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Electronics Design: Schematic Capture

Sunday 23rd November 2014

Schematic Capture

Schematic Capture is the process of defining the logic connections between different components in an Electronic Circuit. At the end of the process you have a diagram or Schematic of the circuit. That’s a complicated way of saying that it shows the connections between the selected components. We use Altium Designer as our EDA or Electronics Design Automation tool.

 

That is a lot of links but this is an important part of the process. Get this wrong, and you have a product that doesn’t work.

 

Electronics Schematic

Electronics Schematic

This the Electronic Circuit Schematic for a 5VDC Switch Mode Power Supply, also known as SMPS. It can deliver up to 0.5A and includes a number of novel features to reduce noise and ripple. The RC damper across D5 is one of these. The other is the 82R series resistor that limits the maximum current through the charge pump diode C14. The measured ripple is less than 1mVRMS.

 

I’ve gone into a bit of detail because this shows how effective Component Selection can lead to a great outcome. We started with the design objective of a non-isolated power supply to get a 5VDC rail for our circuit from the incoming 12VDC rail. I wanted an efficiency above 80%, low noise, small footprint and low cost. So we looked at a wide range of suppliers including some like Texas Instruments, or TI as they are usually referred to, who have tools on their websites that will select suitable components for you. In this case they didn’t have a suitable offering but Microchip did.

 

And the Schematic above is the result of the Component Selection process, review of the datasheet to get the circuit requirements for things like calculating the output voltage feedback divider (R10 and R12) correctly. And now we have our Schematic ready for creating the PCB Layout.

 

Altium

Altium – EDA

Altium have a comprehensive tutorial on the whole process using their tool at Get Started With PCB Design.

 

Successful Endeavours specialise in Electronics Design and Embedded Software Development. Ray Keefe has developed market leading electronics products in Australia for nearly 30 years. This post is Copyright © 2014 Successful Endeavours Pty Ltd

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