[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-request at febo.com wrote:
>>
>> Message: 2
>> Date: Thu, 25 Jan 2018 16:16:59 -0500
>> From: John Ackermann N8UR <jra at febo.com>
>> To: time-nuts at febo.com
>> Subject: Re: [time-nuts] Slightly OT: interest in a four-output,
>> 	ultra-low jitter, synthesizer block?
>> Message-ID: <df6ea5f9-50b4-ecef-7eae-a7bc391fb03b at febo.com>
>> 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