47D-15 Negative Temperature Coefficient Thermistor

47D-15 Negative Temperature Coefficient Thermistor serves as a reliable and efficient power protection component designed to suppress high inrush currents in electronic circuits. This NTC thermistor features a resistance that decreases significantly as its temperature rises. Consequently, the device provides high initial resistance to limit the surge of current when you first power on your equipment, but it then drops to a low-resistance state to maintain high efficiency during steady-state operation. Utilizing a robust ceramic disc construction, the 47D-15 handles substantial energy levels while occupying minimal board space. Furthermore, its high thermal stability ensures long-term protection for sensitive downstream components like capacitors, rectifiers, and power transistors. Therefore, integrating this thermistor into your power supply design effectively prevents blown fuses and hardware damage caused by sudden power spikes.

Key Features:

• High Surge Current Suppression: The device effectively limits the initial current peak during power-up, protecting the entire circuit from thermal and electrical stress.
• Low Steady-State Resistance: After the initial surge, the thermistor heats up and its resistance falls to a negligible level, which minimizes power dissipation.
• Wide Operating Temperature: This component functions reliably across a broad thermal range, making it suitable for industrial and consumer electronics alike.
• Durable Coating: A high-quality silicone or phenolic resin coating provides excellent insulation and moisture resistance for the ceramic element.
• Cost-Effective Protection: It offers a simple, passive solution for inrush current limiting compared to complex active soft-start circuits.

Technical Specifications:

• Zero Power Resistance (R25): 47 Ω ±20% (at 25°C)
• Maximum Steady State Current: 3.0 A
• Approximate Resistance at Max Current: 0.820 Ω
• Thermal Dissipation Constant: ≈ 18 mW/°C
• Thermal Time Constant: ≤ 75 seconds
• Operating Temperature Range: −55°C to +200°C
• Maximum Capacitance: 470 μF (at 240V AC)

Mechanical Specifications:

• Body Material: Metal Oxide Ceramic
• Lead Type: Radial Lead (Straight or Kinked)
• Lead Material: Tinned Copper or Steel Wire
• Coating Material: Flame-Retardant Epoxy/Silicone Resin (UL 94V-0 compliant)

Dimensions:

• Disc Diameter (D): ≈ 15.0 mm
• Body Thickness (T): ≈ 5.0 mm to 6.0 mm
• Lead Pitch (F): 7.5 mm ±1.0 mm
• Lead Length: ≥ 25.0 mm
• Lead Diameter: ≈ 0.8 mm

Pinout and Wiring:

• Polarity: This component is non-polarized; however, you must wire it in series with the AC or DC input line.
• Connection Point: Typically, you should place it between the bridge rectifier and the bulk filter capacitors or directly at the AC input hot lead.
• Spacing Note: Ensure adequate physical clearance from other components because the thermistor becomes quite hot during normal operation.

Datasheet Reference:

• Download 47D-15 NTC Thermistor Datasheet

Commonly Used in:

• Switching Power Supplies (SMPS): Limiting the charging current of large input capacitors.
• Electric Motors: Preventing high torque and current spikes during startup cycles.
• CRT Monitors and Televisions: Protecting degaussing coils and internal power stages.

Applications:

• Inrush Current Limiting: Protecting electronic ballasts and LED drivers from initial power-on surges.
• UPS Systems: Safeguarding inverter circuits and battery charging stages.
• Industrial Heating Elements: Managing the initial current draw in high-wattage resistive loads.

Equivalent Models:

• SCK-473: A common alternative with similar 47-ohm resistance and current handling capacity.
• NTC 47D-15 (Various Brands): Most major manufacturers produce this standard 15mm disc size with identical specifications.
• MF72-47D15: The widely recognized MF72 series equivalent often used in general-purpose applications.

Package Includes:

• 1 x 47D-15 Negative Temperature Coefficient (NTC) Thermistor