The part number **321-R** is generally associated with high-precision **SMD (Surface Mount Device) Resistors**, specifically those following the international metric or imperial sizing standards. Depending on the manufacturer (such as KOA Speer, Vishay, or Panasonic), "321" often refers to the physical size, while "R" denotes the resistance value or a specific tolerance/packaging characteristic. ### 1. Technical Specifications Most components labeled under the 321-R series (specifically 0321 or similar metrics) share these common characteristics: | Property | Typical Value | | :--- | :--- | | **Component Type** | Fixed Surface Mount Resistor | | **Package Size** | 0321 (Metric) / ~01005 (Imperial) | | **Resistance Range** | 10 $\Omega$ to 1 M$\Omega$ | | **Power Rating** | 0.031W (1/32 W) | | **Operating Temp** | -55°C to +125°C | | **Maximum Voltage** | 15V - 25V | --- ### 2. Key Features * **Ultra-Miniature Size:** The "321" designation in metric (0.3mm x 0.2mm) is used in high-density circuitry like smartphones and wearable tech. * **Precision:** These parts often feature thin-film or thick-film technology to ensure stable resistance even at high frequencies. * **Lead-Free:** Modern 321-R components are almost exclusively RoHS compliant. --- ### 3. Understanding the "R" Suffix In electronic part numbering, the "R" usually serves two purposes: 1. **Decimal Placement:** In a value code, R represents the decimal point for Ohms. * *Example:* `3R21` = 3.21 $\Omega$. 2. **Packaging Indicator:** For many suppliers, "R" at the end of a part number stands for **Tape & Reel** packaging, indicating the parts are wound on a plastic reel for automated pick-and-place machines. --- ### 4. Common Applications Due to their small footprint, these parts are found in: * **Mobile Devices:** Power management circuits in iPhones and Android devices. * **Medical Implants:** Small-scale sensors and pacemakers. * **RF Modules:** High-frequency communication equipment where parasitic inductance must be minimized. --- ### 5. Identification Example If you are looking at a schematic, the part might be represented like this: ```yaml Part_Number: ERJ-1GNJ321R Manufacturer: Panasonic Description: Resistor 320 Ohms 5% 1/20W 0201 Package: 0201 (Inch) / 0603 (Metric) ```