Recommend a DC-DC converter IC

[sefton]

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 ?

 

[Gomez]

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

Gomez

 

[sefton]

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

 

[Davood Amerion]

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

 

[khongai]

you may try this:

 

[sefton]

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.

 

[Davood Amerion]

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

 

[sefton]

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.