Regulator to replace LT1940?

[riotubes]

Hi,

I'd like to build a linear psu to replace a 5VDC 2a walwart that feeds an LT1940 dual step down, switching voltage regulator that generates a 3.3 and 1.2 VDC.

I could use an LT1121 for the 3.3V, but haven't worked with 1.2VDC. Any suggestions on a reg so I can toss the LT1940. This powers a cpu in squeezebox and am told that the tolerances must be pretty tight.

thanks!

 

[ezkcdude]

I don't understand why you're making it so complicated. I have a Squeezebox too. You just need another 5V, 2A wallwart. Just get the Elpac that everyone else uses. Why create a "clean" linear supply for something that has switching regulators, anyway?

 

[riotubes]

Hi, I don't use anything inside the SB except the cpu and logic. I don't use the dac or analog stage, and I'm planning to do away with the display. So I only need to power the cpu (1.2v) and logic (3.3v). I'd like to do away with the switching reg that powers these. I'm searching for a linear reg to power the 1.2v

 

[Stocker]

Diodes. They drop voltage. If you can regulate to 1.9-ish and slap a diode on there, you're done.

Just a thought.

 

[mako1138]

The LT1940 is rated for 1.4A, so you need to meet that spec. Go to Digikey and search for a 1.2V regulator with 1.5A or more.

The LT1121 is rated for 150mA. Is that enough, when the original part is rated for 1.4A?

 

[error401]

LP3892? PSRR and regulation specs are pretty good too.

LT1121 is definitely underspeced. Use the ubiquitous LM317, or pretty much anything else really.