On Apr 22, 2012, at 12:32 AM, Guy Sotomayor wrote:
And to finish off my part in this, classic computers
and such are for me a
hobby. I do high tech, leading edge stuff as a job and in that role something
like the 555 doesn't really have a place (at least in the stuff that I'm doing).
While we may have some things that could be done by a 555-like device, there's
so much other stuff going on that it's better (from every dimension) to incorporate
the functionality into micro's or ASICs (FPGAs and CPLDs are only used for
prototypes?they're too costly when you're building x*1,000,000's/quarter).
That is almost true in my world as well. Still, sometimes they're actually
the best solution; we had to provide a ~600KHz clock to a bunch of switching
power supply modules on one board to synchronize them (so they'd switch on
alternate phases, etc). A 555 (well, a modern CMOS version) was the true
obvious choice there, because it was a pretty foolproof part with few
externals in the right frequency range.
Project management at the customer (this is the same project that made us
put the 800 MHz PowerPC on board when a 50 MHz ARM would have done) was
furious at us for not dividing down the 100 MHz system clock on one of the
on-board FPGAs instead. Of course, this was a second spin, designed to fix
the nasty problem of the FPGAs not starting up reliably because the power
supplies were getting thrown off because they weren't in sync. :-)
I'm glad to say it was actually one of my co-workers who pushed for the 555.
Of course, he had background as a technician and would much rather have
something he could adjust himself in the lab without going through the
exercise of finding an FPGA compiler, finding the source code, modifying it,
waiting an hour for the damn thing to compile, then waiting the 15 minutes
(no, really) it took to program the flash.
Project management was less pissed off once they forgot about it a week
later, and it's never given us problems since (and they made thousands of
the board).
Long story short, it's all a matter of choosing the right part. Sometimes
a 555 *is* the right part, and sometimes it's not. For a power supply
frequency reference, I'll choose the analog-ish part over an FPGA/micro
any day, unless there's an astoundingly good reason to go with the other.
- Dave