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Why is it necessary to fix transition violations despite having clean timing? In the Physical Design/Implementation stage of chip design, we address both timing and transition violations. Let's assume the timing violations have been resolved in all corners, but a few transition violations remain to be fixed. Despite having a clean timing analysis, is it still necessary to address these transition violations? What are the different strategies to address transition violations? Answer: Transition Violations occur when the signal transition (rise or fall time) at a logic gate input or output exceeds the maximum allowed transition time specified by the technology library. This happens when the signal changes too slowly, potentially leading to several adverse effects on the circuit's performance and reliability. Importance of Addressing Transition Violations Impact on Signal Integrity: Slow Signal Transitions:  Slow signal transitions can lead to signal integrity issues such as in...

Physical Design Interview Question | VLSI Physical Design | Tcl Programming Let's say you are working on a block/partition and handling physical design tasks from floor-planning to final GDSII. Floor-planning is one of the major tasks, alongside power planning. Define the major tasks performed during floor-planning. What are the key considerations for both floor-planning and power planning? After completing the power planning, assume you encounter approximately 1000 power-ground (PG) shorts in the design on a specific layer, M1. How would you approach fixing these PG shorts? Additionally, write a program to quickly identify and resolve these shorts with built-in tool command. Company : Product Based Experience: 3+ Years Answer: Floor-planning: https://compile-vlsi.blogspot.com/2024/05/floorplan-series-part-1-physical-design.html https://compile-vlsi.blogspot.com/2024/05/floorplan-series-part-2-physical-design.html https://compile-vlsi.blogspot.com/2024/05/floor-planning-part-3-fin...

Why Can't We Swap PMOS & NMOS in a CMOS Inverter Circuit? The CMOS inverter is a fundamental component in VLSI (Very-Large-Scale Integration) circuits. It serves as the building block for many other circuits. In a standard CMOS inverter, the PMOS transistor is placed at the top with its source connected to the power supply (Vdd), while the NMOS transistor is placed at the bottom with its source connected to ground (GND). The drains of both transistors are connected together to form the output node. Before discussing why swapping the PMOS and NMOS transistors is not feasible, let's first understand the operation of a standard CMOS inverter. Standard CMOS Inverter Operation Consider a CMOS inverter with a threshold voltage (Vth) of 0.7V and a power supply voltage (Vdd) of 5V. The threshold voltage is the minimum voltage required to turn on the transistor. Let's analyze the inverter's behavior under two conditions: when the input voltage (Vin) is low (0V) and when it ...

Low Power Design | Physical Design | Dynamic: Switching & Short Circuit Power | Part 3 Dynamic Power: Dynamic power is the energy consumed by a circuit when it's actively switching, processing information, and performing tasks. This type of power consumption is a result of the dynamic currents that flow through the circuit, including capacitance currents and short-circuit currents. Switching Power Dissipation Switching power dissipation occurs when the circuit's capacitances are charged and discharged, resulting in a flow of current. This power dissipation can be calculated using the equation Pswitch = α * (Vdd)^2 * CL * f, where α is the switching activity, Vdd is the supply voltage, CL is the total load capacitance, and f is the frequency of operation. The switching activity, α, is a measure of how often the circuit's outputs change state, and it's a critical parameter in determining the circuit's power consumption. Pswitching = α * (Vdd)^2 * CL * f, where: α ...

Low Power Design | Physical Design | Static & Dynamic Power | Leakage Current | Part 2 The goal of low power design is to reduce the individual components of power as much as possible, thereby reducing the overall power consumption. The power equation contains components for dynamic and static power. Dynamic power is comprised of switching and short-circuit power; whereas static power is comprised of leakage, or current that flows through the transistor when there is no activity.  The higher the voltage, the higher the power consumed by each component, resulting in higher overall power. Conversely, the lower the voltage, the lower the overall power. To achieve the best performance with the lowest power consumption, tradeoffs for each of these different factors are tried and tested via various low power techniques and methodologies. Static Power Consumption When a circuit is in a quiescent state, meaning there is no activity or clock signal, it still consumes power, known a...