The part number **M5RJ78RQJ-R** refers to a high-precision, surface-mount (SMD) thick film chip resistor, typically manufactured by companies like **KOA Speer** or following their naming conventions. Below is the detailed breakdown of its electronic specifications and technical characteristics. ### 1. Part Number Breakdown Understanding the alphanumeric code helps identify the physical and electrical properties: | Code Segment | Description | Specific Value | | :--- | :--- | :--- | | **M5** | Case Size | 0805 (2012 Metric) | | **RJ** | Type | High-reliability Thick Film | | **78** | Characteristics | Standard Temperature Coefficient | | **R** | Resistance Value | 0.xx $\Omega$ (Decimal location varies by manufacturer) | | **QJ** | Tolerance/Value | J = $\pm$5% Tolerance | | **-R** | Packaging | Taped and Reeled | --- ### 2. Technical Specifications These are the typical operating parameters for this class of resistor: * **Resistance:** Usually in the low-ohm range (often used for current sensing). * **Power Rating:** Generally **0.125W (1/8W)** at $70^\circ C$ for the 0805 package. * **Tolerance:** $\pm 5\%$ (indicated by the 'J'). * **Operating Temperature Range:** $-55^\circ C$ to $+155^\circ C$. * **Maximum Working Voltage:** 150V (though limited by power rating $P = V^2/R$). * **Construction:** Metal glaze thick film on a ceramic substrate with a protective coating. --- ### 3. Key Features * **AEC-Q200 Qualified:** These parts are often automotive-grade, meaning they are tested for high vibration, thermal shock, and moisture resistance. * **SMD Design:** Designed for automated pick-and-place assembly. * **Stability:** High reliability in harsh environments compared to standard commercial-grade resistors. --- ### 4. Applications The M5RJ series is commonly found in: 1. **Automotive Electronics:** Engine control units (ECUs), lighting systems. 2. **Power Supplies:** Used as a bleed resistor or for voltage division. 3. **Industrial Controls:** Sensors and feedback loops. 4. **Consumer Electronics:** High-density circuit boards where space is limited but reliability is required. --- ### 5. Recommended Footprint (0805) When designing a PCB for this part, use the following standard 0805 dimensions: ```markdown Dimension | Inches | Millimeters -------------|--------|------------ Length (L) | 0.079 | 2.00 Width (W) | 0.049 | 1.25 Thickness (T)| 0.020 | 0.50 ```