PTC Resettable Fuses

Part Number	Description / PDF	Quantity
YM120D260N150 Thermometrics (Amphenol Advanced Sensors)	PTC RESET FUSE 265V 234MA RADIAL	0
YQS5749PTO Thermometrics (Amphenol Advanced Sensors)	PTC RESET FUSE 25V RADIAL DISC	2874
YS5869PTF Thermometrics (Amphenol Advanced Sensors)	PTC RESET FUSE 120V 60MA RADIAL	1966
YQD120N0006 Thermometrics (Amphenol Advanced Sensors)	PTC RESET FUSE 265V 390MA RADIAL	1446
YQZ120N1.20 Thermometrics (Amphenol Advanced Sensors)	PTC RESET FUSE 18V 700MA RADIAL	0
YQD080N0050 Thermometrics (Amphenol Advanced Sensors)	PTC RESET FUSE 265V 60MA RADIAL	23
YQS5855PTF Thermometrics (Amphenol Advanced Sensors)	PTC RESET FUSE 50V 80MA RADIAL	729
YQS5934PTO Thermometrics (Amphenol Advanced Sensors)	PTC RESET FUSE 480V RADIAL DISC	0
YQS5846PTF Thermometrics (Amphenol Advanced Sensors)	PTC RESET FUSE 25V 370MA RADIAL	0
YQS8120 Thermometrics (Amphenol Advanced Sensors)	PTC RESET FUSE 420V 21MA RADIAL	1590
YQS8067 Thermometrics (Amphenol Advanced Sensors)	PTC RESET FUSE 265V 85MA RADIAL	759
YQS5751PTO Thermometrics (Amphenol Advanced Sensors)	PTC RESET FUSE 25V RADIAL DISC	417
YM120D170R250 Thermometrics (Amphenol Advanced Sensors)	PTC RESET FUSE 265V 161MA RADIAL	0
YQD120N0015 Thermometrics (Amphenol Advanced Sensors)	PTC RESET FUSE 265V 180MA RADIAL	0
YM120D125N450 Thermometrics (Amphenol Advanced Sensors)	PTC RESET FUSE 265V 110MA RADIAL	3851
YS4020 Thermometrics (Amphenol Advanced Sensors)	PTC RESET FUSE 1.0KV RADIAL DISC	2423
YQS8070 Thermometrics (Amphenol Advanced Sensors)	PTC RESET FUSE 265V 22MA RADIAL	1495
YQD120N0025 Thermometrics (Amphenol Advanced Sensors)	PTC RESET FUSE 265V 130MA RADIAL	1350
YQS5898PTO Thermometrics (Amphenol Advanced Sensors)	PTC RESET FUSE 12V RADIAL DISC	1103
YQS8121 Thermometrics (Amphenol Advanced Sensors)	PTC RESET FUSE 265V 35MA RADIAL	3131

PTC Resettable Fuses

1. Overview

PTC (Positive Temperature Coefficient) Resettable Fuses are overcurrent protection devices that exhibit a sharp increase in resistance when fault currents exceed normal operating levels. Unlike traditional fuses, PTC devices automatically reset to low-resistance states after fault conditions clear. This self-recovering makes them critical in applications requiring reliable protection against short circuits and overloads without manual replacement. Their importance in modern electronics spans consumer devices, automotive systems, industrial equipment, and renewable energy installations.

2. Main Types and Functional Classification

Type	Functional Characteristics	Typical Applications
Polymer PTC (PPTC)	Organic polymer matrix with conductive particles, fast response time (ms level), low leakage current	Consumer electronics, USB ports, battery packs
Ceramic PTC	Sintered barium titanate material, higher operating temperature tolerance, stable tripping characteristics	Industrial motors, HVAC systems, automotive ECUs
Hybrid PTC	Combines polymer and ceramic elements for optimized performance, enhanced surge current capability	Telecom infrastructure, solar inverters, medical devices

3. Structure and Composition

Typical PTC fuse construction includes:

PTC Element: Conductive polymer composite (e.g., carbon-black filled polyethylene) or doped ceramic material
Electrodes: Pre-plated nickel/copper layers with solderable termination
Encapsulation: Flame-retardant epoxy resin housing (UL94 V-0 rated)
Termination: Axial leads, SMD pads, or wire leads depending on package type

The resistance-temperature curve exhibits three regions: conductive (normal), transition (trip point), and high-resistance (latched) states.

4. Key Technical Specifications

Parameter	Description	Importance
Hold Current (Ihold)	Maximum operating current before tripping (range: 0.05A-50A)	Determines normal operation compatibility
Tripping Time (Ttrip)	Response time under overcurrent conditions (1ms-10s)	Affects system fault tolerance
Max Voltage (Vmax)	Rated voltage withstand capability (3V-600V)	Safety insulation coordination
Leakage Current	Post-trip residual current ( A level)	Energy efficiency consideration
Operating Temp Range	Functional temperature range (-40 C to 125 C typical)	Environmental reliability

5. Application Areas

Consumer Electronics: Smartphones, laptops, power banks
Automotive: CAN bus protection, ADAS sensors, 12V/48V systems
Industrial: PLCs, motor drives, test equipment
Renewable Energy: Solar charge controllers, wind turbine converters
Medical Devices: Patient monitors, portable diagnostic equipment

6. Leading Manufacturers and Products

Manufacturer	Product Series	Key Features
Littelfuse	PolySwitch VLR	High inrush current tolerance for LED lighting
Bourns	MF-MSM Series	Miniature SMD design for space-constrained applications
TE Connectivity	CR28xx Series	Automotive qualified (AEC-Q200) for EV powertrains
Bel/Standex	0ZCM Series	Vertical through-hole design for industrial controls

7. Selection Guidelines

Key factors to consider:

Calculate normal operating current with 20% safety margin
Evaluate maximum fault current requirements
Match voltage rating with system specifications
Consider package type (SMD vs through-hole) for PCB layout
Analyze thermal derating curves for elevated temperatures

Example: For a 5V USB PD application, select a 0.5A hold current PPTC with 6V rating and <50ms trip time.

8. Industry Trends

Development of ultra-low resistance ( 10m ) devices for high-current applications
Integration with smart monitoring systems via embedded sensors
Growing adoption in electric vehicles for 48V/800V system protection
Nanocomposite material innovations improving response times
Miniaturization driven by 5G infrastructure and IoT device demands

Market projections indicate a CAGR of 7.2% through 2027, with Asia-Pacific region leading adoption growth.