A fully functional spice simulator for switcher applications

Design Automation

15 August 2001 Design Automation

Information from Linear Technology

Linear Technology has released switcher CADIII, a fully functional spice simulator with schematic capture and waveform display tool, for public distribution. The software's internal enhancements to the spice code provide optimised transient simulation of complex switching regulator systems on a cycle-by-cycle basis. The simulator can also calculate the circuit efficiency and generate a bill of material for some demo circuits. A full-featured schematic capture system allows easy entry of the circuits. Circuit models are dynamically linked in the schematic for simulation. Components can be easily changed on the schematic page. A waveform viewer can display both the current and voltage of all circuit components. Besides matching waveform, a waveform calculator is also included for data manipulation.

The figures show screen captures of a switching regulator design. The output waveform viewer shows the load regulation and output ripple of this switching regulator. The total simulation time for the load regulation transient took two minutes on a 700 MHz PentiumIIIPC

One of the biggest problems in designing high performance switching regulators is obtaining CAD tools for system simulation. While equation-based and continuous time models exist, they do not provide the detail of cycle-by-cycle transient behaviour. Some tools have fixed circuits and will not simulate user-designed circuits. Furthermore, most of the tools have a very steep learning curve. With the analog macro models and special convergence control for switching regulators, the switcher CADIII can speed up the simulation by a factor of 10 over the traditional method. There is no spice experience required to exercise the demo circuits, evaluate switching regulator configuration or edit component values. It is all done in minutes on a Windows95/NTPC.

According to Robert Dobkin, Chief Technical Officer of Linear Technology, "This is a breakthrough in switching regulator simulation. It brings a CAD tool to the desktop for fast evaluation of complicated circuits. Also, the spice is fully functional and allows other types of circuits to be simulated in a user-friendly environment."

This spice simulator with schematic capture, comparable to many costly commercial spice programs, is offered free by Linear Technology, see www.linear.com/software

Along with the spice simulation engine are macro models for over 100 switching regulators. This speeds up the initial evaluation of many devices. Circuits and component values of the provided switching regulator circuits can be quickly modified to generate new custom applications. A library of 200 op-amps are also included in the component library along with other analog and mix-mode building blocks.

For further information contact Memec SA, (021) 674 4103.

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A fully functional spice simulator for switcher applications

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