[Arm-netbook] eoma68 router pcb

[luke.leighton]

On Thu, Nov 14, 2013 at 2:28 PM, Derek <dlahouss at mtu.edu> wrote:
> Christopher Thomas <christopher <at> firemothindustries.com> writes:
>
>> PYB20-Q24-S5 is an isolated supply that will output 5V at 4A.
>> But that digikey pricing suggests their not economical
> yet.http://www.digikey.com/product-search/en/power-supplies-board-mount/dc-dc-converters/4325599?k=PYB20-Q24-S5
>>
>>
>> While not the best for the job, it's certainly appealing at .22c versus
> $39.

 the current solution i've put in is around the $1, $1.50 mark.
however as christopher points out and looking at the datasheet the
thermal characteristics may be um.... well, you'd better have a metal
heat sink basically.  so buck converter it's more likely to be.

> But taps out at 3A. if there's a way to cull some wattage from the 20w
> point.

 nope.  2x 5V USBs (0.5A rated each) so that's 5W, 2x 3.3V USBs
(over-current because they're MiniPCIe cards - some of the 3G MiniPCIe
boards draw 0.7A) so that's still 2.5W each x 2 making 10W.  the
RTL81366 is 3W because it's 5-port Gigabit - we're lucky it's even as
low as 3W.  and the CPU Card is going to be around 4 (any more is
pushing it).

 10+3+4 = 17.

 so... 5V * 3A = 15W is not enough.

>
> What about running the voltage regulators in parallel?  2 * 3A = 5.5A, or so.

 maybe... except if it's double the cost of the components to do the
same job, why would you do that? :)

> http://electronicdesign.com/power/double-your-output-current-parallel-voltage-regulators

 will take a look this evening.

 l.