[sdiy] Resistor Networks....

mark verbos markverbos at gmail.com
Sun Aug 30 12:09:37 CEST 2020


Pete,

I have been seduced by the Siren’s call of the resistor network, but I would not recommend it. I use 0603 passives mostly. I used these “1206” sized CTS 4 resistor networks. Even before they all got discontinued (requiring me to redesign everything that uses them), I found them annoying. As Roman said, they reduce 4 placements to 1, which in some very repetitious cases make a big difference. When I have a design with 96 of the same resistor next to each other, it is nice to place just 24 arrays. The size of these is quite big, but more or less the same as having the 4 0603’s next to each other. It is a bit cleaner looking too. But, they seem to have more problems with bad joints out of the oven. These are only 5% tolerance. And more then once I got the design ready and then wanted to change the value of one resistor to tweak something and was stuck. The routing can get annoying when it isn’t replacing 4 resistors that were side by side anyway.

I have also gone down to the next size smaller and it was ok, it placed and reflowed a bit more consistently, but the other points remain. 


Mark




> On Aug 30, 2020, at 5:32 AM, Pete Hartman <pete.hartman at gmail.com> wrote:
> 
> I'm working on laying out a classic through hole module design with SMD parts.  The original uses a fair number of resistor networks, most of them just parallel resistors, not common bus versions.  The resistor networks are, well... huge by comparison.
> 
> Unfortunately the original designer isn't around for me to ask for input.
> 
> My *impression* based on how the networks are being used (often times for things like input resistors and a feedback resistor in a summing op amp config, just as one example) is that part of their purpose was to get parts that were well matched.  But that's not anything but a gut feeling.
> 
> So I'm looking for seasoned opinions about whether there is any important reason to keep resistor networks, when I can sub in 1% SMD parts that will take up less space and be more flexible for placement.  Are the networks either 1) better matched even than 1% parts, or 2) have some other characteristic which I'm not thinking of that might be important?
> 
> Thanks
> 
> Pete
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