Temperature Sensors - PTC Thermistors

Image	Part Number	Description / PDF	Quantity	Rfq
	PRF18BF471QB1RB TOKO / Murata	THERMISTOR PTC 470 OHM 50% 0603	0
	TFPT0805L1000KZ Vishay / Dale	THERMISTOR PTC 100 OHM 10% 0805	0
	KTY82/120/B,215 NXP Semiconductors	THERMISTOR PTC 1K OHM TO236AB	0
	TFPT0603L1500FZ Vishay / Dale	THERMISTOR PTC 150 OHM 1% 0603	0
	TFPT0603L4700FY Vishay / Dale	THERMISTOR PTC 470 OHM 1% 0603	0
	KTY84/150,153 NXP Semiconductors	THERMISTOR PTC 603 OHM DO34	0
	TFPT0603L4700FZ Vishay / Dale	THERMISTOR PTC 470 OHM 1% 0603	0
	PTFT0805L4701JV Vishay / Dale	THERMISTOR PTC 4.7K OHM 5% 0805	0
	PTFT1206L1000JW Vishay / Dale	THERMISTOR PTC 100 OHM 5% 1206	0
	PTFT0805L4700JV Vishay / Dale	THERMISTOR PTC 470 OHM 5% 0805	0
	B59604A85A62 TDK EPCOS	THERMISTOR PTC 470 OHM 50% 0603	0
	PTFT0805L4701JW Vishay / Dale	THERMISTOR PTC 4.7K OHM 5% 0805	0
	TFPT0805L5001FY Vishay / Dale	THERMISTOR PTC 5K OHM 1% 0805	0
	TFPT0805L3300KZ Vishay / Dale	THERMISTOR PTC 330 OHM 10% 0805	0
	PTFT0805L0030JW Vishay / Dale	THERMISTOR PTC 3 OHM 5% 0805	0
	PTFT0805L0220JV Vishay / Dale	THERMISTOR PTC 22 OHM 5% 0805	0
	LT300016T265K1J TE Connectivity AMP Connectors	THERMISTOR PTC 5.1K OHM 5% AXIAL	0
	PR425C050S101H TE Connectivity Measurement Specialties	THERMISTOR PTC 10 OHM RECT	0
	PRF18BB471QB1RB TOKO / Murata	THERMISTOR PTC 470 OHM 50% 0603	0
	TFPT0603L5600FZ Vishay / Dale	THERMISTOR PTC 560 OHM 1% 0603	0

Temperature Sensors - PTC Thermistors

1. Overview

Positive Temperature Coefficient (PTC) thermistors are resistors with a positive temperature coefficient, meaning their resistance increases significantly with temperature rise. Unlike NTC thermistors, PTC devices exhibit a sharp resistance transition at a critical temperature (Curie point). They are widely used in overtemperature protection, self-regulating heating elements, and temperature sensing applications. Their inherent safety features and reliability make them critical components in modern electronics, automotive systems, and industrial equipment.

2. Main Types and Functional Classification

Type	Functional Characteristics	Application Examples
Ceramic PTC Thermistors	High Curie temperature, abrupt resistance change, durable	Overheat protection in motors, heaters, and power supplies
Polymer PTC Thermistors	Lower switching temperature, resettable fuse functionality	USB port protection, battery management systems
Switching PTC	Digital on/off behavior at threshold temperature	Thermal cutoff for appliances, HVAC systems
Linear PTC	Proportional resistance-temperature response	Precision temperature measurement in industrial controllers

3. Structure and Composition

PTC thermistors typically consist of polycrystalline ceramic semiconductor materials (e.g., BaTiO₃ doped with rare earth elements) with embedded silver or platinum electrodes. The core structure includes: - Semiconductor ceramic body with tailored Curie temperature - Metal electrodes for electrical connection - Protective epoxy or glass coating - Lead wires (axial/radial) or SMD terminations The PTC effect arises from the material's phase transition at Curie temperature, causing resistance spikes due to crystal lattice changes.

4. Key Technical Specifications

Parameter	Description	Importance
R₂₅ (Resistance at 25 C)	Baseline resistance value	Determines circuit compatibility
T_switch (Switching Temperature)	Critical temperature for resistance jump	Application-specific threshold setting
R_min/R_max Ratio	Resistance range span	Indicates sensitivity and switching capability
Dissipation Factor (mW/ C)	Power dissipation per temperature unit	Affects thermal response speed
Response Time (ms)	Time to reach 90% resistance change	Critical for real-time protection systems

5. Application Fields

Major application sectors include: - Consumer Electronics: Smartphones (battery protection), 3D printers (hotend monitoring) - Automotive: EV battery thermal management, seat heater control - Industrial: Motor overload protection, pipeline freeze detection - Renewable Energy: Solar charge controllers, wind turbine gear monitoring - Medical: Patient warming systems, diagnostic equipment thermal regulation

6. Leading Manufacturers and Products

Manufacturer	Key Products	Features
Vishay Beyschlag	K2500-Finder	Automotive-grade PTC with 50-150 C range
TE Connectivity	PS224-202	UL-certified resettable fuse for power supplies
Murata Electronics	PXU11S150R0	Miniature SMD PTC for IoT devices
EPCOS (TDK)	B59904C0150A070	High-current PTC for industrial motor protection

7. Selection Guidelines

Key selection criteria: - Required switching temperature vs operating temperature range - Resistance tolerance and stability over lifespan - Package type (through-hole, SMD, bolt-on) - Voltage/current ratings with safety margin - Compliance with standards (UL, RoHS, AEC-Q200 for automotive) - Environmental resistance (humidity, vibration, chemical exposure)

8. Industry Trends

Emerging trends include: - Development of nano-ceramic materials for faster response times (<10ms) - Integration with MEMS technology for IoT sensor nodes - Higher temperature stability beyond 200 C for e-mobility applications - Miniaturization to 0402 SMD package sizes - AI-based predictive thermal management systems using PTC arrays - Increased adoption in hydrogen fuel cell thermal monitoring systems