It would be better to adapt a hot plug type controller based upon +/- 15V
power and FET to the task than a relay, but even that is going to extremes.
I am not proposing this.
Don't you hate it when manufacturers make vague warnings about claims, then
don't characterize them fully?
I looked back at the TI DAC7614P that I recommended, and it is +/-5V or +5V
only. Consequently it doesn't have the power sequencing problem of the
Analog Devices part. But it introduces a new one, requiring precision
amplification to generate 10 volt outputs with 12 bit accuracy. I think
Grant said he was going to op amp buffer the DAC outputs anyway. 12 bit
resolution over 10 volts is about 0.24% accuracy. Scaling using 0.1%
Precision resistors should do it. These are 96 cents each from Mouser. We
need two for each DAC output. So, $8 in resistors, but the 16 pin DIP
DAC7614P is only $16.43 from Digi-Key, not $44.93 like the DAC8420FP. Net
savings is about $20.
You could try matching batches of 1% resistors with a DMM, but a typical 4
digit DMM only has absolute accuracy of 1%. You really need a 5-6 digit DMM
for matching to this precision. I have one, but realize that most DIYers
don't.
John Loffink
The Microtonal Synthesis Web Site
http://www.microtonal-synthesis.comThe Wavemakers Synthesizer Web Site
http://www.wavemakers-synth.com > -----Original Message-----
> From: ComputerVoltageSources@yahoogroups.com
> [mailto:ComputerVoltageSources@yahoogroups.com] On Behalf Of Larry T.
>
> 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.
>
> --- 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.
> >