NTC thermistors for

inrush current limiting

Leaded and coated disks

Series/Type: B57153S0***M0**

Date: May 2013

© EPCOS AG 2013. 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 Ctest please refer to "Application notes", chapter 1.6.

Small size

Manufacturer's logo, NTC and resistance value

stamped on

UL approval (E69802)

Resistance tolerance <20% and alternative lead

configurations available on request

Delivery mode

Bulk (standard) or with cardboard tape on 350-mm reel

Dimensional drawing

Dimensions in mm

Dissipation factor (in air) δth approx. 8 mW/K

Thermal cooling time constant (in air) τcapprox. 30 s

Heat capacity Cth approx. 240 mJ/K

Electrical specification and ordering codes

R25

Imax

(0...65 °C)

Ctest1)

230 V AC

µF

Ctest1)

110 V AC

µF

Rmin

(@ Imax,25°C)

Ordering code

Important notes at the end of this document.

Test Standard Test conditions ∆R25/R25

Duration: 21 days

Termal schock IEC

Lower test temperature: 55 °C

t: 30 min

Upper test temperature: 170 °C

t: 30 min

Time to change from lower to

upper temperature: < 30 s

Number of cycles: 10

Endurance IEC

Ambient temperature: 25 ±5°C

capacitance test

Ambient temperature: 25 ±5°C

Capacitance = Ctest

Number of cycles: 1000

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.

Important notes at the end of this document.

Resistance versus temperature

Important notes at the end of this document.

Resistance versus current

Important notes at the end of this document.

Application notes

Data book 2012". The complete application note can be downloaded from

1.4 Load derating

The power handling capability of an NTC thermistor cannot be fully utilized over the entire temper-

ature range. For circuit dimensioning the derating curve given below provides information on the

extent to which the current must be reduced at a certain ambient temperature (TA).

Derating curve for types S237, P11 and P13

Figure 1

TA= Ambient temperature > 25 °C

Tmax = 170 °C

Important notes at the end of this document.

1.6 Maximum permissible capacitance

The currents during turn-on are much higher than the rated currents during continuous operation.

ing to IEC 60539-1:

Figure 3

Test circuit for evaluating the maximum permissible capacitance of an NTC thermistor

Vload Load voltage [V]

Ctest Test capacitance [µF]

RSSeries resistance [RS=1Ω]

VNTC Voltage drop across the NTC under test [V]

Important notes at the end of this document.

are given in the data sheets.

Important notes at the end of this document.

Taping and packing

1 Taping of radial leaded ICL NTC thermistors according to the

specified lead spacing

Dimensions and tolerances

Lead spacing F = 5.0 mm (taping to IEC 60286-2)

for the following types: S153, S235 and S236

Lead spacing F = 7.5 mm (taping based on IEC 60286-2)

for the following types: P11, P13, S237, S238 and S364

Important notes at the end of this document.

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 inrush current limiters surface temperature can be very high. Ensure that

adjacent components are placed at a sufficient distance from the thermistor to allow for proper

cooling of the NTC inrush current limiters.

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 inrush current limiters are adequately ventilated to avoid overheating.

Avoid contamination of thermistor surface during processing.

must be ensured that no water enters the NTC inrush current limiters (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).

In case of exposure of the NTC inrush current limiters to water, electrolytes or other aggressive

media, these media can penetrate the coating and reach the surface of the ceramic. Low-ohmic

or high-ohmic behavior may occur due to the formation of an electrolyte with metals

(silver/lead/tin from metallization or solder). Low-ohmic behavior is caused by electrochemical

migration, high-ohmic behavior by dissolving of the electrode. In either case, the functionality of

the NTC inrush current limiters can not be assured.

Be sure to provide an appropriate fail-safe function to prevent secondary product damage

Important notes at the end of this document.

Symbols and terms

Imax Maximum current within stated temperature range

INTC NTC current

Pmax Maximum power within stated temperature range

Rmin Minimum resistance

RRRated resistance

∆RR/RRResistance tolerance

RSSeries resistance

RTResistance at temperature T

(e.g. R25 = resistance at 25 °C)

TRRated temperature

V Voltage

Vload Load voltage

VNTC Voltage drop across an NTC thermistor

δth Dissipation factor

τcThermal cooling time constant

Abbreviations / Notes

Important notes at the end of this document.

The following applies to all products named in this publication:

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scribed in the product specification is suitable for use in a particular customer application.

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 applications

requiring a very high level of operational safety and especially in customer applications in

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(e.g. installation of protective circuitry or redundancy) that no injury or damage is sustained by

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