Modelling a surge waveform in PSpice to simulate the effect of transients on your circuit

Transients are high-energy voltage or current spikes. These spikes are short lived but have the potential to affect the product’s signal or power lines. At times, the high-intensity transients can permanently damage the components, thereby making the product unusable. Sources of transients could be electrostatic discharge, lightning/surge, and circuits with high switching frequency.

Transient immunity plays a very vital role in modern-day electronics. Transient-protection devices try to re-route the transient spike energy into the ground to avoid any disruption in signal/power lines. Various transient-protection schemes include using Electrostatic Discharge (ESD) and Transient Voltage Suppressor (TVS) diodes, lightning/surge immunity, and so on. Choosing the right surge-protection device is often a challenge.

PSpice helps you to choose a suitable protection device by enabling you to model and simulate the behavior of a circuit under transient conditions. A Piecewise Linear (PWL) source can be modelled for any transient waveform and the response of the circuit under test can be monitored.

For example, in PSpice, you can simulate the response of a USB interface with ESD protection and choose a suitable ESD diode.

The first step is to model a PWL source for a transient like ESD pulse.

A PWL source is like a voltage/current source available in the modelling application library.

You can now select a suitable ESD diode and use its PSpice model to simulate the behavior under surge.

The simulation can help to understand the current levels flowing through the diode when surge is applied. Such simulations can be helpful in designing a reliable protection scheme and reducing the risk of failure during compliance testing.

PSpice also allows you to choose from a wide variety of pre-defined sources like impulse, pulse, exponential, noise, and so on to test the circuit behavior under different transients. These sources can be accessed from the Independent Sources of Modelling application.

Team DesignTech

Cadence Design Systems