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Analog Angle

The Allure and Risk of Second Sources

Bill Schweber
nathandavidson
nathandavidson
7/2/2018 5:02:06 AM
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Newbie
Re: Second Souirces and Even First Sources
I think that in every scenario, it's important to have a backup plan, and I think that's the idea with this second source right? At the end of the day, we just want to make sure that the network or system is set up in a way that prevents any sort of loss of capacity or any downtime is reduced if there are errors and issues that pop up and while such instalments may complicate the system, they are there for that reason! I'm sure that we will be able to streamline the framework better as we work through the options! 

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steve.taranovich
steve.taranovich
6/28/2018 11:54:54 AM
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Blogger
Re: Second Souirces and Even First Sources
Thanks for sharing that John experience John---we all need to be careful with so-called 'second source' ICs because they are not all true second sources.

 

Back in the early 80s, I had designed the ubiquitous 555 timer into a circuit design. Later, purchasing asked me to provide a second source. 

I had selected a Signetics NE555 (https://spectrum.ieee.org/tech-history/silicon-revolution/chip-hall-of-fame-signetics-ne555 ) as the original part and chose an RCA 555 timer as the second source. After reviewing the data sheets, I was convinced that they were true replacements for each other.

Hans Camenzind had designed the NE555 in the early 70s. He attended the Analog Aficionados dinners hosted by Jim Williams in Silicon Valley---but I digress.

When I tested each timer in my circuit, I found that the RCA 555 timer did not make my circuit perform as designed. After some further investigation, I compared schematics, and 'lo and behold', the RCA circuit had a very seemingly minor design difference that probably worked in 99.9 percent of designs, but not in my design.

I don't remeber which 555 I had chosen next as my second source, but before testing it, I compared schematics and they were identical (Be careful here because identical schematics can have gotchas too---that;s another story for next time---probably John Dunn has experience there as well)

I tested the new second source and it worked in my design (Be careful with second sources when the design or data sheet gets a new revision---that can also bite you)

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John Dunn
John Dunn
6/27/2018 8:17:34 PM
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Blogger
Second Souirces and Even First Sources
I had a 2N6578 power transistor second source issue with Motorola versus RCA way back when, but also a problem with just the one source, Motorola, gradually altering their devices over a time span of several years as they sought to improve production yields.

Please see:  http://licn.typepad.com/my_weblog/2011/09/semiconductor-evolution-john-dunn-consultant-ambertec-pe-pc.html 

 

 

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