[sdiy] Eurorack Grounding Question

Mike Bryant mbryant at futurehorizons.com
Sat Jan 2 23:09:28 CET 2021

I've just used a TI switcher (TPS65131) and the suggested layout just leaves off two connections from the schematic so you have to guess how best to implement those.  Not impressed 

-----Original Message-----
From: Synth-diy [mailto:synth-diy-bounces at synth-diy.org] On Behalf Of Brian Willoughby
Sent: 02 January 2021 21:27
To: mark verbos
Cc: synth-diy at synth-diy.org
Subject: Re: [sdiy] Eurorack Grounding Question

Hi Mark,

I suppose it's a little late - now that you're done with that design - to mention that many switching power chip manufacturers have application notes with the exact layout placement and trace width necessary to meet the needs of their design. Most recently, I designed with an inductive boost regulator, and the exact alignment, orientation, distance, and trace width were all spelled out in notes from the manufacturer. Much of this was to avoid broadcasting the switching noise to every local circuit. For the capacitive switchers I've designed around, the data sheets mention that both input and output capacitance are crucial, even though they don't show this in every example circuit. Some manufacturers explain how the surrounding circuit might provide enough capacitance already, depending upon the distance, but if it's insufficient then local capacitor(s) must be added.

Not surprisingly, many chip manufacturers have dedicated representatives for their power products, presumably to help with these troubling details.


On Jan 2, 2021, at 11:15, mark verbos <markverbos at gmail.com> wrote:
> Fun stuff. Reminds me of the PCB routing nightmare that I just went through with a small DC-DC switching power supply I made. I used TI Webbench Power Architect and found that some of the capacitors had to be moved directly onto the pins (of TSSOP ICs!)  of the ICs for the rail to start up. I redesigned the PCB with the parts moved to right next to the pins and found that the 1 or 2mm away from being on the actual pins made the same problem! Mind you, these are just caps from the power line to ground, but certain pins need them to be very close. Of course, once  the problem is found and a solution found, it seems obvious, but when searching for it...
> Mark

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