AVR-Chat

On Saturday 25 September 2004 10:31, jay marante wrote:

[top-post fixed and excessive quoting deleted!]

> Bernd Felsche wrote:
>> Dave VanHorn wrote:
>> > At 12:23 PM 9/24/2004, jay marante wrote:
>> > >i don't know the rating of my heatsink. anyway, my final board is
>> > >already done. i was just curious why such problem and maybe i can
>> > >work on it without changing my board. maybe the only way to solve
>> > >it is to find a 5V relay or lower down the input voltage.

>> > The regulator heat issue is simply the result of using a linear
>> > regulator in a high current application, with high input-output
>> > differential. Heat = (Vin-Vout)*Current

>> As a solution to the issue of having alread made PCB's and then
>> finding that a linear regulator generates too much heat; one could
>> replace the linear component with a simple switching regulator on a
>> daughter-board that connects to 3 pads on the PCB designated for the
>> linear reg.. The input cap and heat sink can probably be down-sized
>> to make room for the daughter-board if space is tight.

> any particular part number for the switching regulator, 5V at
> about 1A from TI that can replace the 7805?

No single component will replace it, AFAIK. Hence _daughter_board_.
Most semiconductor manufacturers make switchmode controllers. The
high current output requirements are usually met by using an
external power transistor, switched by the controller chip.

It shouldn't take you long to find reference material including
sample applications on the web site of your preferred silicon
pusher.

-- 
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