Contents
How do I stop jitter on my clock?
Decreasing the jitter of the system clock circuit can be achieved in many ways, including improving the clock source, as discussed, as well as filtering, frequency division, and proper choice of clock circuit hardware.
How do you stop the jitter in PLL?
Reducing the loop filter bandwidth increases the amount of jitter attenuation on the reference clock, transferring less jitter from the input to the output. If the reference clock has a significant amount of jitter, using a low PLL bandwidth to filter this noise is typically recommended.
What is jitter in ADC?
Uncertainty of the time instant when the analog-to-digital converter (ADC) samples the signal—defined as clock jitter—increases conversion noise, which reduces the overall system performance. Basically, jitter describes the timing errors in the sampling operation caused by clock disturbances.
What causes clock jitter?
Jitters in clock signals are typically caused by noise or other disturbances in the system. Contributing factors include thermal noise, power supply variations, loading conditions, device noise, and interference coupled from nearby circuits.
What is jitter peaking in PLL?
The jitter characteristic is a complex function of all the noise sources. For phase noise entering at x(t) at the input, the PLL behaves as a low-pass filter. The PLL will track and pass low frequency phase noise and will attenuate high frequency phase noise. This amplification is called jitter peaking.
What is aperture jitter?
This sample-to-sample variation in the instant the switch opens is called aperture uncertainty, or aperture jitter and is usually measured in rms picoseconds. The effects of phase jitter on the external sampling clock (or the analog input for that matter) produce exactly the same type of error.
How do you test a jitter clock?
The standard procedure for measuring cycle-to-cycle jitter involves randomly measuring the duration of two clock periods 10,000 times, and taking the absolute difference between the two.
What causes the jitter in an ADC clock?
There are various contributors to jitter in any scenario, extending from the oscillator to any frequency dividers, clock buffers and any noise acquired due to coupling effects, in addition to the internal aperture jitter of the ADC itself.
How do you get jitter from clock noise?
To simplify the math somewhat, we will take a trapezoidal approximation to obtain the area in each area. To obtain the jitter from this phase noise information, we integrate the phase noise from close in to the fundamental clock frequency out to the encode bandwidth (which is the ADC sample rate).
How does phase noise affect the SNR of an ADC?
We can take this data and integrate the phase noise to find the rms jitter and then derive the effects on the SNR of the ADC. As is shown in MT-008, the close-in phase noise does not have a large impact on the SNR of the ADC. The wide band phase noise has the most impact.
Can you do math on an ADC clock input?
Let’s dig it out of the closet and use it to do a little math on the ADC clock input. As most of us probably know from working in an increasingly mixed-signal world, analog and digital designers often have different ways of viewing the same problem.