2 Jul
2008
2 Jul
'08
10:41 a.m.
On Jul 2, 2008, at 11:50 AM, Ethan Dicks wrote:
DRAM chips tend to draw spikes of current during refresh, as those
little capacitors get charged. If you have adequate low-impedance
bypassing to supply those short-term demands, things should be fine
with the 7660. It's a fairly predictable and dependable chip.
There is some
loss, which goes up as you load the device; ie: if
you
drive it from +5.0V and load it lightly, you will get close to
-5.0V, but
as you draw more current it will drop down to almost -4.0V.
Right. That was what I was a little concerned by - 16 DRAMs do add up
to some measurable current, even at 100-200uA each. What I wasn't
sure
about is how quickly the ICL7660 drops off in a real application (vs a
nice clean curve on a spec sheet). I've seen mini-switchers like that in the past, 5
lead T-220 package,
IIRC, but I don't happen to have any handy, and I wouldn't be able to
get an order from Digikey for nearly 4 months in any case. I have
to use what's on hand.
Good heavens, one would think you're in Antarctica or something.
Oh, wait.. ;)
-Dave
--
Dave McGuire
Port Charlotte, FL