The **PLL500-17BSCL-R** (often identified within the PLL500 series) is a Low Phase Noise VCXO (Voltage Controlled Crystal Oscillator) IC designed for high-performance clock generation. It is commonly used in networking, telecommunications, and professional audio/video equipment. --- ## 1. Component Overview The device functions as a specialized buffer and multiplier for quartz crystals, allowing the output frequency to be "pulled" or adjusted via a control voltage ($V_C$). | Feature | Specification | | :--- | :--- | | **Part Number** | PLL500-17BSCL-R | | **Type** | VCXO (Voltage Controlled Crystal Oscillator) | | **Output Type** | CMOS | | **Package** | SOT23-6L (Small Outline Transistor) | | **Input Frequency Range** | 1MHz to 36MHz (Crystal dependent) | | **Operating Voltage** | 3.3V (Typical) | --- ## 2. Key Internal Electronic Parts The IC integrates several critical stages to ensure high signal integrity: ### A. Crystal Oscillator Core This stage connects to an external fundamental mode crystal. It includes internal load capacitors that can be adjusted through the $V_{control}$ pin. ### B. Varactor Diode (Internal) The "Voltage Control" aspect is managed by internal varactors. When the voltage on the control pin changes, the capacitance changes, which shifts the resonant frequency of the external crystal. ### C. Output Buffer A high-speed CMOS buffer ensures the output clock signal has sharp rise and fall times, making it compatible with FPGAs, DSPs, and Microcontrollers. --- ## 3. Pin Configuration (SOT23-6L) | Pin # | Name | Description | | :--- | :--- | :--- | | 1 | **VC** | Voltage Control Input. Adjusts the output frequency. | | 2 | **GND** | Ground connection. | | 3 | **XIN** | Crystal Input. | | 4 | **XOUT** | Crystal Output. | | 5 | **VDD** | Power Supply (Typically 3.3V). | | 6 | **CLKOUT** | CMOS Clock Output. | --- ## 4. Design Considerations * **Pullability:** This IC is designed for "wide pull range" applications, meaning it can shift the frequency significantly (often $\pm 100$ ppm or more) depending on the crystal characteristics. * **Phase Noise:** It features an optimized design to minimize "jitter," which is crucial for high-speed data transmission. * **Termination:** To prevent signal reflection, a small series resistor (22$\Omega$ to 33$\Omega$) is often placed near the **CLKOUT** pin. ---