[time-nuts] Power supply for time source concerns

[jimlux]

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 <jimlux at earthlink.net> wrote:
>   
>   On 12/22/19 1:18 PM, Poul-Henning Kamp wrote:
>> --------
>> In message <1958104416.2586171.1577043445646 at 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.
> 
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