Modeling and Budgeting of Timing Jitter

A graphical representation of the signal's voltage over time, showing the open space between the eye's upper and lower bounds, indicating signal quality.

The probability of a bit being received incorrectly, expressed as a ratio or percentage.

A method for estimating the worst-case performance of a system by considering the maximum values of all contributors to the signal degradation.

Variation in the timing of a digital signal, affecting the clarity of the data transition.

A table that allocates a certain amount of allowable jitter from each source in a system, ensuring the overall jitter stays within acceptable limits.

Unwanted variations in the voltage level of a signal, degrading the signal clarity.

The process of analyzing all contributing noise sources in a system and allocating a specific amount of acceptable noise from each source.

A technique used to predict the worst-case received eye diagram from the pulse response of a high-speed interconnect channel, considering intersymbol interference and crosstalk.

A visual representation of a digital signal's quality over time, used to evaluate system performance in high-speed designs.

The horizontal axis represents time, typically spanning one or two symbols.

The vertical axis represents the amplitude of the signal.

The eye diagram is constructed by overlaying sections of the time-domain signal waveform, each representing a small number of symbols.

The eye diagram is called 'open' when the signal is clear and undistorted, allowing for ample margin in voltage and timing.

The eye diagram is called 'closed' when the signal is distorted, reducing the margin in voltage and timing.

The minimum height of the eye refers to the difference between the highest and lowest voltage levels of the signal. It must be large enough to satisfy the voltage requirements of the receiver.

The minimum width of the eye refers to the time interval available for the receiver to sample the signal. It must be long enough to satisfy the timing requirements of the receiver.

Timing jitter refers to variations in the timing of the signal, resulting in jitter in the eye diagram.

Voltage noise refers to random fluctuations in the voltage levels of the signal, resulting in noise in the eye diagram.

An eye mask is a graphical representation of the performance requirements (timing and voltage) of a signaling system. The actual eye diagram must stay within the mask for reliable data transmission.

Peak Distortion Analysis (PDA) is a deterministic method used to find the minimum received eye height and width in a signaling system with significant sources of distortion.

Bit Error Rate (BER) is the percentage of bits that are received incorrectly. A lower BER indicates better data transmission quality.

The eye diagram can be used to estimate the probability of receiving erroneous bits, which is known as the bit error rate (BER).

The eye diagram is applicable to both single-ended and differential interfaces, but for differential interfaces, the eye diagram should plot the differential voltage instead of the single-ended voltage.

A high-speed interface standard used in graphics cards, allowing data transfer rates of up to 533 Mb/s.

A digital signal that is synchronized to a clock signal.

A timing characteristic of a receiver that defines the acceptable range of arrival times for the data signal relative to the clock signal.

The variation in the arrival time of a digital signal, caused by various factors like noise and process variations.

The time between two consecutive bit errors in a data stream.

A statistical distribution that describes random events, often used to model timing jitter.

The spread of a Gaussian distribution, representing the typical amount of timing uncertainty.

The unit interval is the time duration of a single bit in a digital signal.

The process of allocating allowable timing uncertainty from various sources in a system to ensure the overall signal quality meets specifications.

The variation in the delay introduced by the transmission medium, including the physical interconnect.

The delay introduced by the electronic circuits responsible for transmitting the signal.

The delay introduced by the electronic circuits responsible for receiving and interpreting the signal.

A commonly used model to express the probability density function (PDF) of deterministic jitter. It treats the jitter as equally distributed at extreme values. It simplifies calculations for jitter budgeting.

The ratio of the number of logic transitions to the total number of bits transmitted. Typically, it is equal to 0.5, indicating 50% of bits change values.

A distribution that describes the probabilities of different values occurring for a random variable. It provides a mathematical model for representing the uncertainty in system parameters.

The value that represents the average of a set of data points. It indicates the central tendency of a distribution.

The standard deviation is a measure of the spread of data points around the mean. A smaller standard deviation indicates less variability in data, while a larger standard deviation indicates more variability.

The cumulative distribution function (CDF) is a function that describes the probability that a random variable will be less than or equal to a given value. It helps to understand the probability of falling within a specific range.

The convolution operation is used to combine two distributions to create a new distribution that represents the sum of the two original distributions.

Inter-symbol interference (ISI) is a form of signal distortion that occurs when the signal from one bit interferes with the signal of a neighboring bit. It can lead to errors in data interpretation.

A measure of the time it takes for a signal to travel through a channel. It is important to consider for high-speed data transmission, as longer propagation delays can lead to decreased bandwidth.

Deterministic jitter is a predictable, bounded variation in signal timing, caused by specific sources like clock skew or signal reflections.

Random jitter is a unpredictable, unbounded variation in signal timing, caused by random noise sources like thermal noise or shot noise.

The peak-to-peak amplitude of deterministic jitter.

The root mean square (RMS) value of random jitter.

A mathematical function used to calculate the probability of a random variable exceeding a certain threshold.

A type of deterministic jitter that repeats at a fixed frequency, caused by modulating effects like spread-spectrum clocking.

A type of deterministic jitter that depends on the data pattern being transmitted.

A type of DDJ caused by variations in the duty cycle of the transmitted signal.

A type of DDJ caused by interference from other signals.

Jitter is the variation in the timing of a digital signal. It is measured as the difference between the actual arrival time of a data bit and its ideal arrival time.

The jitter budget is a table that allocates a specific amount of allowable jitter to each component in a signaling system, ensuring the overall jitter stays within acceptable limits.

DJδδ (deterministic jitter) is the jitter that has a specific pattern or period. It can be predicted and measured.

RJ (random jitter) is the jitter that is random and unpredictable. It is often modeled using a Gaussian distribution.

The system jitter (DJδδ(sys)) is the combination of all the individual jitter sources in a signaling system.

The variation in the timing of a digital signal, caused by multiple periodic sources, each with its amplitude, frequency, and phase.

The probability of a digital signal being at a specific time relative to its ideal edge position. It describes the likelihood of a signal being delayed or advanced due to jitter.

The amount of eye closure due to random jitter that needs to be considered for a given bit error rate (BER).

The PDF for DCD jitter is a sum of two Dirac delta functions, each centered at half the peak-to-peak DCD value.

The deterministic jitter component in the dual Dirac model, calculated by extrapolating the linear slope of the QBER versus jitter plot to a BER of 1.

The total deterministic jitter of a system calculated by summing the deterministic jitter components from all sources.

Deterministic jitter unrelated to the data pattern on the signal, commonly caused by crosstalk.

The total random jitter of a system calculated as the square root of the sum of squared random jitter components from all sources.

A high-frequency clock generated from a low-frequency reference clock and used for data transmission.

The cumulative effect of all deterministic jitter sources in a system, obtained by convolving the PDFs of each source.

The total jitter in a system, obtained by convolving the PDF of the system deterministic jitter with the PDF of the random jitter.

A circuit at the receiver that synchronizes incoming data signals by comparing their timing to a reference clock.

The amount of jitter introduced in a system by the reference clock, affecting the timing of both the transmitter and receiver.

The maximum peak-to-peak deviation of a signal from its ideal timing, determined by examining the system deterministic jitter.

The process of extracting the DJpp from the system deterministic jitter PDF by plotting it on a logarithmic scale.

The jitter originating from the transmitter PLL, caused by noise and imperfections.

The key characteristics of deterministic jitter, which are bounded, non-random, and correlated to the data stream.

The jitter originating from the receiver PLL, also caused by noise and imperfections.

The key characteristics of random jitter, which are unbounded, random, and uncorrelated to the data stream.

The jitter introduced by the channel during signal propagation, due to intersymbol interference (ISI) and crosstalk.

The process by which a receiver's PLL attempts to track the jitter introduced by the transmitter's PLL, effectively subtracting the jitter caused by the transmitter's PLL.

The process of estimating the BER by using the DJpp and the random jitter standard deviation to estimate the jitter distribution.

The specific combination of system components and their respective jitter contributions defining the overall jitter performance.

The difference between the total allowable jitter and the expected jitter contribution from all sources, indicating the margin for error.

Changes in the supply voltage, often caused by current demands in the system. It can be generated externally in the supply distribution system or locally by the I/O circuits.

Noise that affects all signal lines equally, impacting the common mode voltage.

A measure of how sensitive a receiver is to changes in the input voltage. High sensitivity means the receiver needs a smaller voltage change to detect a signal.

Variations in the threshold voltage of a receiver circuit, leading to misinterpretations of the signal.

The variation of the transistors' characteristics, such as gate length and width, and their impact on the receiver's threshold voltage.

The ratio of NMOS and PMOS device characteristics, such as gate length and width, which influences the receiver's threshold voltage.

The extreme values of transconductance parameters, either at the fastest or slowest device settings, leading to significant variations in the receiver's threshold voltage.

The maximum difference between the highest and lowest threshold voltages of an inverter, indicating the worst-case scenario for misinterpretations.

The difference in the threshold voltage of a differential amplifier based on NMOS transistors, influenced by the mismatch between the devices.

The amount of voltage change needed at the receiver's input to generate a specific output swing. It indicates how much voltage is necessary to trigger a clear signal response.

A method that uses the linear superposition principle to find the worst-case bit pattern in a complex signaling channel by considering how ISI from previous pulses affects subsequent pulses.

The amount of voltage degradation caused by intersymbol interference (ISI) from previous pulses at a specific time position in the eye diagram.

A pattern of transmitted bits that results in the most significant signal degradation in terms of eye opening, due to the combined effects of ISI.

The difference between the maximum and minimum voltage levels of the signal, indicating the signal quality.

A technique used for high-speed data transmission that combines the signals from multiple sources to create a single output signal.

The process of identifying the worst-case bit pattern that leads to the smallest eye opening, by analyzing the influence of ISI on the signal.

The minimum voltage difference required for the receiver to distinguish between a logical high and low state, ensuring reliable data reception.

Total noise budget is the sum of noise from all sources in a system. It impacts signal clarity and data quality, as high noise levels can cause errors in data transmission.

A metric that compares the signal swing to the worst-case noise level, indicating the system's resilience to noise.

The superposition property allows you to calculate the output of a system for a complex input by adding the outputs obtained for each individual input component.

The response of a system to a single pulse, used in conjunction with superposition to calculate the response for a complex input signal.

The differential circuit design is less sensitive to noise due to its ability to reject common-mode noise, resulting in improved noise performance.

The single-ended circuit design is susceptible to noise from various sources, including supply noise and crosstalk.

A method of assessing the noise characteristics of a digital system by comparing the signal swing to the total noise level influencing it.

The noise contributed by the power supply, affecting the integrity of the signal.

The noise caused by random fluctuations in the receiver's input due to variations in its sensitivity and offset.

Noise arising from thermal agitation in the electronic components, adding random fluctuations to the signal.

Noise resulting from the random arrival of electrons, contributing to signal fluctuations.

The process of combining individual pulse responses to create the overall waveform for a complex bit pattern.

A bit position in the received signal that immediately follows the bit of interest.

A bit position in the received signal that immediately precedes the bit of interest.

The bit position of interest in the received signal.

The minimum voltage difference between the highest and lowest voltage levels of a signal in an eye diagram.

The minimum time interval for the receiver to sample the signal in an eye diagram.

The mathematical representation of the probability of different jitter values occurring.

A predictable jitter component that can be measured and accounted for.

The root-mean-square (RMS) voltage caused by shot noise, which is proportional to the current through a device, the bandwidth, and the effective resistance.

A statistical distribution that describes random events, often used to model noise sources such as thermal noise and shot noise.

A conservative approach to noise budgeting, where each noise source is assumed to be at its worst-case value, minimizing the probability of encountering noise problems.

The probability of having noise that does not exceed a certain amount, determined using the Gaussian probability density function.

The combination of all noise sources in a system, where individual sources are added in an RMS fashion to calculate the overall noise.

A graphical representation of the probability of observing a particular noise value, depicting the distribution of noise levels.

An example of how noise budgets and margins are applied to single-ended and differential signaling systems, showcasing the difference in their noise immunity.

The process of simulating the noise sources present in a high-speed signaling system, providing a more detailed and accurate understanding of noise behavior.

The variation in the threshold voltage (VT) for a transistor, typically expressed as a positive or negative deviation from the typical value.

The variation in the transconductance parameter (k) for a transistor, reflecting the change in current flow for a given voltage change.

Variation in the transistor's width (W) and length (L) due to manufacturing tolerances.

The difference between the input voltage levels required to switch an inverter on and off, caused by variations in device parameters.

The variation in the reference voltage used in single-ended interfaces as a result of noise or manufacturing tolerances.

Noise introduced by the limited resolution of a D/A converter used in an equalizer, which limits the accuracy of the equalizer coefficient values.

The minimum step size in the output current of a D/A converter, defined by the least significant bit (LSB) of the DAC.

Voltage noise caused by the limited resolution of a D/A converter, expressed as half of the resolution step size.