In the present scenario, it is very hard to design a circuit applying full custom made methodology because of the increase in the complexity because of decrease in the feature size. So , most of companies are pursuing the semi-custom method of reduce the price & a chance to market the most important variables for any effective products.
To follow the approach of semi-custom, designer need a characterized library of standard cells e. g. logic entrances, data chartering, sequential foundations like F/F's etc . For this reason, many companies & fabrication plants provide std. cell catalogue with the data sheets containing information about time, area & power variables.
With this report, I will discuss the advantages of std. cellular material & standard flow for his or her characterization. The topics of discussion are given beneath:
В• Factors behind Characterization
В• Characterization Stream
В• Characterization Parameters
В• Measurement & Verification
В• Library Formats
The use of the standard cells may be summarized while given below:
п‚§Logic units of similar angles (same height)
п‚§Implement simple logic (NAND, NOR, INV, FF, LATCH, complex gates)
п‚§Usually appear in libraries for a specific technology
From the above factors, we can deduce that std. cells provide repeatability during layout design and style which lessens the intricacy & make layout creation easy. Likewise, std. skin cells are technology dependent therefore just by choosing library of one technology; we can build any design according to available cells as demonstrated below.
Causes of Characterization: -
The reasons for the portrayal are given listed below: -
п‚§Extraction of functionality is complicated
п‚§Functional/Delay ruse takes much too long
п‚§Power extraction for a whole computer chip takes very long
п‚§Automatic diagnosis of timing constraints (e. g. Create time) is usually difficult.
Solution: To solve this challenge, a simple unit for delay, function, limitations and electric power on cell/gate level is employed which provides distinct characteristics of the cell & thus known as cell portrayal.
Characterization Circulation: -
The characterization stream for an std. cell is actually a major issue. Aspects worth considering of the portrayal demand work. The major methods are given listed below: -
п‚§Net list Extraction: In this, the layout for the cell being characterized is created using any good layout manager for a specific technology & then validated for the technology guidelines violations & interconnections. Following verifying the look, the parasitic extraction is performed in which resistance; capacitance & other physical parasitic are being extracted from the style.
п‚§Specification of parameters: After the removal, some default, process & design based mostly parameters happen to be defined. For instance , doping density, voltage, temp. Fan away etc .
п‚§Model selection and specification: -- After specifying the parameter values, different models are selected depending on all their accuracy, complexity & requirement. A Model estimates the time, area, electric power & noises parameters of the std. cell. In genuine sense, Designs are mathematical equations used to calculate the o/p variables.
п‚§Measurement: -- The o/p provided by the simulator is then measured to extract the required characterization variables. The o/p may be in various forms electronic. g. visual view, pub chart and shmoo plot etc . From these qualities, different variables like place, power and timing are calculated pertaining to the an std. cell. п‚§Model Generation: -- Using these types of parameters, a characterized o/p model for the an std. cell is usually prepared in a format where a design tool may understand. All the measured parameters are placed on std. cell.
п‚§Verification: -- After the portrayal of the an std. cell, it can be verified several parameters...