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Quick ESR answer needed
Quick ESR answer needed...
Typical 0.22uF ceramic in low voltage application (5V max), what ESR might I expect? Client says 0.2 Ohms I doubt that number, but don't have anything to base my doubt on. What say yee all? ...Jim Thompson -- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona Voice:(480)460-2350 | | | E-mail Address at Website Fax:(480)460-2142 | Brass Rat | | http://www.analog-innovations.com | 1962 | America: Land of the Free, Because of the Brave |
Quick ESR answer needed
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Quick ESR answer needed
Jim Thompson wrote:
Quick ESR answer needed... Typical 0.22uF ceramic in low voltage application (5V max), what ESR might I expect? Client says 0.2 Ohms I doubt that number, but don't have anything to base my doubt on. What say yee all? Much lower IME, more in the range Kevin gave but it depends on the frequency. I guess your client would want a somewhat more "official" story about it, so here goes (the MLC versus Tantalum shoot-out): http://www.avxcorp.com/docs/techinfo/mlc-tant.pdf Ahem, you wouldn't think about counting on the ESR for a loop design, would ya? No, can't be .... -- Regards, Joerg http://www.analogconsultants.com |
Quick ESR answer needed
On Tue, 14 Aug 2007 09:51:38 -0700, Jim Thompson
wrote: Quick ESR answer needed... Typical 0.22uF ceramic in low voltage application (5V max), what ESR might I expect? Client says 0.2 Ohms I doubt that number, but don't have anything to base my doubt on. What say yee all? ...Jim Thompson Sounds about right for a Z5U dielectric low volt cap. These things are the pits. Terrible temp and voltage curves with lots of microphonics and absorbtion. All they are 'good' for is power filtering at the vcc terminals of ICs. |
Quick ESR answer needed
On Tue, 14 Aug 2007 10:41:32 -0700, Joerg
wrote: Jim Thompson wrote: Quick ESR answer needed... Typical 0.22uF ceramic in low voltage application (5V max), what ESR might I expect? Client says 0.2 Ohms I doubt that number, but don't have anything to base my doubt on. What say yee all? Much lower IME, more in the range Kevin gave but it depends on the frequency. I guess your client would want a somewhat more "official" story about it, so here goes (the MLC versus Tantalum shoot-out): http://www.avxcorp.com/docs/techinfo/mlc-tant.pdf Ahem, you wouldn't think about counting on the ESR for a loop design, would ya? No, can't be .... Bet he's designing a chip with built-in LDO! I like the National AnyCap idea, an internal dominant pole that's merely increased by external capacitance, not cascaded with it. Basically, it's Miller capacitance off the output pin. John |
Quick ESR answer needed
John Larkin wrote:
On Tue, 14 Aug 2007 10:41:32 -0700, Joerg wrote: Jim Thompson wrote: Quick ESR answer needed... Typical 0.22uF ceramic in low voltage application (5V max), what ESR might I expect? Client says 0.2 Ohms I doubt that number, but don't have anything to base my doubt on. What say yee all? Much lower IME, more in the range Kevin gave but it depends on the frequency. I guess your client would want a somewhat more "official" story about it, so here goes (the MLC versus Tantalum shoot-out): http://www.avxcorp.com/docs/techinfo/mlc-tant.pdf Ahem, you wouldn't think about counting on the ESR for a loop design, would ya? No, can't be .... Bet he's designing a chip with built-in LDO! Sounds like as much fun as repairing a dry-rot problem. I like the National AnyCap idea, an internal dominant pole that's merely increased by external capacitance, not cascaded with it. Basically, it's Miller capacitance off the output pin. I think that's Analog Devices. Anyhow, yes, you can buy good LDOs but for the privilege of having one that doesn't throw the occasional tantrum you have to pay extra. "Oh, you want a car that doesn't have a wobble at 65mph? Ok, but it'll cost ya." As far as I am concerned I avoid LDOs like the plague. -- Regards, Joerg http://www.analogconsultants.com |
Quick ESR answer needed
"PeteS" wrote in message ... Jim Thompson wrote: Quick ESR answer needed... Typical 0.22uF ceramic in low voltage application (5V max), what ESR might I expect? Client says 0.2 Ohms I doubt that number, but don't have anything to base my doubt on. What say yee all? ...Jim Thompson About a hundredth of that. 2 milliohm is reasonable provided the device is rated at 10V. If it's rated at 6V, then figure about 10 milliohm. Cheers PeteS Just measured one to hand. 100nF, Y5V, 25kHz, 5ohm. 1kHz 55ohm. (for comparison, a 100nF poly' gave 8ohm at 1kHz) Looks like I always end up at the cheap tat end of the market :) |
Quick ESR answer needed
On Tue, 14 Aug 2007 20:46:03 +0100, "john jardine"
wrote: "PeteS" wrote in message .. . Jim Thompson wrote: Quick ESR answer needed... Typical 0.22uF ceramic in low voltage application (5V max), what ESR might I expect? Client says 0.2 Ohms I doubt that number, but don't have anything to base my doubt on. What say yee all? ...Jim Thompson About a hundredth of that. 2 milliohm is reasonable provided the device is rated at 10V. If it's rated at 6V, then figure about 10 milliohm. Cheers PeteS Just measured one to hand. 100nF, Y5V, 25kHz, 5ohm. 1kHz 55ohm. (for comparison, a 100nF poly' gave 8ohm at 1kHz) Those numbers seem extreme, high by 2 or 3 orders of magnitude. How did you measure them? John |
Quick ESR answer needed
On Tue, 14 Aug 2007 11:27:24 -0700, John Larkin
wrote: On Tue, 14 Aug 2007 10:41:32 -0700, Joerg wrote: Jim Thompson wrote: Quick ESR answer needed... Typical 0.22uF ceramic in low voltage application (5V max), what ESR might I expect? Client says 0.2 Ohms I doubt that number, but don't have anything to base my doubt on. What say yee all? Much lower IME, more in the range Kevin gave but it depends on the frequency. I guess your client would want a somewhat more "official" story about it, so here goes (the MLC versus Tantalum shoot-out): http://www.avxcorp.com/docs/techinfo/mlc-tant.pdf Ahem, you wouldn't think about counting on the ESR for a loop design, would ya? No, can't be .... Bet he's designing a chip with built-in LDO! Nope. Dumping said capacitor into a 1.5 Ohm load using a PMOS/NMOS totem pole that uses up 1/3 of the chip :-( I like the National AnyCap idea, an internal dominant pole that's merely increased by external capacitance, not cascaded with it. Basically, it's Miller capacitance off the output pin. John ...Jim Thompson -- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona Voice:(480)460-2350 | | | E-mail Address at Website Fax:(480)460-2142 | Brass Rat | | http://www.analog-innovations.com | 1962 | America: Land of the Free, Because of the Brave |
Quick ESR answer needed
Jim Thompson wrote:
On Tue, 14 Aug 2007 11:27:24 -0700, John Larkin wrote: On Tue, 14 Aug 2007 10:41:32 -0700, Joerg wrote: Jim Thompson wrote: Quick ESR answer needed... Typical 0.22uF ceramic in low voltage application (5V max), what ESR might I expect? Client says 0.2 Ohms I doubt that number, but don't have anything to base my doubt on. What say yee all? Much lower IME, more in the range Kevin gave but it depends on the frequency. I guess your client would want a somewhat more "official" story about it, so here goes (the MLC versus Tantalum shoot-out): http://www.avxcorp.com/docs/techinfo/mlc-tant.pdf Ahem, you wouldn't think about counting on the ESR for a loop design, would ya? No, can't be .... Bet he's designing a chip with built-in LDO! Nope. Dumping said capacitor into a 1.5 Ohm load using a PMOS/NMOS totem pole that uses up 1/3 of the chip :-( Hopefully this one can run on a cheap process then. I like the National AnyCap idea, an internal dominant pole that's merely increased by external capacitance, not cascaded with it. Basically, it's Miller capacitance off the output pin. -- Regards, Joerg http://www.analogconsultants.com |
Quick ESR answer needed
Jim Thompson wrote:
Quick ESR answer needed... Typical 0.22uF ceramic in low voltage application (5V max), what ESR might I expect? Client says 0.2 Ohms I doubt that number, but don't have anything to base my doubt on. What say yee all? ...Jim Thompson About a hundredth of that. 2 milliohm is reasonable provided the device is rated at 10V. If it's rated at 6V, then figure about 10 milliohm. Cheers PeteS |
Quick ESR answer needed
Lynn Richardson wrote:
On Tue, 14 Aug 2007 09:51:38 -0700, Jim Thompson wrote: Quick ESR answer needed... Typical 0.22uF ceramic in low voltage application (5V max), what ESR might I expect? Client says 0.2 Ohms I doubt that number, but don't have anything to base my doubt on. What say yee all? ...Jim Thompson Sounds about right for a Z5U dielectric low volt cap. These things are the pits. Terrible temp and voltage curves with lots of microphonics and absorbtion. All they are 'good' for is power filtering at the vcc terminals of ICs. With ESRs like that, they aren't even good for that. Cheers PeteS |
Quick ESR answer needed
"John Larkin" "john jardine" Just measured one to hand. 100nF, Y5V, 25kHz, 5ohm. 1kHz 55ohm. (for comparison, a 100nF poly' gave 8ohm at 1kHz) Those numbers seem extreme, high by 2 or 3 orders of magnitude. How did you measure them? ** With one of these maybe ? http://www.m3electronix.com/featureslcr.html Told us he owned one back on July 17. God knows how he got those mad results. ........ Phil |
Quick ESR answer needed
"John Larkin" wrote in message ... On Tue, 14 Aug 2007 20:46:03 +0100, "john jardine" wrote: "PeteS" wrote in message .. . Jim Thompson wrote: Quick ESR answer needed... Typical 0.22uF ceramic in low voltage application (5V max), what ESR might I expect? Client says 0.2 Ohms I doubt that number, but don't have anything to base my doubt on. What say yee all? ...Jim Thompson About a hundredth of that. 2 milliohm is reasonable provided the device is rated at 10V. If it's rated at 6V, then figure about 10 milliohm. Cheers PeteS Just measured one to hand. 100nF, Y5V, 25kHz, 5ohm. 1kHz 55ohm. (for comparison, a 100nF poly' gave 8ohm at 1kHz) Those numbers seem extreme, high by 2 or 3 orders of magnitude. How did you measure them? John Measured on a bit of kit I bought last week. http://www.mwinstruments.com/MW1008/MW1008_f.html Cheap but very handy. It measures the component impedance and VI phase displacement. All other secondary components such as LCR are then derived mathematically. Just for comparison I checked a part I can trace. It's a 470n open frame Polyester, EPCOS part #B32560J1474K. The data sheet states a loss factor of 0.008 at 1kHz. The meter (test at 1kHz) shows D=0.0046, L=475.6nF, Series R=1.55ohms. The values tie up nicely. (Had assumed most people would be equipped with fancy HP analyzers and would have posted a measurement or two but haven't see anything come in yet.) |
Quick ESR answer needed
On Wed, 15 Aug 2007 01:21:23 +0100, "john jardine"
wrote: "John Larkin" wrote in message .. . On Tue, 14 Aug 2007 20:46:03 +0100, "john jardine" wrote: "PeteS" wrote in message .. . Jim Thompson wrote: Quick ESR answer needed... Typical 0.22uF ceramic in low voltage application (5V max), what ESR might I expect? Client says 0.2 Ohms I doubt that number, but don't have anything to base my doubt on. What say yee all? ...Jim Thompson About a hundredth of that. 2 milliohm is reasonable provided the device is rated at 10V. If it's rated at 6V, then figure about 10 milliohm. Cheers PeteS Just measured one to hand. 100nF, Y5V, 25kHz, 5ohm. 1kHz 55ohm. (for comparison, a 100nF poly' gave 8ohm at 1kHz) Those numbers seem extreme, high by 2 or 3 orders of magnitude. How did you measure them? John Measured on a bit of kit I bought last week. http://www.mwinstruments.com/MW1008/MW1008_f.html Cheap but very handy. It measures the component impedance and VI phase displacement. All other secondary components such as LCR are then derived mathematically. Just for comparison I checked a part I can trace. It's a 470n open frame Polyester, EPCOS part #B32560J1474K. The data sheet states a loss factor of 0.008 at 1kHz. The meter (test at 1kHz) shows D=0.0046, L=475.6nF, Series R=1.55ohms. The values tie up nicely. (Had assumed most people would be equipped with fancy HP analyzers and would have posted a measurement or two but haven't see anything come in yet.) All those numbers sound very weird to me. And you can't calculate ESR from a single-frequency vector impedance measurement. The polyester loss is most likely dielectric absorption, which does not translate to esr. I just measured an axial-lead 0.1 uF ceramic cap directly, by applying a current pulse and observing the voltage waveform. It's showing about 50 milliohms, but that's close to my resolution limit. John |
Quick ESR answer needed
john jardine wrote:
"PeteS" wrote in message ... Jim Thompson wrote: Quick ESR answer needed... Typical 0.22uF ceramic in low voltage application (5V max), what ESR might I expect? Client says 0.2 Ohms I doubt that number, but don't have anything to base my doubt on. What say yee all? ...Jim Thompson About a hundredth of that. 2 milliohm is reasonable provided the device is rated at 10V. If it's rated at 6V, then figure about 10 milliohm. Cheers PeteS Just measured one to hand. 100nF, Y5V, 25kHz, 5ohm. 1kHz 55ohm. (for comparison, a 100nF poly' gave 8ohm at 1kHz) Looks like I always end up at the cheap tat end of the market :) Well, I don't use anything worse than X7R right now which is where I get my numbers from. The cheaper stuff will always have worse numbers, of course ;) Cheers PeteS |
Quick ESR answer needed
John Larkin wrote:
On Wed, 15 Aug 2007 01:21:23 +0100, "john jardine" wrote: "John Larkin" wrote in message . .. On Tue, 14 Aug 2007 20:46:03 +0100, "john jardine" wrote: "PeteS" wrote in message t... Jim Thompson wrote: Quick ESR answer needed... Typical 0.22uF ceramic in low voltage application (5V max), what ESR might I expect? Client says 0.2 Ohms I doubt that number, but don't have anything to base my doubt on. What say yee all? ...Jim Thompson About a hundredth of that. 2 milliohm is reasonable provided the device is rated at 10V. If it's rated at 6V, then figure about 10 milliohm. Cheers PeteS Just measured one to hand. 100nF, Y5V, 25kHz, 5ohm. 1kHz 55ohm. (for comparison, a 100nF poly' gave 8ohm at 1kHz) Those numbers seem extreme, high by 2 or 3 orders of magnitude. How did you measure them? John Measured on a bit of kit I bought last week. http://www.mwinstruments.com/MW1008/MW1008_f.html Cheap but very handy. It measures the component impedance and VI phase displacement. All other secondary components such as LCR are then derived mathematically. Just for comparison I checked a part I can trace. It's a 470n open frame Polyester, EPCOS part #B32560J1474K. The data sheet states a loss factor of 0.008 at 1kHz. The meter (test at 1kHz) shows D=0.0046, L=475.6nF, Series R=1.55ohms. The values tie up nicely. (Had assumed most people would be equipped with fancy HP analyzers and would have posted a measurement or two but haven't see anything come in yet.) All those numbers sound very weird to me. And you can't calculate ESR from a single-frequency vector impedance measurement. The polyester loss is most likely dielectric absorption, which does not translate to esr. I just measured an axial-lead 0.1 uF ceramic cap directly, by applying a current pulse and observing the voltage waveform. It's showing about 50 milliohms, but that's close to my resolution limit. And it isn't necessarily linear either. When I was a kid I thought I had it all figured out with RF power stuff. Measured the ESR of a largish cap at 21MHz, the frequency where I needed it. Assumed it would remain constant regardless of current level. Yeah, right. Calculated the dissipation this would cause, lots of margin, nothing would get hot here. Or so I thought. Soldered it in place and about five minutes into using it ... KABLOUIE! Molten stuff all over the place. BTW, just curious, does your TDS2024 also lack delayed trigger? My Instek 2204 does, and so do lots of others. Shook my head when I found out. -- Regards, Joerg http://www.analogconsultants.com |
Quick ESR answer needed
"john jardine" Just for comparison I checked a part I can trace. It's a 470n open frame Polyester, EPCOS part #B32560J1474K. The data sheet states a loss factor of 0.008 at 1kHz. The meter (test at 1kHz) shows D=0.0046, L=475.6nF, Series R=1.55ohms. The values tie up nicely. ** The published data for that same cap shows it has an impedance minimum at just over 3 MHz of 33 milliohms. ......... Phil |
Quick ESR answer needed
On Tue, 14 Aug 2007 11:39:34 -0700, Joerg
wrote: John Larkin wrote: On Tue, 14 Aug 2007 10:41:32 -0700, Joerg wrote: Jim Thompson wrote: Quick ESR answer needed... Typical 0.22uF ceramic in low voltage application (5V max), what ESR might I expect? Client says 0.2 Ohms I doubt that number, but don't have anything to base my doubt on. What say yee all? Much lower IME, more in the range Kevin gave but it depends on the frequency. I guess your client would want a somewhat more "official" story about it, so here goes (the MLC versus Tantalum shoot-out): http://www.avxcorp.com/docs/techinfo/mlc-tant.pdf Ahem, you wouldn't think about counting on the ESR for a loop design, would ya? No, can't be .... Bet he's designing a chip with built-in LDO! Sounds like as much fun as repairing a dry-rot problem. I like the National AnyCap idea, an internal dominant pole that's merely increased by external capacitance, not cascaded with it. Basically, it's Miller capacitance off the output pin. I think that's Analog Devices. Yeah, I was thinking of the National C-load opamps, like the LM8261. John |
Quick ESR answer needed
On Tue, 14 Aug 2007 18:20:45 -0700, Joerg
wrote: John Larkin wrote: On Wed, 15 Aug 2007 01:21:23 +0100, "john jardine" wrote: "John Larkin" wrote in message ... On Tue, 14 Aug 2007 20:46:03 +0100, "john jardine" wrote: "PeteS" wrote in message et... Jim Thompson wrote: Quick ESR answer needed... Typical 0.22uF ceramic in low voltage application (5V max), what ESR might I expect? Client says 0.2 Ohms I doubt that number, but don't have anything to base my doubt on. What say yee all? ...Jim Thompson About a hundredth of that. 2 milliohm is reasonable provided the device is rated at 10V. If it's rated at 6V, then figure about 10 milliohm. Cheers PeteS Just measured one to hand. 100nF, Y5V, 25kHz, 5ohm. 1kHz 55ohm. (for comparison, a 100nF poly' gave 8ohm at 1kHz) Those numbers seem extreme, high by 2 or 3 orders of magnitude. How did you measure them? John Measured on a bit of kit I bought last week. http://www.mwinstruments.com/MW1008/MW1008_f.html Cheap but very handy. It measures the component impedance and VI phase displacement. All other secondary components such as LCR are then derived mathematically. Just for comparison I checked a part I can trace. It's a 470n open frame Polyester, EPCOS part #B32560J1474K. The data sheet states a loss factor of 0.008 at 1kHz. The meter (test at 1kHz) shows D=0.0046, L=475.6nF, Series R=1.55ohms. The values tie up nicely. (Had assumed most people would be equipped with fancy HP analyzers and would have posted a measurement or two but haven't see anything come in yet.) All those numbers sound very weird to me. And you can't calculate ESR from a single-frequency vector impedance measurement. The polyester loss is most likely dielectric absorption, which does not translate to esr. I just measured an axial-lead 0.1 uF ceramic cap directly, by applying a current pulse and observing the voltage waveform. It's showing about 50 milliohms, but that's close to my resolution limit. And it isn't necessarily linear either. When I was a kid I thought I had it all figured out with RF power stuff. Measured the ESR of a largish cap at 21MHz, the frequency where I needed it. Assumed it would remain constant regardless of current level. Yeah, right. Calculated the dissipation this would cause, lots of margin, nothing would get hot here. Or so I thought. Soldered it in place and about five minutes into using it ... KABLOUIE! Molten stuff all over the place. BTW, just curious, does your TDS2024 also lack delayed trigger? My Instek 2204 does, and so do lots of others. Shook my head when I found out. No delayed trigger, and only as much memory as fills the screen. We have a bigger one, 500 MHz, forget the model number, that has more memory and delay. John |
Quick ESR answer needed
On Tue, 14 Aug 2007 09:51:38 -0700, Jim Thompson
wrote: Quick ESR answer needed... Typical 0.22uF ceramic in low voltage application (5V max), what ESR might I expect? At what frequency? That makes a big difference. Client says 0.2 Ohms I doubt that number, but don't have anything to base my doubt on. What say yee all? ...Jim Thompson |
Quick ESR answer needed
"The Phantom" Jim Thompson Typical 0.22uF ceramic in low voltage application (5V max), what ESR might I expect? At what frequency? That makes a big difference. ** Not to the minimum impedance the cap can exhibit - which is the series resistance that counts for supply bypass and filtering applications. No one is too bothered about di-electric losses for that as they only help ! ........ Phil |
Quick ESR answer needed
John Larkin wrote:
On Tue, 14 Aug 2007 18:20:45 -0700, Joerg wrote: John Larkin wrote: On Wed, 15 Aug 2007 01:21:23 +0100, "john jardine" wrote: "John Larkin" wrote in message m... On Tue, 14 Aug 2007 20:46:03 +0100, "john jardine" wrote: "PeteS" wrote in message news:IcSdncGmicnHYVzbnZ2dnUVZ8vidnZ2d@pipex. net... Jim Thompson wrote: Quick ESR answer needed... Typical 0.22uF ceramic in low voltage application (5V max), what ESR might I expect? Client says 0.2 Ohms I doubt that number, but don't have anything to base my doubt on. What say yee all? ...Jim Thompson About a hundredth of that. 2 milliohm is reasonable provided the device is rated at 10V. If it's rated at 6V, then figure about 10 milliohm. Cheers PeteS Just measured one to hand. 100nF, Y5V, 25kHz, 5ohm. 1kHz 55ohm. (for comparison, a 100nF poly' gave 8ohm at 1kHz) Those numbers seem extreme, high by 2 or 3 orders of magnitude. How did you measure them? John Measured on a bit of kit I bought last week. http://www.mwinstruments.com/MW1008/MW1008_f.html Cheap but very handy. It measures the component impedance and VI phase displacement. All other secondary components such as LCR are then derived mathematically. Just for comparison I checked a part I can trace. It's a 470n open frame Polyester, EPCOS part #B32560J1474K. The data sheet states a loss factor of 0.008 at 1kHz. The meter (test at 1kHz) shows D=0.0046, L=475.6nF, Series R=1.55ohms. The values tie up nicely. (Had assumed most people would be equipped with fancy HP analyzers and would have posted a measurement or two but haven't see anything come in yet.) All those numbers sound very weird to me. And you can't calculate ESR from a single-frequency vector impedance measurement. The polyester loss is most likely dielectric absorption, which does not translate to esr. I just measured an axial-lead 0.1 uF ceramic cap directly, by applying a current pulse and observing the voltage waveform. It's showing about 50 milliohms, but that's close to my resolution limit. And it isn't necessarily linear either. When I was a kid I thought I had it all figured out with RF power stuff. Measured the ESR of a largish cap at 21MHz, the frequency where I needed it. Assumed it would remain constant regardless of current level. Yeah, right. Calculated the dissipation this would cause, lots of margin, nothing would get hot here. Or so I thought. Soldered it in place and about five minutes into using it ... KABLOUIE! Molten stuff all over the place. BTW, just curious, does your TDS2024 also lack delayed trigger? My Instek 2204 does, and so do lots of others. Shook my head when I found out. No delayed trigger, and only as much memory as fills the screen. We have a bigger one, 500 MHz, forget the model number, that has more memory and delay. Why on earth didn't they provide delayed trigger? It's so easy .... banging head on table In single channel the TDS2024 should yield about five times the screen. But that ain't enough for me which is one reason why I bought the Instek (has 25K memory). At least that gets me to 25usec single channel. Still drooling over the 1M or so of the Hameg 2008 but it's just too large in size. -- Regards, Joerg http://www.analogconsultants.com |
Quick ESR answer needed
On Tue, 14 Aug 2007 23:42:47 -0700, The Phantom
wrote: On Tue, 14 Aug 2007 09:51:38 -0700, Jim Thompson wrote: Quick ESR answer needed... Typical 0.22uF ceramic in low voltage application (5V max), what ESR might I expect? At what frequency? That makes a big difference. Client says 0.2 Ohms I doubt that number, but don't have anything to base my doubt on. What say yee all? ...Jim Thompson If frequency makes a difference then isn't it "ESL" rather than ESR? Application has capacitor charged to +1.8V, it is then connected (4ns full-on connect time) thru a 1.5 Ohm "strap" to -1.8V. In other words, over 2A peak current. ...Jim Thompson -- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona Voice:(480)460-2350 | | | E-mail Address at Website Fax:(480)460-2142 | Brass Rat | | http://www.analog-innovations.com | 1962 | America: Land of the Free, Because of the Brave |
Quick ESR answer needed
On Tue, 14 Aug 2007 17:58:13 -0700, John Larkin
wrote: On Wed, 15 Aug 2007 01:21:23 +0100, "john jardine" wrote: "John Larkin" wrote in message . .. On Tue, 14 Aug 2007 20:46:03 +0100, "john jardine" wrote: "PeteS" wrote in message .. . Jim Thompson wrote: Quick ESR answer needed... Typical 0.22uF ceramic in low voltage application (5V max), what ESR might I expect? Client says 0.2 Ohms I doubt that number, but don't have anything to base my doubt on. What say yee all? ...Jim Thompson About a hundredth of that. 2 milliohm is reasonable provided the device is rated at 10V. If it's rated at 6V, then figure about 10 milliohm. Cheers PeteS Just measured one to hand. 100nF, Y5V, 25kHz, 5ohm. 1kHz 55ohm. (for comparison, a 100nF poly' gave 8ohm at 1kHz) Those numbers seem extreme, high by 2 or 3 orders of magnitude. How did you measure them? John Measured on a bit of kit I bought last week. http://www.mwinstruments.com/MW1008/MW1008_f.html Cheap but very handy. It measures the component impedance and VI phase displacement. All other secondary components such as LCR are then derived mathematically. Just for comparison I checked a part I can trace. It's a 470n open frame Polyester, EPCOS part #B32560J1474K. The data sheet states a loss factor of 0.008 at 1kHz. The meter (test at 1kHz) shows D=0.0046, L=475.6nF, Series R=1.55ohms. The values tie up nicely. (Had assumed most people would be equipped with fancy HP analyzers and would have posted a measurement or two but haven't see anything come in yet.) All those numbers sound very weird to me. And you can't calculate ESR from a single-frequency vector impedance measurement. Why not? http://en.wikipedia.org/wiki/Equival...ies_resistance The polyester loss is most likely dielectric absorption, which does not translate to esr. I just measured an axial-lead 0.1 uF ceramic cap directly, by applying a current pulse and observing the voltage waveform. It's showing about 50 milliohms, but that's close to my resolution limit. John |
Quick ESR answer needed
On Wed, 15 Aug 2007 07:11:54 -0700, Jim Thompson
wrote: On Tue, 14 Aug 2007 23:42:47 -0700, The Phantom wrote: On Tue, 14 Aug 2007 09:51:38 -0700, Jim Thompson wrote: Quick ESR answer needed... Typical 0.22uF ceramic in low voltage application (5V max), what ESR might I expect? At what frequency? That makes a big difference. Client says 0.2 Ohms I doubt that number, but don't have anything to base my doubt on. What say yee all? ...Jim Thompson If frequency makes a difference then isn't it "ESL" rather than ESR? ESR (with the meaning as used by the capacitor manufacturers) does vary with frequency. See: http://www.avxcorp.com/docs/techinfo/mlc-tant.pdf Of course, capacitors have an ESL as well as an ESR (the E stands for Equivalent, which means a simple model), and the *impedance* of the capacitor is dominated by ESL above the series resonant frequency. The Kemet folks show the impedance vs. frequency characteristic for their various MLC's in this file: http://www.kemet.com/kemet/web/homepage/kechome.nsf/weben/B3D6942FD742E4A5CA2570A500160908/$file/F3102_CerPerChar.pdf Given the short connect time, 4ns, of your application it looks like you will care about the (typical) capacitor's impedance well above series resonance, which will probably be dominated by ESL. You might want to use a COG dielectric. Application has capacitor charged to +1.8V, it is then connected (4ns full-on connect time) thru a 1.5 Ohm "strap" to -1.8V. In other words, over 2A peak current. ...Jim Thompson |
Quick ESR answer needed
On Wed, 15 Aug 2007 07:55:33 -0700, The Phantom
wrote: On Tue, 14 Aug 2007 17:58:13 -0700, John Larkin wrote: On Wed, 15 Aug 2007 01:21:23 +0100, "john jardine" wrote: "John Larkin" wrote in message ... On Tue, 14 Aug 2007 20:46:03 +0100, "john jardine" wrote: "PeteS" wrote in message .. . Jim Thompson wrote: Quick ESR answer needed... Typical 0.22uF ceramic in low voltage application (5V max), what ESR might I expect? Client says 0.2 Ohms I doubt that number, but don't have anything to base my doubt on. What say yee all? ...Jim Thompson About a hundredth of that. 2 milliohm is reasonable provided the device is rated at 10V. If it's rated at 6V, then figure about 10 milliohm. Cheers PeteS Just measured one to hand. 100nF, Y5V, 25kHz, 5ohm. 1kHz 55ohm. (for comparison, a 100nF poly' gave 8ohm at 1kHz) Those numbers seem extreme, high by 2 or 3 orders of magnitude. How did you measure them? John Measured on a bit of kit I bought last week. http://www.mwinstruments.com/MW1008/MW1008_f.html Cheap but very handy. It measures the component impedance and VI phase displacement. All other secondary components such as LCR are then derived mathematically. Just for comparison I checked a part I can trace. It's a 470n open frame Polyester, EPCOS part #B32560J1474K. The data sheet states a loss factor of 0.008 at 1kHz. The meter (test at 1kHz) shows D=0.0046, L=475.6nF, Series R=1.55ohms. The values tie up nicely. (Had assumed most people would be equipped with fancy HP analyzers and would have posted a measurement or two but haven't see anything come in yet.) All those numbers sound very weird to me. And you can't calculate ESR from a single-frequency vector impedance measurement. Why not? http://en.wikipedia.org/wiki/Equival...ies_resistance Well, it depends on your definition of "equivalent." Certainly you can measure the vector impedance at some frequency and razzle-dazzle some equations and come up with both an "equivalent" series resistance or, if you prefer, an "equivalent" shunt resistance. Somebody here just did that and got 800+ ohms ESR for a ceramic cap. But that "ESR" is absolutely meaningless for, say, designing a bypass system or compensating a switching regulator, because it's about 10,000 or so times the true series resistance. And the equivalent shunt resistance is even-worse useless if you're doing DC design, because it's maybe a million times off of being predictive of real leakage current. So, OK, I was wrong: you can certainly do the calculation, or let some fancy instrument do it for you, and display it to 5 digits of precision, and that's fine for people who don't mind being off by 4 to 6 orders of magnitude. About the only thing a single-frequency ESR measurement does is sort of predict how the cap will work *at that frequency* John |
Quick ESR answer needed
On Wed, 15 Aug 2007 07:11:54 -0700, Jim Thompson
wrote: On Tue, 14 Aug 2007 23:42:47 -0700, The Phantom wrote: On Tue, 14 Aug 2007 09:51:38 -0700, Jim Thompson wrote: Quick ESR answer needed... Typical 0.22uF ceramic in low voltage application (5V max), what ESR might I expect? At what frequency? That makes a big difference. Client says 0.2 Ohms I doubt that number, but don't have anything to base my doubt on. What say yee all? ...Jim Thompson If frequency makes a difference then isn't it "ESL" rather than ESR? Application has capacitor charged to +1.8V, it is then connected (4ns full-on connect time) thru a 1.5 Ohm "strap" to -1.8V. In other words, over 2A peak current. ...Jim Thompson Tricky. Assuming a 1 ns risetime, 4 volts available, only 2 nH or so will get you into trouble. A cap and its leads will get you to about 2 nH, then there's all your wirebonds, not to mention the load itself. We usually parallel several caps, on a lot of copper, to supply a lot of fast peak current, like through a gaasfet to drive an SRD or a laser. (Gotta get ready for a Board meeting. What a nuisance.) John |
Quick ESR answer needed
On Wed, 15 Aug 2007 08:38:09 -0700, John Larkin
wrote: On Wed, 15 Aug 2007 07:11:54 -0700, Jim Thompson wrote: On Tue, 14 Aug 2007 23:42:47 -0700, The Phantom wrote: On Tue, 14 Aug 2007 09:51:38 -0700, Jim Thompson wrote: Quick ESR answer needed... Typical 0.22uF ceramic in low voltage application (5V max), what ESR might I expect? At what frequency? That makes a big difference. Client says 0.2 Ohms I doubt that number, but don't have anything to base my doubt on. What say yee all? ...Jim Thompson If frequency makes a difference then isn't it "ESL" rather than ESR? Application has capacitor charged to +1.8V, it is then connected (4ns full-on connect time) thru a 1.5 Ohm "strap" to -1.8V. In other words, over 2A peak current. ...Jim Thompson Tricky. Assuming a 1 ns risetime, 4 volts available, only 2 nH or so will get you into trouble. A cap and its leads will get you to about 2 nH, then there's all your wirebonds, not to mention the load itself. Face-down ball bonded. ~0.5nH connections. We usually parallel several caps, on a lot of copper, to supply a lot of fast peak current, like through a gaasfet to drive an SRD or a laser. (Gotta get ready for a Board meeting. What a nuisance.) John Me, my wife and my oldest daughter ARE the board... no nuisance ;-) ...Jim Thompson -- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona Voice:(480)460-2350 | | | E-mail Address at Website Fax:(480)460-2142 | Brass Rat | | http://www.analog-innovations.com | 1962 | America: Land of the Free, Because of the Brave |
Quick ESR answer needed
Jim Thompson wrote:
On Wed, 15 Aug 2007 08:38:09 -0700, John Larkin wrote: On Wed, 15 Aug 2007 07:11:54 -0700, Jim Thompson wrote: On Tue, 14 Aug 2007 23:42:47 -0700, The Phantom wrote: On Tue, 14 Aug 2007 09:51:38 -0700, Jim Thompson wrote: Quick ESR answer needed... Typical 0.22uF ceramic in low voltage application (5V max), what ESR might I expect? At what frequency? That makes a big difference. Client says 0.2 Ohms I doubt that number, but don't have anything to base my doubt on. What say yee all? ...Jim Thompson If frequency makes a difference then isn't it "ESL" rather than ESR? Application has capacitor charged to +1.8V, it is then connected (4ns full-on connect time) thru a 1.5 Ohm "strap" to -1.8V. In other words, over 2A peak current. ...Jim Thompson Tricky. Assuming a 1 ns risetime, 4 volts available, only 2 nH or so will get you into trouble. A cap and its leads will get you to about 2 nH, then there's all your wirebonds, not to mention the load itself. Face-down ball bonded. ~0.5nH connections. We usually parallel several caps, on a lot of copper, to supply a lot of fast peak current, like through a gaasfet to drive an SRD or a laser. (Gotta get ready for a Board meeting. What a nuisance.) John Me, my wife and my oldest daughter ARE the board... no nuisance ;-) Same here, but no daughter. -- Regards, Joerg http://www.analogconsultants.com |
Quick ESR answer needed
John,
A bit off this topic, I saw a post where you talk about 11801 ("When you start getting powerup timebase errors, which you will, call me.") I have an 11801 that has this problem. Would you be able to help me fix it? Thank you, Leo "John Larkin" wrote in message ... On Wed, 15 Aug 2007 07:11:54 -0700, Jim Thompson wrote: On Tue, 14 Aug 2007 23:42:47 -0700, The Phantom wrote: On Tue, 14 Aug 2007 09:51:38 -0700, Jim Thompson wrote: Quick ESR answer needed... Typical 0.22uF ceramic in low voltage application (5V max), what ESR might I expect? At what frequency? That makes a big difference. Client says 0.2 Ohms I doubt that number, but don't have anything to base my doubt on. What say yee all? ...Jim Thompson If frequency makes a difference then isn't it "ESL" rather than ESR? Application has capacitor charged to +1.8V, it is then connected (4ns full-on connect time) thru a 1.5 Ohm "strap" to -1.8V. In other words, over 2A peak current. ...Jim Thompson Tricky. Assuming a 1 ns risetime, 4 volts available, only 2 nH or so will get you into trouble. A cap and its leads will get you to about 2 nH, then there's all your wirebonds, not to mention the load itself. We usually parallel several caps, on a lot of copper, to supply a lot of fast peak current, like through a gaasfet to drive an SRD or a laser. (Gotta get ready for a Board meeting. What a nuisance.) John |
Quick ESR answer needed
On Wed, 15 Aug 2007 08:30:05 -0700, John Larkin
wrote: On Wed, 15 Aug 2007 07:55:33 -0700, The Phantom wrote: On Tue, 14 Aug 2007 17:58:13 -0700, John Larkin wrote: On Wed, 15 Aug 2007 01:21:23 +0100, "john jardine" wrote: "John Larkin" wrote in message m... On Tue, 14 Aug 2007 20:46:03 +0100, "john jardine" wrote: "PeteS" wrote in message .. . Jim Thompson wrote: Quick ESR answer needed... Typical 0.22uF ceramic in low voltage application (5V max), what ESR might I expect? Client says 0.2 Ohms I doubt that number, but don't have anything to base my doubt on. What say yee all? ...Jim Thompson About a hundredth of that. 2 milliohm is reasonable provided the device is rated at 10V. If it's rated at 6V, then figure about 10 milliohm. Cheers PeteS Just measured one to hand. 100nF, Y5V, 25kHz, 5ohm. 1kHz 55ohm. (for comparison, a 100nF poly' gave 8ohm at 1kHz) Those numbers seem extreme, high by 2 or 3 orders of magnitude. How did you measure them? John Measured on a bit of kit I bought last week. http://www.mwinstruments.com/MW1008/MW1008_f.html Cheap but very handy. It measures the component impedance and VI phase displacement. All other secondary components such as LCR are then derived mathematically. Just for comparison I checked a part I can trace. It's a 470n open frame Polyester, EPCOS part #B32560J1474K. The data sheet states a loss factor of 0.008 at 1kHz. The meter (test at 1kHz) shows D=0.0046, L=475.6nF, Series R=1.55ohms. The values tie up nicely. (Had assumed most people would be equipped with fancy HP analyzers and would have posted a measurement or two but haven't see anything come in yet.) All those numbers sound very weird to me. And you can't calculate ESR from a single-frequency vector impedance measurement. Why not? http://en.wikipedia.org/wiki/Equival...ies_resistance Well, it depends on your definition of "equivalent." Of course it does. I have been explaining the definition used by the capacitor manufacturers. It's the only (resistance; ESL is another number) number you will find in their specs, and they get it by simple measurement. Certainly you can measure the vector impedance at some frequency and razzle-dazzle some equations and come up with both an "equivalent" series resistance That's just what they do, and if a person wants to make sense of their numbers, he should realize how they got them. if you prefer, an "equivalent" shunt resistance. Somebody here just did that and got 800+ ohms ESR for a ceramic cap. I provided that number, and it would accurately tell you the dissipation in that capacitor if it were handling a 20 Hz current. But that "ESR" is absolutely meaningless for, say, designing a bypass system It's not meaningless at all. The ESR at a given frequency, for example 120 Hz, tells you just how much power is dissipated in the capacitor for a given ripple current (assuming the fundamental is 120 Hz. The harmonics contribute some heat in a typical 120 Hz power supply, but the fundamental dominates). In a switcher, the ripple current is typically trapezoidal and the magnitude of the fundamental ripple frequency is still dominant; the ESR at that frequency gives a good first cut at the dissipation in the capacitor. Look at the ripple current ratings of these capacitors: http://www.cde.com/catalogs/066.pdf Notice how the ripple current rating is less at lower frequencies. That's because the ESR increases at low frequencies. The ESR determines how much heating the ripple current will cause, and it tells it accurately because the ESR includes all the losses in the capacitor. or compensating a switching regulator, because it's about 10,000 or so times the true series resistance. This is only true at very low audio frequencies. Up around switching regulator frequencies, it's probably quite close to the true series resistance (R1 in your model). And the equivalent shunt resistance is even-worse useless if you're doing DC design, because it's maybe a million times off of being predictive of real leakage current. This is why I asked in another post how we would define DC ESR. It doesn't make sense at DC, and it's never given at DC. At low audio frequencies it's defined the same way it's defined at higher frequencies. It's the real part of the impedance measured at a given frequency. The model you gave is well known, and it's a good tool for design, but it's not what the manufacturers give you. You will have to derive it yourself from a series of measurements, as you said. So, OK, I was wrong: you can certainly do the calculation, or let some fancy instrument do it for you, and display it to 5 digits of precision, and that's fine for people who don't mind being off by 4 to 6 orders of magnitude. About the only thing a single-frequency ESR measurement does is sort of predict how the cap will work *at that frequency* And this is quite useful in those situations where the ripple current has a dominant fundamental component, such as in power supply applications. It tells you what the heating in the cap will be with fair accuracy. In fact, the error from neglecting the harmonics is probably less that the error from neglecting the variance in the ESR at a given frequency in a group of capacitors nominally the same. Of course, there will be applications where the harmonics are important, and then the designer will have to derive the more complicated and more accurate model. But this doesn't detract from the usefulness of the plain old ESR model in many other cases. John |
Quick ESR answer needed
On Tue, 14 Aug 2007 09:51:38 -0700, Jim Thompson
wrote: Quick ESR answer needed... Typical 0.22uF ceramic in low voltage application (5V max), what ESR might I expect? Client says 0.2 Ohms I doubt that number, but don't have anything to base my doubt on. What say yee all? While I was waiting for The Board to show up, I cobbled up this: http://s2.supload.com/free/Setup.JPG/view/ http://s2.supload.com/free/Ramp.JPG/view/ It's a 0.1 uF, 0805 cap soldered across a 50 ohm transmission line. It's being driven from (we pause for this commercial message...) http://www.highlandtechnology.com/DSS/P400DS.html which is setup for 5 volts out, 50 ohms, so it's dumping a 100 mA step into the cap with about a 1 ns risetime. The scope bandwidth is 20 GHz. The first glitch is L di/dt, roughly estimated as 1.5 nH. Extrapolating the slope back to the start gives very roughly 20 milliohms, but it's hard to resolve that small a resistance with this rig. The glitch at about 10 ns is a cable reflection. This cap is pretty much a dead short in the, say, 3 ns time frame. John |
Quick ESR answer needed
On Wed, 15 Aug 2007 15:00:47 -0400, "Leo" wrote:
John, A bit off this topic, I saw a post where you talk about 11801 ("When you start getting powerup timebase errors, which you will, call me.") I have an 11801 that has this problem. Would you be able to help me fix it? Thank you, Leo If you email me privately, I'll tell you what it probably is and how to fix it. But promise me you won't spread it around publicly... I just got a dead 11801A on ebay for $300, and if everybody learns this trick, they'll all go back up to $3K. What sort of sampling heads do you have? John |
Quick ESR answer needed
On Wed, 15 Aug 2007 14:58:47 -0700, John Larkin
wrote: On Tue, 14 Aug 2007 09:51:38 -0700, Jim Thompson wrote: Quick ESR answer needed... Typical 0.22uF ceramic in low voltage application (5V max), what ESR might I expect? Client says 0.2 Ohms I doubt that number, but don't have anything to base my doubt on. What say yee all? While I was waiting for The Board to show up, I cobbled up this: http://s2.supload.com/free/Setup.JPG/view/ http://s2.supload.com/free/Ramp.JPG/view/ It's a 0.1 uF, 0805 cap soldered across a 50 ohm transmission line. It's being driven from (we pause for this commercial message...) http://www.highlandtechnology.com/DSS/P400DS.html which is setup for 5 volts out, 50 ohms, so it's dumping a 100 mA step into the cap with about a 1 ns risetime. The scope bandwidth is 20 GHz. The first glitch is L di/dt, roughly estimated as 1.5 nH. Extrapolating the slope back to the start gives very roughly 20 milliohms A detailed description of this technique is to be found at: http://emcesd.com/tt020100.htm , but it's hard to resolve that small a resistance with this rig. The glitch at about 10 ns is a cable reflection. This cap is pretty much a dead short in the, say, 3 ns time frame. John |
Quick ESR answer needed
"The Phantom" wrote in message
... http://emcesd.com/tt020100.htm Thanks for the link, Phantom. John -- since you're not exactly enamored with Howard Johnson, do you have an opinion on Doug Smith there? I met him once and he seems to be considerably more "hands on" than Howard is. (That picture on his web site looks about 10 years old though!) ---Joel |
Quick ESR answer needed
"The Phantom" wrote in message ... On Wed, 15 Aug 2007 08:30:05 -0700, John Larkin wrote: On Wed, 15 Aug 2007 07:55:33 -0700, The Phantom wrote: On Tue, 14 Aug 2007 17:58:13 -0700, John Larkin wrote: On Wed, 15 Aug 2007 01:21:23 +0100, "john jardine" wrote: "John Larkin" wrote in message om... On Tue, 14 Aug 2007 20:46:03 +0100, "john jardine" wrote: "PeteS" wrote in message .. . Jim Thompson wrote: Quick ESR answer needed... Typical 0.22uF ceramic in low voltage application (5V max), what ESR might I expect? Client says 0.2 Ohms I doubt that number, but don't have anything to base my doubt on. What say yee all? ...Jim Thompson About a hundredth of that. 2 milliohm is reasonable provided the device is rated at 10V. If it's rated at 6V, then figure about 10 milliohm. Cheers PeteS Just measured one to hand. 100nF, Y5V, 25kHz, 5ohm. 1kHz 55ohm. (for comparison, a 100nF poly' gave 8ohm at 1kHz) Those numbers seem extreme, high by 2 or 3 orders of magnitude. How did you measure them? John Measured on a bit of kit I bought last week. http://www.mwinstruments.com/MW1008/MW1008_f.html Cheap but very handy. It measures the component impedance and VI phase displacement. All other secondary components such as LCR are then derived mathematically. Just for comparison I checked a part I can trace. It's a 470n open frame Polyester, EPCOS part #B32560J1474K. The data sheet states a loss factor of 0.008 at 1kHz. The meter (test at 1kHz) shows D=0.0046, L=475.6nF, Series R=1.55ohms. The values tie up nicely. (Had assumed most people would be equipped with fancy HP analyzers and would have posted a measurement or two but haven't see anything come in yet.) All those numbers sound very weird to me. And you can't calculate ESR from a single-frequency vector impedance measurement. Why not? http://en.wikipedia.org/wiki/Equival...ies_resistance Well, it depends on your definition of "equivalent." Of course it does. I have been explaining the definition used by the capacitor manufacturers. It's the only (resistance; ESL is another number) number you will find in their specs, and they get it by simple measurement. Certainly you can measure the vector impedance at some frequency and razzle-dazzle some equations and come up with both an "equivalent" series resistance That's just what they do, and if a person wants to make sense of their numbers, he should realize how they got them. if you prefer, an "equivalent" shunt resistance. Somebody here just did that and got 800+ ohms ESR for a ceramic cap. I provided that number, and it would accurately tell you the dissipation in that capacitor if it were handling a 20 Hz current. But that "ESR" is absolutely meaningless for, say, designing a bypass system It's not meaningless at all. The ESR at a given frequency, for example 120 Hz, tells you just how much power is dissipated in the capacitor for a given ripple current (assuming the fundamental is 120 Hz. The harmonics contribute some heat in a typical 120 Hz power supply, but the fundamental dominates). In a switcher, the ripple current is typically trapezoidal and the magnitude of the fundamental ripple frequency is still dominant; the ESR at that frequency gives a good first cut at the dissipation in the capacitor. Look at the ripple current ratings of these capacitors: http://www.cde.com/catalogs/066.pdf Notice how the ripple current rating is less at lower frequencies. That's because the ESR increases at low frequencies. The ESR determines how much heating the ripple current will cause, and it tells it accurately because the ESR includes all the losses in the capacitor. or compensating a switching regulator, because it's about 10,000 or so times the true series resistance. This is only true at very low audio frequencies. Up around switching regulator frequencies, it's probably quite close to the true series resistance (R1 in your model). And the equivalent shunt resistance is even-worse useless if you're doing DC design, because it's maybe a million times off of being predictive of real leakage current. This is why I asked in another post how we would define DC ESR. It doesn't make sense at DC, and it's never given at DC. At low audio frequencies it's defined the same way it's defined at higher frequencies. It's the real part of the impedance measured at a given frequency. The model you gave is well known, and it's a good tool for design, but it's not what the manufacturers give you. You will have to derive it yourself from a series of measurements, as you said. So, OK, I was wrong: you can certainly do the calculation, or let some fancy instrument do it for you, and display it to 5 digits of precision, and that's fine for people who don't mind being off by 4 to 6 orders of magnitude. About the only thing a single-frequency ESR measurement does is sort of predict how the cap will work *at that frequency* And this is quite useful in those situations where the ripple current has a dominant fundamental component, such as in power supply applications. It tells you what the heating in the cap will be with fair accuracy. In fact, the error from neglecting the harmonics is probably less that the error from neglecting the variance in the ESR at a given frequency in a group of capacitors nominally the same. Of course, there will be applications where the harmonics are important, and then the designer will have to derive the more complicated and more accurate model. But this doesn't detract from the usefulness of the plain old ESR model in many other cases. John Go to this link and download SpiCap 3.0 in the software section. http://www.avxcorp.com/prodinfo_catlist.asp?ParentID=1 Enter in your favorite cap and dielectric, vary the frequency as you watch the ESR change. Most fun I have had with my cloths on in a long time. See that ESL does not change with frequency. That is why we do not use large MLC caps to do AC line filtering, they will let the smoke out. Regards, Harry |
Quick ESR answer needed
John,
I'll not spread it around. I just got mine (11801A) for about the same price, but it has an error on power-up. I would like to use for measuring the input impedance of the microstrip antennas. I have an old sd-24 sampling head (hopefully working one). what is your email? Thanks, Leo leomats at gmail.com ----- Original Message ----- From: "John Larkin" Newsgroups: alt.binaries.schematics.electronic,sci.electronics .design Sent: Wednesday, August 15, 2007 6:04 PM Subject: Quick ESR answer needed On Wed, 15 Aug 2007 15:00:47 -0400, "Leo" wrote: John, A bit off this topic, I saw a post where you talk about 11801 ("When you start getting powerup timebase errors, which you will, call me.") I have an 11801 that has this problem. Would you be able to help me fix it? Thank you, Leo If you email me privately, I'll tell you what it probably is and how to fix it. But promise me you won't spread it around publicly... I just got a dead 11801A on ebay for $300, and if everybody learns this trick, they'll all go back up to $3K. What sort of sampling heads do you have? John "John Larkin" wrote in message ... On Wed, 15 Aug 2007 15:00:47 -0400, "Leo" wrote: John, A bit off this topic, I saw a post where you talk about 11801 ("When you start getting powerup timebase errors, which you will, call me.") I have an 11801 that has this problem. Would you be able to help me fix it? Thank you, Leo If you email me privately, I'll tell you what it probably is and how to fix it. But promise me you won't spread it around publicly... I just got a dead 11801A on ebay for $300, and if everybody learns this trick, they'll all go back up to $3K. What sort of sampling heads do you have? John |
Quick ESR answer needed
On Wed, 15 Aug 2007 15:56:03 -0700, "Joel Kolstad"
wrote: "The Phantom" wrote in message .. . http://emcesd.com/tt020100.htm Thanks for the link, Phantom. Another one well worth looking at is: http://www.avxcorp.com/docs/Catalogs/smpsas&p.pdf John -- since you're not exactly enamored with Howard Johnson, do you have an opinion on Doug Smith there? I met him once and he seems to be considerably more "hands on" than Howard is. (That picture on his web site looks about 10 years old though!) ---Joel |
Quick ESR answer needed
On Wed, 15 Aug 2007 08:50:38 -0700, Jim Thompson
wrote: On Wed, 15 Aug 2007 08:38:09 -0700, John Larkin wrote: On Wed, 15 Aug 2007 07:11:54 -0700, Jim Thompson wrote: On Tue, 14 Aug 2007 23:42:47 -0700, The Phantom wrote: On Tue, 14 Aug 2007 09:51:38 -0700, Jim Thompson wrote: Quick ESR answer needed... Typical 0.22uF ceramic in low voltage application (5V max), what ESR might I expect? At what frequency? That makes a big difference. Client says 0.2 Ohms I doubt that number, but don't have anything to base my doubt on. What say yee all? ...Jim Thompson If frequency makes a difference then isn't it "ESL" rather than ESR? Application has capacitor charged to +1.8V, it is then connected (4ns full-on connect time) thru a 1.5 Ohm "strap" to -1.8V. In other words, over 2A peak current. ...Jim Thompson Tricky. Assuming a 1 ns risetime, 4 volts available, only 2 nH or so will get you into trouble. A cap and its leads will get you to about 2 nH, then there's all your wirebonds, not to mention the load itself. Face-down ball bonded. ~0.5nH connections. We usually parallel several caps, on a lot of copper, to supply a lot of fast peak current, like through a gaasfet to drive an SRD or a laser. (Gotta get ready for a Board meeting. What a nuisance.) John Me, my wife and my oldest daughter ARE the board... no nuisance ;-) ...Jim Thompson I wasn't bad: Plant tour, 10 minutes; shareholders' meeting, 5 minutes; board meeting, 35 minutes; lunch at Zuni Cafe, 1 hour. Chairman John |
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