
Contact of NTC thermistors with any liquids and solvents should be prevented. It must be
ensured that no water enters the NTC thermistor (e.g. through plug terminals). For
measurement purposes (checking the specified resistance vs. temperature), the component
must not be immersed in water but in suitable liquids (e.g. Galden).
Avoid dewing and condensation.
Be sure to provide an appropriate fail-safe function to prevent secondary product damage
caused by malfunction (e.g. use VDR for limitation of overvoltage condition).
Inrush current limiters
B57237
ICLs, insulation voltage 1000 VDC for 1 s
S237
Page 5 of 6
Please read Important notes and
Cautions and warnings at the end of this document.
The following applies to all products named in this publication:
1.
Some parts of this publication contain statements about the suitability of our products for
certain areas of application. These statements are based on our knowledge of typical re-
quirements that are often placed on our products in the areas of application concerned. We
nevertheless expressly point out that such statements cannot be regarded as binding
statements about the suitability of our products for a particular customer application.
As a rule, EPCOS is either unfamiliar with individual customer applications or less familiar
with them than the customers themselves. For these reasons, it is always ultimately incum-
bent on the customer to check and decide whether an EPCOS product with the properties de-
scribed in the product specification is suitable for use in a particular customer application.
2.
We also point out that in individual cases, a malfunction of passive electronic compon-
ents or failure before the end of their usual service life cannot be completely ruled out
in the current state of the art, even if they are operated as specified. In customer applica-
tions requiring a very high level of operational safety and especially in customer applications
in which the malfunction or failure of a passive electronic component could endanger human
life or health (e.g. in accident prevention or life-saving systems), it must therefore be ensured
by means of suitable design of the customer application or other action taken by the customer
(e.g. installation of protective circuitry or redundancy) that no injury or damage is sustained by
third parties in the event of malfunction or failure of a passive electronic component.
3.
The warnings, cautions and product-specific notes must be observed.
4.
In order to satisfy certain technical requirements, some of the products described in this
publication may contain substances subject to restrictions in certain jurisdictions (e.g.
because they are classed as "hazardous"). Useful information on this will be found in our
Material Data Sheets on the Internet (www.epcos.com/material). Should you have any more
detailed questions, please contact our sales offices.
5.
We constantly strive to improve our products. Consequently, the products described in this
publication may change from time to time. The same is true of the corresponding product
specifications. Please check therefore to what extent product descriptions and specifications
contained in this publication are still applicable before or when you place an or-
der.
We also reserve the right to discontinue production and delivery of products. Con-
sequently, we cannot guarantee that all products named in this publication will always be
available.
6.
Unless otherwise agreed in individual contracts, all orders are subject to the current ver-
sion of the "General Terms of Delivery for Products and Services in the Electrical In-
dustry" published by the German Electrical and Electronics Industry Association
(ZVEI).
7.
The trade names EPCOS, EPCOS-JONES, Baoke, CeraDiode, CSSP, MLSC, PhaseCap,
PhaseMod, SIFI, SIKOREL, SilverCap, SIMID, SIOV, SIP5D, SIP5K, UltraCap, WindCap are
trademarks registered or pending in Europe and in other countries. Further information will
be found on the Internet at www.epcos.com/trademarks.
Important notes
Page 6 of 6
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