# What is RC delay model?

## What is RC delay model?

The RC delay model is a metric used in VLSI design to calculate the signal delay between the input voltage and output voltage of the input signal. The input signal is a step function. In this case the transistor can be considered as a switch in series with a resistor.

## What is Ecsm library?

The ECSM standard is the most complete open library format available and holistically models the effects of timing, noise, power, and variation. IP providers will benefit from greater simplicity and efficiency in the library creation process as well as a simplified distribution model.

**What is inverter delay?**

The propagation delay of a logic gate e.g. inverter is the difference in time (calculated at 50% of input-output transition), when output switches, after application of input. The delay is usually calculated at 50% point of input-output switching, as shown in above figure.

**How is RC delay calculated?**

Thus, the transient response or a series RC circuit is equivalent to 5 time constants. This transient response time T, is measured in terms of τ = R x C, in seconds, where R is the value of the resistor in ohms and C is the value of the capacitor in Farads.

### What causes propagation delay?

Propagation delay typically refers to the rise time or fall time in logic gates. This is the time it takes for a logic gate to change its output state based on a change in the input state. It occurs due to inherent capacitance in the logic gate.

### What is noise margin of inverter?

Noise margin is the amount of noise that a CMOS circuit could withstand without compromising the operation of circuit. Consider the following output characteristics of a CMOS inverter. Ideally, When input voltage is logic ‘0’, output voltage is supposed to logic ‘1’.

**What is the difference between NLDM and CCS driver?**

Other significant shortcoming of NLDM is in the receiver model. NLDM receiver model fails capture miller effect. This effects dominates delay calculation of STA for very small impedance nets. CCS driver model is characterized by capturing current waveform flowing into the load capacitor of the cell.

**Which two parameters are used to synthesize NLDM driver model?**

These two parameters – delay and transition times are used to synthesize NLDM driver model shown in the picture below: NLDM receiver model is simply a single capacitor for the entire transition with no sensitivity.

## What is non linear delay model (NLDM)?

Non-Linear Delay Model. NLDM uses a voltage source for driver modeling. It is must simpler than the other two mentioned above. It uses lookup tables with load and slope as indexes. Pre-driver method is as if the output of a PWL source is parsed through a low-pass filter.

## What is the NLDM receiver model?

NLDM receiver model is simply a single capacitor for the entire transition with no sensitivity. NLDM only captures 3 output points, which is not sufficient to reflect non-linearities of circuits at lower geometries (65nm and below) in synthesized driver model during static timing analysis.