Chip Designing Made Easy


Introduction

The word of Chip designing means building an integrated Chip, by integrating billions of transistors to
achieve an application. An Application could be suiting a particular requirement like Microprocessor, Router, cell phone, etc. An Integrated circuit designed for a specific application is called as ASIC(Application Specific Integrated Circuits).

Todays ASIC Chips is prettly complex packed with larger chunk of transistors targeted to a specific
manufacturing process for fabricating the integrated circuits, in a sub nanometer regime, involving lots and lots of challenges, like knowledge of various protocols, architectures, models, formats, standards, knowledge about CMOS logic, Digital Design concepts, taming the EDA tool for the various design requirement’s like area, timing, power, thermal, noise, routability, lithography aware, freechip knowledge about Various variabilities like channel length, Vt, line width variations, lens abrreations, IR drop effects,inter-die, intra die-variations, effects, and various noise-effects like Package noise,EMI noise,power grid noise,cross-talk noise and ability to test and validate and know to model and characterize all these effects upfront in the design-phase,steps to increase yield to increase profitability curve, with short span of time-to market to minimize the risk and maximize the predictability and an modular approach to Success. Now let’s dwelve in to the “Art of Chip Designing”

Used lot of Technical Jargons, nothing to worry about we will get in there soon…Be with me promise you to understand the Concepts behind Chip Desiging.

Before Designing a Chip? Need to Brain Storm

1. What market the Chip is targeted for?

2. What are the Protocols involved in the Chip?

3. What is going to be our Processor/Bus Architecutes?

4. what is the power/IR-drop/timing/Area/Yield/ targets and how to budget it in the Chip?

5. What is the process in which the Chip going to be manufactured?

7. what are the various third party IP’s/Memory requirements?

8. what is our Design flow and EDA tools and methodology involved?

9. What is the estimated Chip Cost?

10. Above all the bottom line of any business model is money, What will be our Profit model ,estimation of our ROI(Return of investment).

Analogy of Chip Design Architecture Vs Building Architecture.

Why an Analogy with Building Architecture,It is just to understand the concepts of Chip desiging in a better way, as we are very familiar with Building Architecture, then it will be easy for us to map Chip Design architecture.

VLSI(Very large scale Integration) flow was evolved similar to the flow involved in Building Construction.Now let us dwelve in to the construction flow to better understand the VLSI Chip design flow development.

When ever we start to construct a building, we will have an architecture, how the building should look like , the exterior looks and all, similar to that we will be designing an architecture in the chip-design, based on the requirement of the product, what the product is addressed for and whom to serve what needs, the so called specification, will having the modules.

Now lets go in to the implementation part of both the Building & Chip.

We at first come with the floorplan of the building, similarly we come with the floorplan of the Chip, Based on the connectivity/accessibility/vaasthu we place our rooms, similarly we have the constraints to place the blocks. Like we build the building with bricks, for Chip Design we have libraries, which are like pre-designed bricks, for a specific functionality.

Now let us try to understand the power-structure or electrical connectivity in our Building. Initially we have an Electrical plan for our building, where we have a requirement that all our electrical gadgets needs to get power. Similar to that we have a Chip power requirement, The required power is supplied through the power-pads, over a ring like topology to have a uniform distribution across all corners of the chip, and the supply has to reach all the standard-cells(bricks for Chip-Designing).,this is called as power-grid topology in the Chip-Design, now the requirement is how well we design our Power-grid, to reduce the IR-drop so that our standard-cells get proper power requirement.

I would not make justice, if I don’t discuss about clock and clock-tree in the Chip-Design flow. We have
synchronous way of designing and asynchronous way of designing(difficult to verify). Majority of chips follow Synchronous way of coding, for which Static Timing Analysis is possible. For the relevancy of the flops the clock to those flops should reach at the same time from the crystal, with in some skew targets with in the chip.In order to make this happen, a step called as clock-tree is performed after power-grid is created.

 


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