Sorry I was at work and kinda jumped tracks. I got called to check on
some of our process control gear on the floor. The cap idea on the 3
volt line should give the memory chips time to settle into the sleep
state where they will only draw the minimum rated amount of current.
The only pratical experience I have besides the Peavey DPM's is with
the Roland MT-32 battery backup mod. One way uses expensive DS1210
chips to clamp the memory chip enable line (CE) when the power is
removed. The second solution just backs up the 5 volts with a fast
diode to provide the 3 volts to hold the memory intact. Either way
will provide a glitch free memory backup. The second solution also
provides an easy (and cheap) way to provide the extra voltage needed
to recharge the battery pack so 3.6 volt NiMh batteries from a
cordless phone can be used.
Acid you say??? "Mr Watson, Come here, I want you!"
--- In
korgpolyex@yahoogroups.com, "korgpolyex800"
<korgpolyex800@...> wrote:
>
> Fran,
>
> What do mean by "Letting the current settle will help a lot getting
to
> the 2uA state in these ram chips." ?
>
> I am not following what you're saying.
>
> Mike.
>
> --- In korgpolyex@yahoogroups.com, "narfman96" <narfman96@> wrote:
> >
> > Mike,
> > Button cells are available in larger sizes too. Some of the gear
I
> > have uses a CR2450 which has 620 mAh of storage. I have a problem
> > with some of the rechargeables especially the NiCad nightmares
I've
> > seen in the Peavey equipment. I replace them with cell phone
> > batteries mounted in a remote location away from all boards and
> > switches.
> > Letting the current settle will help a lot getting to the 2uA
state
> > in these ram chips.
> > Fran
> > --- In korgpolyex@yahoogroups.com, "korgpolyex800"
> > <korgpolyex800@> wrote:
> > >
> > > Hi Atom,
> > >
> > > I will see if I can measure the current but at low current
draws the
> > > meter may not be entirely accurate. I'll give it a go though.
> > >
> > > According to the datasheet, if I take CS1 high or CS2 low
before the
> > > power supply drops from 5V to battery 3V, then the current draw
will
> > > be 2uA (typical) up to 100uA (max). But the datasheet seems a
bit
> > non
> > > specific about the timing of the chip select lines being at
correct
> > > levels prior to the supply dropping to 3V.
> > >
> > > So I have a couple of theories as to why the battery is going
flat
> > > fast. First, the CS2 chip select line was not being pulled down
to
> > 0V.
> > > I've placed a 10K pull down on that line. I am hoping that
this,
> > easy
> > > to install, extra resistor will fix the problem.
> > >
> > > Second, perhaps the timing of the shutdown of power from 5V to
3V
> > (on
> > > battery) is critical. If that is the case, then I can see a
> > situation
> > > where the chip select lines could be in the wrong state when
the
> > power
> > > down occurs. In that circumstance, the battery will pull alot
more
> > > current while on battery. As I said though, the datasheet is
doesn't
> > > explain the timing very well. Nevertheless, if the one pull down
> > > resistor doesn't fix the problem then I'll add a capacitor on
the 3V
> > > battery side of the power supply to the two static RAMs. This
will
> > > ensure that the chip select lines settle into their correct
state
> > long
> > > before the memory power supply falls from 5 to 3V.
> > >
> > > So I don't think this is a big problem, it is just going to
take a
> > > while to work out exactly what has to be done. I am hoping that
the
> > > single 10K ohm pull down resistor is all that is needed.
> > >
> > > Zoinky makes a good point though. The button cell most
certainly can
> > > be replaced by two AA batteries. I like the button cell because
it's
> > > guaranteed not to leak all over the insides of your precious
> > synth's.
> > >
> > > I cringe thinking about the number of Poly's that have been
sitting
> > in
> > > storage with batteries slowly decomposing all of the PCB's. I
bought
> > > one on ebay specifically because the case, joystick etc was in
> > perfect
> > > condition while the insides were completely acid wrecked.
> > >
> > > I think the button cell should be OK in the long run. It is
just
> > going
> > > to take a few months to be certain that it is set up just
right.
> > And I
> > > wanted to warn everyone before they lose their patches.
> > >
> > > Mike.
> > >
> > > --- In korgpolyex@yahoogroups.com, Atom Smasher <atom@> wrote:
> > > >
> > > > On Tue, 27 May 2008, korgpolyex800 wrote:
> > > >
> > > > > So, I had a look at the design and think I might have
missed a
> > > pull down
> > > > > resistor that would reduce the current by about half. I've
> > added the
> > > > > pull down onto both of the HAWK-800 kits and I guess in
about
> > six
> > > weeks
> > > > > I'll know if it made any difference at all.
> > > > =================
> > > >
> > > > do you have a multi-meter? measure how much current is moving
> > > through the
> > > > battery...
> > > >
> > > >
> > > > > A single 6264 static RAM in standby mode uses between 2 and
> > 50uA.
> > > > ==============
> > > >
> > > > that's a big range... what determines the actual current?
> > > >
> > > >
> > > > > The longer term solution is now being looked at. There are
two
> > > ways to
> > > > > go about this. One way would be to use a rechargeable
battery
> > > scenario.
> > > > > The other, would be to write patches into flash memory.
I'll
> > post
> > > again
> > > > > as soon as I come up with a solution.
> > > > ================
> > > >
> > > > a slightly larger rechargeable battery (1/3 AA) would have a
> > better
> > > > amp-hour rating, and would last longer than a 2032. i've seen
> > gear with
> > > > original 10-15 year old lithium batteries running strong.
> > > >
> > > >
> > > > --
> > > > ...atom
> > > >
> > > > ________________________
> > > > http://atom.smasher.org/
> > > > 762A 3B98 A3C3 96C9 C6B7 582A B88D 52E4 D9F5 7808
> > > > -------------------------------------------------
> > > >
> > > > "In peace, sons bury their fathers.
> > > > In war, fathers bury their sons."
> > > > -- Herodotus
> > > >
> > >
> >
>