Based on the part number **I641-31BC3O2-155.520**, this component is a high-precision **Voltage Controlled Crystal Oscillator (VCXO)**, typically manufactured by companies like ILSI or MMD (now part of Abracon). --- ### 1. Part Number Breakdown The alphanumeric string defines the electrical and physical characteristics of the oscillator: | Segment | Meaning | Specification | | :--- | :--- | :--- | | **I641** | Series/Package | 5.0 x 7.0 mm Surface Mount (SMD) | | **3** | Operating Voltage | 3.3 Volts DC | | **1** | Frequency Stability | ±50 ppm (Commonly) | | **BC** | Operating Temp Range | -20°C to +70°C | | **3** | Pullability | ±100 ppm Min (APR) | | **O2** | Output Type | LVPECL | | **155.520** | Nominal Frequency | 155.520 MHz | --- ### 2. Technical Specifications This device is designed for high-speed data applications requiring low jitter and precise frequency adjustment. * **Frequency:** 155.520 MHz (Standard frequency for SDH/SONET networking). * **Output Logic:** **LVPECL** (Low-Voltage Positive Emitter-Coupled Logic). This is a differential output known for high-speed performance and low noise. * **Package Size:** 7.0 x 5.0 mm (6-pad ceramic package). * **Function:** VCXO (The output frequency can be "pulled" or adjusted slightly by changing the voltage on the control pin). --- ### 3. Pin Configuration For this standard 6-pad 7x5mm VCXO package: | Pin # | Function | Description | | :--- | :--- | :--- | | **1** | **V_c** | Control Voltage (to adjust frequency) | | **2** | **OE or NC** | Output Enable or No Connect | | **3** | **GND** | Ground | | **4** | **Output** | Differential Output (Positive) | | **5** | **Output** | Complementary Output (Negative) | | **6** | **Vdd** | Supply Voltage (+3.3V) | --- ### 4. Common Applications Due to the **155.520 MHz** frequency and **LVPECL** output, this part is predominantly used in: * **Optical Networking:** SONET/SDH (OC-3/STM-1) clock generation. * **Phase-Locked Loops (PLLs):** Used as a local oscillator that locks to a reference signal. * **Data Communications:** Gigabit Ethernet and Fiber Channel synchronization. ---