Product Description

Composite PTC thermistor is with double protection function of over-voltage and over-current protection. Tianrui Electronics has creatively packaged a PTC thermistor with overcurrent protection and a varistor with overvoltage protection into one device. Making them coupled with each other has both over-current protection and over-voltage protection. These products have been widely used in smart meters, high-performance small switching power supplies, and LED lighting applications, which have produced good economic and social benefits.

Specification

Product Name: PTC Thermistor
Action Current(25℃) : 80-450℃
Curie Temperature : 85-115℃
Diameter : 12-22mm
Application : Smart meters, high-performance small switching power supplies, and LED lighting applications
Color : Green

Models	Curie Temperature	Action Current （25℃）	Not action Current （60℃）	Pressure sensitive Voltage （25℃）	Rated Maximum Work Voltage	Overall Dimensions
	Tc（℃）	It(mA)	Ih(mA)	V(V)	Vmax(V)	Dmax	Hmax
SPMZ11-08E300-600R/14D121	115±7	200	60	120	65	16	10
SPMZ11-08E400-800R/14D181	115±7	200	50	180	120	16	10
SPMZ11-10E300-500R/14D181	115±7	250	70	180	120	16	10
SPMZ11-06E201-401R/10D391	85±7	80	20	390	265	12	10
SPMZ11-06E151-251R/10D391	115±7	100	25	390	265	12	10
SPMZ11-08E600-121R/12D391	115±7	180	40	390	265	14	10
SPMZ11-10E300-500R/14D391	115±7	250	90	390	265	16	10
SPMZ11-10E400-800R/14D491	115±7	220	70	390	330	16	10
SPMZ11-16E200-300R/20D391	115±7	450	130	390	265	22	12

Features

Functional Integration and Collaborative Protection:

VDR Function: Under normal voltage, it exhibits a high-resistance state, without affecting the circuit. When subjected to surge overvoltage (such as from lightning strikes or inductive load switching), its resistance drops dramatically, rapidly absorbing and dissipating the enormous energy, suppressing the voltage spike and protecting downstream equipment.

PTC Function: Under normal temperature and current, it exhibits a low-resistance state. When V is continuously heated due to prolonged overvoltage or abnormally high current, causing its temperature to rise sharply, the tightly coupled PTC heats up, causing its resistance to increase suddenly ("trip"), effectively limiting the current in the circuit to an extremely low level.

Self-Protection and Fail-Safe Mode:

This is the most core feature. Traditional standalone varistors, when absorbing surges exceeding their rated energy, may overheat and crack, emit smoke, or even catch fire, posing a safety hazard.

In this composite component, when the VDR overheats due to an abnormal condition, the PTC rapidly activates, virtually shutting off the circuit. This protects the VDR from thermal collapse and mitigates the potential fire risk caused by VDR failure. It implements a "fail-safe high-resistance" safety mode.

Status Indication and Recoverability:

When the PTC activates, the circuit is shut off and remains in a high-resistance state. This serves as a fault indicator, alerting maintenance personnel to an overvoltage or overcurrent fault.

After the fault is corrected and the power is removed, the PTC automatically returns to a low-resistance state due to cooling, automatically resetting the component and eliminating the need for manual replacement (unless the VDR has been physically damaged by a single, high-energy shock). This reduces maintenance costs and downtime.

Space Saving and Simplified Design:

Combining two components into one saves mounting space on the PCB and simplifies circuit layout and assembly.

Application

This composite component is widely used in applications requiring both overvoltage protection and overcurrent/overtemperature backup protection, particularly in unmanned equipment or those requiring extremely high safety requirements.

Communications Equipment:

Protection of wide area network (WAN) interface lines (such as ADSL2+) in xDSL modems, routers, and switches. This is its most classic application scenario, protecting against lightning surges and power cross-connections.

Power Systems:

Serves as primary protection at the AC input of a switch-mode power supply (SMPS). It effectively absorbs grid surges and disconnects the circuit in the event of a sustained abnormality, protecting the power supply itself.

Input protection for smart meters and industrial control power supplies.

Safety-critical Electronic Equipment:

Any equipment requiring protection against varistor failure and fire, such as high-end home appliances, medical devices, and charging modules for new energy vehicles.

Surge Protective Devices (SPDs):

Serves as the core protection unit in some small or modular surge protection devices, providing safe and reliable protection.

In summary, the VDR-PTC composite thermistor is an innovative, "smart" protection component. It not only provides excellent overvoltage protection but, more importantly, incorporates a built-in safety mechanism to prevent self-failure, enabling automated and highly reliable protection. It is an ideal choice for front-end protection in modern electronic devices.