The advantage of a forum like this is, of course, thart you are free to use any information
here for your own PC board design. I will be interested to see the schematics when you
publish them.
The nature of democracy is that many good ideas appear simultaneously, each with
advantages and disadvantages. Freedom is the possibility of choosing.
My only concern is simplicity and expediency. Perfection I leave to those more worthy than
my humble self.
--- In ComputerVoltageSources@yahoogroups.com, "Larry T." <larry@...> wrote:
>
> Would it be possible to use a small pc mounted relay to
> connect/disconect the +5 and Vref based on +15 being present? That
> way loss of +15 protects the part? In which case +5 being from +15
> makes no difference.
>
> Larry T.
>
> (If I designed software the way some engineers design hardware, I'd be
> out of a job. Interesting that this part is designed for a perfect,
> failure proof world!)
>
> --- In ComputerVoltageSources@yahoogroups.com, "Grant Richter"
> <grichter@> wrote:
> >
> > The note on power supply sequencing is on page 12 of the
> DAC8420_a.pdf file.
> >
> > They say it can take some milliseconds of fault condition, but not
> how many.
> >
> > I would rather not gamble.
> >
> > --- In ComputerVoltageSources@yahoogroups.com, "Grant Richter"
> <grichter@> wrote:
> > >
> > > On the CVS board, we have to have control of power supply
> sequencing to prevent
> > blowing
> > > up the expensive DAC chip (see the datasheet). The +5 and Vref
> supplies HAVE to come
> > > up AFTER the +/- 15 volts. And they can NOT stay on if the 15
> volts goes away even for
> > a
> > > few milliseconds. The only way to assure this is to derive these
> supplies from +15
> > supply
> > > and minimize the energy stored in capacitors after the 5v regulator.
> > >
> > > You have to double check your power supply sequencing, otherwise
> magic smoke will
> > > appear. On multi supply devices, there are substrate diodes
> connecting 5 and 15 volts
> > that
> > > don't appear on the schematic. If the 15 volts supply fails or is
> temporarily shorted, but
> > > not the 5 volt supply, this can reverse bias substrate diodes and
> blow metal vapor all
> > over
> > > the inside of a chip.
> > >
> > > For an LCD display board. I sure hope the 200 ma backlight
> connector is on a seperate
> > pad
> > > from the main 5 volt so the wires can be run seperately. A display
> module probably
> > > doesn't need 15 volts at all.
> > >
> > > But we will have to consider the case where 5 volts is on but
> either the +15 or -15 volt
> > > supply is off. We don't want the LCD module supplying destructive
> currents BACK to the
> > > CVS in a fault condition.
> > >
> > > --- In ComputerVoltageSources@yahoogroups.com, "Larry T." <larry@>
> wrote:
> > > >
> > > > If you only want to supply pads, thats okay, but PLEASE supply the
> > > > pads, polyswitches and diode locations for all 3 voltages. It
> should
> > > > be very easy to make all of the boards switch between using the +15
> > > > w/a regulator and using +5 direct by choosing between the regulator
> > > > and parts or the polyswitch and parts. I will point out that
> more and
> > > > more +5v components are showing up in our analog systems and
> probably
> > > > has a lot to do with MOTM moving to a 6 pin conector and a 3 voltage
> > > > supply.
> > > >
> > > > Larry T.
> > > >
> > > > --- In ComputerVoltageSources@yahoogroups.com, Harry Bissell Jr
> > > > <harrybissell@> wrote:
> > > > >
> > > > > Damn good idea.
> > > > >
> > > > > The polyswitch fuses can also improve on-card
> > > > > power supply filtering (by being slightly resistive)
> > > > > and cause a softer start on the power supply.
> > > > >
> > > > > H^) harry
> > > > >
> > > > > Grant Richter <grichter@> wrote: Here is a practical
> idea.
> > > > >
> > > > > You have three pads labeled +V, Ground and -V. These go to
> > > > resetable polyfuses and
> > > > > 1N4001 diodes to protect the circuitry in case the 12 year old
> > > > science fair student hooks
> > > > > something up wrong.
> > > > >
> > > > > direct link to schematic:
> > > > > http://www.blacet.com/techPS.gif
> > > > >
> > > > > From John Blacets fine technical page.
> > > > >
> > > > > http://www.blacet.com/tech.html
> > > > >
> > > > > Then the end user can wire up ANY kind of connector he wants to
> > > > hook up to those three
> > > > > pads.
> > > > >
> > > > > The 1/3 square inch of board spaced used can substitute for
> the 2
> > > > square inches of board
> > > > > space it would take to support every possible connector type
> that
> > > > will probably change or
> > > > > go obsolete anyway, and who has all the mechanical drawings need
> > > > to make the custom
> > > > > PC board connector footprints? And who is going to take
> > > > responsibility for everything
> > > > > being correct with each connector type, and what if the
> > > > manufacturer changes the pinout
> > > > > or adds something new??????
> > > > >
> > > > > Just take an existing "fill in the blank" system power
> cable, chop
> > > > one end off and solder
> > > > > the appropriate three wires to the three pads on the CVS
> board and
> > > > be done with it.
> > > > >
> > > > > --- In ComputerVoltageSources@yahoogroups.com, "John Loffink"
> > > > <jloffink@> wrote:
> > > > > >
> > > > > > Good point. Here's what could be supported based upon PCB
> > > > stuffing options:
> > > > > >
> > > > > > Synthesizers.com 6 pin 0.100"
> > > > > > MOTM/Blacet 4 pin 0.156" add 5 V regulator
> > > > > > MOTM 6 pin 0.156"
> > > > > > Modcan 3 pin 0.156" add 5 V regulator
> > > > > >
> > > > > > Any others?
> > > > > >
> > > > > > John Loffink
> > > > > > The Microtonal Synthesis Web Site
> > > > > > http://www.microtonal-synthesis.com
> > > > > > The Wavemakers Synthesizer Web Site
> > > > > > http://www.wavemakers-synth.com
> > > > > >
> > > > > >
> > > > > > > -----Original Message-----
> > > > > > > From: ComputerVoltageSources@yahoogroups.com
> > > > > > > [mailto:ComputerVoltageSources@yahoogroups.com] On Behalf Of
> > > > Larry T.
> > > > > > >
> > > > > > > I would like to suggest that, if at all possible, we include
> > > > both the
> > > > > > > Blacet/MOTM 4 pin +/-15v power connector. and the
> Synthesizers.com
> > > > > > > +5/+/-15v 6 pin connector. The board could allow for the
> > > > optional +15
> > > > > > > to +5 regulators when using the 4 pin connector. Some of us
> > > > already
> > > > > > > have +5 in our systems, and generally, no matter how much
> > > > ANYTHING you
> > > > > > > come up with will use (short of a room heater), the +5v
> supply is
> > > > > > > never anywhere near being used to it's rated output. I note
> > > > that some
> > > > > > > of the newer MOTM boards also use a seperate +5v supply.
> > > > > > >
> > > > > > > I bring this up in part because of the LED/LCD/VFD
> > > > discussions, and
> > > > > > > partly because the MPU in consideration has requirements for
> > > > +5v, and
> > > > > > > I really don't want to add more +15 to +5 regulators to
> my already
> > > > > > > stressed out +15v supply, when I have 4-6A of un-touched
> +5 just
> > > > > > > sitting around asking to be used.
> > > >
> > >
> >
>