[sdiy] Pro One CEM3340 Sync magic

[ASSI]

On Monday 19 April 2010, Simon Brouwer wrote:
> I assumed an opamp-type buffer. I cannot be expected to have the
> detailed knowledge of the implementation that you have.

Reading what I wrote again, that came off way too harsh, sorry for 
that - no offense intended.

What I wanted to say is that you have to be very careful with anything 
that purports to show you the inside of an IC.  Don't let your mind 
play games with you seeing things that aren't there (and just as often 
there are things that aren't shown).  Not unlike those books that show 
you an electron as a ball of negative charge that rolls uphill on 
potential surfaces, any assumptions you make about the implementation 
may help you to get a first glimmer of understanding only to stand in 
the way later when you need to know what's _really_ happening.

So, when a datasheet tells you you can pull the output of a buffer to 
discharge a cap on the input of that same buffer, it might tell you 
something about the possible implementations of that buffer.  Or... 
there might be a circuit that is not shown that detects you pulling on 
the output and discharging the cap.  In this case measuring the 
voltages on the two nodes would quickly show you which is which, but 
in other cases it might not be so obvious.  For instance, that same 
buffer output also feeds into some other circuits and I haven't 
determined yet what effects pulling it below ground has there, besides 
obviously crossing some comparator thresholds and steering some 
currents.


Achim.
-- 
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