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Timing in digital circuits refers to the sequence of events that happen or need to happen once power is applied to the circuit. Think of timing in a digital circuit as a traffic light at an intersection. Regardless of whether the intersection is busy, the traffic light’s operation helps guide traffic efficiently through the intersection and onto another intersection, where another traffic light will continue the sequence until the individual cars reach their destination. In the same way, electronic timing circuits set in motion the sequence of triggers like dominoes.

Without timing, the digital world as we know it would not exist. Depending on the circuit, if the timing is off or gets disrupted, then the effects will cascade through the machine’s primary systems and subsystems to the individual board or card level in the form of an error, which can halt the entire machine or, worse, the whole operation.

This week, we examine why timing is critical in digital circuits and the devices that help keep a timing circuit ticking properly.

Right On Time

Crystal oscillators are widely used in various applications, providing a sizeable range of frequencies, from a few kHz to several hundred MHz. They offer exceptional frequency stability due to the precise resonance of quartz crystals. These oscillators are commonly used in applications that require high accuracy and stability, such as radio transmitters and receivers, satellite communication systems, and cellular networks, providing clock signals for microcontrollers, processors, and digital circuits.

Crystal oscillators are critical in providing precise timing for microprocessor operations, ensuring accurate coordination of tasks in the closed-loop system. Without a stable oscillator, the system's timing accuracy may be compromised, leading to errors or inefficiencies in data processing and feedback generation.

The most common types of crystal oscillators include:

• Clock oscillators (XO)
• Temperature-compensated oscillators (TCXO)
• Oven-controlled crystal oscillators (OCXO)
• Voltage-controlled oscillators (VCXO)

Oscillators are not the only electronic circuit components that aid in maintaining synchronization. Timing circuit devices such as counters, clocks, and timers have specific functions in maintaining system timing:

• Timers measure or control time intervals. They can operate in monostable (producing time delays) and astable (generating continuous pulses) modes.
• Clocks produce regular, periodic signals to synchronize operations within a system, providing time reference signals and enabling coordination between different components.
• Counters tally occurrences of input signals or generate sequences of binary numbers. They increment or decrement a numerical value based on the occurrence of external signals, enabling tasks like frequency measurement, event counting, or position tracking.

The Newest Products for Your Newest Designs^®

This week’s New Tech Tuesday features clock evaluation tools from Texas Instruments and Analog Devices that can provide engineers with invaluable insights into timing circuit development.

The Texas Instruments LMK5B33216EVM Evaluation Module (EVM) is a comprehensive platform designed to assess and validate the functionality and performance of the LMK5B33216 network clock generator and synchronizer. The LMK5B33216EVM provides easy access to its 16-output capability, three digital phase-locked loops (DPLLs), and three analog phase-locked loops (APLLs), ensuring comprehensive evaluation and testing. With an integrated 2.5GHz bulk acoustic wave voltage-controlled oscillator (VCO), the LMK5B33216EVM delivers precise clock generation and synchronization, essential for providing precise timing solutions to diverse electronic systems.

The Analog Devices EV-ADF4382A Evaluation Board provides a comprehensive platform to evaluate the functionality and performance of the ADF4382A frequency synthesizer. The EV-ADF4382A board enables efficient testing and validation of the ultra-low-jitter fractional-N PLL with an integrated VCO.

Tuesday’s Takeaway

Timing is vital for electronic circuits, orchestrating event sequences that ensure smooth operations. Circuits maintain timing even in sleep mode, guaranteeing synchronized background tasks and uninterrupted timekeeping. Oscillators form the circuit's timing core, generating a precise base frequency, while timers measure intervals, clocks synchronize signals, and counters tally events. Together, these components enable precise timing control across electronic systems.