10+ Hnb Engineers Interview Questions and Answers

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 time violations include adjusting clock skew, buffering sign...read more

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.

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 adjusted by inserting buffers or adjusting routing paths.

• Exampl...read more

A good floor plan should optimize area, minimize congestion, and ensure signal integrity.

• Optimize area utilization

• Minimize congestion and routing complexity

• Ensure signal integrity and minimize noise

• Consider power and thermal constraints

• Ensure ease of design changes and modifications

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 lines, using shielded cables, and implementing signal integri...read more

Checks after floor plan in physical design engineering

• Timing analysis to ensure timing constraints are met

• Power analysis to ensure power constraints are met

• Signal integrity analysis to ensure signal quality

• Design rule check to ensure adherence to design rules

• Physical verification to ensure layout is correct

• Noise analysis to ensure noise constraints are met

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.

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 destinations.

• Jitter is the variation in the period of the clock s...read more

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 communication.

• Tools like simulation software and oscilloscopes ar...read more

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: Verify design meets all requirements before tapeout