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How are clock signals used in digital circuits?
In these applications, low-bandwidth PLL-based clocks provide jitter filtering to ensure that network-level synchronization is maintained. For example, synchronizing all SerDes (serialization-deserialization) reference clocks to a highly accurate network reference clock (e.g., Stratum 3 or GPS) guarantees synchronization across all system nodes.
Is the oscillator external to the clock generator?
In most cases, the oscillator is external to the clock generator, although it is becoming more common that oscillators are combined into the same package as the clock generator in an effort to consolidate bill of material cost and complexity, alongside other advantages.
How are clock and oscillator frequency measurements done?
Modern high-performance digital can run measurements on signal cycles that are acquired within a single capture. Unfortunately, memory limitations often force them to capture only a small time slice of a signal (typically up to 1 msec) at their maximum sampling rate. This effectively limits the measurement accuracy.
What kind of probe is used to measure clock frequency?
One way to minimize such difficulties is to use a low-capacitance scope probe. For example, Tektronix makes a probe called the TPP1000 that is designed to be used with its MDO3000 scope which exhibits just 3.9 pF of capacitive loading.
What kind of circuit is a clock circuit?
A clock circuit is a circuit that can produce clock signals. These signals are digital square waveforms, which alternate between on and off. This is important because many different types of chips need clock signals in order to operate. Many chips such as counter chips, digital potentiometers,…
How does a clock switch work on a computer?
Figure 1 shows a simple implementation of a clock switch, using an AND-OR type multiplexer logic. The multiplexer has one control signal, named SELECT, which either propagates CLK0 to the output when set to “zero” or propagates CLK1 to the output when set to “one.”
Do you need to switch the source of the clock?
With more and more multi-frequency clocks being used in today’s chips, especially in the communications field, it is often necessary to switch the source of a clock line while the chip is running.
How does clock signal affect delta-sigma ADCs?
For signals with higher frequency content, you can expect the input signal slew rate to be higher and the SNR degradation from clock jitter to be worse. One key benefit to oversampling converters like delta-sigma ADCs is that the ideal SNR improves when using higher oversampling ratios (OSRs).
Why are quartz crystals used for clock signals?
Quartz crystals are more commonly used since the frequency generated from quartz crystals are more resistant to changes in temperature. If an internal RC resonator was used instead, changes in temperature would affect the behavior of the oscillator, leading to changes in the output frequency.
Why are clocks important in a precision DAQ system?
More importantly, the system clock signal enables the user to sample the inputs and send data whenever he requires such that the entire system operates as intended. Although you may think of clocks as digital input signals, these components can affect the analog performance of precision DAQ systems.