Zener Diode Silicon Epitaxial Type# Technical Documentation: CRY68 Crystal Oscillator
## 1. Application Scenarios
### 1.1 Typical Use Cases
The CRY68 is a surface-mount crystal oscillator designed for precision timing applications in digital systems. Its primary use cases include:
- Microcontroller Clock Sources : Providing stable clock signals for 8-bit to 32-bit microcontrollers requiring 68 MHz operation
- Digital Signal Processing : Clocking for DSP chips in audio processing, telecommunications, and image processing systems
- Communication Interfaces : Timing reference for Ethernet PHYs, USB controllers, and serial communication protocols (SPI, I²C, UART)
- Real-Time Clocks : Base oscillator for RTC circuits when combined with appropriate divider circuits
### 1.2 Industry Applications
#### Consumer Electronics
- Smart TVs and set-top boxes for video decoding synchronization
- Gaming consoles for graphics processing unit timing
- High-end audio equipment for digital-to-analog conversion clocking
#### Telecommunications
- Network switches and routers for packet synchronization
- Base station equipment for frequency reference
- VoIP equipment for voice packet timing
#### Industrial Automation
- PLC timing circuits
- Motor control systems requiring precise PWM generation
- Sensor data acquisition systems
#### Automotive Electronics
- Infotainment systems
- Advanced driver assistance systems (ADAS)
- Telematics control units
### 1.3 Practical Advantages and Limitations
#### Advantages
- Frequency Stability : ±50 ppm over operating temperature range (-40°C to +85°C)
- Low Jitter : Typically <1 ps RMS phase jitter, critical for high-speed digital interfaces
- Fast Startup : <5 ms startup time from power application
- Low Power Consumption : Typically 15 mA at 3.3V operation
- Small Form Factor : 5.0 × 3.2 × 1.2 mm SMD package
- Wide Temperature Range : Suitable for industrial applications
#### Limitations
- Fixed Frequency : 68 MHz fixed output, not programmable
- Load Capacitance Sensitivity : Requires precise matching with circuit load capacitance
- Limited Drive Strength : May require buffer for driving multiple loads
- Shock and Vibration Sensitivity : Typical of crystal-based oscillators, though improved in SMD packages
## 2. Design Considerations
### 2.1 Common Design Pitfalls and Solutions
#### Pitfall 1: Improper Power Supply Decoupling
Problem : Insufficient decoupling causes frequency instability and increased jitter
Solution :
- Place 100 nF ceramic capacitor within 5 mm of VDD pin
- Add 10 μF bulk capacitor on power rail
- Use separate power plane if possible
#### Pitfall 2: Incorrect Load Capacitance Matching
Problem : Frequency deviation from specified 68 MHz
Solution :
- Calculate total load capacitance: CL = (C1 × C2)/(C1 + C2) + Cstray
- Typical values: C1 = C2 = 18 pF for 12 pF load specification
- Account for PCB trace capacitance (typically 2-5 pF)
#### Pitfall 3: Thermal Management Issues
Problem : Frequency drift under temperature variations
Solution :
- Avoid placing near heat-generating components (processors, regulators)
- Provide adequate ventilation in enclosure
- Consider thermal vias for heat dissipation
### 2.2 Compatibility Issues with Other Components
#### Voltage Level Compatibility
- CRY68 Output : 3.3V CMOS compatible
- Issues with 5V Systems : Requires level shifting or voltage divider
- Issues with 1.8V Systems : May exceed maximum input voltage; use voltage clamp
#### Timing Margin
