Re: [time-nuts] power supply design Re: Slightly OT: interest in a four-output, > ultra-low jitter, synthesizer block?

[Gerhard Hoffmann]

Am 26.01.2018 um 05:26 schrieb Mark Goldberg:

On Thu, Jan 25, 2018 at 8:51 PM, jimlux  wrote:


What we've done is switcher from wide range bus (9-24V) to 8V, 60 dB
ultimate attenuation low pass, switcher 8V to 5V(e.g.), 60 db low pass,
linear with great HF rejection (i.e. the LT3042) to 3V


If it is any help to someone, I did some research on low noise regulators
to drive a low phase noise oscillator. You will have to look at this in a
fixed width font. LT3042 is indeed a spectacular part with way less noise
than the baseline LT3009. Hopefully no mistakes below. Pricing is about 2
years old.


Yes, the LT3042 is in a completely different league than the ordinary
LM317, LM350, LM2940, 7805. It has simply 40 dB less noise than the rest.

Don't overdo it with the output capacitor, 4.7u is ideal. 22u produces
a noise peak at 15KHz.

< 
https://www.flickr.com/photos/137684711@N07/24070698809/in/album-72157662535945536/ 
  >


The high current version with the external NPN is also fine.
< 
https://www.flickr.com/photos/137684711@N07/29452163806/in/album-72157662535945536/ 
>


The test circuit is quite small, 1:1 from the data sheet.
< 
https://www.flickr.com/photos/137684711@N07/29197476530/in/album-72157662535945536/ 
>


The steep rise below 100 Hz is an artefact of the too small coupling 
capacitor

of my preamp and the 1/f behavior of the 89441A that I used as FFT analyzer.

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Re: [time-nuts] power supply design Re: Slightly OT: interest in a four-output, > ultra-low jitter, synthesizer block?

[Mark Goldberg]

On Thu, Jan 25, 2018 at 8:51 PM, jimlux  wrote:

> What we've done is switcher from wide range bus (9-24V) to 8V, 60 dB
> ultimate attenuation low pass, switcher 8V to 5V(e.g.), 60 db low pass,
> linear with great HF rejection (i.e. the LT3042) to 3V
>

If it is any help to someone, I did some research on low noise regulators
to drive a low phase noise oscillator. You will have to look at this in a
fixed width font. LT3042 is indeed a spectacular part with way less noise
than the baseline LT3009. Hopefully no mistakes below. Pricing is about 2
years old.


Part Manufacturer  Price  Packages   mA  Added  Added  RMS
NoiseRMS Noise Spot Noise   Noise at 100 Hz  Noise at 1000
Hz  100 Hz Noise  1000 Hz Noise
 Caps   Resistors  10 Hz -
100 kHz  100 Hz - 100 kHz  10 kHz   nV/Sqrt(Hz)  nV/Sqrt(Hz)
Ratio dB  Ratio dB

uVrmsuVrms nV/Sqrt(Hz)

LT3009   Linear Tech  SC70-8 20
150 6000
2500  0.0   0.0
LT3042   Linear Tech   $4.90  10MSOP 3x3DFN  200 2 5
0.8210
1.5   -55.6 -64.4
ADM7154  Analog Dev$5.95  8LFCSP 8SOIC   600 4
1.6  0.9   1.5  10
1.8   -55.6 -62.9
TPS7A47  TI$4.69  UQFN20 10002
4   100
20-35.6 -41.9
LP38798  TI$3.19  WSON12  4X4800 2 2
5   100
40-35.6 -35.9
LP5907   TI$0.57  SOT23-5250 1
6.5 180
50-30.5 -34.0
LP5900   TI$0.70  WSON6  150 1
6.5 300
40-26.0 -35.9
MAX8510  Maxim $1.22  SC70-5 TDFN120
2  11
300  60-26.0 -32.4
LT1962   Linear Tech   $2.39  8MSOP  300 2
20  300
80-26.0 -29.9


Mark
W7MLG
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[time-nuts] power supply design Re: Slightly OT: interest in a four-output, > ultra-low jitter, synthesizer block?

[jimlux]

On 1/25/18 7:17 PM, Joseph Gwinn wrote:

On Thu, 25 Jan 2018 21:13:44 -0500, time-nuts-requ...@febo.com wrote:


Message: 2
Date: Thu, 25 Jan 2018 16:16:59 -0500
From: John Ackermann N8UR 
To: time-nuts@febo.com
Subject: Re: [time-nuts] Slightly OT: interest in a four-output,
ultra-low jitter, synthesizer block?
Message-ID: 
Content-Type: text/plain; charset=utf-8; format=flowed

Yes, I was planning to include bypasses, and I've been convinced to put
at least the 1.8V regulator on the board as well.  And to think about
the interconnects.


What I've seen widely done in circuits requiring low phase noise is to
have a cascade of regulators, all but the last one (that feeds the RF
component in question) beings switchers of different switching
frequency, with simple low-pass filters between the regulators, and
between the last regulator and the RF component being powered.
   Between the filtration due to the regulators and that due to the
LPFs, one can achieve very large ripple and noise attenuations.




What we've done is switcher from wide range bus (9-24V) to 8V, 60 dB 
ultimate attenuation low pass, switcher 8V to 5V(e.g.), 60 db low pass, 
linear with great HF rejection (i.e. the LT3042) to 3V


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