The **MF-R075/90U-2** is a specific electronic component belonging to the **Multifuse® (PPTC)** family, manufactured primarily by Bourns. It is a polymer-based resettable fuse used for overcurrent protection. --- ## 1. Component Overview The MF-R series consists of **Polymer Positive Temperature Coefficient (PPTC)** devices. Unlike traditional fuses that blow and must be replaced, these "resettable fuses" increase their resistance significantly during a fault and return to a low-resistance state once the fault is cleared and power is cycled. ### Key Specifications | Parameter | Value | | :--- | :--- | | **Hold Current ($I_{hold}$)** | 0.75 Amps | | **Trip Current ($I_{trip}$)** | 1.50 Amps | | **Rated Voltage ($V_{max}$)** | 90 Volts | | **Max Current ($I_{max}$)** | 40 Amps | | **Packaging** | Bulk or Tape & Reel (Suffix -2 indicates Tape & Reel) | | **Mounting Type** | Radial Leaded (Through-hole) | --- ## 2. Technical Characteristics ### How it Works 1. **Normal Operation:** The polymer contains conductive carbon black particles, creating a low-resistance path for current. 2. **Fault Condition:** When excessive current flows, $I^2R$ heating causes the polymer to expand. 3. **Tripped State:** The expansion breaks the carbon chains, causing resistance to spike and limiting the current to a safe leakage level. 4. **Resetting:** Once the fault is removed, the device cools down, the polymer contracts, and the conductive paths are restored. ### Environmental & Physical Specs * **Operating Temperature:** -40°C to +85°C. * **Agency Approvals:** Generally UL, CSA, and TUV recognized. * **RoHS Compliant:** Lead-free and halogen-free options available. --- ## 3. Part Number Breakdown Understanding the nomenclature helps in identifying variants: | Segment | Meaning | | :--- | :--- | | **MF-R** | Multifuse® Radial Leaded Series | | **075** | Hold current of 0.75 Amps | | **90** | Maximum rated voltage (90V) | | **U** | High voltage/Uncoated or specific sub-series designation | | **-2** | Tape and Reel packaging (standard for automated assembly) | --- ## 4. Typical Applications * **Power Supplies:** Protection against short circuits in DC power rails. * **Industrial Controls:** Safeguarding PLC I/O ports. * **Telecommunications:** Protection for line cards and networking equipment. * **Security Systems:** Overcurrent protection for sensors and sirens.