Re: [PEDA] off topic supply SOS
I traced a nasty set of spikes on the 1.8v supply with my storage scope. The largest is 0.11v. This drops the 1.8v just outside the minimum spec for the EP20K200E I'm using. I'm going re-hook up everything get an FFT plot later this afternoon. Brian Guralnick [EMAIL PROTECTED] Voice (514) 624-4003 Fax (514) 624-3631 - Original Message - From: Terry Harris [EMAIL PROTECTED] To: Protel EDA Forum [EMAIL PROTECTED] Sent: Sunday, September 08, 2002 11:39 PM Subject: Re: [PEDA] off topic supply SOS On Sun, 08 Sep 2002 21:45:51 -0400, Brian Guralnick wrote: Having not placed enough power supply decoupling caps on a beta PCB, I'm looking for a temporary overpriced decoupling solution until the next beta boards are printed. I'm looking for the lowest ESR possible caps. I found this company WIMA. http://www.wima.de/smd2220.htm 1.0uf, 0.1uf, 0.01uf. - 0.07 Ohm thru ~0.15 Well who knows what your exact requirement is but putting better capacitors in not enough places probably isn't a fix. Also those capacitors tan delta is specified at 1, 10, 100 kHz - not intended for high frequency decoupling, the SMT 100n looks like it is self resonant around 6 or 7 MHz. Actually it looks like you read that graph to get the ESR figures you quoted but as I read it the line on the graph shows impedance at resonance not ESR. Is it high speed logic? Do you *know* you have a problem? Boards tend to be way over decoupled anyway especially if you have decently coupled power planes. I would wait till you know you have a problem and strap some extra capacitors across chip leads if you really need to. Cheers, Terry. * Tracking #: 4DFFA14C1C300E4AA51F7DAF4685AD9A6EC611BC * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * To post a message: mailto:[EMAIL PROTECTED] * * To leave this list visit: * http://www.techservinc.com/protelusers/leave.html * * Contact the list manager: * mailto:[EMAIL PROTECTED] * * Forum Guidelines Rules: * http://www.techservinc.com/protelusers/forumrules.html * * Browse or Search previous postings: * http://www.mail-archive.com/proteledaforum@techservinc.com * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
Re: [PEDA] off topic supply SOS
Brian, Measuring spikes on the supply lines is not trivial. Where you put the scope probe ground is everything. The best way to measure is with a differential probe, placed across the power pins of the chip in question. Anything less may not give you the true picture. Don't misunderstand, this is not a criticism, but a heads up. Be alert when making this kind of measurement. Richard Cheesecote Mountain CAMAC, 24 Halley Drive; Pomona, NY 10970 voice: 845 364 0211, fax: 845 362 6947, www.cmcamac.com * Tracking #: FD6D883A80FDAD4CBE28A8F34C309861BFE3E3E7 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * To post a message: mailto:[EMAIL PROTECTED] * * To leave this list visit: * http://www.techservinc.com/protelusers/leave.html * * Contact the list manager: * mailto:[EMAIL PROTECTED] * * Forum Guidelines Rules: * http://www.techservinc.com/protelusers/forumrules.html * * Browse or Search previous postings: * http://www.mail-archive.com/proteledaforum@techservinc.com * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
Re: [PEDA] off topic supply SOS
Don't worry about the way I measure the spikes. I do use J-Fet buffered 1.5GHz probes with the miniature GND spike pin which is right next to the probe signal pin. On my PCB, I placed GND supply test points around the PLD just for such an emergency. I do know that when measuring any signals here, even stuff in the 10 MHz range, the conventional 10x probes suck royally. Scope snapshot coming in 2 hours... Brian Guralnick [EMAIL PROTECTED] Voice (514) 624-4003 Fax (514) 624-3631 - Original Message - From: Richard Sumner [EMAIL PROTECTED] To: 'Protel EDA Forum' [EMAIL PROTECTED] Sent: Monday, September 09, 2002 2:24 PM Subject: Re: [PEDA] off topic supply SOS Brian, Measuring spikes on the supply lines is not trivial. Where you put the scope probe ground is everything. The best way to measure is with a differential probe, placed across the power pins of the chip in question. Anything less may not give you the true picture. Don't misunderstand, this is not a criticism, but a heads up. Be alert when making this kind of measurement. Richard Cheesecote Mountain CAMAC, 24 Halley Drive; Pomona, NY 10970 voice: 845 364 0211, fax: 845 362 6947, www.cmcamac.com * Tracking #: FD6D883A80FDAD4CBE28A8F34C309861BFE3E3E7 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * To post a message: mailto:[EMAIL PROTECTED] * * To leave this list visit: * http://www.techservinc.com/protelusers/leave.html * * Contact the list manager: * mailto:[EMAIL PROTECTED] * * Forum Guidelines Rules: * http://www.techservinc.com/protelusers/forumrules.html * * Browse or Search previous postings: * http://www.mail-archive.com/proteledaforum@techservinc.com * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
Re: [PEDA] off topic supply SOS
On Mon, 09 Sep 2002 17:32:58 -0400, Brian Guralnick wrote: Don't worry about the way I measure the spikes. I do use J-Fet buffered 1.5GHz probes with the miniature GND spike pin which is right next to the probe signal pin. On my PCB, I placed GND supply test points around the PLD just for such an emergency. Well you better solder some caps across them immediately :). Cheers, Terry. * Tracking #: F4DBDE3B3E636245B7682083D73C5401D62C18B0 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * To post a message: mailto:[EMAIL PROTECTED] * * To leave this list visit: * http://www.techservinc.com/protelusers/leave.html * * Contact the list manager: * mailto:[EMAIL PROTECTED] * * Forum Guidelines Rules: * http://www.techservinc.com/protelusers/forumrules.html * * Browse or Search previous postings: * http://www.mail-archive.com/proteledaforum@techservinc.com * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
Re: [PEDA] off topic supply SOS
On 02:24 PM 9/09/2002 -0400, Richard Sumner said: Brian, Measuring spikes on the supply lines is not trivial. Where you put the scope probe ground is everything. The best way to measure is with a differential probe, placed across the power pins of the chip in question. Anything less may not give you the true picture. Off topic but maybe of some interest...and I am sure many of you have similar techniques. A trick I learnt way back in 1986 when designing my first switchmode supply - make your own *low* impedance probe. A low impedance probe is less susceptible to high speed transients nearby that cause false readings. A series cap (with suitable resonance characteristics - possibly made with multiple caps) and a shunt low impedance resistor. The CRO probe connects across the resistor using the spring gnd clip that should be available with any high speed cro probe. If a short spring gnd is not available make one using a paper clip bent and cut to make as short a gnd spring as possible. Be careful if using the CRO probe as a former when you bend the paper clip - it can break them. Choose a slightly larger drill bit and then crush the small spring you have made to make a tight fit onto the CRO GND sleeve. You now have a spring to slip over the CRO GND sleeve (remove the scope condom to expose the GND sleeve). Bend and cut the other end of the paper clip to make a nice stiff probe point. If you cut at an angle it will be a sharp point. To choose the resistor you may want to try a range of values - there will be a flat spot where the low impedance probe is not so low as to load the cct but not so high as to give a false reading due to pickup. For power supply work I sometimes go as low as 47 ohm (impedances are low so the low R is not adding any loading). For decoupling tracing this may be a little low but 1k or 4k7 may be OK. This is a useful trick, especially when you don't really trust the diff mode of your CRO or when your high speed active probes have died. You have to think about the results as the low probe impedance can affect the results of course. Sorry for those that the above is old news but it may be useful for some. Ian * Tracking #: 53D7B142AFF8B646AB9B2FCDF73D75C2DE43004C * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * To post a message: mailto:[EMAIL PROTECTED] * * To leave this list visit: * http://www.techservinc.com/protelusers/leave.html * * Contact the list manager: * mailto:[EMAIL PROTECTED] * * Forum Guidelines Rules: * http://www.techservinc.com/protelusers/forumrules.html * * Browse or Search previous postings: * http://www.mail-archive.com/proteledaforum@techservinc.com * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
Re: [PEDA] off topic supply SOS
Sounds like inductance and ground bounce. Use small (0603 or 0402) caps close, and try bypassing ground to VCC using a multiple via connections to the ground plane. Ive seen Tpd measurements improve about 15% just adding 'ground bypasses' close to the chip leg grounds. Brian Guralnick [EMAIL PROTECTED] on 10/09/2002 12:33:14 AM Please respond to Protel EDA Forum [EMAIL PROTECTED] To: Protel EDA Forum [EMAIL PROTECTED] cc:(bcc: Clive Broome/sdc) Subject: Re: [PEDA] off topic supply SOS I traced a nasty set of spikes on the 1.8v supply with my storage scope. The largest is 0.11v. This drops the 1.8v just outside the minimum spec for the EP20K200E I'm using. I'm going re-hook up everything get an FFT plot later this afternoon. Brian Guralnick [EMAIL PROTECTED] Voice (514) 624-4003 Fax (514) 624-3631 - Original Message - From: Terry Harris [EMAIL PROTECTED] To: Protel EDA Forum [EMAIL PROTECTED] Sent: Sunday, September 08, 2002 11:39 PM Subject: Re: [PEDA] off topic supply SOS On Sun, 08 Sep 2002 21:45:51 -0400, Brian Guralnick wrote: Having not placed enough power supply decoupling caps on a beta PCB, I'm looking for a temporary overpriced decoupling solution until the next beta boards are printed. I'm looking for the lowest ESR possible caps. I found this company WIMA. http://www.wima.de/smd2220.htm 1.0uf, 0.1uf, 0.01uf. - 0.07 Ohm thru ~0.15 Well who knows what your exact requirement is but putting better capacitors in not enough places probably isn't a fix. Also those capacitors tan delta is specified at 1, 10, 100 kHz - not intended for high frequency decoupling, the SMT 100n looks like it is self resonant around 6 or 7 MHz. Actually it looks like you read that graph to get the ESR figures you quoted but as I read it the line on the graph shows impedance at resonance not ESR. Is it high speed logic? Do you *know* you have a problem? Boards tend to be way over decoupled anyway especially if you have decently coupled power planes. I would wait till you know you have a problem and strap some extra capacitors across chip leads if you really need to. Cheers, Terry. * Tracking #: 4DFFA14C1C300E4AA51F7DAF4685AD9A6EC611BC * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * To post a message: mailto:[EMAIL PROTECTED] * * To leave this list visit: * http://www.techservinc.com/protelusers/leave.html * * Contact the list manager: * mailto:[EMAIL PROTECTED] * * Forum Guidelines Rules: * http://www.techservinc.com/protelusers/forumrules.html * * Browse or Search previous postings: * http://www.mail-archive.com/proteledaforum@techservinc.com * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
Re: [PEDA] off topic supply SOS
I've had really good results with Tektronix P6245 / TDS500/600 active powered JFET probe. 1pf, 1MOhm, 1.5GHz, 40v p-p max. Got 4 probes which are a perfect match with my TDS3054 scope. Brian Guralnick [EMAIL PROTECTED] Voice (514) 624-4003 Fax (514) 624-3631 - Original Message - From: Ian Wilson [EMAIL PROTECTED] To: Protel EDA Forum [EMAIL PROTECTED] Sent: Monday, September 09, 2002 9:16 PM Subject: Re: [PEDA] off topic supply SOS On 02:24 PM 9/09/2002 -0400, Richard Sumner said: Brian, Measuring spikes on the supply lines is not trivial. Where you put the scope probe ground is everything. The best way to measure is with a differential probe, placed across the power pins of the chip in question. Anything less may not give you the true picture. Off topic but maybe of some interest...and I am sure many of you have similar techniques. A trick I learnt way back in 1986 when designing my first switchmode supply - make your own *low* impedance probe. A low impedance probe is less susceptible to high speed transients nearby that cause false readings. A series cap (with suitable resonance characteristics - possibly made with multiple caps) and a shunt low impedance resistor. The CRO probe connects across the resistor using the spring gnd clip that should be available with any high speed cro probe. If a short spring gnd is not available make one using a paper clip bent and cut to make as short a gnd spring as possible. Be careful if using the CRO probe as a former when you bend the paper clip - it can break them. Choose a slightly larger drill bit and then crush the small spring you have made to make a tight fit onto the CRO GND sleeve. You now have a spring to slip over the CRO GND sleeve (remove the scope condom to expose the GND sleeve). Bend and cut the other end of the paper clip to make a nice stiff probe point. If you cut at an angle it will be a sharp point. To choose the resistor you may want to try a range of values - there will be a flat spot where the low impedance probe is not so low as to load the cct but not so high as to give a false reading due to pickup. For power supply work I sometimes go as low as 47 ohm (impedances are low so the low R is not adding any loading). For decoupling tracing this may be a little low but 1k or 4k7 may be OK. This is a useful trick, especially when you don't really trust the diff mode of your CRO or when your high speed active probes have died. You have to think about the results as the low probe impedance can affect the results of course. Sorry for those that the above is old news but it may be useful for some. Ian * Tracking #: 53D7B142AFF8B646AB9B2FCDF73D75C2DE43004C * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * To post a message: mailto:[EMAIL PROTECTED] * * To leave this list visit: * http://www.techservinc.com/protelusers/leave.html * * Contact the list manager: * mailto:[EMAIL PROTECTED] * * Forum Guidelines Rules: * http://www.techservinc.com/protelusers/forumrules.html * * Browse or Search previous postings: * http://www.mail-archive.com/proteledaforum@techservinc.com * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
[PEDA] off topic supply SOS
Having not placed enough power supply decoupling caps on a beta PCB, I'm looking for a temporary overpriced decoupling solution until the next beta boards are printed. I'm looking for the lowest ESR possible caps. I found this company WIMA. http://www.wima.de/smd2220.htm 1.0uf, 0.1uf, 0.01uf. - 0.07 Ohm thru ~0.15 http://www.wima.de/mks2.htm 10uf. - 0.007 Ohm Before I buy, has anyone seen even lower ESRs? Where? Brian Guralnick [EMAIL PROTECTED] Voice (514) 624-4003 Fax (514) 624-3631 * Tracking #: C6B1582544A9A54E86F065BC0ECCD4523A783153 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * To post a message: mailto:[EMAIL PROTECTED] * * To leave this list visit: * http://www.techservinc.com/protelusers/leave.html * * Contact the list manager: * mailto:[EMAIL PROTECTED] * * Forum Guidelines Rules: * http://www.techservinc.com/protelusers/forumrules.html * * Browse or Search previous postings: * http://www.mail-archive.com/proteledaforum@techservinc.com * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
Re: [PEDA] off topic supply SOS
Brian, What are you looking for? Tantalems? Ceramics? What is the frequency you are having problems with? Can you piggy back different values such as a 0.1uF and 100pF ceramic? JaMi - Original Message - From: Brian Guralnick [EMAIL PROTECTED] To: Protel EDA Forum [EMAIL PROTECTED] Sent: Sunday, September 08, 2002 6:45 PM Subject: [PEDA] off topic supply SOS Having not placed enough power supply decoupling caps on a beta PCB, I'm looking for a temporary overpriced decoupling solution until the next beta boards are printed. I'm looking for the lowest ESR possible caps. I found this company WIMA. http://www.wima.de/smd2220.htm 1.0uf, 0.1uf, 0.01uf. - 0.07 Ohm thru ~0.15 http://www.wima.de/mks2.htm 10uf. - 0.007 Ohm Before I buy, has anyone seen even lower ESRs? Where? Brian Guralnick [EMAIL PROTECTED] Voice (514) 624-4003 Fax (514) 624-3631 * Tracking #: C00C1E9A5BECCA42BABBDAA58FD36811E1462A4B * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * To post a message: mailto:[EMAIL PROTECTED] * * To leave this list visit: * http://www.techservinc.com/protelusers/leave.html * * Contact the list manager: * mailto:[EMAIL PROTECTED] * * Forum Guidelines Rules: * http://www.techservinc.com/protelusers/forumrules.html * * Browse or Search previous postings: * http://www.mail-archive.com/proteledaforum@techservinc.com * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
Re: [PEDA] off topic supply SOS
Brian, Panasonic also makes an extremely low ESR Cap(radial), I used them in a switching PWR, supply. Usually off shore only availability I was able to get them years ago with a 20 Wk Lead. Pink Body, very distinctive. Joe - Original Message - From: JaMi Smith [EMAIL PROTECTED] To: Protel EDA Forum [EMAIL PROTECTED] Cc: JaMi Smith [EMAIL PROTECTED] Sent: Sunday, September 08, 2002 10:10 PM Subject: Re: [PEDA] off topic supply SOS Brian, What are you looking for? Tantalems? Ceramics? What is the frequency you are having problems with? Can you piggy back different values such as a 0.1uF and 100pF ceramic? JaMi - Original Message - From: Brian Guralnick [EMAIL PROTECTED] To: Protel EDA Forum [EMAIL PROTECTED] Sent: Sunday, September 08, 2002 6:45 PM Subject: [PEDA] off topic supply SOS Having not placed enough power supply decoupling caps on a beta PCB, I'm looking for a temporary overpriced decoupling solution until the next beta boards are printed. I'm looking for the lowest ESR possible caps. I found this company WIMA. http://www.wima.de/smd2220.htm 1.0uf, 0.1uf, 0.01uf. - 0.07 Ohm thru ~0.15 http://www.wima.de/mks2.htm 10uf. - 0.007 Ohm Before I buy, has anyone seen even lower ESRs? Where? Brian Guralnick [EMAIL PROTECTED] Voice (514) 624-4003 Fax (514) 624-3631 * Tracking #: C00C1E9A5BECCA42BABBDAA58FD36811E1462A4B * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * To post a message: mailto:[EMAIL PROTECTED] * * To leave this list visit: * http://www.techservinc.com/protelusers/leave.html * * Contact the list manager: * mailto:[EMAIL PROTECTED] * * Forum Guidelines Rules: * http://www.techservinc.com/protelusers/forumrules.html * * Browse or Search previous postings: * http://www.mail-archive.com/proteledaforum@techservinc.com * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
Re: [PEDA] off topic supply SOS
it's not exactly off topic, the board and the planes play a big role what makes you say you have not placed enough? Dennis Saputelli Brian Guralnick wrote: Having not placed enough power supply decoupling caps on a beta PCB, I'm looking for a temporary overpriced decoupling solution until the next beta boards are printed. I'm looking for the lowest ESR possible caps. I found this company WIMA. http://www.wima.de/smd2220.htm 1.0uf, 0.1uf, 0.01uf. - 0.07 Ohm thru ~0.15 http://www.wima.de/mks2.htm 10uf. - 0.007 Ohm Before I buy, has anyone seen even lower ESRs? Where? Brian Guralnick [EMAIL PROTECTED] Voice (514) 624-4003 Fax (514) 624-3631 * Tracking #: C6B1582544A9A54E86F065BC0ECCD4523A783153 * -- ___ www.integratedcontrolsinc.comIntegrated Controls, Inc. tel: 415-647-04802851 21st Street fax: 415-647-3003San Francisco, CA 94110 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * To post a message: mailto:[EMAIL PROTECTED] * * To leave this list visit: * http://www.techservinc.com/protelusers/leave.html * * Contact the list manager: * mailto:[EMAIL PROTECTED] * * Forum Guidelines Rules: * http://www.techservinc.com/protelusers/forumrules.html * * Browse or Search previous postings: * http://www.mail-archive.com/proteledaforum@techservinc.com * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *