[hpsdr] [Fwd: Re: Tiny Demeter]

[Ahti Aintila]

Jeroen and Greg,

It may be a good idea to use discrete linear regulators together with
switch mode preregulators assuming that you can prevent the conduction
and radiation of the switching transients.
In order to keep the power dissipation low in the series pass
transistors, use power MOSFETs with the drain on the output side. That
way you can use minimal preregulator output voltage and still provide
good gate voltage level to the MOSFET. Naturally you have to use
P-channel devices for the positive voltages and N-channel for the
negative voltages.

73, Ahti OH2RZ


On 15/06/2008, Greg - ZL3IX <zl3ix at inet.net.nz> wrote:
> ***** High Performance Software Defined Radio Discussion List *****
>
> Hi folks,
>
> Phil VK6APH asked me to comment on the proposal for Tiny Demeter.  My
> comments and his reply copied below.
>
> 73, Greg, ZL3IX
>
> Hi Greg,
>
> Agree with your comments - we may want to have the GPS power on at all times
> to lock the associated xtal.  Suggest we have this discussion on the forum
> so that others can join in on the suggestions. Would you like to move you
> comments overthere.
>
> Thanks
>
> Phil...
> ----- Original Message -----
> From: "Greg - ZL3IX" <zl3ix at inet.net.nz>
> To: "Phil Harman" <phil at pharman.org>
> Sent: Sunday, June 15, 2008 3:29 AM
> Subject: Tiny Demeter
>
>
>> Hi Phil,
>>
>> I had a look at this as you asked.  Just two comments.
>>
>> 1)  I would use the DC/DC converter to pre-reg the 5V supply to, say
>> 6V.  As it is, that series pass transistor is dissipating over 12 W at
>> 1.5A output.  The -12V can then be taken from a flyback winding or
>> something like that.
>> 2) The original Demeter spec talks about a supply for a GPS module.
>> Many of these require 3V3 today.  Not sure if Tiny is also supposed to
>> power a GPS module, but if so, this should be taken into account.  Could
>> be a linear reg from the 6V, as these modules don't draw a lot of current.
>>
>> My 2 cents.
>>
>> 73, Greg
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