The part number **I640-62AC8O2-155.520** refers to a high-precision **Voltage Controlled Crystal Oscillator (VCXO)**, typically manufactured by companies like ILSI or MMD (now part of Abracon). These components are designed for high-speed networking and telecommunications equipment. --- ### Technical Specification Overview The part number is a composite code representing specific electrical and physical characteristics: | Parameter | Specification | Description | | :--- | :--- | :--- | | **Base Series** | I640 | Represents a 5.0 x 7.0 mm Surface Mount (SMD) VCXO. | | **Output Type** | LVPECL | Low-Voltage Positive Emitter-Coupled Logic (Differential). | | **Supply Voltage** | 3.3V | Standard operating voltage for digital circuits. | | **Frequency** | 155.520 MHz | The fundamental operating frequency (Common for OC-3/STM-1). | | **Stability** | ±50 ppm | Total stability including temperature and aging. | | **Package** | 6-Pad SMD | Standard ceramic package for automated assembly. | --- ### Component Breakdown #### 1. Frequency (155.520 MHz) This specific frequency is the industry standard for **SONET/SDH** (Synchronous Optical Networking). It corresponds to the STM-1 (Synchronous Transport Module level-1) and OC-3 (Optical Carrier level-3) rates used in fiber-optic transmission. #### 2. Output Logic: LVPECL * **Performance:** Provides high-speed switching with very low phase noise and jitter. * **Differential Signaling:** Uses two complementary signals to reject common-mode noise, which is critical for maintaining signal integrity over PCB traces at 155 MHz. #### 3. Voltage Control (VCXO Function) Unlike a standard fixed-frequency crystal, this part allows the output frequency to be "steered" or adjusted slightly (usually ±50ppm to ±100ppm) by applying an external control voltage to **Pin 1**. This is essential for: * Phase-Locked Loops (PLLs). * Clock and Data Recovery (CDR). * Synchronizing local clocks to a master network reference. #### 4. Physical Dimensions The **7.0 x 5.0 mm** footprint is a "large" format by modern standards but remains a staple in industrial and infrastructure hardware due to its thermal stability and robust mechanical properties. --- ### Typical Applications * **Telecommunications:** Base stations, switches, and routers. * **Optical Networking:** SONET/SDH/ATM equipment. * **Data Centers:** High-speed server backplanes. * **Test Equipment:** Frequency synthesizers and signal generators.