[Elecraft] [KX3] Boost Buck 13.8 V Regulator

[Rich Heineck]

An LDO is also a simple option for a higher voltage pack.   KX3 RX 
current decreases as voltage goes up due to the internal switching 
regulators, but minimum TX current at 10W out will likely be somewhere 
around 13V.  The optimum between the two will probably be around 13.5V, 
so that would be a good place to set the LDO output. An LDO with very 
low  drop is the MIC29502.   Typical dropout voltage for 2A will be 
about 200mV, and at RX currents will be around 65mV.  This low a drop 
really isn't necessary here though.

But if the goal is to run the TX at 10W CW, the best power efficiency 
will occur with an external supply voltage ~11.8V (or the lowest voltage 
before rollback to 5W).  So an efficient buck regulator set for about 
11.8V ought to give the best battery life. The trade-off will be TX SSB 
IMD, where a higher voltage will help.

73,
Rich  AC7MA


On 05/12/2013 11:38 PM, Glen Torr wrote:
> Hi All,
>
> I have a KX3 and am doing some SOTA activations.
>
> I have obtained a 4S LiPo battery which is somewhere north of 16 V with
> full charge.
>
> I would like to get a DC-DC regulator as a more elegany solution than
> series diodes.
>
> I have searched and searched but no solid outcomes.
>
> Anyone have any input on where to find such a regulator?
>
> Many Thanks,
>
> Glen
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