New Monitor: Spot Killer & microprocessor issues

From: <nelsonjjjj_at_didactics.com>
Date: Tue Nov 09 1999 - 16:14:12 EST

Hi everyone!

I have been looking over the spot killer and safety requirements
carefully with my design. The LM3886 looks like it would address
some of the key reasons we were thinking of a microprocessor,
such as: transistor overdrive.

I was planning to using a charge pump on each axis to activate
a comparator. Upon activation of either output, each z axis
input would be pulled down to ground by it's own mosfet. (Of
course there will be a ~1K resistor between the mosfet and the
game board.)

Outputs active will light an led or two as desired. Spot killer
activation characteristics could be modified with resistor changes
or it could be made to be adjustable, if desired.

Deflection Protection should be handled well by the LM3886 and
total transistor failure would be handled by the in-line 3 amp
fuse.

Please comment on this.

Clay, do you still want a micro on board? If so we need to hash
out what exactly it will do. The amp has a shutdown (mute) mode
that could be activated if we had a good reason to use it. Let's
re-iterate the microprocessor function again. I am a little
concerned about the support it will require in terms of buffering,
power supply, crystal, and cost increment. On the other hand,
it could be made to be a solder-in option or better yet, a daughtercard
like you are famous for could offload all of this functionality
to a second design! The daughtercard sounds viable, if we can
agree on a good cheap and physically stable thus reliable connector
to use for it.

Sincerely,
James

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Received on Tue Nov 9 15:14:16 1999

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