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FW: vrf 5V 3.3V Level shifting ..

Question asked by VRFuser on Aug 8, 2005
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"><HTML><HEAD><META http-equiv=Content-Type content="text/html; charset=us-ascii"><META content="MSHTML 6.00.2900.2180" name=GENERATOR></HEAD><BODY><DIV dir=ltr align=left><FONT face=Arial color=#0000ff size=2><SPAN class=749534716-09082005>Hi;</SPAN></FONT></DIV><DIV dir=ltr align=left><FONT face=Arial color=#0000ff size=2><SPAN class=749534716-09082005></SPAN></FONT> </DIV><DIV dir=ltr align=left><FONT face=Arial color=#0000ff size=2><SPAN class=749534716-09082005>You might want to try simply putting a 3.3 v zener diode on each 5 v output (48 times). This should clamp the output high level to the required 3.3v.</SPAN></FONT></DIV><DIV dir=ltr align=left><FONT face=Arial color=#0000ff size=2><SPAN class=749534716-09082005></SPAN></FONT> </DIV><DIV dir=ltr align=left><FONT face=Arial color=#0000ff size=2><SPAN class=749534716-09082005>Mark Carangi</SPAN></FONT></DIV><DIV dir=ltr align=left><FONT face=Arial color=#0000ff size=2><SPAN class=749534716-09082005>Gulton, Inc</SPAN></FONT></DIV><DIV dir=ltr align=left><FONT face=Arial color=#0000ff size=2><SPAN class=749534716-09082005>Metuchen, NJ USA</SPAN></FONT></DIV><BR><DIV class=OutlookMessageHeader lang=en-us dir=ltr align=left><HR tabIndex=-1><FONT face=Tahoma size=2><B>From:</B> Kathy Wright [mailto:kathy_wright_ca@yahoo.com] <BR><B>Sent:</B> Tuesday, August 09, 2005 3:26 AM<BR><B>To:</B> VRF<BR><B>Subject:</B> Re: [vrf] 5V > 3.3V Level shifting ..<BR></FONT><BR></DIV><DIV></DIV><DIV>Hi,</DIV><DIV> </DIV><DIV>First I'd make sure the requirment is real.  Quite  a bit of the 3.3 v logic is actually 5 V logic tolerant.  If it's not, then I'd look at what the output stage of your 48 channels looks like .. if it's hardwired to the logic supply, you're stuck.  Some chips have a seperate logic supply voltage input, but not usually.  Otherwise, you'll need a buffer stage to do the level shifting - a simple open collector buffer with pullup resistor would do (48 times).  Don't know of a canned solution for this, though.  Of course, this is all talking about your DIO driving a 3.3 V DUT input.  The other way around, you might be OK since 3.0-3.3V would drive TTL or CMOS logic OK.</DIV><DIV> </DIV><DIV>Kathy Wright</DIV><DIV>Endwave<BR><BR><B><I>Alex.Barrett@raytheon.co.uk</I></B> wrote:</DIV><BLOCKQUOTE class=replbq style="PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #1010ff 2px solid">Hi   vrf, - not strictly a VEE question I know, but desperately need   some<BR>help!<BR><BR>The Test System I'm currently getting to work (note term   of phrase that<BR>we've already built it!) needs to convert 48 channels of 5V   logic to 3.3V<BR>logic (ok, so I bought a 5V card and programmed it all up).   Has any of you<BR>guys (or gals) had to do this? - and what would you use?? -   I'm looking for<BR>if anyone has a test equipnment 'buy off the shelf quickly'   solution,<BR>rather than using individual devices.<BR><BR>Please help if you   can, and apologies for this slight mis-use of the   vrf...<BR><BR>Alex.<BR><BR>(Embedded image moved to <BR>file: pic29213.gif)   <BR><BR>(Embedded Alex Barrett <BR>image moved Test Development Engineer   <BR>to file: Raytheon Systems Limited <BR>pic07627.gif) The Pinnacles   <BR>Harlow <BR>Essex CM19 5BB <BR>United Kingdom <BR>( +44 (0) 1279 407768   <BR>( +44 ( 0) 1279 407620 fax <BR>* <BR>Alex.Barrett@raytheon.co.uk   <BR><BR><BR><BR><BR><BR><BR>---<BR>You are currently subscribed to vrf as:   kathy_wright_ca@yahoo.com<BR>To subscribe send a blank email to   "join-vrf@it.lists.it.agilent.com".<BR>To unsubscribe send a blank email to   "leave-vrf@it.lists.it.agilent.com".<BR>To send messages to this mailing list,   email "vrf@agilent.com". <BR>If you need help with the mailing list send a   message to "owner-vrf@it.lists.it.agilent.com".</BLOCKQUOTE>--- You are currently subscribed to vrf as: mcarangi@gulton.com To subscribe send a blank email to "join-vrf@it.lists.it.agilent.com". To unsubscribe send a blank email to "leave-vrf@it.lists.it.agilent.com". To send messages to this mailing list, email "vrf@agilent.com". If you need help with the mailing list send a message to "owner-vrf@it.lists.it.agilent.com".<BR>---<BR>You are currently subscribed to vrf as: rsb@soco.agilent.com<BR>To subscribe send a blank email to "join-vrf@it.lists.it.agilent.com".<BR>To unsubscribe send a blank email to "leave-vrf@it.lists.it.agilent.com".<BR>To send messages to this mailing list,  email "vrf@agilent.com".  <BR>If you need help with the mailing list send a message to "owner-vrf@it.lists.it.agilent.com".</BODY></HTML>  

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