Ignitarium Technology Solutions Vlsi Engineer Interview Questions and Answers

Basic aptitude-10 question,digital moderate -Question,analog moderate -10 question,verilog and system verilog -10 question

Q1. Latches and flip flop all characteristics equation and proof of the characteristics equation in flip flop.applications of flip flop
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Q2. OOPS,INHERITANCE,VERILOG,BLOCKING - NON BLOCKING ASSIGNMENT OPERATOR and all the basic operations of verilog .
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Q3. Discussion on work experience.
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Q1. Write code randc behaviour
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randc behavior generates random complex numbers with specified distribution
• Use randc to generate random complex numbers

• Specify distribution using arguments like mean, variance, etc.

• Example: randc(10, 1, 2) generates 10 random complex numbers with mean 1 and variance 2
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Q2. Functinal coverage
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Q3. Code coverage related questions
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Q4. Monitor and scoreboard connections
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Q5. Project related questions
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40 aptitude qns and some mcqs on basic programming

Q1. I was asked to write two sum, palindrome function and merge sort code in whatever language I'm comfortable in
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Q2. Two sum- return true or false
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Given an array of integers, determine if there are two numbers that add up to a specific target.
• Iterate through the array and store each element in a hash set.

• For each element, check if the difference between the target and the element exists in the hash set.

• If the difference exists, return true; otherwise, continue iterating.

• Example: nums = [2, 7, 11, 15], target = 9. The function should return true as 2 + 7 = 9.
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Q3. Merge sort function code
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Q4. Palindromic string or not
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Q1. Is setup and hold uncertainty values are different
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Yes, setup and hold uncertainty values are different in physical design engineering.
• Setup uncertainty is related to the arrival time of the data signal at the input of the flip-flop, while hold uncertainty is related to the removal time of the data signal.

• Setup time is the minimum amount of time the data input must be stable before the clock edge, while hold time is the minimum amount of time the data input must be sta...read more
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Q1. What are the PD inputs and outputs
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PD inputs are design specifications and constraints, while outputs are physical layout of the design.
• Inputs include design specifications, constraints, technology libraries, and floorplan.

• Outputs include physical layout, placement of components, routing of wires, and design verification.

• Example: Input - RTL design, clock frequency, power constraints. Output - GDSII layout, timing analysis report.
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Q2. Describe each stage of PNR flow
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PNR flow consists of synthesis, floorplanning, placement, clock tree synthesis, routing, and signoff stages.
• Synthesis: Convert RTL code to gate-level netlist

• Floorplanning: Define chip area, core, and I/O locations

• Placement: Place gates in specific locations to meet timing constraints

• Clock tree synthesis: Create clock distribution network

• Routing: Connect gates with wires while considering timing and congestion

• Signoff: V...read more
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Q3. What are the different techniques to minimize congestion?
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Techniques to minimize congestion include buffer insertion, wire spreading, and layer assignment.
• Buffer insertion: Adding buffers to critical paths to improve timing and reduce congestion.

• Wire spreading: Distributing wires evenly to reduce congestion in specific areas.

• Layer assignment: Properly assigning different signal layers to reduce congestion on a single layer.
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Q4. What is the setup and hold time and different techniques to fix the setup and hold time violations?
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Setup and hold time are timing constraints in digital circuits. Techniques to fix violations include adjusting clock skew, buffering signals, and optimizing routing.
• Setup time is the minimum amount of time a data input must be stable before the clock edge for proper operation.

• Hold time is the minimum amount of time a data input must be stable after the clock edge for proper operation.

• Techniques to fix setup and hold ti...read more
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Q5. What is signal integrity?
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Signal integrity refers to the quality of an electrical signal as it travels through a circuit or system.
• It involves ensuring that the signal remains clear and undistorted from the transmitter to the receiver.

• Factors affecting signal integrity include impedance matching, noise, crosstalk, and reflections.

• Signal integrity analysis is crucial in high-speed digital design to prevent data errors and ensure reliable communi...read more
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Q6. What is crosstalk and noise and how to fix it?
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Crosstalk is unwanted interference between signals on adjacent lines, while noise is random unwanted signals that can degrade performance.
• Crosstalk occurs when signals on adjacent lines interfere with each other due to coupling effects.

• Noise is random unwanted signals that can be caused by various sources such as electromagnetic interference or power supply fluctuations.

• To fix crosstalk, techniques like spacing out lin...read more
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Q7. What is clock latency, skew and jitter?
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Clock latency is the delay between the clock signal being generated and reaching the destination, skew is the variation in arrival times of the clock signal at different destinations, and jitter is the variation in the period of the clock signal.
• Clock latency is the delay between the clock signal being generated and reaching the destination.

• Skew is the variation in arrival times of the clock signal at different destina...read more
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Q8. What is useful skew, negative skew and positive skew?
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Useful skew, negative skew, and positive skew are terms used in physical design to describe timing constraints.
• Useful skew refers to intentional delay added to certain paths to meet timing requirements.

• Negative skew occurs when data arrives later than expected, leading to potential timing violations.

• Positive skew occurs when data arrives earlier than expected, potentially causing setup time violations.

• Skew can be adjus...read more
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Q1. What is an ICG? How would you use it in the design?
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ICG stands for Inter-Chip Global. It is a network that connects multiple chips in a system.
• ICG is used to transfer data between different chips in a system

• It helps in reducing the number of wires required for communication between chips

• ICG can be used in various design aspects such as clock distribution, power management, and data transfer

• Example: In a multi-chip system, ICG can be used to transfer clock signals from o
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Q2. How will MSCTS help at SOC level CTS
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MSCTS can help in achieving better clock distribution and reducing skew at SOC level CTS.
• MSCTS (Multi-Source Clock Tree Synthesis) can optimize the clock tree for better skew and jitter performance.

• It can also help in reducing power consumption by optimizing the clock network.

• MSCTS can handle multiple clock sources and ensure proper synchronization.

• It can also help in meeting timing constraints and reducing clock tree ...read more
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Q1. What was the most difficult challenge faced in the projects you worked?
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Q2. How will you fix setup and hold time when both are violating at the same time.
Ans. 
Fixing setup and hold time violations simultaneously requires adjusting clock timing and/or data path delays.
• Identify the critical path causing the violations

• Adjust the clock timing to meet setup and hold requirements

• Adjust the data path delays to meet setup and hold requirements

• Use tools like static timing analysis and delay calculation to determine necessary adjustments

• Iteratively adjust timing and delays until viola
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Q1. Asked the working experience and the related skills to the new job
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Q1. Coding questions in Verilog, Systemverilog, random constraints such as how to write a onehot in different ways
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Q1. Asked the expectation of the base salary and overall compensation
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