Interpolator PCB Design

Although we successfully prototyped a working quadrature interpolator, I can't really use a breadboarded circuit as part of my 3d printer.  Had the IC-NV been available as a through hole component I might have just thrown some perfboard into a project box, but the TSSOP-20 package is really looking for a PCB.  My previous experiences with PCBs all involve a frustrating toner transfer process that produced fairly ugly single-sided boards.  This will be my first attempt at sending a design out to be manufactured.

I basically just stumbled through a few EagleCAD tutorials and figured things out along the way.  The first step was to put together a schematic.  This is just the circuit from my previous post with a few more capacitors.


Next it's time to lay out the PCB.  The circuit itself is quite simple, but space restrictions kept things interesting.  I ended up redoing the design as I learned about proper PCB routing and settled on the following layout.




Finally I did a test fit using cardstock before sending it out to be manufactured.  Since the components I chose are so small, I decided to integrate the circuit into the connector.  This saves the space and trouble of preparing a project box.  The PCB slips between two rows of pins which means I had to specify a non-standard 0.8mm PCB thickness when ordering.


Overall, designing a PCB was both easier and cheaper than I expected.  The one drawback is that the low-cost fabs are all in China and shipping can take several weeks.  This part of the project will be on hold for quite some time until the boards arrive.

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