Way to go John. Appreciate your contribution. Regards Ibrahim Khan -----Original Message----- From: John Barnes [mailto:jrbarnes@xxxxxxxxx]=20 Sent: Wednesday, August 07, 2002 9:09 AM To: ruston_matt@xxxxxxx; si-list@xxxxxxxxxxxxx Subject: [SI-LIST] Re: Antwort: Re: Placement of Decoupling Caps Matt, I haven't tested any X5R capacitors, so I can't comment on them at this time. If you can get me some samples I'd be happy to check them on the HP 4195A Network/Spectrum Analyzer, and report back here. Thanks! John Barnes dBi Corporation 216 Hillsboro Ave Lexington, KY 40511-2105 http://www.dbicorporation.com/ ruston, matt wrote: >=20 > Istvan, John: >=20 > Hi. Any thoughts on using X5R caps instead of X7R. I believe these=20 > caps are becoming more popular, give almost an order of magnitude more > capacitance per body size (in 0402 sizes), and have similar=20 > dissapation factors and aging rates as an X7R cap. >=20 > The X5R cap has a better temperature range (-55C to 85C) and=20 > tolerance than Y5V and Z5U. The cap can be used above 85C with some=20 > degradation in tolerance, but since they pack more capacitance in the=20 > same package and decoupling isn't all that sensitive to a few more=20 > percent of lower capacitance, X5R seem like a win over X7R (assuming=20 > you subscribe to the decoupling methodology described by John below;=20 > higher capacitance is better). I could see running X5R up to at least=20 > 100C with no major problems. >=20 > X5R does have a have a cost penalty. My limited pricing experience=20 > shows X5R may be 50% -100% more costly. Does anyone have any better=20 > information on this? >=20 > Any other thoughts on X5R (good or bad)? >=20 > Regards, >=20 > Matt >=20 > -----Original Message----- > From: Istvan Novak [mailto:istvan.novak@xxxxxxxxxxxxxxxx] > Sent: Wednesday, August 07, 2002 7:25 AM > To: jrbarnes@xxxxxxxxx; si-list@xxxxxxxxxxxxx > Subject: [SI-LIST] Re: Antwort: Re: Placement of Decoupling Caps >=20 > John, >=20 > I agree with all three of your statements/conclusions below. >=20 > Thanks for posting the Appendix of your design guide. A couple of=20 > comments: > - as you mentioned, ESR tends to be a function of several things,=20 > therefore the quoted ESR value of around 100 milliohms for capacitors=20 > with X7R and Z5Y dielectrics is true today only for the smaller-valued > capacitors. In the uF range, some X7R capacitors have less than 10=20 > milliohms ESR. > - I would not limit the useful frequency range of Z5U and Y5U=20 > capacitors just because their dissipation factor increases with=20 > frequency. In fact, the ideal bypass capacitor would have zero=20 > current leakage at DC and arbitrarily high conduction (loss tangent)=20 > at any AC frequencies: this would in fact help > bypassing. But as you say, the huge variation of capacitance over > temperature > and voltage (plus aging) make them an inferior choice anyway. >=20 > Regards >=20 > Istvan Novak > SUN Microsystems >=20 > ----- Original Message ----- > From: "John Barnes" <jrbarnes@xxxxxxxxx> > To: <istvan.novak@xxxxxxxxxxxxxxxx>; <si-list@xxxxxxxxxxxxx> > Sent: Tuesday, August 06, 2002 10:50 AM > Subject: Re: [SI-LIST] Re: Antwort: Re: Placement of Decoupling Caps >=20 > > Istvan, > > I was developing Design Guidelines on Power Distribution for my=20 > > previous employer back in 2000. I found conflicting advice about=20 > > choosing bypass/decoupling capacitors in the engineering literature. > > So I measured a bunch of different types and values of capacitors on > > an HP 4195A Network/Spectrum Analyzer to try to resolve these=20 > > questions for > > myself: > > > > 1. You should go for the smallest package you can. > > > > Answer: Seems to be true. ESL is usually lower in a smaller > > package with the same length:width ratio, but ESR showed no obvious > > pattern of changes. For a given length, a wider package will > > usually have a lower ESL. > > > > 2. You should go for the largest capacitance that you can get in a > > package. > > > > Answer: Seems to be true. ESL showed no obvious relation to > > capacitance, but ESR often dropped as the capacitance increased. > > > > 3. The dielectric does not affect ESR and ESL. > > > > Answer: Seems to be true until you reach/exceed the SRF. The > > impedance of C0G/NP0 capacitors then follows an inductive path, > > while X7R/Z5U/Y5U/Y5V capacitors wallow around near the ESR for a > > while then start rising slowly. This is probably good, because the > > lossy behavior will prevent sharp resonances that could cause > > unwanted peaks in the power-distribution network's impedance. > > > > I personally prefer the X7R dielectric for bypass/decoupling=20 > > capacitors, as high as it will go. The reasonably tight tolerance=20 > > over temperature/ voltage gives me confidence that all production=20 > > units will be reasonably close to the units we characterized and=20 > > qualified during Design Verification Test (DVT). I use some Y5U's=20 > > as "bulk" ceramic capacitors, usually between 1 and 4 per integrated > > circuit, to cover the frequency region between the X7R's and the=20 > > aluminum electrolytic bypass capacitors. > > > > To help people choose an appropriate dielectric for a capacitor,=20 > > here is an appendix from these design guidelines. > > > > John Barnes KS4GL > > dBi Corporation > > http://www.dbicorporation.com/ > > > > > > > > APPENDIX E: CAPACITOR DIELECTRICS > > > > Ceramic capacitors are commonly available in four dielectrics: > > * C0G or NP0 (titanium oxide, neodymium oxide): > > - Dielectric constant K of 85-170 > > - Best stability > > - -55 to 125C operating range > > - 0 to +/-30ppm/C variation over temperature > > - 0 to +/-30ppm/C variation over temperature and 0 to rated voltage > > - Dissipation factor (DF =3D ESR / Xc) under 0.001 at 25C > > - Aging rate 0%/decade > > - Capacitance little affected by frequency > > - Has the lowest ESR, especially above 30MHz. > > - Tends to be most expensive for a given capacitance and voltage > > (CV). > > * X7R and BX (barium titanate): > > - K of 600-4000 > > - Poorer stability than C0G > > - -55 to 125C operating range > > - +/-15% variation over temperature versus capacitance at 25C > > - BX has +15 to -25% variation over temperature and 0 to rated > > voltage > > - X7R may drop 20-45% from 0 to rated voltage > > - DF <=3D 0.025 over temperature, drops as temperature and DC voltage > > increase, increases as AC voltage and frequency increase. > > - Aging rate maximum -2.5% per decade, typically -0.8 to -2% per > > decade time > > - Capacitance may drop 10-18% from DC to 10MHz > > - ESR is about 100 milliohms from 10-30MHz. > > * Z5U (barium titanate): > > - K of 4000-18,000 > > - Poorer stability than X7R > > - 10 to 85C operating range > > - +22 to -56% variation over temperature versus capacitance at 25C > > - May drop 60% from 0 to rated voltage > > - DF <=3D 0.030 over temperature, drops as temperature and DC voltage > > increase, increases as AC voltage and frequency increase, > > increases greatly above 1 to 20MHz, so maximum usable frequency is > > about 50MHz. > > - Aging rate -3% to -5% per decade time > > - Capacitance may drop 20% from DC to 10MHz > > - ESR is about 100 milliohms at 5MHz. > > - Is piezoelectric-- can generate voltage spikes if jolted or > > vibrated. > > * Y5U and Y5V (lead perovskite): > > - Highest K > > - Poorest stability. > > - -30 to 85C operating range > > - Y5U has +22 to -56% variation over temperature versus capacitance > > at 25C > > - Y5V has +22 to -82% variation over temperature versus capacitance > > at 25C > > - May drop 60 to 80% from 0 to rated voltage > > - DF <=3D 0.050 over temperature, drops as temperature and DC voltage > > increase, increases as AC voltage and frequency increase, > > increases greatly above ??MHz, so maximum usable frequency is > > about ??MHz. > > - Aging rate about -5% per decade time > > - Capacitance may double or treble from DC to 2MHz > > - ESR is about 10-60 milliohms > > > > EIA RS-198 designations for temperature-stable Class 1 dielectrics: > > * First (letter) significant digits of temperature coefficient: > > - C =3D 0.0 > > - M =3D 1.0 > > - P =3D 1.5 > > - R =3D 2.2 > > - S =3D 3.3 > > - T =3D 4.7 > > - U =3D 7.5 > > * Second (number), multiplier of temperature coefficient: > > - 0 =3D -1 part per million / degree C (ppm/C) > > - 1 =3D -10 ppm/C > > - 2 =3D -100 ppm/C > > - 3 =3D -1000 ppm/C > > - 4 =3D -10,000 ppm/C > > - 5 =3D +1 ppm/C > > - 6 =3D +10 ppm/C > > - 7 =3D +100 ppm/C > > - 8 =3D +1000 ppm/C > > - 9 =3D +10,000 ppm/C > > * Third (letter), tolerance of temperature coefficient: > > - G =3D +/-30 ppm/C > > - H =3D +/-60 ppm/C > > - J =3D +/-120 ppm/C > > - K =3D +/-250 ppm/C > > - L =3D +/-500 ppm/C > > - M =3D +/-1000 ppm/C > > - N =3D +/-2500 ppm/C > > > > Examples: > > * R2G =3D -220 ppm/C +/-30 ppm/C =3D -250 to -190 ppm/C (N220) > > * S2H =3D -330 ppm/C +/-60 ppm/C =3D -390 to -270 ppm/C (N330) > > * U2H =3D -750 ppm/C +/-60 ppm/C =3D -810 to -690 ppm/C (N750) > > * M7G =3D +100 ppm/C +/-30 ppm/C =3D +70 to +130 ppm/C (P100) > > > > * C0G =3D NP0 =3D MIL-C-20D CG > > * S1G =3D N030 =3D MIL-C-20D HG > > * U1G =3D N080 =3D MIL-C-20D LG > > * P2G =3D N150 =3D MIL-C-20D PG > > * R2G =3D N220 =3D MIL-C-20D RG > > * S2H =3D N330 =3D MIL-C-20D SH > > * T2H =3D N470 =3D MIL-C-20D TH > > * U2J =3D N750 =3D MIL-C-20D UJ > > * P3K =3D N1500 > > * R3L =3D N2200 > > > > > > EIA RS-198 designations for general-purpose Class 2 dielectrics: > > * First (letter), lowest rated temperature: > > - X =3D -55C minimum > > - Y =3D -30C minimum > > - Z =3D +10C minimum > > * Second (number), highest rated temperature: > > - 2 =3D +45C maximum > > - 4 =3D +65C maximum > > - 5 =3D +85C maximum > > - 6 =3D +105C maximum > > - 7 =3D +125C maximum > > * Third (letter) tolerance: > > - A =3D +/-1.0% tolerance > > - B =3D +/-1.5% tolerance > > - C =3D +/-2.2% tolerance > > - D =3D +/-3.3% tolerance > > - E =3D +/-4.7% tolerance > > - F =3D +/-7.5% tolerance > > - P =3D +/-10% tolerance > > - R =3D +/-15% tolerance > > - S =3D +/-22% tolerance > > - T =3D +22 to -33% tolerance > > - U =3D +22 to -56% tolerance > > - V =3D +22 to -82% tolerance >=20 > ------------------------------------------------------------------ > To unsubscribe from si-list: > si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field >=20 > or to administer your membership from a web page, go to:=20 > //www.freelists.org/webpage/si-list >=20 > For help: > si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field >=20 > List archives are viewable at: > //www.freelists.org/archives/si-list > or at our remote archives: > http://groups.yahoo.com/group/si-list/messages > Old (prior to June 6, 2001) list archives are viewable at: > http://www.qsl.net/wb6tpu >=20 > ------------------------------------------------------------------ > To unsubscribe from si-list: > si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field >=20 > or to administer your membership from a web page, go to:=20 > //www.freelists.org/webpage/si-list >=20 > For help: > si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field >=20 > List archives are viewable at: > //www.freelists.org/archives/si-list > or at our remote archives: > http://groups.yahoo.com/group/si-list/messages > Old (prior to June 6, 2001) list archives are viewable at: > http://www.qsl.net/wb6tpu > ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List archives are viewable at: =20 //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages=20 Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu =20 ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu