The **MF-R185-AP** is a specific model of a **Polymeric Positive Temperature Coefficient (PPTC)** resettable fuse, manufactured by **Bourns Inc.** It is widely used in electronic circuits to protect against overcurrent conditions. --- ## 1. Technical Specifications Below are the primary electrical characteristics of the MF-R185-AP: | Parameter | Specification | Description | | :--- | :--- | :--- | | **Hold Current ($I_{hold}$)** | 1.85 A | The maximum current the device can carry without tripping. | | **Trip Current ($I_{trip}$)** | 3.70 A | The minimum current at which the device will switch to high resistance. | | **Max Voltage ($V_{max}$)** | 60 V | Maximum voltage the device can withstand without damage. | | **Max Current ($I_{max}$)** | 40 A | Maximum fault current the device can safely interrupt. | | **Power Dissipation** | 1.0 W | Typical power dissipated when in a tripped state. | | **Mounting Type** | Through-Hole | Radial leaded package. | | **Packaging** | Ammo Pack (AP) | Indicated by the "-AP" suffix, used for automated assembly. | --- ## 2. Key Features and Behavior The MF-R185-AP functions differently than a standard one-time fuse: * **Resettable Nature:** Unlike a standard fuse that "blows" and must be replaced, this part increases its resistance drastically when an overcurrent occurs. Once the fault is removed and the device cools down, it returns to a low-resistance state. * **Temperature Sensitivity:** Because it is a PTC device, it is triggered by heat (either ambient or generated by $I^2R$ losses). High ambient temperatures will cause the device to trip at a lower current. * **The "-AP" Suffix:** This indicates **Ammo Pack** packaging. The components are taped together in a continuous fan-fold box, designed for automatic radial lead insertion machines. --- ## 3. Applications The MF-R185-AP is commonly found in: 1. **Telecommunications:** Protection for line cards and network equipment. 2. **Industrial Controls:** Safeguarding sensors and motor control circuits. 3. **Power Supplies:** Used as a secondary protection layer for transformers or DC outputs. 4. **Computing:** USB port protection and peripheral power rails. --- ## 4. Typical Connection Diagram In a standard circuit, the PPTC is placed in series with the load. ```mermaid graph LR A[Power Source] --- B[MF-R185-AP] B --- C[Protected Load] C --- D[Ground/Return] ``` ---