Converter question

[squirrel64]

I was looking at the site that sells these http://www.mdfly.com/index.php?main_page=product_info&products_id=55

I noticed near the bottom of the page it stated this *Note: The input voltage must be 3V higher than the desired output voltage.

Have you guys been doing this or did I miss something ?

 

[Para]

I was looking at the site that sells DC-DC Step-Down Converter Module [POW-SD3018] - $6.95 : MDFLY electronics, Your electronics supplier!

I noticed near the bottom of his website it said *Note: The input voltage must be 3V higher than the desired output voltage.

Have you guys been doing this or was I have I missed something ?

You missed the link....fix that so people know what you are referring to

See....it only shows up in a response.

 

[squirrel64]

sorry,,,, internet going in and out tonight

 

[dgr]

Hop over to this thread.
http://www.e-cigarette-forum.com/fo...vv-mod-w-switching-regulator.html#post1886821

I'd say that the 3V differential isn't correct based on looking at the output on that page. There's also a link to that same seller on ebay but they are in stock.

 

[squirrel64]

Yeah that was the thread I was following but I never saw anything about the differential. Thanks

 

[Switched]

I believe the reference means you need at least 6V for the reg to operate e.g a 3V delta from nominal required input. Mine works fine.

 

[dgr]

squirrel,
There is a huge datasheet available on that chip. My reading of the charts on page 7 and 8 says the minimum operating voltage is 3 to 4 V and the voltage differential is < 1.75 V http://www.national.com/ds/LM/LM2576.pdf

I don't have any real world experience with that chip. However, on the earlier thread we were discussing, he shows 5.8V off of two 3.7 V batteries. Even if they were just charged and were near 4.2 V, that is 2.6V differential, with the average charge of 3.7, it would be 1.6V differential.

 

[squirrel64]

Thanks guys,,,, appreciate your input