[time-nuts] FE-5680A Voltage?

[Orin Eman]

Yes, my reading of the datasheet was the same.  18V in would be fine for
15V output.  My concern would be how noisy the output would be.  I have 9
of the from China ebay boards here (gave one to my boss to play with).  I
should wire one up and take a look.  At any rate, I think a turn or two of
the output wires through a ferrite bead would be in order.  The data sheet
shows a secondary filter of 3uH/180uF as well which I'd certainly want to
use to feed a 5680A.  Shouldn't do any harm, might do some good.

Orin.


On Thu, Sep 12, 2013 at 7:19 PM, Robert LaJeunesse <
rlajeunesse at sbcglobal.net> wrote:

> Looking at the LM2596 datasheet the switch transistor saturation voltage
> is 1.5V max at 3A (1.16v typ). That and an educated guess of about 0.25V
> for inductor loss combine to set the minimum difference between input and
> output. The 1.23V reference is about +/-3% accurate, so after setting the
> "buckboard" to 15.00V out (at 25C) expect it to shift at most 0.5V over
> time and temp. Add that to the minimum in-out difference and now you are at
> a minimum safe input of 2.25V above the nominal 15V output, or 17.25V in.
>  An old 19V 3A laptop supply might be a good supply to use for this, if you
> were local I'd hand you one.
>
> As for efficiency, that just tells you the amount of heat the regulator,
> plus inductor, plus diode, etc. will throw off. FWIW the datasheet Figure 5
> indicates you should expect about 88% or better efficiency for 15V out and
> at least 2V higher input voltage. (Doing some switching power supply design
> for a living does help with my understanding of them, but not ever enough!)
>
> Bob LaJeunesse
>