MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Newsgroups: comp.arch.fpga X-MimeOLE: Produced By Microsoft Exchange V6.0.6375.0 NNTP-Posting-Host: exchnews1.main.ntu.edu.sg 127.0.0.1 content-class: urn:content-classes:message Subject: Active Probe Date: Thu, 24 Jul 2003 11:31:07 +0800 Message-ID: X-MS-Has-Attach: X-MS-TNEF-Correlator: Thread-Topic: Active Probe Thread-Index: AcNRlASWBD2Plg+fTMaaEk3Dp9+fJg== Lines: 14 From: "Basuki Endah Priyanto" Path: chonsp.franklin.ch!pfaff.ethz.ch!news-zh.switch.ch!switch.ch!news.mailgate.org!newsfeed.icl.net!newsfeed.fjserv.net!proxad.net!usenet-fr.net!mephistopheles.news.clara.net!news.clara.net!peony.singnet.com.sg!news.ntu.edu.sg!exchnews1.main.ntu.edu.sg Xref: chonsp.franklin.ch comp.arch.fpga:31125 Dear all, Have you ever measured the signal level of your FPGA pin out using Oscilloscope ? At the clock speed of 50 MHz, I observed the signal is destroyed. The oscilloscope sales guy pretends that I need to use active probe which is quite expensive. He said it was a circuit loading issues. Is there any such away to overcome this problem without buying the active probe ? Thanks. Best regards, Basuki ###### From: Peter Wallace Newsgroups: comp.arch.fpga Subject: Re: Active Probe Date: Wed, 23 Jul 2003 21:41:12 -0700 Organization: Posted via Supernews, http://www.supernews.com Message-ID: References: User-Agent: Pan/0.11.4 (Unix) Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 8bit X-Comment-To: "Basuki Endah Priyanto" X-Complaints-To: abuse@supernews.com Lines: 35 Path: chonsp.franklin.ch!pfaff.ethz.ch!news-zh.switch.ch!switch.ch!news.imp.ch!news.imp.ch!newsfeed.vmunix.org!peer02.cox.net!cox.net!pd2nf1so.cg.shawcable.net!residential.shaw.ca!sn-xit-03!sn-xit-01!sn-post-01!supernews.com!corp.supernews.com!not-for-mail Xref: chonsp.franklin.ch comp.arch.fpga:31117 On Wed, 23 Jul 2003 21:31:07 -0700, Basuki Endah Priyanto wrote: > Dear all, > > Have you ever measured the signal level of your FPGA pin out using > Oscilloscope ? > > At the clock speed of 50 MHz, I observed the signal is destroyed. The > oscilloscope sales guy pretends that I need to use active probe which is > quite expensive. > > He said it was a circuit loading issues. > > Is there any such away to overcome this problem without buying the > active probe ? High impedance divider probes tend to have high input capacitance (10 pF or greater) and lousy transient response. Easiest thing is to build your own passive divider probe: Put a 453 (for 10/1) Ohm non inductive (non spiraled) resistor on the end of a 50 Ohm coax going into the 50 Ohm input of your Scope (Or a high impedance scope input with 50 Ohm terminator) This will give you a 500 Ohm input resistance 10/1 divider probe with < 1 PF of input capacitance and frequency response > 1 GHz. Keep input lead (signal end of resistor) and ground lead _very_ short... PCW > > Thanks. > > Best regards, > > Basuki ###### From: Bassman59a@yahoo.com (Andy Peters) Newsgroups: comp.arch.fpga Subject: Re: Active Probe Date: 24 Jul 2003 13:31:02 -0700 Organization: http://groups.google.com/ Lines: 33 Message-ID: <9a2c3a75.0307241231.37b972f@posting.google.com> References: NNTP-Posting-Host: 24.221.131.16 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8bit X-Trace: posting.google.com 1059078666 7933 127.0.0.1 (24 Jul 2003 20:31:06 GMT) X-Complaints-To: groups-abuse@google.com NNTP-Posting-Date: 24 Jul 2003 20:31:06 GMT Path: chonsp.franklin.ch!pfaff.ethz.ch!news-zh.switch.ch!switch.ch!news.mailgate.org!cyclone.bc.net!newsfeed.stanford.edu!postnews1.google.com!not-for-mail Xref: chonsp.franklin.ch comp.arch.fpga:31168 "Basuki Endah Priyanto" wrote in message news:... > Dear all, > > Have you ever measured the signal level of your FPGA pin out using > Oscilloscope ? Yes -- it's the second thing I do when I'm bringing up a new board for the first time. The first thing, of course, is to put a voltmeter on each of the power supplies. > At the clock speed of 50 MHz, I observed the signal is destroyed. The > oscilloscope sales guy pretends that I need to use active probe which is > quite expensive. > > He said it was a circuit loading issues. > > Is there any such away to overcome this problem without buying the > active probe ? OK, what's your 'scope's bandwidth? What's your probe's bandwidth? You can't look at a 50 MHz clock signal on a 100 MHz 'scope or with a 100 MHZ probe and expect to see anything other than a cruddy sine wave. Also, what's your probe's ground connection like? Is it a six-inch piece of wire? Or are you making a very short connection to a nearby ground? Passive 10x probes are perfectly fine for what you're doing, as long as they have sufficient bandwidth. Sounds like the sales guy needs to make another payment on the Porsche. -a ###### From: Peter Alfke Newsgroups: comp.arch.fpga Subject: Re: Active Probe Date: Thu, 24 Jul 2003 16:04:20 -0700 Organization: Xilinx,Inc Lines: 46 Message-ID: <3F2065F5.581459C2@xilinx.com> References: <9a2c3a75.0307241231.37b972f@posting.google.com> NNTP-Posting-Host: peter.xilinx.com Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Mailer: Mozilla 4.77C-CCK-MCD {C-UDP; EBM-APPLE} (Macintosh; U; PPC) X-Accept-Language: en To: Andy Peters Path: chonsp.franklin.ch!pfaff.ethz.ch!news-zh.switch.ch!switch.ch!news.mailgate.org!enews.sgi.com!nntp.wetware.com!attdv1!ip.att.net!newsgate.xilinx.com!cliff.xsj.xilinx.com!not-for-mail Xref: chonsp.franklin.ch comp.arch.fpga:31136 Howard Johnson once gave me a nice tip: Use a 50 Ohm cable driving a 50 Ohm-terminated input to the oscilloscope. Then solder a 470 Ohm resistor to the cable front end, and you have a 10:1 passive probe with GHz bandwidth. Doesn't make the scope any faster, but avoids the loss of bandwidth in the probe. You pay for it by throwing away a factor 10 in sensitivity, and you load the circuit under test with 520 Ohm, but both these restrictions are acceptable, most of the time... Peter Alfke =================== Andy Peters wrote: > > "Basuki Endah Priyanto" wrote in message news:... > > Dear all, > > > > Have you ever measured the signal level of your FPGA pin out using > > Oscilloscope ? > > Yes -- it's the second thing I do when I'm bringing up a new board for > the first time. The first thing, of course, is to put a voltmeter on > each of the power supplies. > > > At the clock speed of 50 MHz, I observed the signal is destroyed. The > > oscilloscope sales guy pretends that I need to use active probe which is > > quite expensive. > > > > He said it was a circuit loading issues. > > > > Is there any such away to overcome this problem without buying the > > active probe ? > > OK, what's your 'scope's bandwidth? What's your probe's bandwidth? > You can't look at a 50 MHz clock signal on a 100 MHz 'scope or with a > 100 MHZ probe and expect to see anything other than a cruddy sine > wave. > > Also, what's your probe's ground connection like? Is it a six-inch > piece of wire? Or are you making a very short connection to a nearby > ground? > > Passive 10x probes are perfectly fine for what you're doing, as long > as they have sufficient bandwidth. Sounds like the sales guy needs to > make another payment on the Porsche. > > -a ###### From: "Peter C. Wallace" Newsgroups: comp.arch.fpga Subject: Re: Active Probe Date: Thu, 24 Jul 2003 16:29:19 -0700 Organization: Posted via Supernews, http://www.supernews.com Message-ID: References: <9a2c3a75.0307241231.37b972f@posting.google.com> <3F2065F5.581459C2@xilinx.com> User-Agent: Pan/0.11.4 (Unix) Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 8bit X-Comment-To: "Peter Alfke" X-Complaints-To: abuse@supernews.com Lines: 18 Path: chonsp.franklin.ch!pfaff.ethz.ch!news-zh.switch.ch!switch.ch!news.mailgate.org!news-spur1.maxwell.syr.edu!news.maxwell.syr.edu!sn-xit-03!sn-xit-06!sn-post-01!supernews.com!corp.supernews.com!not-for-mail Xref: chonsp.franklin.ch comp.arch.fpga:31190 On Thu, 24 Jul 2003 16:04:20 -0700, Peter Alfke wrote: > Howard Johnson once gave me a nice tip: Use a 50 Ohm cable driving a 50 > Ohm-terminated input to the oscilloscope. Then solder a 470 Ohm resistor > to the cable front end, and you have a 10:1 passive probe with GHz > bandwidth. Doesn't make the scope any faster, but avoids the loss of > bandwidth in the probe. You pay for it by throwing away a factor 10 in > sensitivity, and you load the circuit under test with 520 Ohm, but both > these restrictions are acceptable, most of the time... > > Peter Alfke > =================== Plus 520 Ohms resistive load is a lot better for pulse fidelity than the 159 Ohms capacitive reactance of a 10 PF scope probe at just 100 MHz... PCW ###### From: symon_brewer@hotmail.com (Symon) Newsgroups: comp.arch.fpga Subject: Re: Active Probe Date: 25 Jul 2003 11:43:40 -0700 Organization: http://groups.google.com/ Lines: 27 Message-ID: References: <9a2c3a75.0307241231.37b972f@posting.google.com> <3F2065F5.581459C2@xilinx.com> NNTP-Posting-Host: 67.121.165.32 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8bit X-Trace: posting.google.com 1059158620 24029 127.0.0.1 (25 Jul 2003 18:43:40 GMT) X-Complaints-To: groups-abuse@google.com NNTP-Posting-Date: 25 Jul 2003 18:43:40 GMT Path: chonsp.franklin.ch!pfaff.ethz.ch!news-zh.switch.ch!switch.ch!news.imp.ch!news.imp.ch!news-spur1.maxwell.syr.edu!news.maxwell.syr.edu!newsfeed.stanford.edu!postnews1.google.com!not-for-mail Xref: chonsp.franklin.ch comp.arch.fpga:31175 Here's a nice link:- http://www.emcesd.com/1ghzprob.htm Nice piccies! Also :- http://www.sigcon.com/ HTH, Syms "Peter C. Wallace" wrote in message news:... > On Thu, 24 Jul 2003 16:04:20 -0700, Peter Alfke wrote: > > > Howard Johnson once gave me a nice tip: Use a 50 Ohm cable driving a 50 > > Ohm-terminated input to the oscilloscope. Then solder a 470 Ohm resistor > > to the cable front end, and you have a 10:1 passive probe with GHz > > bandwidth. Doesn't make the scope any faster, but avoids the loss of > > bandwidth in the probe. You pay for it by throwing away a factor 10 in > > sensitivity, and you load the circuit under test with 520 Ohm, but both > > these restrictions are acceptable, most of the time... > > > > Peter Alfke > > =================== > > > Plus 520 Ohms resistive load is a lot better for pulse fidelity than the 159 > Ohms capacitive reactance of a 10 PF scope probe at just 100 MHz... > > PCW