Maybe I misinterpreted your post (#266), in response to the AD829 suggestion of Elso's?: -
"I am building one to see what happens. If it doesn't work, one can always power the IC from another superegulator!!!"
From which I can tell you it won't work, unless you make modifications.
Andy.
Hi,
Andy, does this mean that these regs shouldn't be used for supplying dac chips (could I use a ad817 to do this???) that run at 5v?
thanks Raja
Andy, does this mean that these regs shouldn't be used for supplying dac chips (could I use a ad817 to do this???) that run at 5v?
thanks Raja
Raj1 said:Hi,
Andy, does this mean that these regs shouldn't be used for supplying dac chips (could I use a ad817 to do this???) that run at 5v?
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Why not try it, and let us know.
I think there is an error in the instructions, on the -ve regulator. R8 and R9 are 1k regardless of the output voltage.
ALW - is this so?
No it doesn't; you can use the AD817 for 5V regs to things like DAC's.
Yes you're correct, the component overlay shows 1K's, these should be select on test / build. The parts list does correctly show the SOT nature of these resistors.
The output voltage calculations are the same as for the +ve reg.
Another one for the errata 😉
Andy.
Yes you're correct, the component overlay shows 1K's, these should be select on test / build. The parts list does correctly show the SOT nature of these resistors.
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ALW
How does the spec of the LED matter? Vishays are getting difficult to get!
😀 😀 😀
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ALW
How does the spec of the LED matter? Vishays are getting difficult to get!
😀 😀 😀
LED's
The Vishay data sheet is here.
The voltage drop of the LED will affect the current from the Isource, so something similarly specced will be most suitable.
I've used Green, Red and Yellow in the past, depending upon application.
The Vishays are really easy to get in the UK - why do you think they are hard to get, they are still current product: -
http://www.vishay.com/product?docid=83011&query=TLHG5205
I've just checked Farnell and they are ex-stock, currently.
Andy.
The Vishay data sheet is here.
The voltage drop of the LED will affect the current from the Isource, so something similarly specced will be most suitable.
I've used Green, Red and Yellow in the past, depending upon application.
The Vishays are really easy to get in the UK - why do you think they are hard to get, they are still current product: -
http://www.vishay.com/product?docid=83011&query=TLHG5205
I've just checked Farnell and they are ex-stock, currently.
Andy.
Re: LED's
The Vishays are really easy to get in the UK - why do you think they are hard to get, they are still current product: -
http://www.vishay.com/product?docid=83011&query=TLHG5205
I've just checked Farnell and they are ex-stock, currently.
Andy. [/B][/QUOTE]
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NOT EASY TO COMPREHEND FARNELL CATALOG AS TO WHAT IS WHAT. THE ONLY LISTED ELECTRONICALLY TLLR5401. ON THE PAPER CATALOG TLHR540X IS LISTED AS FAIRCHILD!!
What catalog no were you looking at?
The Vishays are really easy to get in the UK - why do you think they are hard to get, they are still current product: -
http://www.vishay.com/product?docid=83011&query=TLHG5205
I've just checked Farnell and they are ex-stock, currently.
Andy. [/B][/QUOTE]
-----------------------------------------------------------------------------
NOT EASY TO COMPREHEND FARNELL CATALOG AS TO WHAT IS WHAT. THE ONLY LISTED ELECTRONICALLY TLLR5401. ON THE PAPER CATALOG TLHR540X IS LISTED AS FAIRCHILD!!
What catalog no were you looking at?
Farnell
The Farnell no. is 656770.
The easiest way to find the parts is to use the advanced search and enter the Vishay no. (or any manufacturers no. - the Farnell website is crap for browsing!
If I get a moment, I'll tidy up the spreadsheet BOM with part no's for you and try and post it here.
Andy.
The Farnell no. is 656770.
The easiest way to find the parts is to use the advanced search and enter the Vishay no. (or any manufacturers no. - the Farnell website is crap for browsing!
If I get a moment, I'll tidy up the spreadsheet BOM with part no's for you and try and post it here.
Andy.
Re: Farnell
See post 192 of this thread and download the Attachment: wiki.zip, the partslist with farnell numbers is on the second sheet.
😎
ALW said:
See post 192 of this thread and download the Attachment: wiki.zip, the partslist with farnell numbers is on the second sheet.
😎
Re: Re: Clock Spikes
I shall soon settle this, by powering a Tent or Valpey Fisher clock with the 5V version, and measuring then listening to the combied units.
The Audiocom 5V regulator totally collapse when feeding 30mA or so to a XO; even though it is excellent with a resistor!
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I have just made the 5V version and loaded it to just below 200mA. With a small heatsink on Q1, it is running at around 60 C. I am using local sense.
I measured 4uV over 1MHz bandwidth; 2uV A weighted.
Next step, power an XO and see what happens
I shall soon settle this, by powering a Tent or Valpey Fisher clock with the 5V version, and measuring then listening to the combied units.
The Audiocom 5V regulator totally collapse when feeding 30mA or so to a XO; even though it is excellent with a resistor!
------------------------------------------------------------------------------
I have just made the 5V version and loaded it to just below 200mA. With a small heatsink on Q1, it is running at around 60 C. I am using local sense.
I measured 4uV over 1MHz bandwidth; 2uV A weighted.
Next step, power an XO and see what happens
Re: Clock Spikes
Besides that I tried that approach for a analog supply i.e. using the output as supply for the opamp, and it did not give any audible improvement.
For a supply for a clock circuit I don't believe any feedback from the output is good. Well that rules out the opamp..... Back to Jocko's follower?😉
The thread you advised a good place to start? It was one of the most confusing threads I ever participated in...... [/B][/QUOTE]
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Settled. I powered a 11.xx Tent XO with a few cm of twisted wire.
With no decoupling at the XO, there are spikes in the PS. However, a 620uF OSCON at thje XO pins knocked the measured noise level back to 2 uV 1MHz bandwidth. There are hf waves of about 1 mV on my scope with 60MHz probe.
Adding the OSCON to the board was less effective.
Also ALW is right, adding a 0.01 uF pp cap to C5 caused oscillations - nice looking sine wave.
Conclusion, the ALW regulator can be safely used on digital systems but I would advise measurement/extra decoupling/playing around with sensing to make the best out of it.
Thanks ALW.
Besides that I tried that approach for a analog supply i.e. using the output as supply for the opamp, and it did not give any audible improvement.
For a supply for a clock circuit I don't believe any feedback from the output is good. Well that rules out the opamp..... Back to Jocko's follower?😉
The thread you advised a good place to start? It was one of the most confusing threads I ever participated in...... [/B][/QUOTE]
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Settled. I powered a 11.xx Tent XO with a few cm of twisted wire.
With no decoupling at the XO, there are spikes in the PS. However, a 620uF OSCON at thje XO pins knocked the measured noise level back to 2 uV 1MHz bandwidth. There are hf waves of about 1 mV on my scope with 60MHz probe.
Adding the OSCON to the board was less effective.
Also ALW is right, adding a 0.01 uF pp cap to C5 caused oscillations - nice looking sine wave.
Conclusion, the ALW regulator can be safely used on digital systems but I would advise measurement/extra decoupling/playing around with sensing to make the best out of it.
Thanks ALW.
I would tend to avoid long remote sensing in high-bandwidth digital environments, choosing instead to get the reg's as close as practical to the cct.
Local decoupling is ALWAYS a good idea though in high frequency app's, you don't want the HF stuff flowing around large loops. The regulators bandwidth is finite and high frequencies are far better handled by a good cap close to the circuit in question. The wiring inductance is often enough to bring about stability at HF with high-Q caps, so it's worth looking at playing around a bit with the actual implementation.
Anyway, what does it sound like?
Andy.
P.S. Are you using the pre-reg, I strongly recommend it's use (as a tracking pre-reg), it improves line rejection by a significant amount.
Digital clock supply design
It is helpful to remember that there are three parameters that are of major importance in a regulator. Power supply rejection of input noise on the the supply to the regulator, low noise from the regulator's reference and error amplifier, and low output impedance (small changes in output voltage from changes in load current). It quite possible to optimize all three of these for a clock supply. I think it is a very reasonable assumption that audio frequency load current changes are negligible in a fixed frequency clock and very very small in even a VCO (voltage controlled oscillator). The load currents at the clock frequency and it's harmonics can be pretty high in amplitude. As such, I think that a low ESR cap (or caps) are doing the decoupling since the regulator output impedance has risen open loop output impedances at these RF frequencies. I wonder if remote sensing is even useful much less practical in this application. My line of attack would be to use local sensing on the supply and an RC network on the output of the supply of 0.5 ohms and 10 times the capacitance of the local RF/digital decoupling capacitance at the clock circuit. You can probably even get away with a small resistor (a couple of ohms down to maybe 0.5 ohms) or resistor damped air-core inductor in series with regulator output. I think I might start with a value of inductance that will form resonance at about 100KHz with the regulator output capacitor (not the digital decoupling cap which should be a much smaller value than the output cap at the regulator) and damp it with 1 to 10 ohms. This should achieve good stability along with the op amp based regulator's excellent low noise and PSSR, two things that should be very benificial to a low jitter clock circuit. Knowing what the current demands of your load are will help you optimize all these parameters simultaneously. These suggestions are a starting point and I recommend a bit of experimentation for your particular circuit.
It is helpful to remember that there are three parameters that are of major importance in a regulator. Power supply rejection of input noise on the the supply to the regulator, low noise from the regulator's reference and error amplifier, and low output impedance (small changes in output voltage from changes in load current). It quite possible to optimize all three of these for a clock supply. I think it is a very reasonable assumption that audio frequency load current changes are negligible in a fixed frequency clock and very very small in even a VCO (voltage controlled oscillator). The load currents at the clock frequency and it's harmonics can be pretty high in amplitude. As such, I think that a low ESR cap (or caps) are doing the decoupling since the regulator output impedance has risen open loop output impedances at these RF frequencies. I wonder if remote sensing is even useful much less practical in this application. My line of attack would be to use local sensing on the supply and an RC network on the output of the supply of 0.5 ohms and 10 times the capacitance of the local RF/digital decoupling capacitance at the clock circuit. You can probably even get away with a small resistor (a couple of ohms down to maybe 0.5 ohms) or resistor damped air-core inductor in series with regulator output. I think I might start with a value of inductance that will form resonance at about 100KHz with the regulator output capacitor (not the digital decoupling cap which should be a much smaller value than the output cap at the regulator) and damp it with 1 to 10 ohms. This should achieve good stability along with the op amp based regulator's excellent low noise and PSSR, two things that should be very benificial to a low jitter clock circuit. Knowing what the current demands of your load are will help you optimize all these parameters simultaneously. These suggestions are a starting point and I recommend a bit of experimentation for your particular circuit.
Anyway, what does it sound like?
Andy.
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One thing at a time; not yet at instal stage.
Made a 15V unit and this works well, with 4 uV/1MHz going into 150R resistor.
However, the D44xx got very hot and measured 90 C with an infra red thermometer (in practice higher) and definitelt needs a heat sink; so does the LM317.
Heatsinks should be part of the spec for use with anything other than nominal current.
Andy.
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One thing at a time; not yet at instal stage.
Made a 15V unit and this works well, with 4 uV/1MHz going into 150R resistor.
However, the D44xx got very hot and measured 90 C with an infra red thermometer (in practice higher) and definitelt needs a heat sink; so does the LM317.
Heatsinks should be part of the spec for use with anything other than nominal current.
I am glad to report as of today all North American shipments have been mailed.
That is if anyone cares enough to read my updates!
Regards
Anthony
That is if anyone cares enough to read my updates!
Regards
Anthony
Received my boards today…they look great.
A huge thank you to Anthony, Andy and all else involved in this group buy.
Your time, effort and expertise are very much appreciated. I know they’ll be great since I already have some boards that I bought from Andy last year.
You guys are great. My DAC, preamp and crossover will be very happy.
A huge thank you to Anthony, Andy and all else involved in this group buy.
Your time, effort and expertise are very much appreciated. I know they’ll be great since I already have some boards that I bought from Andy last year.
You guys are great. My DAC, preamp and crossover will be very happy.
I also received my boards last night, thanks to everyone who made this possible!
I'm compiling a parts list from Digikey.ca and Electrosonic, if any of the Canadian builders are interested. I've had to substitute some parts that are not available at either of these suppliers. Caps are Panasonic FC series, resistors are BC Components MBB0207 series (from Electrosonic, Digikey doesn't stock 0.6W resistors!). For the TL431 I picked a part by Texas Instruments.
I'm having trouble locating a proper LED though, my understanding is that it is a 5mm/T1-3/4 10mA 2.4V part, correct? Can anyone point me to a suitable part? The rest should be fine.
Thanks,
Ron
I'm compiling a parts list from Digikey.ca and Electrosonic, if any of the Canadian builders are interested. I've had to substitute some parts that are not available at either of these suppliers. Caps are Panasonic FC series, resistors are BC Components MBB0207 series (from Electrosonic, Digikey doesn't stock 0.6W resistors!). For the TL431 I picked a part by Texas Instruments.
I'm having trouble locating a proper LED though, my understanding is that it is a 5mm/T1-3/4 10mA 2.4V part, correct? Can anyone point me to a suitable part? The rest should be fine.
Thanks,
Ron
Thanks Anthony for the update!!
Yes we do care.
Although this just steps up the anticipation.
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Thanks.
Craig
Yes we do care.
Although this just steps up the anticipation.
--
Thanks.
Craig
I agree, although this shouldn't only be necessary for the pass device, at these currents.
The junction to ambient thermal resistance of the pass device is nominally 75 deg C / W. I use a pair of 15V reg's, without heatsinks and with a similar load and they don't get this hot.
It's easy to calculate this stuff, the pass device has 2.5V nom. across it (maintained by the pre-reg), so for your 15V reg, with a 150R load it's dissipating around 0.25 W.
The temp rise above ambient is nominally 0.25 x 75 = approx 19 deg.
If ambient is around 25 deg C then I'd expect a figure closer to 25 + 19 = 44 deg. Even with the large margins of error here that's a world away from 90 deg C.
Something doesn't seem right here - you do have the pre-reg configured in the tracking arrangement, don't you (i.e. adj terminal to super-reg output)?
For the pre-reg it obviously drops the remaining voltage, i.e. input voltage - (output voltage + 2.5V). In many cases this will need a heatsink, unless run close to dropout.
Andy.
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