VSS importance

[jdzura at csc.com]

The problem with doing a one-shot solution is the analog nature of the frequency
multiplication. Over time and temperature there will most likely be problems. The
classic way to do this is to implement a phase locked loop with a divide by 2
(D-FF) in the feedback path to the phase comparator. The output of the PLL before
the flip flop will be exactly 2x the input frequency. I  can't remember the
series, but there used to be a 4000 series Cmos PLL that had great application
notes.

The other purely "digital" way requires an oscillator to run a series of Flip
flops that can be used to do the 2x frequency multiplication. This is essentially
a zero order PLL. In either digital case, the circuit will take a few chips and
some additional power. I believe I have read where someone sells an adapter for
$50-60 already done. If it has been done and is only $50, you should probably buy
it. Designing one will probably cost at least half that by the time you consider
packaging, connectors, and a wirewrap board. Just my humble opinion and I have
been an electronic designer for more than 15 years. If you still insist, let me
know, and I will look up the reference to the cmos PLL chip. CMOS has the
advantage of being run from 12 VDC and won't incur the overhead of voltage
regulation.

Joe D





"Bruce Plecan" <nacelp at bright.net> on 09/28/98 01:48:00 PM

Please respond to diy_efi at efi332.eng.ohio-state.edu

To:   diy_efi at efi332.eng.ohio-state.edu
cc:    (bcc: Joe Dzura/SED/CSC)
Subject:  Re: VSS importance





-----Original Message-----
From: Mike Hoenes <MHoenes at dhr.state.nc.us>
To: Jake Sternberg <chickens at ccwf.cc.utexas.edu>;
diy_efi at esl.eng.ohio-state.edu <diy_efi at esl.eng.ohio-state.edu>
Date: Monday, September 28, 1998 1:00 PM
Subject: RE: VSS importance

>anyone figure out how to get a 730  with a 91 L98 eprom to accept input
from
>a 2000ppm vss?

Been figuring but not done yet.
I'm assuming you want a 4000ppm, and only have a 2000ppm.
What I think will work is use two 555 as monostables.  Trigger
one off the - edge of the input signal, and one off of the + edge,
then combine the two signals with a 4011 or some such, tie
that to a Mosfet, and a resistor off of that and use the resistor's
input as the VSS signal.
______            ______            ______            ______
             I_____I             I_____I             I_____I
______   ___    ____    _____    ____   ____    ____
             I_I      I_I          I_I           I_I         I_I         I_I
Hard to type with Doc laughing at my wave patterns
Maybe some EE has input?.
Cheers
Bruce