not fully pin-compatible, was Re: [sdiy] DG413 question

[Scott Gravenhorst]

John Mahoney <jmahoney at gate.net> wrote:
>At 04:13 PM 2/2/2007, Ian Fritz wrote:
>>At 09:50 AM 2/2/2007, John Mahoney wrote:
>>>On the subject of not-quite-identical, "pin-compatible" chips, even 
>>>the venerable 555 timer comes in a variety of slightly different 
>>>flavors. Look at Table 2 in Tony van Roon's 555 tutorial:
>>>         http://www.uoguelph.ca/~antoon/gadgets/555/555.html
>>>--
>>>john
>>
>>Yes, but as he states: "In all circuit diagrams below I used the 
>>LM555CN timer IC from National, but the NE555 and others should not 
>>give you any problems. "
>
>Indeed. But it's still interesting to note the differences, and there 
>are presumably cases where those differences would, uh, make  difference.

Also interesting about this particular part (555) is that one might expect the CMOS
version of the part (7555) would have obvious or radical differences from the bipolar
part.  In fact, the differences contribute to a better part for many applications. 
Used in a VCO, the 7555 performs better than a 555 because it doesn't cause a huge
current spike at reset time.  In a FatMan, a 7555 is a drop in replacement and by that
replacement, most of the softsynch problem vanishes.

-- ScottG

---------------------------------------------------------
-- Scott Gravenhorst
-- Xilinx Spartan-3E Based Music Synthesizers
-- FatMan: home1.gte.net/res0658s/fatman/
-- NonFatMan: home1.gte.net/res0658s/electronics/