The part number **I641-31FC8O2-155.520** refers to a high-precision **Voltage Controlled Crystal Oscillator (VCXO)**, typically manufactured by ILSI America (now part of Abracon). This component is designed for telecommunications and high-speed networking applications. --- ### 1. Part Number Breakdown The alphanumeric string follows a specific coding scheme that defines the electrical and mechanical characteristics of the device: | Segment | Meaning | Specification Details | | :--- | :--- | :--- | | **I641** | Series Model | 5.0 x 7.0 mm Surface Mount (SMD) VCXO | | **3** | Supply Voltage | 3.3V DC operation | | **1** | Stability | ±50 ppm (standard stability) | | **FC** | Operating Temp | -40°C to +85°C (Industrial Grade) | | **8** | Pullability | ±80 ppm min (range of frequency adjustment) | | **O2** | Output Type | LVPECL (Low-Voltage Positive Emitter-Coupled Logic) | | **155.520** | Frequency | **155.520 MHz** (Standard SONET/SDH frequency) | --- ### 2. Key Electronic Specifications This oscillator is engineered for low-jitter performance, which is critical for timing in fiber-optic circuits. * **Center Frequency:** 155.520 MHz. * **Logic Output (LVPECL):** This is a differential output signal. It provides excellent noise immunity and is used in high-speed data transmission where signal integrity is paramount. * **Voltage Control (VC):** The "VC" in VCXO means the output frequency can be slightly adjusted (pulled) by applying a control voltage to Pin 1. * **Jitter Performance:** Usually features sub-picosecond integrated phase jitter (e.g., <1ps), making it suitable for 10GbE and optical transport networks. --- ### 3. Common Applications Due to the specific frequency and output logic, this part is commonly found in: 1. **SONET / SDH:** Standard frequency for OC-3 and STM-1 transmission. 2. **Phase-Locked Loops (PLLs):** Used as a local oscillator that can be synchronized to a reference clock. 3. **Fiber Channel:** High-speed storage networking. 4. **Base Stations:** Synchronizing timing in cellular infrastructure. --- ### 4. Technical Footprint The "641" series uses a standard **6-pad FR4 or Ceramic package**: * **Dimensions:** 7.0mm x 5.0mm. * **Pinout:** 1. Voltage Control (V_c) 2. Enable/Disable (or No Connect) 3. Ground (GND) 4. Output (Q) 5. Complementary Output ($\bar{Q}$) 6. Supply Voltage ($V_{dd}$)