On Sep 2, 2013, at 22:08, Mark Webb-Johnson wrote:
I'll try to rough up a schematic, to see how many components this
can be brought down to. For China manufacturers, saving even 1
component brings the cost of both materials and assembly down. I
remember working with the factory to remove 1 single chip costing
US$1.10 down to a bunch of passive components costing US$0.10 -
resulting price difference was US$3 (I think they really didn't
want to use that chip, not just for the cost but also for the
hassle of obtaining it). So, passives do not count as a whole component, not compared to a
chip?Supposedly not. Or, at least they don't concern themselves with
them. I suspect that the factories have rolls of hundreds of
thousands of these components, ready to go. Sometimes if I specify
a 2.3k resistor, for example, they will come back and ask to
substitute with 2.2k - but that happens surprisingly rarely. Their
biggest concern seems to be the ICs - or maybe they are just
concentrating on things that cost more than a buck.
I find myself wondering whether the MCP2551 could be replaced with 2
or 4 transistors and a handful of passives. Unfortunately, it would
add significantly to the research effort to design a discrete
circuit. The block diagram shows a fairly complex setup with a
reference voltage that would probably require an IC anyway, so I
don't there's much to gain by removing a chip if it requires another
chip in addition to some discrete parts.
Brian