The **MF-R090-0-9** is a specific model of a Resettable Fuse, part of the Multifuse® polymer positive temperature coefficient (PPTC) series manufactured by **Bourns**. --- ### 1. Key Technical Specifications | Parameter | Value | Description | | :--- | :--- | :--- | | **I-hold** | 0.90 A | Maximum current at which the device will not trip (at 23°C). | | **I-trip** | 1.80 A | Minimum current at which the device is guaranteed to trip. | | **V-max** | 60 V | Maximum voltage the device can withstand without damage. | | **I-max** | 40 A | Maximum fault current the device can safely handle. | | **P-d** | 0.91 W | Power dissipated from the device when in a tripped state. | | **Mounting Type** | Radial Lead | Through-hole mounting (PC board). | --- ### 2. Physical Characteristics and Package The "0-9" suffix in the part number provides specific information regarding the packaging and lead style: * **Form Factor:** It is a circular/disc-shaped component, usually coated in a yellow or tan flame-retardant epoxy polymer. * **Dimensions:** Typically around 7.4mm in diameter and 3.1mm in thickness. * **Lead Spacing:** Standard 5.1mm lead spacing. --- ### 3. How it Works (PPTC Principle) The MF-R090-0-9 acts as a non-linear thermistor: 1. **Normal State:** The conductive particles inside the polymer form low-resistance chains, allowing current to flow freely. 2. **Fault State (Overcurrent):** Excessive current generates heat ($I^2R$). The polymer expands, breaking the conductive chains. 3. **Tripped State:** Resistance increases dramatically, reducing current flow to a "trickle" level to protect the circuit. 4. **Reset:** Once the power is removed and the fault is cleared, the device cools down, the polymer contracts, and the conductive paths are restored. --- ### 4. Common Applications * **Computer Peripherals:** USB ports and internal circuitry. * **General Electronics:** Power supplies and battery chargers. * **Industrial Controls:** Protection for sensors and small motors. * **Automotive:** Electronic control units and small motor protection. --- ### 5. Part Number Breakdown ```text MF - R 090 - 0 - 9 | | | | | | | | | +-- Lead Style / Coating (Special variant code) | | | +------ Bulk Packaging (usually '0' denotes bulk) | | +------------ Hold Current (0.90 Amps) | +--------------- Radial Leaded Series +-------------------- Multifuse® (Bourns Brand) ```