The MF72 series 33D-7 directly heated power negative temperature coefficient thermistor is specifically designed for inrush current suppression in electronic equipment. This device establishes a high-resistance state of 33Ω at the moment circuit power is applied, effectively limiting capacitor charging current. Through self-heating, its resistance dynamically decays to a residual resistance of 1.49Ω, optimizing steady-state efficiency. Its 2950K material constant ensures highly accurate and consistent resistance-temperature characteristics.
The device has a rated zero-power resistance of 33Ω ±20%, calibrated at 1.5VDC at 25°C. A 30-second thermal time constant coupled with a 9mW/°C dissipation factor results in a heat capacity of 270mJ/°C, providing strong surge protection. Its maximum steady-state current of 0.5A supports capacitive loads of 68μF in 240V systems or 270μF in 120V systems.
It operates over a wide temperature range of -40°C to 150°C and has passed 200°C extreme temperature cycling certification and 1000 cycles of 0.5A electrical stress aging testing. This device is suitable for switching power supplies, heating controllers, and display systems. Its low residual resistance significantly reduces steady-state power consumption and improves power system reliability.
Its miniaturized 9mm diameter wafer design with a 5mm thickness utilizes a phenolic resin package and CP leads. It is available in standard inward-curved, outward-curved, side-curved, and straight-leg mounting options.