حفاظت مدار فیوز خودبازگشت (پی‌تی‌سی)

Product Attributes

Introduction

Surface mount PTC (Positive Temperature Coefficient thermistor) consists of a block of polymeric material containing conductive filler, bonded between two conductive planar terminals. At currents below the device's IHOLD rating and temperatures below 100°C, the PTC maintains a resistance below its R1 MAX rating. As the device temperature approaches 130°C — whether due to elevated ambient temperature or current exceeding its ITRIP rating — the volumetric expansion of the filled polymer disrupts most of the conductive pathways formed by the chain contact of adjacent filler particles between the terminals, causing the device resistance to increase sharply by several orders of magnitude. At the higher "tripped" resistance, only sufficient leakage current flows to maintain internal heating that keeps the device "held" in the tripped state (approximately 125°C) until power is interrupted. Once power is removed, the PTC core cools and contracts, allowing the conductive chains to re-form and the device to return to its low-resistance state. The catalog data for each device specifies a "typical power" value; the approximate resistance of a "tripped" PTC can be determined using the formula $R = E^2 / W$, where "E" is the voltage across the PTC and "W" is the typical power value for the specific PTC. Since a PPTC maintains a constant internal temperature, its apparent resistance varies with the applied voltage and, to a lesser extent, with ambient conditions.

Features

• High-density boards
• Surface mountable
• Solid state
• Faster time to trip than standard SMD devices
• RoHS2 Compliant & Halogen-Free
• Pure Tin-Plated Copper
• MSL: 2a (According to IPC J-Std-020)

Applications

All High-Density Circuit Boards