13 Jan
2012
13 Jan
'12
3 a.m.
On Thu, Jan 12, 2012 at 4:49 PM, David Riley <fraveydank at gmail.com> wrote:
I have two working Defender board sets that I'm
almost ready to start building cabinets for.
Nice.
I know the 5v is going to pull a lot because it's
used for most of the logic
Sure.
and the regulated 12v and -5v are probably somewhat
heavy since they power the sense amps for the 24 4116s0.
Not so much current there... if you can't find official specs, I
_know_ the 4116 datasheets aren't hard to find. ISTR it's a few mA
per chip for -5V, and I think it's a bit more of +12V. I do remember
that I wanted to replace a 7905 with an ICL7990 charge-pump negative
voltage supply and it was way too small for 16 4116s.
One thing to be careful of is that 4116s are sensitive to the order
that rail voltages are applied and removed. Some classic memory
circuits explicitly control the order, but others I've seen are less
stringent, depending on, I think, charging a large electolytic cap on
the rail that is supposed to be brought up last (can't remember the
proper order - someone else here might, or it should be in the
datasheet). You should be able to find the schematics for the
Defender power supply - be on the lookout for any parts that look odd
or look like they might affect on/off or rise time.
Good luck!
-ethan