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Towards Multicores: Technology and Software Complexity
Published in Marcello Coppola, Miltos D. Grammatikakis, Riccardo Locatelli, Giuseppe Maruccia, Lorenzo Pieralisi, Design of Cost-Efficient Interconnect Processing Units, 2020
Marcello Coppola, Miltos D. Grammatikakis, Riccardo Locatelli, Giuseppe Maruccia, Lorenzo Pieralisi
System correctness and robustness are based on the clock period, since signals must obey certain inequalities (margins) in respect to timing. The clock cannot be distributed at the same instant to all on-chip components, because of the clock skew, defined as the maximum difference in clock arrival times (positive or negative phase shift) in any two periods, i.e. the clock signal in a synchronous circuit arrives at different components at different times. Clock skew is caused by unavoidable variations in buffer load, interconnect wire lengths, manufacturing process spread across die changing resistance, inductance, capacitance values, or temperature gradients. While performance of digital circuits is generally more immune to mismatch than analog circuits, synchronous design is sensitive to skew variations in the clock distribution network. Clock skew contribution to clock cycle time can be reduced by minimizing total wire length using an H-tree (or other possibly hybrid structures) with non-uniformly placed intermediate dummy buffers. Jitter slightly changes the clock period due to variations in Phased Lock Loop (PLL) oscillation frequency and noise sources. Jitter can be reduced by minimizing power supply noise (IR and Ldi/dt). Moreover, jitter due to PLL noise also improves with CMOS scaling.
Telecommunications Network Synchronization
Published in Jerry D. Gibson, The Communications Handbook, 2018
The current synchronization impairment model used for the telecommunications signal is based mainly on the source of the impairments. It refers to the higher frequency components of the phase (error) oscillations as jitter and to the lower frequency components as wander, with 10 Hz being the demarcation frequency. Jitter is produced mainly by regenerative repeaters and asynchronous multiplexers, and normal levels of it can readily be buffered and filtered out. However, excessive jitter is a potential source of bit errors in the digital network. Wander, on the other hand, has many causes. These include temperature cycling effects in cables, waiting time effects in asynchronous multiplexers, and the effects of frequency and phase quantization in slave clocks which employ narrowband filters in their servocontrol loops. Since it contains very low-frequency components, wander cannot be completely filtered out and,
Integrated Circuits
Published in Jerry C. Whitaker, Microelectronics, 2018
One of the most important design parameters for PLL is the output jitter. The output jitter is demonstrated by the random deviation of the output clock’s phase from the reference clock signal. Significant peak-to-peak jitter will effectively reduce the clock period. The main contributor of the output jitter is the noise on the input of the VCO. Additional jitter can be induced by the noise on power supply rails that are common to high-speed VLSI circuits. Furthermore, acquisition time of PLL, in the several microsecond range, is often longer than desirable. This is mainly attributed to the response time of the VCO. In a typical scenario where clock skew is caused by the imbalance of the distribution network, the skewed clock often has the correct frequency. What needs to be corrected is the relative phase of the clock signals. Therefore, there is no need to have a VCO. Rather, a simple delay logic can be used to modify the clock signal’s phase. This type of simplified phase correct circuit is referred to as a delay-locked loop. By replacing the VCO with a simple programmable delay line, DLL is simpler, yet exhibits less jitter than its PLL counterpart.
Simultaneous switching noise mitigation in high speed pcb using novel planar EBG structure
Published in International Journal of Electronics, 2023
Due to the non-ideal effects of the transmission line, such as PCB substrate, impedance variation, crosstalk coupling, etc., the signals will be distorted both in amplitude and time. Eye diagram is a typical method for assessing the quality of signals sent across a connection. Pseudorandom bit sequences (PRBS) are sliced and then superimposed on top of one other to create the desired length of symbol segments. Quantifying voltage and timing mistakes may be done with the use of two metrics: eye height and timing jitter. The jitter must be kept to a minimum in order to provide the receiver adequate time to sample the received signal effectively. To guarantee that voltage levels are within the threshold, the eye height must also be big enough.
Time jitter influence on the performance of gamma–gamma turbulence FSO links with various modulation schemes
Published in Journal of Modern Optics, 2020
G.D. Roumelas, H.E. Nistazakis, W. Gappmair, P.J. Gripeos, V. Christofilakis
A major effect with strong impact on the error performance of the communication systems is the time jitter. Its influence is getting stronger as the throughput of the system is increasing and thus, the duration of each information pulse decreases [26]. Consequently, by taking into account that the FSO link achieves very high data rates, the TJ effect should be considered when designing an optical wireless system. This phenomenon is caused by various reasons, such as moving transmitters and receivers or synchronization problems for electronic circuits inside the transceiver units. It has to be noticed that the ‘on time’ detection is getting much more difficult for higher data rates and thus, for very narrow information pulses.
A new low power current steering logic circuit for the design of digital subsystem
Published in International Journal of Electronics, 2022
Mithilesh Kumar, Abir J. Mondal
The delay obtained with AC current ramps in third column is noted to change minimally than the 1.1 V 0A. Typically, the delay is the effect of the input capacitance of the gates. In addition to so, CPU core is also pumping 0A to 40–10A in 10ns. Even so, the chip senses an I(t) of 40A in 10ns to generate a maximum AC voltage drop (∆Vmin). This happens due to LdI/dt noise and corresponds to 0.374V. This, in turn, results in a Vdd of 0.726V (≈ 1.1–0.374). The jitter is the standard deviation of the fluctuation of the time period. It is measured by strobing the very fall time as the noise changes it courses from minimum to zero voltage drop.