2 Jul
2008
2 Jul
'08
9:46 a.m.
On Wednesday 02 July 2008 05:05, Ethan Dicks wrote:
The dynamic PET, since it has soldered-in DRAMs, is a
bit more complicated.
Unless I care to remove the DRAM and fit another ROM/RAM board for the SRAM
or adapt a 62256 in some other way, I need +12V and -5V for Vdd and Vbb on
the 4116 chips. My question (after all this background info) is... does
anyone have enough knowledge of the ICL7660 chip to give an opinion on how
well it would work for supplying -5VDC? Looking at datasheets, the max
draw I can find on Intel uP416s is 200uA @ -5VDC (along with all its other
needs). It looks like the ICL7660 will provide up to 10mA @ -5VDC, but at
some higher amount of inefficiency than at lower draws. 16x0.200 is 3.2mA,
well under the max draw of the ICL7660, so I think I'm OK, but I wanted to
ask other folks about this in case I'm overlooking some important detail.
That might be workable in terms of current draw, but that's not what I'd be
worried about there. I'm not real sure about the 4116 chips, but I seem to
recall that at least some of that early stuff that needed multiple supplies
needed to have that Vbb supply present _first_ and going away _last_. It's
getting it to come up first that I'd be worried about....
(Snip)
One memory that's filtering up to the surface is
that ISTR some
order-of-DC-powerup requirement for 4116s, like don't apply -5V
first or remove it last or some such. I plan to power the ICL7660
off of the +5V rail, but if there is a very specific order that
really matters, I might consider running it off the +12V rail
(with a 78L05 in-between) instead.
Just what I was thinking, above. But it's been so long that I really don't
remember in detail. It might not even have been the 4116 I was thinking of,
as there were a bunch of other chips that used multiple power supplies like
that, the 2708 coming to mind as well.
--
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space, ?a critter that can
be killed but can't be tamed. ?--Robert A. Heinlein, "The Puppet Masters"
-
Information is more dangerous than cannon to a society ruled by lies. --James
M Dakin