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<DIV><FONT color=#0000ff face=Arial size=2><SPAN
class=281230708-09012002>Depends on what you want. If precision performance is
not crucial, a series resistor of some kOhm</SPAN></FONT></DIV>
<DIV><FONT color=#0000ff face=Arial size=2><SPAN class=281230708-09012002>might
do. I think this is mandatory to prevent latchup.</SPAN></FONT></DIV>
<DIV><FONT color=#0000ff face=Arial size=2><SPAN
class=281230708-09012002></SPAN></FONT> </DIV>
<DIV><FONT color=#0000ff face=Arial size=2><SPAN class=281230708-09012002>If you
want to keep the input offset from wandering due to stress, additional clamping
diodes</SPAN></FONT></DIV>
<DIV><FONT color=#0000ff face=Arial size=2><SPAN class=281230708-09012002>might
be a good idea. Comparators naturally work with high differential input
vol</SPAN></FONT><FONT face=Tahoma><FONT size=2><SPAN
class=281230708-09012002><FONT color=#0000ff face=Arial>tage, some
designs</FONT></SPAN></FONT></FONT></DIV>
<DIV><FONT face=Tahoma><FONT size=2><SPAN class=281230708-09012002><FONT
color=#0000ff face=Arial>seem not to be too happy with this situation
(surprising, if you think that this is the normal
application).</FONT></SPAN></FONT></FONT></DIV>
<DIV><FONT face=Tahoma><FONT color=#0000ff face=Arial size=2><SPAN
class=281230708-09012002><FONT color=#0000ff face=Arial size=2><SPAN
class=281230708-09012002>This would mean diodes to both supplies as well as
between + and - input.</SPAN></FONT></SPAN></FONT></FONT></DIV>
<DIV><FONT color=#0000ff face=Arial size=2><SPAN class=281230708-09012002>Of
course, any additional components introduce parasitics (capacitance, junction
capacitance, leakage).</SPAN></FONT></DIV>
<DIV><FONT color=#0000ff face=Arial size=2><SPAN class=281230708-09012002>It
really depends on the application, on the chip and on the
environment.</SPAN></FONT></DIV>
<DIV> </DIV>
<DIV><FONT color=#0000ff face=Arial size=2><SPAN class=281230708-09012002>NS and
AD have some good application notes, Bob Pease gives some good hints in his
book, as </SPAN></FONT></DIV>
<DIV><FONT color=#0000ff face=Arial size=2><SPAN
class=281230708-09012002>well.</SPAN></FONT></DIV>
<DIV> </DIV>
<DIV><FONT color=#0000ff face=Arial size=2><SPAN
class=281230708-09012002></SPAN></FONT> </DIV>
<DIV><FONT color=#0000ff face=Arial size=2><SPAN class=281230708-09012002>m.c.
(mars lander builder)</SPAN></FONT></DIV>
<DIV><FONT face=Tahoma><FONT size=2><SPAN
class=281230708-09012002></SPAN></FONT></FONT> </DIV>
<DIV><FONT face=Tahoma><FONT size=2><SPAN
class=281230708-09012002> </SPAN>-----Ursprüngliche
Nachricht-----<BR><B>Von:</B> John Speth
[mailto:JohnS@molectron.com]<BR><B>Gesendet:</B> Dienstag, 8. Januar 2002
18:33<BR><B>An:</B> Synth-DIY List (E-mail)<BR><B>Betreff:</B> [sdiy] Module
input isolation?<BR><BR></DIV></FONT>
<BLOCKQUOTE
style="BORDER-LEFT: #0000ff 2px solid; MARGIN-LEFT: 5px; MARGIN-RIGHT: 0px; PADDING-LEFT: 5px"></FONT>
<P><FONT size=2>Hi list!</FONT> </P>
<P><FONT size=2>Is there any kind of isolation needed to protect silicon
devices that serve as inputs to the outside world?</FONT> </P>
<P><FONT size=2>Let's say I have a synth module that uses an LM311
comparator. And the input to this module needs to go directly one of the
LM311 input pins. Does this pin need any protection circuitry? I'm
afraid I'm not familiar with any kind of bad stuff that might happen at that
pin.</FONT></P>
<P><FONT size=2>I'll probably hang a 1M resistor to ground to keep it from
floating when not connected.</FONT> </P>
<P><FONT size=2>Thanks, John Speth</FONT> </P></BLOCKQUOTE></BODY></HTML>