What are on chip variations?
On-chip variation (OCV) is a recognition of the intrinsic variability of semiconductor processes and their impact on factors such as logic timing. If the design passed these two tests, the chip could be considered to have met its timing constraints.
What is AOCV and POCV?
What is POCV? POCV stands for Parametric On-Chip Variation. POCV was proposed to address shortcomings of AOCV/SBOCV for granularity, accuracy, Common path pessimism removal and half cycle paths. POCV eliminates the need for stages, path type and corner delay to find delay derate during characterization phase.
What is SOCV in VLSI?
Statistical OCV (SOCV) is a simplified approach to SSTA that uses a single local variable. It solves the major limitations of AOCV, including variation dependency on slew and load, and the assumption that the same cell, or load, is in the path.
Why is OCV needed?
Junction temperature is always much greater than the ambient temperature and the characteristics of any transistors majorly depend on the junction temperature. Ambient temperature can be taken care in PVT but for the junction temperature variations, we need to take care in OCV.
What are corners in VLSI?
In Very-Large-Scale Integration (VLSI) integrated circuit microprocessor design and semiconductor fabrication, a process corner represents a three or six sigma variation from nominal doping concentrations (and other parameters) in transistors on a silicon wafer.
What is AOCV depth?
Depth is used to index the random. component of variation, and distance is used to index the systematic component in an Advanced OCV derate table, as shown in. Figure 6. The tables can be annotated on a design, library cells, or hierarchical cells, in a pre-defined prioritized order.
What are the differences between OCV and POCV?
POCV is more realistic approach than that of OCV and AOCV. This method does not use distance and depth based derate factor. It uses delay sigma to model the delay variation of the cell. In POCV it is assumed that the normal delay value of a cell follows the normal distribution curve.
What is Moment based LVF?
Moment-based LVF models non-Gaussian timing variation observed at ultra-low voltage corners. To capture more detailed timing variation distributions, moment-based LVF extensions include mean-shift, standard deviation and skewness.
What is Sigma in VLSI?
Standard Deviation (also known as Sigma or σ) determines the spread around this mean/central tendency. The more number of standard deviations between process average and acceptable process limits fits, the less likely that the process performs beyond the acceptable process limits, and it causes a defect.
What is the difference between OCV AOCV and POCV?
POCV is more realistic approach than that of OCV and AOCV. This method does not use distance and depth based derate factor. It uses delay sigma to model the delay variation of the cell. In POCV instead of applying the specific derate factor to a cell, cell delay is calculated based on delay variation (σ) of the cell.
What is STA in VLSI?
Static Timing Analysis (STA) is one of the techniques to verify design in terms of timing. This kind of analysis doesn’t depend on any data or logic inputs, applied at the input pins. The input to an STA tool is the routed netlist, clock definitions (or clock frequency) and external environment definitions.
What is on-chip variation?
On-chip variation (OCV) is a recognition of the intrinsic variability of semiconductor processes and their impact on factors such as logic timing.
What is on-chip variation in static timing analysis?
And On-Chip Variation (OCV) is one of them, specifically for Static Timing Analysis. The first task is to find all possible sources variation, and find out how these can affect a delay of a cell and hence, timing. In this article I will focus on the various sources of on chip variation:
What is advanced on-chip variation (aocv)?
In order to overcome the extra pessimism added due to OCV, advanced on-chip variation (AOCV) technique was introduced for nodes below 65nm. AOCV technique adds derates in the design based on the logic depth and distance of the cell in the timing path.
How can I compute a stagestage based OCV derate?
Stage based OCV derates can be computed using foundry models, LPE netlists and liberty timing libraries. The models and SPICE netlists help to define the cells’ sensitivity to variation while the timing libraries can be used to identify timing arcs and desired ranges for input slew and ouput load.