Re: Wanna see what happens when you don't read the data ***?

On 2/28/2007 12:01 PM, The digits of John Popelish's hands composed the following:
The low ESR capacitor plus resistor guarantees a stable RC zero over the life and operating conditions of the system. Getting the zero from some poorly controlled and unstable resistance from a high ESR capacitor is a ticking time bomb.

Gotcha. Do you have any data to show trends of ESR change over time and temp. In the case of the regulator in question it can use a fairly wide range so if you hit in in the middle I wonder if it is overkill to assume it could fall outside that range.

Does the client expect the circuit to work for several years and over a range of ambient temperature beyond normal room temperature? If so, proving that the cheap capacitor is stable enough to expect success may cost more than using more predictable parts.


Oh I am with you on that but you gotta understand clients.

I do contract engineering and while I can advice I have to accept what my clients want in the end. Most clients are reasonable in there desires although some want me to over analyze things beyond nessasary and some the other way. Usually the other way is because they are bean counters, or non technical or because they can't "see" theory.

In the case of this "cheap" client it has been a real struggle to try to get them to understand why just because I power it up on the bench and it appears to work does not mean the design is ready to ship.
I can't tell you how many times they have built a product with parts other than I specified and even if I find it has issues with those parts (that I can prove on the bench) if they don't see it then it isn't real to them.

Reality is these kinds of clients are not uncommon. They are not technical and run by bean counters. I get so sick of "well the capacitance and voltage are the same - who gives a !@#$ about other specs".

Hawker
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