Battery power supply DC-DC which?

[nachus001]

Hi all:

I´m designing a battery powered Pow supply as a module to an existing equipment.

My already designed board needs 3.3V and 5V which I normally get from a mains connected transformer, and is provided thru a 5v and 3.3V LDO's.

But now I need to connect a NiMh battery pack (4 AA cells in series) to make the board autonomous.

I investigated on the myriad of DC-DC converters in the market , but the problem is that the vast majority of them does have a minimum VCC of 3V (buck or boost mode)

There are some ON semi parts like the MC33463 with a minimum VCC of 0.9 V
but I don´t know how much standard they are. (they are sold in reels of 3K pcs and I need a few 100's)

On the other hand I've found the ubiquitous LM1578 to have a 2V min VCC and i think if I run it bootstraped this value could go lower.

Now tell me please which IC do you use for maximum battery life as a stepup DC DC converter for such applications.
I plan to convert from battery -max 4.8V to 6.6V then (using LDO's postregs) to 5V
and 3.3V

Thanks in advance

Nachus

 

[VVV]

So what is the absolute minimum input voltage for a 4-pack AA NiMH ?
I use in a design a Maxim MAX668. Take a look at it. It might help. The quiescent current is 220uA.
Linear Technology also offer something, as well as National and Texas Instruments.

As far a s these parts being standard, that is really a remote possibility. It's only the old LM... that are being made by more than one manufacturer. I think some National parts are second-sourced by Micrel, too.

 

[moda]

Ti has some parts that will do what you need.
look at some parts:
https://focus.ti.com/lit/ds/symlink/bq24205.pdf

 

[tocal09]

I don't know much but I used Lm317 for project similar your but it's voltage is higher (7VDC) .In my town ,it's hard to find types as you have