PTC Thermistors POSISTOR® Application Manual

Product catalog summary

Introduction
The document is an application manual for PTC Thermistors, specifically the POSISTOR® by Murata Manufacturing Co., Ltd. It highlights the importance of adhering to specified ratings and cautions to prevent hazards such as smoking or burning. The manual also notes compliance with EU RoHS directives.

Characteristics of POSISTOR®
The POSISTOR® is a Positive Temperature Coefficient (PTC) Thermistor, which increases its resistance as temperature rises, contrary to conventional thermistors. This property is utilized in various applications such as temperature sensing, overheat protection, and current control.

Basic Design Data

Resistance-Temperature Characteristics: The resistance of POSISTOR® increases exponentially beyond its Curie-point (Cp), which can range from 40°C to 280°C. This characteristic is crucial for applications requiring temperature compensation and sensing.
Voltage-Current Characteristics: POSISTOR® can function as a constant temperature heater and provide over-current protection. Its resistance increases sharply when the current exceeds a certain point, thus protecting circuits from over-current.
Current-Time Characteristics: When a voltage above the maximum current point is applied, the POSISTOR® self-heats, increasing its resistance over time until the current stabilizes.

Structure of POSISTOR®
The POSISTOR® is made from barium titanate, a ferroelectric substance that becomes a semiconductor when doped with rare earth elements. Murata began commercial production in 1961.

Practical Applications
POSISTOR® is used in various devices for temperature sensing, current control, and overheat protection. Applications span across AV equipment, information equipment, communications equipment, car electronics, home electronics, and power supply systems.

Terms and Notices
The document concludes with a section on strict observance of guidelines and notices to ensure proper handling and application of POSISTOR® products.

Overview: The document provides technical details on POSISTOR® devices, focusing on their specifications, applications, and operational guidelines. POSISTORs are used for temperature sensing, compensation, and overheat protection in various electronic circuits.

Specifications:

Initial Resistance (R25): Measured at 25°C under specific conditions.
Curie Point (C.P.) Temperature: The temperature at which resistance sharply increases.
Maximum Operating Voltage: The highest continuous voltage within the operating temperature range.
Withstanding Voltage: Maximum voltage the POSISTOR can endure for three minutes at 25°C.
Heat Dissipation Factor (D): Heat lost per unit time based on temperature difference.
Thermal Time Constant (γsec): Time to reach 63.2% of the temperature difference.

Applications:

Temperature Compensation: Used in circuits without changing input impedance, suitable for pulse circuits and amplifiers.
Overheat Sensing: Protects motors, transformers, and transistors by shutting down circuits upon overheating.
Current Control: Limits inrush current in power supplies, acting as a current limiter.
Delay Circuits: Utilizes dynamic characteristics for relay delay operations.
Temperature Indication: Simple circuits using POSISTORs to indicate temperature changes.

Operational Guidelines:

POSISTORs are not hermetically sealed and should not be used in corrosive, volatile, or high humidity environments.
Ensure evaluation and confirmation of rated values before use.

Figures and Data:

Fig. 6-1 to 6-3: Illustrate current-time characteristics under various conditions.
Fig. 7: Shows changes in dynamic characteristics with series or parallel resistance.
Fig. 9-2: Demonstrates connection of multiple POSISTORs for multi-spot sensing.
Fig. 10: Examples of overheat protection circuits.

Catalog excerpts

PTC Thermistors POSISTOR® Application Manual-1

Open the catalog to page 1

PTC Thermistors POSISTOR® Application Manual-2

Note • Please read rating and CAUTION (for storage and operating, rating, soldering and mounting, handling) in this catalog to prevent smoking and/or burning, etc. • This catalog has only typical specifications. Therefore, please approve our product specifications or transact the approval sheet for product specifications before ordering. for EU RoHS Compliant All the products on this catalog are complied with EU RoHS. EU RoHS is "the European Directive 2011/65/EC on the Restriction of the Use of Certain Hazardous Substances in Electrical and Electronic Equipment". • For more details, please refer...

Open the catalog to page 2

PTC Thermistors POSISTOR® Application Manual-3

Note • Please read rating and CAUTION (for storage and operating, rating, soldering and mounting, handling) in this catalog to prevent smoking and/or burning, etc. • This catalog has only typical specifications. Therefore, please approve our product specifications or transact the approval sheet for product specifications before ordering. POSISTOR® Application and Variety List————2 2 The basic design data 3 Structure of POSISTOR® ——————————————— 4 Practical applications of POSISTOR® POSISTOR® and "POSISTOR" in this manual are the trademarks of Murata Manufacturing Co., Ltd. The basic design data...

Open the catalog to page 3

PTC Thermistors POSISTOR® Application Manual-4

Note • Please read rating and CAUTION (for storage and operating, rating, soldering and mounting, handling) in this catalog to prevent smoking and/or burning, etc. • This catalog has only typical specifications. Therefore, please approve our product specifications or transact the approval sheet for product specifications before ordering. POSISTOR® Application and Variety List Over current Protection Application Target device Information equipment Communications equipment Home electronics Household equipment Power supply Plasma TV LCD TV Projection TV CATV STB Video camera Digital camera DVD recorder...

Open the catalog to page 4

PTC Thermistors POSISTOR® Application Manual-5

Note • Please read rating and CAUTION (for storage and operating, rating, soldering and mounting, handling) in this catalog to prevent smoking and/or burning, etc. • This catalog has only typical specifications. Therefore, please approve our product specifications or transact the approval sheet for product specifications before ordering. 1 Characteristics of POSISTOR® 1. Introduction Barium titanate (BaTiO3) is a ferroelectric substance that was first identified in 1944. Its resistivity at room temperature becomes an n-type controlled-valency semiconductor with 1-106ohm · cm, if a slight amount...

Open the catalog to page 5

PTC Thermistors POSISTOR® Application Manual-6

Note • Please read rating and CAUTION (for storage and operating, rating, soldering and mounting, handling) in this catalog to prevent smoking and/or burning, etc. • This catalog has only typical specifications. Therefore, please approve our product specifications or transact the approval sheet for product specifications before ordering. 2 The basic design data 1. Resistance - temperature characteristics can be changed as shown in Fig. 2 and Fig. 3. In the case where a POSISTOR is used for temperature compensation, of a transistor for example, this method is useful to obtain suitable temperature...

Open the catalog to page 6

PTC Thermistors POSISTOR® Application Manual-7

Note • Please read rating and CAUTION (for storage and operating, rating, soldering and mounting, handling) in this catalog to prevent smoking and/or burning, etc. • This catalog has only typical specifications. Therefore, please approve our product specifications or transact the approval sheet for product specifications before ordering. The basic design data 2. Voltage - current characteristics (Static characteristics) All POSISTOR characteristic : AR Ambient temperature : at 25°C Fig. 4-2 Changing dimension and resistance value Ambient temperature Fig. 4-3 Changing ambient temperature 1000...

Open the catalog to page 7

PTC Thermistors POSISTOR® Application Manual-8

Note • Please read rating and CAUTION (for storage and operating, rating, soldering and mounting, handling) in this catalog to prevent smoking and/or burning, etc. • This catalog has only typical specifications. Therefore, please approve our product specifications or transact the approval sheet for product specifications before ordering. The basic design data 3. Current - time characteristics (Dynamic Characteristics) Fig. 6-3 Inrush current and attenuation 6 1000 PTGL07AR Ta=25°C Rs=KRpo Rpo : Resistance value of a POSISTOR at 25°C Fig. 6-1 Current - time characteristic (AC) If a specific voltage,...

Open the catalog to page 8

PTC Thermistors POSISTOR® Application Manual-9

^ Not6 * Please read rating and &CAUTION (for storage and operating, rating, soldering and mounting, handling) in this catalog to prevent smoking and/or burning, etc. • This catalog has only typical specifications. Therefore, please approve our product specifications or transact the approval sheet for product specifications before ordering. 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...

Open the catalog to page 9

PTC Thermistors POSISTOR® Application Manual-10

Note • Please read rating and CAUTION (for storage and operating, rating, soldering and mounting, handling) in this catalog to prevent smoking and/or burning, etc. • This catalog has only typical specifications. Therefore, please approve our product specifications or transact the approval sheet for product specifications before ordering. 4 Practical applications of POSISTOR® 1. For temperature sensor and temperature compensation 1. For temperature compensation and overheat sensing of transistors More than two pieces of POSISTOR can cover multi hot spots working with a comparator. Fig. 9-2 shows...

Open the catalog to page 10