Recommend a DC-DC converter IC

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sefton

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pcb l4978

Can someone recommend a DC-DC step down converter IC which works at a high switching frequency, uses few components and is not too expensive. I require a high switching frequency (about 1 Mhz) so that the components will be small. Specs: Input 12V, Output 5V @ 1A and 3.6V @ 1A.
I can use either a dual converter or 2 single converters.
The LT1940 is perfect except that it is quite expensive - about $7 over here.
Any suggestions ?
 

You can take a chip, which is older and not so expensive, for example si9145 from Siliconix.

Gomez
 

Thanks Gomez, but the si9145 has a maximum input of 7V - any other suggestions would be welcome.
 

Hi;
you can use L4978, or L4972 (i think!).
i use L4978 for some of my project and i think it is perfect.
with good efficiancy and smal size, (no need to heat sink).

Regards
Davood
Amerion
 

you may try this:
 

Thanks Davood, the L4978 is not bad, but it only works up to 300 kHz, and I dont have much space on my pcb for big inductors, etc.
Khongai, that link is for a linear regulator, but thanks.
 

Dear sefton;
may be you know, step down switching regulator can work in 2 mode.
continus current and non continus currect mode!!
if you insist to use small inductor, your current model going to discret (non continus) mode. it is not bad.

Regards
Davood Amerion
 

Thanks Davood

What I meant was the LT1940 runs at 1 MHz which means you can use smaller inductor and capacitor, but maybe I can use 300 Khz.
 

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