In SX Microcontrollers, SX/B Compiler and SX-Key Tool, Beau Schwabe wrote:

[url=http://forums.parallax.com/forums/profile.aspx?f=7&m=304658&p=653]william chan[/url],
 


<SPAN style="FONT-SIZE: 10pt; COLOR: black; FONT-FAMILY: Verdana">"Wouldn't negative spikes like be eaten up by C5 470uf? Is it possible for a spike to be much faster than the response of the capacitor? ( i doubt it )"<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" /><o:p></o:p>

<SPAN style="FONT-SIZE: 10pt; COLOR: black; FONT-FAMILY: Verdana">This design was derived from an ESD protection device common in IC's where the capacitor is usually small.  Your same analogy with reference to C5 can also be applied to a positive pulse, but in either case what if the capacitor is discharged?<o:p></o:p>

<SPAN style="FONT-SIZE: 10pt; COLOR: black; FONT-FAMILY: Verdana"> <o:p></o:p>

<SPAN style="FONT-SIZE: 10pt; COLOR: black; FONT-FAMILY: Verdana">"The snubber circuit of Q3 and Q5 does not stay "on" because the 12v line is actually only 10v due to use of the 10v zener." --- The D1 zener isn't necessary.<o:p></o:p>

<o:p>[3] [/3]</o:p>

<o:p>[3] [/3]</o:p>

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