Re: [time-nuts] Power supply for time source concerns
I just found something funny. I have been thinking "clean" power supplies that connects to AC mains. Then I thought, what about lead acid batteries?? So I went to my lab and took some measurement. This is a 12V 7A lead acid sealed battery, the kind commonly found on UPS devices. The result? Surprise? The battery is oscillating at 5MHz and noise level is 15mV peak-to-peak Of course, not...! Battery is pure DC and while voltage might drift, this is not that. For the record, a charger of any kind is not hooked up. It's one battery all by itself. Battery is not oscillating but that's what the measurement actually shows. That brings another point in my quest to "clean" power source. It's not just the power supply but the whole lab eco system has to be considered. Having one master 24V source (my original plan) is not the answer if mV level noise is going to be a problem. This "discovery" puts whole new layer to having a nice power supply. Just as a point of reference, I hooked up a common cheap float charger. The charger itself has 2V p-p noise. Connected to battery, it still have 100mV p-p noise. There goes battery = noise sponge theory --- (Mr.) Taka Kamiya KB4EMF / ex JF2DKG On Tuesday, December 24, 2019, 3:00:50 PM EST, Bob kb8tq wrote: Hi > On Dec 24, 2019, at 6:40 AM, Poul-Henning Kamp wrote: > > > >> That again depends on topology and control type. The canned converters >> are almost always optimized to have the lowest number of switches and >> work with cheap magnetics (single coil) without easily entering >> problematic operation modes, noise is only a secondary concern. > > That depends a LOT on which canned converter you decide to buy, > if you only go after price, or W/mm³ capacity, then certainly yes. > > But for a one-off application like this, any money saved on a > cheap model is easily lost many times over in the trouble it will > cause. > > But returning to the original post: Has anybody ever characterized > how much difference it makes to use two different PSU's for heater > vs. electronics sides of telecom Rb's ? The “old time” answer was that a poorly regulated / poorly filtered supply was considered “ok” for a heater. For the active electronics you wanted something nice and stable / clean. To your point, once you get around to *measuring* this, stability wise that answer often does not hold up. Noise wise, you are right back to “what frequency?” …. The somewhat more complex “old time” answer was that you don’t want the honking big current of the heater coming off the supply you have tried so hard to super-regulate. ( = it’s the supply that’s the issue not the Rb it’s self). Obviously that’s going to depend on how the supply was designed. Of course next layer to the onion is …. where does the ground current go? …. hmm…. Bob > > I'm sure there is a reason why they make it two different pins ? > > -- > Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 > p...@freebsd.org | TCP/IP since RFC 956 > FreeBSD committer | BSD since 4.3-tahoe > Never attribute to malice what can adequately be explained by incompetence. > > ___ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] Power supply for time source concerns
Hi > On Dec 24, 2019, at 6:40 AM, Poul-Henning Kamp wrote: > > > >> That again depends on topology and control type. The canned converters >> are almost always optimized to have the lowest number of switches and >> work with cheap magnetics (single coil) without easily entering >> problematic operation modes, noise is only a secondary concern. > > That depends a LOT on which canned converter you decide to buy, > if you only go after price, or W/mm³ capacity, then certainly yes. > > But for a one-off application like this, any money saved on a > cheap model is easily lost many times over in the trouble it will > cause. > > But returning to the original post: Has anybody ever characterized > how much difference it makes to use two different PSU's for heater > vs. electronics sides of telecom Rb's ? The “old time” answer was that a poorly regulated / poorly filtered supply was considered “ok” for a heater. For the active electronics you wanted something nice and stable / clean. To your point, once you get around to *measuring* this, stability wise that answer often does not hold up. Noise wise, you are right back to “what frequency?” …. The somewhat more complex “old time” answer was that you don’t want the honking big current of the heater coming off the supply you have tried so hard to super-regulate. ( = it’s the supply that’s the issue not the Rb it’s self). Obviously that’s going to depend on how the supply was designed. Of course next layer to the onion is …. where does the ground current go? …. hmm…. Bob > > I'm sure there is a reason why they make it two different pins ? > > -- > Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 > p...@freebsd.org | TCP/IP since RFC 956 > FreeBSD committer | BSD since 4.3-tahoe > Never attribute to malice what can adequately be explained by incompetence. > > ___ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] Power supply for time source concerns
>That again depends on topology and control type. The canned converters >are almost always optimized to have the lowest number of switches and >work with cheap magnetics (single coil) without easily entering >problematic operation modes, noise is only a secondary concern. That depends a LOT on which canned converter you decide to buy, if you only go after price, or W/mm³ capacity, then certainly yes. But for a one-off application like this, any money saved on a cheap model is easily lost many times over in the trouble it will cause. But returning to the original post: Has anybody ever characterized how much difference it makes to use two different PSU's for heater vs. electronics sides of telecom Rb's ? I'm sure there is a reason why they make it two different pins ? -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] Power supply for time source concerns
Am 23.12.2019 um 16:03 schrieb jimlux: It is tough to build a "small" input filter that has good rejection at low frequencies (<100kHz?) Yes if you want a passive filter, but you can view an LDO as an active low-pass in some sense. Again you need to take care that noise cannot bypass it, but most of it should be conducted noise in the LF case. Active filtering is also a good option if the power you need to deliver is low. Buck converter to 8V (boost converters seem to have more noise) That again depends on topology and control type. The canned converters are almost always optimized to have the lowest number of switches and work with cheap magnetics (single coil) without easily entering problematic operation modes, noise is only a secondary concern. Producing less noise in the first place is possible if you change those constraints; i.e. allow more switches, more complicated energy storage (capacitors and magnetics) or employ control algorithms that are less robust and hence need to be tuned to the load to be stable. -- Achim. (on the road :-) ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] Power supply for time source concerns
On 12/23/19 1:08 PM, Charles Steinmetz wrote: I wrote: > To get even that far, one needs multiple shielding > (see list member Gerhard Hoffman's construction photos for ideas) John wrote: Being a relative newcomer here, how do I search the archives for a specific author's input? I found some random posts from Gerhard but I don't see how to search for all of his input to find these construction photos. Of course, the first step in searching is to get the author's name right, and I misled you in that regard. Gerhard's last name is "Hoffmann," with two "n"s. (Sorry, Gerhard!) As I recall, Gerhard maintains archived photos on one or more of the photo-sharing sites. Hopefully, he will see the thread and post further information. Best regards, Charles when doing google searches, add "site:febo.com" and that helps.. so hoffmann site:febo.com ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] Power supply for time source concerns
On 12/23/19 10:17 AM, Taka Kamiya via time-nuts wrote: I think the conversation is going into an area way beyond my initial intent. My goal is to have a "good enough" source for 24V to run multiple time sources. Yesterday, I measured the output of switcher I've been using for testing purpose only. Holy cow it's dirty! 120mV peak-to-peak wide band noise. Put one ferrite bead on plus side and it had an amazing result. Broadband noise disappearance and periodic pulse (still 120mV p-p) My goal is to have about 5mV p-p or lower capable of delivering 20Amp in switching arrangement. It's easy to do with linear regulators but it makes the room awfully warm. Why 5mV? Because it is good enough. If more is necessary, it will have to be dealt with locally inside the time source itself. Cabling can pick up that much easily. Check out Jim Brown K9YC's compendia of filters - he's done measurements on a variety of ferrite mixes in a variety of configurations (number of turns, number of cores, etc.) http://audiosystemsgroup.com/RFI-Ham.pdf http://k9yc.com/2018Cookbook.pdf He's done a lot of work to take the raw material data sheets and turn it into practical recipes. Of course, you could get yourself a copy of Snelling's book on "Soft ferrites: properties and applications" which is the recognized tome on this. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] Power supply for time source concerns
I wrote: > To get even that far, one needs multiple shielding > (see list member Gerhard Hoffman's construction photos for ideas) John wrote: Being a relative newcomer here, how do I search the archives for a specific author's input? I found some random posts from Gerhard but I don't see how to search for all of his input to find these construction photos. Of course, the first step in searching is to get the author's name right, and I misled you in that regard. Gerhard's last name is "Hoffmann," with two "n"s. (Sorry, Gerhard!) As I recall, Gerhard maintains archived photos on one or more of the photo-sharing sites. Hopefully, he will see the thread and post further information. Best regards, Charles ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] Power supply for time source concerns
I think the conversation is going into an area way beyond my initial intent. My goal is to have a "good enough" source for 24V to run multiple time sources. Yesterday, I measured the output of switcher I've been using for testing purpose only. Holy cow it's dirty! 120mV peak-to-peak wide band noise. Put one ferrite bead on plus side and it had an amazing result. Broadband noise disappearance and periodic pulse (still 120mV p-p) My goal is to have about 5mV p-p or lower capable of delivering 20Amp in switching arrangement. It's easy to do with linear regulators but it makes the room awfully warm. Why 5mV? Because it is good enough. If more is necessary, it will have to be dealt with locally inside the time source itself. Cabling can pick up that much easily. --- (Mr.) Taka Kamiya KB4EMF / ex JF2DKG On Monday, December 23, 2019, 1:09:58 PM EST, jimlux wrote: On 12/23/19 5:42 AM, Bob kb8tq wrote: > Hi > > If you dig into the app notes on the LT304x parts after a lot of extolling the > wonders and virtues, they eventually get into magnetic coupling between the > “upstream” and “downstream” bypass components. Taking care of that with > proper layout is possible, but non-trivial. And not entirely predictable by modeling, even with the fancy multiphysics signal integrity modeling. It is one of those things where you will probably need a few iterations. > > Is milivolts of noise “ok”? Maybe it is. There are a lot of devices out there > that > run with 10’s of milivolts of noise on the supply line. Do you need <100uV p-p > over 10KHz to 100 MHz? There are devices that do. If that’s what you need, > it’s going to be a struggle. There is no one single “good enough” number. > > The power supply world still stops at pretty low frequencies. Very common IC’s > these days are quite happy to produce crud at the “many GHz” level. There are > a few folks who carry around cell phones that put out signals up there as > well. > Regulator IC’s will only do part of the job, filtering in one form or the > other (likely > several forms) is still needed. Yes, I think, though, that filtering (even over multiple decades) is easier at higher frequencies - Assuming you can tolerate the IR voltage drop through the filters. > > Past that system layout begins to get into the act. You can spend a couple of > fun > weeks in intro level classes on this sort of stuff. You can be the prof > presenting the > class and pretty quickly get to “that would require some research” as the > answer > to this or that seemingly basic question. It’s not in any way a trivial topic. > > So what to do? > > Bottom line is still that test equipment is your friend. Spectrum analyzers > that cover > a wide range of frequencies (and have good sensitivity) *are* part of the > “kit” that > allows you to keep things quiet. You can only go just so far ( = not very > far) before > you are into the “verify” stage of things. Indeed sound cards and SDR’s can > collect > some of this data so there *are* a range of tools you can use. > > Checking cabling / grounding / cross talk is very much part of setting up any > RF > bench. It always has been. Tracking down that stupid whatever on the other > side > of the room that is putting out a ton of noise *is* part of the drill. > Repeating the > process from time to time also is part of the fun. Looking at the data you > collect to > spot “strange” stuff *is* part of the deal …… There is work involved and you > need > to understand what you are doing. > I think understanding how the effect of unwanted interference (by whatever path) manifests itself in the desired output is part of the challenge - In many cases, the most sensitive detector of interference is the unit under test (certainly this is the case for a low noise receiver). One thing that can help evaluate a design is it artificially introduce interference or noise into the power supply - if you can't see a change in the output of the UUT, then the filtering/isolation scheme must be working. If the artificial interference is at a level that is >> the level you'd see in expected use, then you're in great shape. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] Power supply for time source concerns
Date: Mon, 23 Dec 2019 07:51:49 -0500 From: Charles Steinmetz mailto:csteinm...@yandex.com>> To: time-nuts@lists.febo.com<mailto:time-nuts@lists.febo.com> Subject: Re: [time-nuts] Power supply for time source concerns Message-ID: <5e00b865.4000...@yandex.com<mailto:5e00b865.4000...@yandex.com>> Content-Type: text/plain; charset=utf-8; format=flowed Charles wrote: [... To get even that far, one needs multiple shielding (see list member Gerhard Hoffman's construction photos for ideas) and may very well need PC boards with more than two layers.] Being a relative newcomer here, how do I search the archives for a specific author's input? I found some random posts from Gerhard but I don't see how to search for all of his input to find these construction photos. Sorry to be so dim. Regards - John ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] Power supply for time source concerns
On 12/23/19 5:42 AM, Bob kb8tq wrote: Hi If you dig into the app notes on the LT304x parts after a lot of extolling the wonders and virtues, they eventually get into magnetic coupling between the “upstream” and “downstream” bypass components. Taking care of that with proper layout is possible, but non-trivial. And not entirely predictable by modeling, even with the fancy multiphysics signal integrity modeling. It is one of those things where you will probably need a few iterations. Is milivolts of noise “ok”? Maybe it is. There are a lot of devices out there that run with 10’s of milivolts of noise on the supply line. Do you need <100uV p-p over 10KHz to 100 MHz? There are devices that do. If that’s what you need, it’s going to be a struggle. There is no one single “good enough” number. The power supply world still stops at pretty low frequencies. Very common IC’s these days are quite happy to produce crud at the “many GHz” level. There are a few folks who carry around cell phones that put out signals up there as well. Regulator IC’s will only do part of the job, filtering in one form or the other (likely several forms) is still needed. Yes, I think, though, that filtering (even over multiple decades) is easier at higher frequencies - Assuming you can tolerate the IR voltage drop through the filters. Past that system layout begins to get into the act. You can spend a couple of fun weeks in intro level classes on this sort of stuff. You can be the prof presenting the class and pretty quickly get to “that would require some research” as the answer to this or that seemingly basic question. It’s not in any way a trivial topic. So what to do? Bottom line is still that test equipment is your friend. Spectrum analyzers that cover a wide range of frequencies (and have good sensitivity) *are* part of the “kit” that allows you to keep things quiet. You can only go just so far ( = not very far) before you are into the “verify” stage of things. Indeed sound cards and SDR’s can collect some of this data so there *are* a range of tools you can use. Checking cabling / grounding / cross talk is very much part of setting up any RF bench. It always has been. Tracking down that stupid whatever on the other side of the room that is putting out a ton of noise *is* part of the drill. Repeating the process from time to time also is part of the fun. Looking at the data you collect to spot “strange” stuff *is* part of the deal …… There is work involved and you need to understand what you are doing. I think understanding how the effect of unwanted interference (by whatever path) manifests itself in the desired output is part of the challenge - In many cases, the most sensitive detector of interference is the unit under test (certainly this is the case for a low noise receiver). One thing that can help evaluate a design is it artificially introduce interference or noise into the power supply - if you can't see a change in the output of the UUT, then the filtering/isolation scheme must be working. If the artificial interference is at a level that is >> the level you'd see in expected use, then you're in great shape. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] Power supply for time source concerns
Hi If you dig into the app notes on the LT304x parts after a lot of extolling the wonders and virtues, they eventually get into magnetic coupling between the “upstream” and “downstream” bypass components. Taking care of that with proper layout is possible, but non-trivial. Is milivolts of noise “ok”? Maybe it is. There are a lot of devices out there that run with 10’s of milivolts of noise on the supply line. Do you need <100uV p-p over 10KHz to 100 MHz? There are devices that do. If that’s what you need, it’s going to be a struggle. There is no one single “good enough” number. The power supply world still stops at pretty low frequencies. Very common IC’s these days are quite happy to produce crud at the “many GHz” level. There are a few folks who carry around cell phones that put out signals up there as well. Regulator IC’s will only do part of the job, filtering in one form or the other (likely several forms) is still needed. Past that system layout begins to get into the act. You can spend a couple of fun weeks in intro level classes on this sort of stuff. You can be the prof presenting the class and pretty quickly get to “that would require some research” as the answer to this or that seemingly basic question. It’s not in any way a trivial topic. So what to do? Bottom line is still that test equipment is your friend. Spectrum analyzers that cover a wide range of frequencies (and have good sensitivity) *are* part of the “kit” that allows you to keep things quiet. You can only go just so far ( = not very far) before you are into the “verify” stage of things. Indeed sound cards and SDR’s can collect some of this data so there *are* a range of tools you can use. Checking cabling / grounding / cross talk is very much part of setting up any RF bench. It always has been. Tracking down that stupid whatever on the other side of the room that is putting out a ton of noise *is* part of the drill. Repeating the process from time to time also is part of the fun. Looking at the data you collect to spot “strange” stuff *is* part of the deal …… There is work involved and you need to understand what you are doing. Bob > On Dec 22, 2019, at 8:29 PM, jimlux wrote: > > On 12/22/19 3:16 PM, Taka Kamiya via time-nuts wrote: >> Yes. >> I considered float charging a battery bank and switching power supply + >> linear regulator combination as well. >> Concern with the first is safety in charging. I was intending to use GEL >> cell lead acid battery. 24V chargers are plentiful but there is no telling >> what they actually do. Adding a series regulator won't work because of the >> required voltage drop with most of the 3 terminal kind. I still want to try >> this as it will double as UPS as well. >> Switcher + linear regulator sounds promising. One unknown is, how much high >> frequency ripples/noises those regulators actually remove. > > LT3042 removes 60-80 dB up to 10MHz. 20V, 200mA > https://www.analog.com/media/en/technical-documentation/data-sheets/3042fb.pdf > > CHeck out also the LT3045 (500 mA) > LT3093, LT3094 (negative voltages, 200, 500mA, 0.8 uV noise) > > > I guess I'll just have to try this out. Ferrite sleeves, low pass filters, > chokes, etc, etc, etc are under consideration. >> I have a very nice lab grade switching power supply but unfortunately, this >> stupid thing resets to ZERO every time power cycled and starts up in current >> limiting mode. Meaning if I forget to switch modes, it can go as high as 60 >> volts. By then, all devices are GONE! >> My main usage will be just for time standard for my lab. Stable 10MHz and 1 >> pps is all I need to sync everything up. I am not going to multiply output >> to GHz range or do anything else exotic. I wonder how much ripple will >> actually affect? >> --- >> (Mr.) Taka Kamiya >> KB4EMF / ex JF2DKG >> On Sunday, December 22, 2019, 6:00:32 PM EST, jimlux >> wrote: >>On 12/22/19 1:18 PM, Poul-Henning Kamp wrote: >>> >>> In message <1958104416.2586171.1577043445...@mail.yahoo.com>, Taka Kamiya >>> via t >>> ime-nuts writes: >>> First question to the group is, how do YOU manage this problem? >>> >>> It used to be that there were only one kind of switching power-supply: The >>> noisy ones. >>> >>> That is no longer true by definition, but there is no easy road to this >>> particular Damascus. >> My strategy is DC/DC converter to get close, and high PSRR LDO linear >> regulator to the final voltage. Close attention to the DC/DC converter >> input and output so you don't couple to the ultimate output through >> radiated or parasitic conducted paths. >> The LT3042 series regulators have high PSRR, are available with negative >> voltages now, and can be paralleled for more current capacity. >> ___ >> time-nuts mailing list -- time-nuts@lists.febo.com >> To unsubscribe, go to >>
Re: [time-nuts] Power supply for time source concerns
On 12/23/19 5:01 AM, Achim Gratz wrote: Am 22.12.2019 um 20:37 schrieb Taka Kamiya via time-nuts: > Most commercially manufactured time and frequency sources use > switching power supply. [...] The suggestion to "just use a linear power supply", especially if it was designed some decades ago is probably not getting the desired results these days. There is a lot more conducted noise on the power lines than there used to be, starting from several kHz right into RF territory. An excellent point - The plethora of "offline SMPS" such as phone chargers, and various and sundry USB power supplies, means that even if they have reasonable conducted emissions, there's a lot of them all contributing. Linear regulators generally have bad PSRR at higher frequencies (often starting to degrade in the low kHz region already) and unless you have a clean input supply you pass any HF noise almost directly to the load. SPS are not necessarily worse than linear supplies when it comes to noise, but it generally shows up in different places frequency-wise (the detailed characteristics depend a lot on the exact topology chosen, so that's a whole 'nother dimension of things to consider when chosing). It is also harder to contain the switching noise as you have several high-current loops typically whose area must be kept as small as possible to not radiate noise. Conducted noise can be more easily filtered, but it gets out both through the input and the output side. The input side is often neglected a bit, which can come back to bite you when you have multiple supply rails in the system. Most switching topologies (or at least the ones that can be "clean" enough for the purposes under discussion) will produce a triangular ripple at the output at the switching frequency. You can make it smaller and smaller at the expense of load regulation, but it usually is easier to just deal with whichever number of millivolts that you're left with by putting an LDO post-regulator directly at the load (you put it at the load so you have better regulation and you can also use the supply line between the SPS and the LDO as part of a Pi filter). The LDO needs to have good PSRR at the switching frequency and maybe the first or second harmonic, the rest of the spectrum should already have been dealt with by filtering. It is tough to build a "small" input filter that has good rejection at low frequencies (<100kHz?) What we wound up doing for a low noise design was cascade the following: Unregulated 9-15V bus input filter Buck converter to 8V (boost converters seem to have more noise) Buck converter to "usage voltage" + 0.5-1V (i.e. if it's destined for 3.3V, buck down to around 4-4.3V) Pi filter with 60 dB "design" attenuation (probably less on the board) Board to board connector Pi filter with 60 dB "design" attenuation LT3042 LDO to load. We did some experimentation to measure the voltage drop across the filters, and then adjusted the output of the second buck converter so the LDO would have enough headroom over temperature. The layout was 4 layer boards, nothing exotic, other than the usual separation of pre & post regulation power & ground planes. Late Jim Williams' (RIP) application notes are always a good read: https://www.analog.com/media/en/technical-documentation/application-notes/an70.pdf https://www.analog.com/media/en/technical-documentation/application-notes/an101f.pdf https://www.analog.com/media/en/technical-documentation/application-notes/AN118fb.pdf ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] Power supply for time source concerns
Jim wrote: LT3042 removes 60-80 dB up to 10MHz. 20V, 200mA https://www.analog.com/media/en/technical-documentation/data-sheets/3042fb.pdf Achieving 60-80 dB in practice with typical DIY printed circuit layout and construction (by this I mean amateur PCB layout, typical board-house fabrication, and typical amateur packaging) is extremely unlikely. Even 30 dB is highly optimistic. To get even that far, one needs multiple shielding (see list member Gerhard Hoffman's construction photos for ideas) and may very well need PC boards with more than two layers. Not impossible, but not what the average amateur is used to designing and building every day. Best regards, Charles ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] Power supply for time source concerns
Am 22.12.2019 um 20:37 schrieb Taka Kamiya via time-nuts: > Most commercially manufactured time and frequency sources use > switching power supply. [...] The suggestion to "just use a linear power supply", especially if it was designed some decades ago is probably not getting the desired results these days. There is a lot more conducted noise on the power lines than there used to be, starting from several kHz right into RF territory. Linear regulators generally have bad PSRR at higher frequencies (often starting to degrade in the low kHz region already) and unless you have a clean input supply you pass any HF noise almost directly to the load. SPS are not necessarily worse than linear supplies when it comes to noise, but it generally shows up in different places frequency-wise (the detailed characteristics depend a lot on the exact topology chosen, so that's a whole 'nother dimension of things to consider when chosing). It is also harder to contain the switching noise as you have several high-current loops typically whose area must be kept as small as possible to not radiate noise. Conducted noise can be more easily filtered, but it gets out both through the input and the output side. The input side is often neglected a bit, which can come back to bite you when you have multiple supply rails in the system. Most switching topologies (or at least the ones that can be "clean" enough for the purposes under discussion) will produce a triangular ripple at the output at the switching frequency. You can make it smaller and smaller at the expense of load regulation, but it usually is easier to just deal with whichever number of millivolts that you're left with by putting an LDO post-regulator directly at the load (you put it at the load so you have better regulation and you can also use the supply line between the SPS and the LDO as part of a Pi filter). The LDO needs to have good PSRR at the switching frequency and maybe the first or second harmonic, the rest of the spectrum should already have been dealt with by filtering. Late Jim Williams' (RIP) application notes are always a good read: https://www.analog.com/media/en/technical-documentation/application-notes/an70.pdf https://www.analog.com/media/en/technical-documentation/application-notes/an101f.pdf https://www.analog.com/media/en/technical-documentation/application-notes/AN118fb.pdf -- Achim. (on the road :-) ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] Power supply for time source concerns
On 12/22/19 3:16 PM, Taka Kamiya via time-nuts wrote: Yes. I considered float charging a battery bank and switching power supply + linear regulator combination as well. Concern with the first is safety in charging. I was intending to use GEL cell lead acid battery. 24V chargers are plentiful but there is no telling what they actually do. Adding a series regulator won't work because of the required voltage drop with most of the 3 terminal kind. I still want to try this as it will double as UPS as well. Switcher + linear regulator sounds promising. One unknown is, how much high frequency ripples/noises those regulators actually remove. LT3042 removes 60-80 dB up to 10MHz. 20V, 200mA https://www.analog.com/media/en/technical-documentation/data-sheets/3042fb.pdf CHeck out also the LT3045 (500 mA) LT3093, LT3094 (negative voltages, 200, 500mA, 0.8 uV noise) I guess I'll just have to try this out. Ferrite sleeves, low pass filters, chokes, etc, etc, etc are under consideration. I have a very nice lab grade switching power supply but unfortunately, this stupid thing resets to ZERO every time power cycled and starts up in current limiting mode. Meaning if I forget to switch modes, it can go as high as 60 volts. By then, all devices are GONE! My main usage will be just for time standard for my lab. Stable 10MHz and 1 pps is all I need to sync everything up. I am not going to multiply output to GHz range or do anything else exotic. I wonder how much ripple will actually affect? --- (Mr.) Taka Kamiya KB4EMF / ex JF2DKG On Sunday, December 22, 2019, 6:00:32 PM EST, jimlux wrote: On 12/22/19 1:18 PM, Poul-Henning Kamp wrote: In message <1958104416.2586171.1577043445...@mail.yahoo.com>, Taka Kamiya via t ime-nuts writes: First question to the group is, how do YOU manage this problem? It used to be that there were only one kind of switching power-supply: The noisy ones. That is no longer true by definition, but there is no easy road to this particular Damascus. My strategy is DC/DC converter to get close, and high PSRR LDO linear regulator to the final voltage. Close attention to the DC/DC converter input and output so you don't couple to the ultimate output through radiated or parasitic conducted paths. The LT3042 series regulators have high PSRR, are available with negative voltages now, and can be paralleled for more current capacity. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] Power supply for time source concerns
Yes. I considered float charging a battery bank and switching power supply + linear regulator combination as well. Concern with the first is safety in charging. I was intending to use GEL cell lead acid battery. 24V chargers are plentiful but there is no telling what they actually do. Adding a series regulator won't work because of the required voltage drop with most of the 3 terminal kind. I still want to try this as it will double as UPS as well. Switcher + linear regulator sounds promising. One unknown is, how much high frequency ripples/noises those regulators actually remove. I guess I'll just have to try this out. Ferrite sleeves, low pass filters, chokes, etc, etc, etc are under consideration. I have a very nice lab grade switching power supply but unfortunately, this stupid thing resets to ZERO every time power cycled and starts up in current limiting mode. Meaning if I forget to switch modes, it can go as high as 60 volts. By then, all devices are GONE! My main usage will be just for time standard for my lab. Stable 10MHz and 1 pps is all I need to sync everything up. I am not going to multiply output to GHz range or do anything else exotic. I wonder how much ripple will actually affect? --- (Mr.) Taka Kamiya KB4EMF / ex JF2DKG On Sunday, December 22, 2019, 6:00:32 PM EST, jimlux wrote: On 12/22/19 1:18 PM, Poul-Henning Kamp wrote: > > In message <1958104416.2586171.1577043445...@mail.yahoo.com>, Taka Kamiya via > t > ime-nuts writes: > >> First question to the group is, how do YOU manage this problem? > > It used to be that there were only one kind of switching power-supply: The > noisy ones. > > That is no longer true by definition, but there is no easy road to this > particular Damascus. My strategy is DC/DC converter to get close, and high PSRR LDO linear regulator to the final voltage. Close attention to the DC/DC converter input and output so you don't couple to the ultimate output through radiated or parasitic conducted paths. The LT3042 series regulators have high PSRR, are available with negative voltages now, and can be paralleled for more current capacity. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] Power supply for time source concerns
On 12/22/19 1:18 PM, Poul-Henning Kamp wrote: In message <1958104416.2586171.1577043445...@mail.yahoo.com>, Taka Kamiya via t ime-nuts writes: First question to the group is, how do YOU manage this problem? It used to be that there were only one kind of switching power-supply: The noisy ones. That is no longer true by definition, but there is no easy road to this particular Damascus. My strategy is DC/DC converter to get close, and high PSRR LDO linear regulator to the final voltage. Close attention to the DC/DC converter input and output so you don't couple to the ultimate output through radiated or parasitic conducted paths. The LT3042 series regulators have high PSRR, are available with negative voltages now, and can be paralleled for more current capacity. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] Power supply for time source concerns
Back when I used to accumulate time nuts gear, I also used to accumulate various linear power supplies (mostly surplus / used HP lab supplies.). Approx 10 years later I should probably should look at the noise levels, regulation etc again. I also have a 24 volt lead acid battery system for backup in the event of a power failure and for use if I want to avoid using AC powered supplies. One of my nagging / never resolved issues was how to arrange for long term 24 volt backup power for my BVA OCXO. The 24 volt backup battery bank is float charged at somewhat more than 24 volts, and I was hesitant to subject the BVA to those voltages. The short term solution was to run the BVA from an HP linear lab supply that in turn is powered from a UPS. I never got around to replacing that with something more elegant. Mark S m...@alignedsolutions.com 604 762 4099 > On Dec 22, 2019, at 11:37 AM, Taka Kamiya via time-nuts > wrote: > > Most commercially manufactured time and frequency sources use switching power > supply. However, when contacted, tech support for SRS says, in regards to > PRS-10, use linear power supply. I am guessing, when manufacturers design > complete units, they take switching noise into consideration and deal with it > with filtering, etc. > I've seen data on TVB's site and others that demonstrates effects of power > supply noise. > Now, when I make DIY timing sources, I started including linear power > supplies. My PRS-10/GPS unit has 2.4A 24V linear supply for PRS10 and > switching supply for stuff that really doesn't care. It seem to work well. > But the problem is HEAT! Almost all timing devices are heat sensitive and > drift accordingly. Open frame linear supplies has efficiency of somewhere > around 65 to 70%. I could, for example, partition inside the case and fan > cool the P/S only but doing so for every single DIY unit becomes tedious. > First question to the group is, how do YOU manage this problem? > My thought now is, what about making an external linear supply ONLY and > supply all the voltages connected units could possibly need. I could fan > cool that! I happen to have a rack mounted UPS unit that is well beyond > service life. I can gut it and stuff open frame supplies to 24V, +/-12V, and > 5V. Does anyone see issue with this? Of course, on timing device side, I > will have to put large enough cap to decouple. > PS. I was bit by a telecom surplus time source bug. I have various one > already running and more on the way. > > --- > (Mr.) Taka Kamiya > KB4EMF / ex JF2DKG > ___ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] Power supply for time source concerns
Hi Each project is a different “experience”. Some things are way more susceptible to switching noise than others. Some switchers put out way more noise than others. You would not run a linear supply on a computer. The low noise front end of a radio is going to need a quiet supply ….. There are a lot of linear supplies that come in dissipating more heat than they deliver to the load. You can also do fancy designs that are up above 90% efficient. (count on using BGA’s for that one ….). First and easiest question: Does this beast *really* need to be powered up all the time? Second question: really :) There aren’t a lot of devices that need to be / should be run 100% of the time …. My biggest answer - turn it off. Bob > On Dec 22, 2019, at 2:37 PM, Taka Kamiya via time-nuts > wrote: > > Most commercially manufactured time and frequency sources use switching power > supply. However, when contacted, tech support for SRS says, in regards to > PRS-10, use linear power supply. I am guessing, when manufacturers design > complete units, they take switching noise into consideration and deal with it > with filtering, etc. > I've seen data on TVB's site and others that demonstrates effects of power > supply noise. > Now, when I make DIY timing sources, I started including linear power > supplies. My PRS-10/GPS unit has 2.4A 24V linear supply for PRS10 and > switching supply for stuff that really doesn't care. It seem to work well. > But the problem is HEAT! Almost all timing devices are heat sensitive and > drift accordingly. Open frame linear supplies has efficiency of somewhere > around 65 to 70%. I could, for example, partition inside the case and fan > cool the P/S only but doing so for every single DIY unit becomes tedious. > First question to the group is, how do YOU manage this problem? > My thought now is, what about making an external linear supply ONLY and > supply all the voltages connected units could possibly need. I could fan > cool that! I happen to have a rack mounted UPS unit that is well beyond > service life. I can gut it and stuff open frame supplies to 24V, +/-12V, and > 5V. Does anyone see issue with this? Of course, on timing device side, I > will have to put large enough cap to decouple. > PS. I was bit by a telecom surplus time source bug. I have various one > already running and more on the way. > > --- > (Mr.) Taka Kamiya > KB4EMF / ex JF2DKG > ___ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] Power supply for time source concerns
In message <1958104416.2586171.1577043445...@mail.yahoo.com>, Taka Kamiya via t ime-nuts writes: > First question to the group is, how do YOU manage this problem? It used to be that there were only one kind of switching power-supply: The noisy ones. That is no longer true by definition, but there is no easy road to this particular Damascus. I have had good results modernizing my HP5065A with a high end DC/DC converter, in order to reduce the heat, and in this particular case, improve stability: http://phk.freebsd.dk/hacks/HP5065A/20150930_dcdc/ Almost no switchmodes (AC/DC or DC/DC) are spec'ed to run into a serious pi-filter, but so far I have never had problems with it. The best way to find out if your filtering works, is to switch the supply between lead-acid (possibly with a linear regulator) and the switch-mode solution, and see if you can measure any kind of difference, be it frequency stability or noise spectrum. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
