[hpsdr] LPU & Multiple boards on Atlas

[Dick Faust]

You might consider using some 3A [like MR508] or  5A silicon power 
diodes in series to either replace the resistor or lower its value and 
power requirements.  It is an old trick.  At 2 - 3 Amps most power 
diodes exhibit slightly more than 0.6VDC drop so 4 in series would 
approach a 2.5V drop.  The diodes will still generate some heat, but not 
as much as a resistor.  Remember to keep the leads rather long as they 
are part of the heat sink for the chips.  Might also need some bypass 
caps to eliminate any RF.

I do not recall from memory the minimum supply voltage for the regulator 
[thats is why older guys get a data sheet for reference] , but  be sure 
you leave a little head room or the regulator will drop out.

Dick Faust K9IVB

Erich Heinzle wrote:
> ***** High Performance Software Defined Radio Discussion List *****
>
> I am about to build another LPU.
>
> would it be worth me adding a facility to power the 5V
> regulator with a separate lower voltage supply (i.e.
> less than 12V, i.e. perhaps 6V or 7v) to help it cope
> with multiple boards drawing high current, and by
> bypassing the dropping resistor, avoid the power
> dissipation/heat issues with high current draw at 5V?
>
> Or should I just have the option to bypass the 5V
> regulator entirely (as it is apparently limited to 2A),
> and make provision for an external 5V supply if required?
>
> Just thinking out loud.
>
> Cheers,
>
> Erich
> VK5HSE
>
>
>
>
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