Specific Step Down Regulator

[garagefactory]

Hi everyone I have a question about voltage regulators. I'm trying to design a board for a project that requires 4 different voltages 1v, 1.15v, 3.3v and 5v each line draws approximately 2.25A and I am going to be stepping down to these voltages from a 3400mah li-ion battery at 7.4v. Does anyone have an ic or component they would recommend I use in this type of project thanks for the help!

[Nusa]

Something like this?
http://cds.linear.com/docs/en/datasheet/4644fd.pdf

If you meant 2.25A continuous load for each voltage, that battery isn't going to last very long.

[Rick Law]

2.25A in 4 voltages makes 9Amps total.  Most if not all 18650 protected batteries on the market wont even be able to put out 9Amp.

[Nusa]

2.25A in 4 voltages makes 9Amps total.  Most if not all 18650 protected batteries on the market wont even be able to put out 9Amp.

Bzzt, math error! You can't just add amps from different voltages together and get a meaningful result. Convert each load to watts, sum them, then divide by battery voltage to get current draw at the battery. Add a smidge for conversion losses and I get about 3.3 Amps. That's still a lot, but should be within the battery's ability. It just isn't going to last terribly long.

[mariush]

Maybe a couple of TPS54395PWPR ( 2 x 3A regulators) : http://www.digikey.com/product-detail/en/texas-instruments/TPS54395PWPR/296-30581-6-ND/3478059

Yeah, keep in mind that you have 1 x 2.25 + 1.15x2.25 + 3.3 x 2.25 + 5x2.25 = 23.5 watts. Assuming 85% efficiency, you're looking at ~ 27.5 watts or / 7.4v = 3.7A constant load on the battery. This may be a bit too much.

Can't you optimize your design so that you won't have 1.0v and 1.15v , couldn't you maybe make them 1.05v or something like that, to use just one regulator but designed for higher current? 

depending on how much room you have, it may be cheaper to have a stronger 1.15v rail (for 5A+ for example) and use a LDO to get 1.0v @ 2.25A from it. Maybe you're space constrained on the pcb and then the tiny losses (0.15v x 2.25a = 0.33w) would be acceptable. See for example ISL80103 from intersil or MIC59300

Linear parts are sexier but expensive and maybe harder to use (in particular the bga or lga parts)

[Rick Law]

2.25A in 4 voltages makes 9Amps total.  Most if not all 18650 protected batteries on the market wont even be able to put out 9Amp.

Bzzt, math error! You can't just add amps from different voltages together and get a meaningful result. Convert each load to watts, sum them, then divide by battery voltage to get current draw at the battery. Add a smidge for conversion losses and I get about 3.3 Amps. That's still a lot, but should be within the battery's ability. It just isn't going to last terribly long.

Not a math error.  My error is, since he is talking voltage regulation, I mind-locked into thinking he was using linear regulator which (unless I am mistaken) takes the same amps in as amps out and just drop the voltage.  So, he wants 2.25 amps out, he has to put 2.25 amps in.

Of course if he is bucking, than it doesn't need the same amp.