[time-nuts] Switching regulator replacement for 7805

[jimlux]

On 12/4/16 2:59 PM, Attila Kinali wrote:
> On Sun, 4 Dec 2016 13:28:44 -0800
> jimlux <jimlux at earthlink.net> wrote:
>
>> I little series L and another C (so you have a pi low pass) can make a
>> huge difference.  If the load current is reasonably constant, then the
>> drop across the series R of the L will be constant, so you can bump the
>> dc/dc output to compensate.  It's pretty easy to get 60dB of rejection
>> from a C-L-C pi, and for 2MHz, the parts are physically small.
>
> Wouldn't it be better to use a ferrite bead instead, for this application?
> The much lower series capacitance and thus higher self-resonance frequency
> should help damping the spurs.
>
sure, if you can get enough L.  The other thing is that SMD inductors 
can be placed by machine, which isn't necessarily the case with ferrite 
beads (depending on how you do them).