Re: [PEDA] off topic supply SOS

2002-09-09 Thread Brian Guralnick

 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
 *
 

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Re: [PEDA] off topic supply SOS

2002-09-09 Thread Richard Sumner

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
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Re: [PEDA] off topic supply SOS

2002-09-09 Thread Brian Guralnick

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
 *
 

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Re: [PEDA] off topic supply SOS

2002-09-09 Thread Terry Harris

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
*


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Re: [PEDA] off topic supply SOS

2002-09-09 Thread Ian Wilson

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
*


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Re: [PEDA] off topic supply SOS

2002-09-09 Thread Clive . Broome



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
 *
 






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Re: [PEDA] off topic supply SOS

2002-09-09 Thread Brian Guralnick

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
 *
 

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[PEDA] off topic supply SOS

2002-09-08 Thread Brian Guralnick

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
*


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Re: [PEDA] off topic supply SOS

2002-09-08 Thread JaMi Smith

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
*


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Re: [PEDA] off topic supply SOS

2002-09-08 Thread Joe Sapienza

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
 *
 


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Re: [PEDA] off topic supply SOS

2002-09-08 Thread Dennis Saputelli

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
 *
 

-- 
___
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