PTC Thermistor (POSISTOR®)

Home , Heating element

!Note • This PDF catalog is downloaded from the website of Murata Manufacturing co., ltd. Therefore, it’s specifications are subject to change or our products in it may be discontinued without advance notice. Please check with our sales representatives or product engineers before ordering. R16E.pdf • This PDF catalog has only typical specifications because there is no space for detailed specifications. Therefore, please approve our product specifications or transact the approval sheet for product specifications before ordering. 08.9.25

Application Manual

Murata Manufacturing Co., Ltd. Cat.No.R16E-4 !Note • This PDF catalog is downloaded from the website of Murata Manufacturing co., ltd. Therefore, it’s specifications are subject to change or our products in it may be discontinued without advance notice. Please check with our sales representatives or product engineers before ordering. R16E.pdf • This PDF catalog has only typical specifications because there is no space for detailed specifications. Therefore, please approve our product specifications or transact the approval sheet for product specifications before ordering. 08.9.25

for EU RoHS Compliant • All the products on this catalog are complied with EU RoHS. • EU RoHS is "the European Directive 2002/95/EC on the Restriction of the Use of Certain Hazardous Substances in Electrical and Electronic Equipment". • For more details, please refer to our website 'Murata's Approach for EU RoHS' (http://www.murata.com/info/rohs.html). !Note • This PDF catalog is downloaded from the website of Murata Manufacturing co., ltd. Therefore, it’s specifications are subject to change or our products in it may be discontinued without advance notice. Please check with our sales representatives or product engineers before ordering. R16E.pdf • This PDF catalog has only typical specifications because there is no space for detailed specifications. Therefore, please approve our product specifications or transact the approval sheet for product specifications before ordering. 08.9.25

POSISTOR® Application and Variety ListYYYYY02

1 Characteristics of POSISTOR®Y YYYYYYYYYYYYYY03 CONTENTS

1. Introduction ...... 03 2. Characteristics of POSISTOR®...... 03

2 Y YYYYYYYYYYYYYYYYYYYYYYY04 The basic design data Characteristics of 1. Resistance - temperature characteristics...... 04 1 POSISTOR® 2. Voltage - current characteristics (Static characteristics)...... 05 3. Current - time characteristics (Dynamic characteristics) ...... 06 The basic design data 3 Structure of POSISTOR®YYYYYYYYYYYYYYYYYYYYY07 2

4 Practical applications of POSISTOR®Y YYYYYYY08 Structure of POSISTOR® 1. Heating (Automatic temperature adjustment heater) ...... 08 3 2. For temperature sensor and temperature compensation ...... 09 3. For current control...... 011 Practical applications of ® 5 TermsY YYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYY012 4 POSISTOR

!Strict observance ...... 012 !Notice ...... 012 5 Terms

POSISTOR® and "POSISTOR" in this manual are the trademarks of Murata Manufacturing Co., Ltd. !Note • This PDF catalog is downloaded from the website of Murata Manufacturing co., ltd. Therefore, it’s specifications are subject to change or our products in it may be discontinued without advance notice. Please check with our sales representatives or product engineers before ordering. R16E.pdf • This PDF catalog has only typical specifications because there is no space for detailed specifications. Therefore, please approve our product specifications or transact the approval sheet for product specifications before ordering. 08.9.25 POSISTOR® Application and Variety List

Temp com- Motor Over current Protection Overheat Sensing Heater pensation starter Case type Application Target device Lead type Contact type Chip type Lead type Chip type Lead type Hot air type PTH6M PTFL PTWSB PRG PTGL PRF PTRL PTWH PTH7M PTFM PTWTA PTHTM Plasma TV K K K K K LCD TV K K K K Projection TV K K K K CATV K STB K Video camera K K Digital camera K K DVD recorder K K K AV equipment VTR K K K Audio K K K K Electric keyboard, Electronic music K K K K instrument Digital mobile audio K K MD/CD player K K TV game K K K Portable game K K Laptop K K Desktop computer K K Server K K K K Printer K K K K Scanner K K Information LCD display K K K K equipment USB access device K HDD K CD/DVD-ROM/RAM K K Copy machine K K K K Electronic dictionary/databook K K Electronic blackboard K K K K Electronic automatic exchange K Transmission equipment K PBX K Cordless telephone K Communica- Fax machine K K K K tions equip- Modem K ment Cellular phone K K Headset K Cellular phone base station K K K K Intercom K K Engine control ECU K K Drive control ECU K K Air-bag K Anticollision radar K ABS/ESC K K Instrument/display panel, Meter K Rechargeable battery for EV/HEV K K Car air conditioner K K Heater, HVAC K Car HID/LED headlight, AFS K K K electronics LED tail light K K K LED interior light K K Retractable electric mirror K Door lock, trunk opener K Power seat K Shock absorber K VICS, ETC K Burglar alarm K K Car navigation K K K Car audio K K K K Refrigerator K K K K Microwave, Oven K K K Electric rice-cooker K K K IH cooking device K K Air conditioner K K K K K Fan heater K K Cleaner K K Bath dryer K Clothes washer, cloth dryer K K Futon dryer K Home Hot-air heater K electronics Electric pot K Household Ventilator K equipment hot-water pot K K K Humidifying device K Inhaler K Illumination device K K K K Massage chair, healthcare equipment K K K K K Curling iron K Potable compact iron K Hot water spray toilet seat K K K K Electric power tool K K K K Electric mosquito extermination, K fragrance device Switching supply K K K K Power supply Inverter power K K K K AC adapter, battery charger K K K !Note • This PDF catalog is downloaded from the website of Murata Manufacturing co., ltd. Therefore, it’s specifications are subject to change or our products in it may be discontinued without advance notice. Please check with our sales representatives or product engineers before ordering. R16E.pdf • This PDF catalog has only typical specifications because there is no space for detailed specifications. Therefore, please approve our product specifications or transact the approval sheet for product specifications before ordering. 08.9.25 1 Characteristics of POSISTOR®

1. Introduction

Barium titanate (BaTiO3) is a ferroelectric substance Since then, it has been applied to several applications that was first identified in 1944. Its resistivity at room under the name of POSISTOR. temperature becomes an n-type controlled-valency 1 semiconductor with 1-106ohm · cm, if a slight amount POSISTOR is Positive Temperature Coefficient of rare earth elements are added to Barium titanate. Thermistor (PTC Thermistor). Normally when the It was first made in 1951. Murata was extremely temperature increases, the resistance of conventional interested in this semiconductor and successfully Thermistor decreases. But, the resistance of PTC starting the first commercial production of the Thermistor rises sharply when its temperature exceeds POSISTOR in 1961. a specific temperature.

2. Characteristics of the POSISTOR®

Basically, the POSISTOR increases its resistance value, three characteristics can be made, which are described when its temperature rises. From this phenomenon, below.

!Table 1 Characteristics of POSISTOR Resistance - temperature Voltage - current characteristics Current - time characteristics characteristics (Static Characteristic, (Dynamic characteristic, (time independent) time independent) time dependent)

104

3 10 Constant Power

102 Basic 10

characteristics Current (A) log I Current 1 Constant Resistance Resistance Value (Ω) Resistance Value

0 50 100 150 200 10 15 20 25 log V Voltage Temperature (°C) Time (sec.)

Resistance Value up

Resistance Resistance Value up Resistance Value up log R log I at 25degC (Ω) Current (A)

Temperature (°C) log V Time (sec.)

Ta up

Ambient Ta up log R log I temperature (Ta) (Ω) Current (A)

Temperature (°C) log V Time (sec.)

Temperature change can be detected This characteristic shows the relation This characteristic shows the because the resistance of POSISTOR between the applied voltage and relation between current and time is changed by ambient temperature. stable current, when the Thermistor as equilibrium is achieved between internal self-heating equals the heat internal self-heating and heat Features dissipated by the Thermistor to the dissipation under the applied voltage. outside (state of equilibrium). Each above chart is composed of constant resistance area, maximum current point and constant power area. 1. Temperature sensing, temperature 1. Current control, over current 1. Motor starter element compensation protection (Motor starter relay) Functions 2. Overheat protection of electric 2. Constant temperature heater 2. Timer delay element & applications equipment, electric devices, Heater 3. Detector element using change of devices, Power supplies. Power IC/ heat dissipation factor FET 4. Constant voltage and constant current equipment !Note • This PDF catalog is downloaded from the website of Murata Manufacturing co., ltd. Therefore, it’s specifications are subject to change or our products in it may be discontinued without advance notice. Please check with our sales representatives or product engineers before ordering. R16E.pdf • This PDF catalog has only typical specifications because there is no space for detailed specifications. Therefore, please approve our product specifications or transact the approval sheet for product specifications before ordering. 08.9.25 2 The basic design data

1. Resistance - temperature characteristics

The POSISTOR® has resistance - temperature can be changed as shown in Fig. 2 and Fig. 3. In the characteristics that cause its resistance to exponentially case where a POSISTOR is used for temperature increase when the part’s temperature exceeds its Curie- compensation, of a transistor for example, this method point (Cp), the critical temperature where the resistance is useful to obtain suitable temperature characteristics. value increases dramatically. Typically above the Cp, the resistance of POSISTOR increase at rate of 15% to !Table 3 Temp. Characteristics (T.C.) and Cp 2 60% per degC. There are many kinds of Cp available T.C. Cp (degC) T.C. Cp (degC) (from 40degC to 280degC, as shown in Fig. 1, table 2 AD 280 BA 110 and table 3) which allows for the easy selection of a AE 260 BB 100 suitable Cp for each application. AF 240 BC 90 Some special POSISTOR, products with a Cp below AG 220 BD 80 room temperature, exhibit a more linear rate of AH 200 BE 70 resistance increase of 5% per degC, above its Cp. AK 180 BF 60 If a resistor is connected with the POSISTOR in series AL 170 BG 50 AM 160 BH 40 or parallel, the resistance - temperature characteristics AN 150 T (−50) AP 140 AS 130 AR 120 105 BD BB AS AN BC AR AP AM

AK 104 10 BG AH BH AG PTRL07BT102M2A51B0 AF 103 AE AD

K=2.0 102

K=1.0 T R/Rpo 1 K=0.5 Rp Rs 10

Rate of Resistance Change (R/25°C) Single POSISTOR (characteristic T) AD ~ BD R=Rp+Rs 1 BG Rs=KRpo BH Rpo : Resistance value of a POSISTOR at 25°C 10-1 10-1 -20 -10 0 10 20 30 40 50 60 T Temperature (°C) -50 0 25 50 100 150 200 250 300 Temperature (°C)

Fig. 2 Insertion of fixed resistance in series with POSISTOR Fig. 1

!Table 2 Resistance - temperature characteristics Temper- 10 Clas- PTRL07BT102M2A51B0 ature sifi- Description of characteristics Applications Rp charac- cation teristics RF

Exhibits a generally uniform R=Rp · RF/(Rp+RF) RF=hRpo positive resistance temperature Temp. Rpo : Resistance value (ⅰ) T characteristics (about 5%/degC) compensation, of a POSISTOR h=2.0 within the temperature range of Temp. sensing at 25°C room temperature to 60degC R/Rpo 1 h=1.0 Single POSISTOR Exhibits an almost linear (characteristic T) resistance increase between room h=0.5 Temp. sensing, temp and the Cp, with an abrupt Overheat (ⅱ) BH-AR resistance increase above the Cp. sensing, Motor Cp is available in a range from starting, Heaters 40degC to 120degC, selected by temperature characteristics 10-1 Temp. sensing, -20 -10 0 10 20 30 40 50 60 Exhibits a less than linear Overheat Temperature (°C) resistance increase from room sensing, (ⅲ) AR-AD temperature to the Cp, with an Over current abrupt resistance rise over the Cp. protection, Motor starting, Heaters Fig. 3 Insertion of fixed resistance in parallel with POSISTOR !Note • This PDF catalog is downloaded from the website of Murata Manufacturing co., ltd. Therefore, it’s specifications are subject to change or our products in it may be discontinued without advance notice. Please check with our sales representatives or product engineers before ordering. R16E.pdf • This PDF catalog has only typical specifications because there is no space for detailed specifications. Therefore, please approve our product specifications or transact the approval sheet for product specifications before ordering. 08.9.25

The basic design data 2

2. Voltage - current characteristics (Static characteristics)

The POSISTOR® can be used as a constant temperature 103 ) All POSISTOR heater with an automatic temperature adjustment Ω ) characteristic : AR function and can maintain constant wattage, even Ω Ambient temperature : at 25°C PTGL18 (2.2 ) over voltage fluctuation, if the current through the Ω PTGL14 (2.2

POSISTOR is maintained above its maximum current 102 PTGL09 (4.7) point. Ω

) The POSISTOR can provide over-current protection if Ω 2 it is connected in series in a circuit. If current through Current (mA) PTGL07 (22 PTGL07 (47 the POSISTOR is less than the maximum current 10 point provided as “protective current” in the spec, the POSISTOR acts like a regular fixed value resistor. If current exceeds the protective current, the POSISTOR 1 10 100 will sharply increase in resistance due to self heating Voltage (V) and reduce the current flow, providing protection to the Fig. 4-2 Changing dimension and resistance value rest of the circuit. By adding a series or parallel resistor to the POSISTOR, PTWSB2AG

the voltage-current characteristics can be changed as Ambient shown in Fig. 5. As an example, a resistor in parallel 100 temperature 0°C 10°C with the POSISTOR can provide a constant current 25°C 40°C function with increasing voltage (see curves 1, 2, and 3 Current (mA) 60°C in Fig. 5.) 10 When voltage is applied to the POSISTOR, self- heating can occur due to current flow. If current flow 10 100 Voltage (V) through the POSISTOR, exceeds the maximum current point, then self heating of the POSISTOR may cause Fig. 4-3 Changing ambient temperature the temperature of the part to exceed the CP and its 1000 resistance raises dramatically. As long as the maximum Rp Rs PTGL07AR Ta=25°C Rs=KRpo current point is exceeded, the POSISTOR will stabilize Rpo : Resistance value of a POSISTOR at 25°C above the Cp and high resistance will be maintained. As POSISTOR current is reduced below the maximum current point, (K=0) K=2 K=3 K=5 self heating is reduced and the POSISTOR will cool to below the CP, assuming an external heat source is not 100

present. Current (mA) With the voltage - current characteristics shown in a double logarithmic graph, the line (charted as I vs. V) is shown to increase in a 45 deg. straight line (constant resistance region of the chart, where the Thermistor’s 10 resistance is stable) until the maximum current point 1 10 is reached. Beyond the maximum current point, the Voltage (V)

line decreases at a 45deg straight line (constant power 1000 PTGL07AR region of the chart, where the Thermistor’s resistance sharply increases). 1. (h=2) 2. (h=3) 3. (h=5)

POSISTOR Itself (h=∞) PTWSB All POSISTORs in characteristic AR Ambient 100 temperature 25°C

Current (mA) RP 100 RF AG AH Ta=25°C Rp=hRpo Rpo : Resistance value AS of a POSISTOR Current (mA) BC at 25°C

10 10 1 10 Voltage (V) 10 100 Voltage (V) Fig. 5 Change of static characteristic of POSISTOR by series Fig. 4-1 Changing Curie point and parallel resistance !Note • This PDF catalog is downloaded from the website of Murata Manufacturing co., ltd. Therefore, it’s specifications are subject to change or our products in it may be discontinued without advance notice. Please check with our sales representatives or product engineers before ordering. R16E.pdf • This PDF catalog has only typical specifications because there is no space for detailed specifications. Therefore, please approve our product specifications or transact the approval sheet for product specifications before ordering. 08.9.25

2 The basic design data

3. Current - time characteristics (Dynamic Characteristics)

If a specific voltage, above the V-I chart’s maximum current point, is applied to the POSISTOR® a large

amount of current will flow through POSISTOR, PTGL09AR220M6B52B0 Ta=25°C because its resistance is low. The POSISTOR will start 1.5 to self-heat due to the current, and over a period of time the temperature of the POSISTOR will exceed the Cp

2 and its resistance will sharply increase. Due to this, 1.0 the current will eventually stabilize at a constant level. Current Value (A) Current Value (Fig. 6-1 and 6-2) If the initial applied voltage is increased, the time 0.5 needed for the POSISTOR to self-heat beyond its Cp is reduced, due to the larger current flow causing faster self-heating of the POSISTOR. (Fig. 6-3) 0 2 4 6 8 10 12 If a resistor is connected with POSISTOR in series or in Time (sec.) parallel, the dynamic characteristics can be changed as well. (Fig. 7) Fig. 6-3 Inrush current and attenuation

6 1000 Rp Rs PTGL07AR 4 900 Ta=25°C Rs=KRpo Ta=25°C Rpo : Resistance value 16V of a POSISTOR 800 at 25°C 2 700

0 600 K=2

Current Value (A) Current Value 500 -2 K=3 Current (mA) 400

-4 300 K=5

200 0 50 100 150 200 250 300 350 400 100 Time (msec.)

0 2 4 6 8 10 Fig. 6-1 Current - time characteristic (AC) Time (sec.)

1000 PTGL07AR 900 Rp

8 800 RF 16V 700 Ta=25°C RF=hRpo 6 600 Rpo : Resistance value of a POSISTOR Ta=-10 °C at 25°C 500

4 Current (mA) 400 h=2

Current Value (A) Current Value 300 25°C h=3 60°C 2 200 h=5

100 0 0 1 2 3 4 5 0 2 4 6 8 10 Time (sec.) Time (sec.)

Fig. 6-2 Current - time characteristic (DC, Ambient temperature change) Fig. 7 Change of dynamic characteristic of POSISTOR by series or parallel resistance

Leaded products of POSISTOR, as shown in Fig. 8, can have their POSISTOR element either: soldered to lead wires and its surface then coated with epoxy resin, or the element can be held in place by spring terminals and encased in a plastic housing. In the case of the latter, the spring terminals also provide the electrical connection and exit the housing as lead terminals. The shape of the POSISTOR can either be square or round. Recently, chip type POSISTORs are becoming more common.

PRF · PRG (Bulk type) PTGL PTFM PTH6M/7M PTWSB 3 7 7 5 < > = 9 7 = : < 9 9 = = PRG (Multi-layer type) ; 5 < 9 = 8 ; 6 9

= 9

qBarium titanate ceramics eCoated resin tLead wire uCase oTerminal wTerminal rSoldering yCover iSpring terminal pRadiative plate & terminal

Fig. 8

1. Heating (Automatic temperature adjustment heater)

1. For general heater !Applications POSISTOR can be used as a constant temperature Electric rice cooker / Electric pot / Hot plate / Inhaler heater that is self-regulating. It does not need a / Humidifying device / General heater / Antifreeze / thermostat to control temperature and inherently Fax machine / Copy machine / Portable compact iron / protects against abnormal temperature rise and failure. Aromatic instrument and so on. Constant temperature can be maintained by the varying

applied voltage. 10

!General heaters t=5mm 5 t=3mm t=2mm

E=120Vr.m.s. 2 Ta=25°C Power Consumption (W) Radiative Plate : Aluminum Plate Same power marked as is obtained without radiative plate when water (20-30 cc) is 4 PTWTA PTWSB supplied and boiled on the PTH. 1 100 200 300 500 1000 2000 ! Low thermal resistance type heaters capable of Surface Area of Radiative Plate (cm2) larger power output Fig. 9 Characteristics of power consumprion

PTWLB

2. For Air Heating !Applications POSISTOR pills (pellets) are mounted in an aluminum Bath dryer / Clothes dryer / Futon dryer / Dish dryer / radiator that is suitable for air heating. Hot-air heater / Auxiliary heater and so on The power and the temperature can be easily adjusted by varying the speed of the fan that blows air over the PTWHC3AF351Y260D00 Ambient radiator. Also, its power characteristics will change with Temperature 800 changes in ambient temperature, as shown Fig. 10. 25℃ When the ambient temperature decreases, the power 15℃ 700 5℃ increases. When the ambient temperature increases, the -5℃ Heat Value (W) Heat Value power is reduced. 600

Applied Voltage : AC220Vrms 500

0 2 4 6 8 10 Wind Velocity (m/sec)

0 0.25 0.5 0.75 1.0 1.25 1.5 1.75 Airflow (m3/sec) PTWHC Fig. 10 Heating power characteristics of Air heater

3. For constant temperature control: !Applications If a POSISTOR is connected to another heater in series, Keep-warm plate / Humidifier and so on the POSISTOR can be used to detect the change of the other heater’s temperature and the change of the

ambient temperature. (Fig. 11) POSISTOR Heater

Heat connection

Power Source

PTWTA PTWSB Fig. 11 Heater control

Practical applications of POSISTOR® 4

2. For temperature sensor and temperature compensation

1. For temperature compensation and overheat sensing of transistors (1) (2) (3)

L Fig. 12(1) shows a basic circuit for temperature R’B R’ RL RL RB RB compensation. In biasing the transistor, the resistance POSISTOR POSISTOR of POSISTOR is used. If the transistor overheats, the POSISTOR will heat up as well. As the POSISTOR RA RA RA passes the Cp, it will go high resistance and unbiased RE POSISTOR RE the circuit, and turning off the transistor. In case of Fig. 12(2) and 12(3), it also can be used as an over heat sensor as well. Fig. 12 Temperature compensation and protection of When POSISTOR is used for temperature transistor compensation, it does not change the input impedance, like a negative temperature coefficient Thermistor (NTC Thermistor), because the POSISTOR is not connected to input circuit in parallel. Therefore, the POSISTOR is 4 suitable for circuits which do not need a change of input impedance as a pulse circuits, regional amplifier, and measurement equipment.

More than two pieces of POSISTOR can cover multi hot spots working with a comparator. Fig. 12-2 shows Vcc

basic circuit idea to connect multiple POSISTOR in R4 R1 series. When One POSISTOR detects overheat at least, Vcc a comparator can work by the sharp temperature- PTC1 R2 resistance characteristic. It easily allows changing a V+in PTC2 + Comp number of POSISTOR or sensing temperature in the R3 V–in Comp Out PTC3 – same basic circuit design. PTC4

Fig. 12-2 Connection of multiple POSISTOR

PTFM04 PTFL04 PRF18/15

For overheat protection of power transistor or IC

2. Overheat sensing for motors and transformers Motor (1) Power Transistor (2) Transformer (3) A POSISTOR can be used for the overheat sensing POSISTOR

Relay of motors, transformer winding, bearings, power POSISTOR transistors, and other machinery. Fig. 13(1) shows an M POSISTOR Power example of overheat sensing for motor using a relay. Source Power Source In case of small regular operating current, the circuit Power can be directly stopped by POSISTOR. In case of larger Transistor regular operating currents, the circuit can be stopped by using the POSISTOR with a relay or a thyristor. In Fig. 13 Protection from overheat by POSISTOR either case, POSISTOR is a very easy to use device, because it’s small, light, and a two terminals device.

4 Practical applications of POSISTOR®

3. For temperature indication Fig. 14 shows most simple example of a temperature (1) (2) 20KΩ indicator. Temperature is sensed by POSISTOR. If the POSISTOR target temperature is exceeded (determined by which

POSISTOR is used), a neon tube lights up. Neon Lamp Neon Lamp

100V 100V POSISTOR 20KΩ 60Hz 60Hz

Fig. 14 Temperature indication by POSISTOR

PTGL PTRL

4 For temp. indication, overheat protection

10 !Note • This PDF catalog is downloaded from the website of Murata Manufacturing co., ltd. Therefore, it’s specifications are subject to change or our products in it may be discontinued without advance notice. Please check with our sales representatives or product engineers before ordering. R16E.pdf • This PDF catalog has only typical specifications because there is no space for detailed specifications. Therefore, please approve our product specifications or transact the approval sheet for product specifications before ordering. 08.9.25

Practical applications of POSISTOR® 4

3. For current control

1. Over current protection Transistor (1) Motor (2) If a circuit’s current limit is exceed, a POSISTOR can POSISTOR 100K -B 100K RL -B POSISTOR react to the higher current (self heating) and quickly Ω RL Ω protect the circuit. (Fig. 15) POSISTOR Motor M 10K 10K Power Source Ω 0.1µF Ω 2.2Ω 10µF

Power circuit (3) POSISTOR POSISTOR Antenna Coaxial Cable Power 75Ω 27Ω Booster Source T.V 160V 30µF 160V 30µF Power POSISTOR Source PTGL04 PTGL07 PTGL12 Fig. 15 Protection from over current 4 2. Delay Circuit A delay function can be created by using the dynamic (1) (2) (3) characteristics of POSISTOR. There are two methods: For POSISTOR Delaying POSISTOR R Time one is with the POSISTOR connected in parallel with a Adjustment

relay as in Fig. 16(1) and the other is similar but with Power For Heater Source Relay

series connection, as in Fig. 16(2) and (3). Relay Relay POSISTOR

Fig. 16 Delay operation of relay

PTGL

3. For the control of inrush current A switching power supply has large inrush current Thyristor when it first turns on. If POSISTOR is used, instead of a resistor or an NTC Thermistor, the POSISTOR works as inrush current limiter. The POSISTOR self heats due POSISTOR to over current in the case of relay or thyristor’s failure and will trip to high resistance, quickly shutting off the current. (Fig. 17)

Fig. 17 Inrush current limit circuit

4. For motor starter If the POSISTOR is used as a contactless starter rely, (1) (2) (3) (4) for compressors as in refrigerators, freezers and air RSI Motor CSIR Motor CRS Motor PSC Motor conditioners, strong starting torque can be generated. (Fig. 18(1) to (4))

Fig. 18 Motor starting

PTH6M PTH7M PTHTM

11 !Note • This PDF catalog is downloaded from the website of Murata Manufacturing co., ltd. Therefore, it’s specifications are subject to change or our products in it may be discontinued without advance notice. Please check with our sales representatives or product engineers before ordering. R16E.pdf • This PDF catalog has only typical specifications because there is no space for detailed specifications. Therefore, please approve our product specifications or transact the approval sheet for product specifications before ordering. 08.9.25 5 Terms

Definitions of typical terms for POSISTOR®s are listed !Strict observance: here. POSISTOR is not hermetically sealed, do not use 1. Initial resistance (R25) it under the below conditions. If POSISTOR is This is the part’s resistance value at 25degC which is used in such conditions, they may cause decline of measured under conditions of 1.0VDC or less, and 10mA characteristics or may lead to short-circuit type failure.

or less without self-heating. · Corrosive gas atmosphere (Cl2, NH3, SOx, NOx and so on) 2. Curie point (C.P.) temperature (Resistance - · Volatile, flammable gas atmosphere temperature characteristics) · Dusty area A POSISTOR maintains almost the same resistance, · Pressurized air or vacuum atmosphere until certain temperature. After this temperature is · Direct contact with water, standing water on the part, exceeded, the resistance of POSISTOR rises up sharply. or high humidity. This transition point is called the “Curie point” or “C.P.”. · Exposure to salt, grease, chemicals, organic solvents Murata defines this critical temperature to be the ‘Curie · Place with a lot of vibration point’ temperature, where the actual resistance value is · Anything equivalent to the above mentions twice the reference value measured at 25degC. !Notice: 3. Maximum operating voltage POSISTOR should be evaluated, after confirmation Within the operating temperature range of POSISTOR, of rated value, and using precautions as given in the 5 it is the largest voltage that can be applied continuously. catalog.

4. Withstanding voltage The maximum voltage which the POSISTOR can withstand over a three minute period, at 25deg. To test, the input voltage is raised to withstanding voltage from zero voltage gradually.

5. Heat dissipation factor (D) It is the amount of heat which is lost, over a unit of time, based on 1degC temperature difference between heating element and ambient temperature.

W=I · V=D(T–T0)

T: temperature of heating element

T0: ambient temperature D: heat dissipation factor (W/degC) Generally this value is decided by a size, a structure and material of heating element.

6. Thermal time constant (γsec) It is the time needed, to achieve 0.632 times the

temperature difference between T0 to T1. γ=H/D, Here D, Heat dissipation factor (W/degC), H: Heat capacity (Wsec/degC) This formula is related to dynamic characteristics.

7. Operation point It is an equilibrium condition between self-heating of the POSISTOR and the external radiator.

12 !Note • This PDF catalog is downloaded from the website of Murata Manufacturing co., ltd. Therefore, it’s specifications are subject to change or our products in it may be discontinued without advance notice. Please check with our sales representatives or product engineers before ordering. R16E.pdf • This PDF catalog has only typical specifications because there is no space for detailed specifications. Therefore, please approve our product specifications or transact the approval sheet for product specifications before ordering. 08.9.25