What is digital integrated circuit design?

Digital IC design is a procedural interaction that involves converting determinations and highlights into computerized blocks, which are then further transformed into basic circuits. A significant number of the imperatives related with advanced IC plan come from the foundry cycle and innovative restrictions.

Physical design of a digital integrated circuit design
Figure 1

Plan, expertise and creativity are keys at the more significant level phases of computerized IC plan. The advancement of frameworks and cycles that guarantee a plan meets particular as proficiently could be expected.

In contrast to a basic course in digital electronics or digital system design, which deals with combination of logic gates to make a combined or sequential logic, digital IC design deals with the non idealities one may face in the process of implementing the logic gates on actual silicon.

It mainly deals with various logic families, trade between power consumption and delay and methods to optimize them, working of transistor in linear and subthreshold region of operation. If it is a more advanced course, then one will also learn lay-out techniques for circuits.

What is hardware description language?

The advanced squares with conduct depictions created in the beginning stages of computerized plan should be converted into an hardware description language (HDL) like Verilog or VHDL. This stage is frequently called the Register Transfer Level (RTL) stage, which for the most part incorporates utilitarian check to guarantee that the logic execution meets particulars at a significant level.

An example of HDL code and the circuit.
Figure- 2

Following this progression, the device description is then transformed into an entry-level netlist, during which various execution and improvement plans may be attempted to meet the plan goals more easily. Important considerations at this stage include power financial planning, speed, impression and reliability.

We use HDL in digital IC design because the compiler can identify blocks like multipliers and adders then create them out of target technology. Without HDL, one would be using technology specific logic gates. It would be hard to use the design in, for example, both FPGA (Field Programmable Gate Array) and ASIC (Application Specific Integrated Circuit).

10K designs in schematic capture are about as large as one can go maintaining any kind of organization. It takes too long to add things and rearrange things. It has been done before and it couldn’t be ported.

What is physical integrated circuit layout?

Combined and affirmed, the entry-level netlist becomes a real organization, a digital description of the IC's hierarchy and real development. A floor planner is used to ensure that the squares and pads are usually met by the IC to meet the arrangement goals. Due to the coordinated and transitional nature of several cutting-edge blocks such as memory and registers, automatic IC configuration is often accomplished using scripts and motorized programming processes. At this stage, the location of the external IP location is similar, and the basic point of association part of the IP is only shown by the project.

What is NMOS logic gate?  

NMOS is built on a p-type substrate with n-type source and drain diffused on it. An n-type material has 5 electrons in outsell, whereas semiconductor SI from Group IV from periodic table has 4 valency electrons. So, after covalent bond, there will be an extra electron used to excite the circuit with voltage with conduction band physics one has to study.

In NMOS, the majority carriers are electrons. When a high voltage is applied to the gate, the NMOS will conduct as source is biased to ground and a diode theory applicable here. Gate and source are forwarded biased as voltage crosses threshold voltage electrons move as voltage is increased eventually gathered at drain.

Figure 2

What is CMOS logic gate?

A p-channel improvement semiconductor works correlative to an n-channel upgrade semiconductor. This is the justification behind the name of the logic family, CMOS, or correlative MOS logic.

Though an n-channel semiconductor behaves like a shut switch when its gate voltage is high, a p-channel semiconductor behaves like a shut switch when its entryway voltage is low. While an n-channel semiconductor behaves like an open switch when its gate voltage is low, a p-channel semiconductor behaves like an open switch when its gate voltage is high.

Once again, this is an extremely short-sighted estimation that will be explained in ongoing sections. However, it is a satisfactory model to comprehend the logic work being executed by numerous customary CMOS gates.

 N-channel and p-channel enhancement transistor.
Figure- 5

What are digital integrated circuit design flows?

Design specification

  • Qualifications
  • Constraints
  • Tech bench progress

High-level system design

  • Plan partition
  • Entry-Verilog behavior modeling
  • Functional verification
  • Combination and verification

Logic synthesis

  • Register Transfer Level (RTL) conversion into a netlist
  • Plan partitioning into physical blocks  
  • Timing margin and timing constraints  
  • RTL and gate-level netlist confirmation  
  • Static timing examination


  • Hierarchical IC blocks placement
  • Control and clock planning


  • Timing constraints and optimization
  • Static timing analysis
  • Update placement
  • Inform power and clock planning

Block Level Layout

  • Complete placement and routing of blocks

IC Level Layout

  • IC integration of all block
  • Cell placement
  • Scan chain/clock tree placing
  • Cell routing
  • Physical and electrical design rules check (DRC)
  • Layout versus schematic (LVS)
  • Parasitic Extraction
  • Post-layout timing verification
  • GDSII formation
  • Tape-out

Common Mistakes

  • The coordinated circuit (IC) can deal with just a restricted measure of force.
  • It is hard to accomplish a low-temperature coefficient.
  • The curls or markers can't be manufactured.
  • Low commotion and high voltage activity are not effortlessly acquired.

Context and Applications

In each of the expert exams for undergraduate and graduate publications, this topic is mainly used for:

  • Bachelor of Electrical Engineering
  • Bachelor of Electronics Engineering
  • Bachelor of Mechanical Engineering
  • Masters of Electrical Engineering
  • Masters of Electronics Engineering
  • Analog integrated circuit plan
  • RF integrated circuit plan
  • Mixed signal IC plan
  • VHDL

Practice Problems

Q1 Which of the following logic families has the shortest propagation delay?

      (a) S-TTL

      (b) AS-TTL

      (c) HS-TTL

      (d) HCMOS

Correct option – (b)

Explanation - AS-TTL has a greatest clock recurrence that is 105 MHz. In this way, the engendering defer will be given by 1/105 sec which is the least one. It is trailed by S-TTL and HCMOS as far as expanding proliferation delay.

Q2 What is the static charge that can be stored by a human body while walking across a carpet?

      (a) 300 volts

      (b) 3000 volts

      (c) 30000 volts

      (d) Over 30000 volts

Correct option – (d)

Explanation - At the point when an individual strolls across a covered or tile floor electric energize works in the body because of the grating among shoes and floor material. In the event that the contact static is more noteworthy, the voltage potential creates in the body will be more prominent. One begins to go about as a capacitor. This is called Electrostatic release. The potential static charge that can create from strolling on tile floors is more noteworthy than 15000 volts while covered floors can produce north of 30000 volts.

Q3 Which of the following will not normally be found on a data sheet?

      (a) Minimum HIGH-level output voltage

      (b) Maximum LOW-level output voltage

      (c) Minimum LOW-level output voltage

      (d) Maximum HIGH-level input voltage

Correct option – (c)

Explanation- Least LOW-level result voltage won't regularly be found on an information sheet.

Q4 What causes low-power Schottky TTL to use less power than the 74XX series TTL?

        (a) The Scotty-clamped transistor

        (b) A larger value resistor

        (c) The Scotty-clamped MOSFET

        (d) A small value resistor

Correct option – (b)

Explanation - A bigger worth resistor causes low power low-power Scotty TTL to utilize less power than the 74XX series TTL.

Q5 Which of the following statements apply to CMOS devices?       

      (a) The devices should not be inserted into circuits with the power on             

      (b) All tools, test equipment, and metal workbenches should be tied to earth ground      

      (c) The devices should be stored and shipped in antistatic tubes or conductive foam        

      (d) All of the Mentioned

Correct option – (d)

Explanation - For CMOS gadgets, every one of the referenced assertions are relevant. The gadgets ought not be embedded into circuits with the power on. All devices, test gear, and metal workbenches ought to be attached to earth ground. Likewise, the gadgets ought to be put away and delivered in antistatic tubes or conductive froth.

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