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Owen
03-23-2007, 01:34 PM
I am revising a pcb board I just built to handle a larger range of voltages (12v-24v). My previouse design used a single linear regulator to supply 5v and a second regulator to supply 3.3v to the propellar chip but the linear regulator although it can handle the large voltage difference it gets Hotter than I would like. I am thinking about using a switching regulator instead to go from 24v to 5 and then the same linear regulator to go to 3.3v for the propellar chip. I'm a little worried about the switching regulator creating noise problems, most notably for the bluetooth module on the board that acording to spark fun electronics web site it is very sensitive to proper voltage and low noise power. I dont know that the bluetooth would be a problem given that it's power would be coming from the 3.3v linear regulator but I have read that switching regulators can be a problem with RF devices and some times need to be shielded (which I would like to avoid). Can anyone give me some advice as too what switching regulator would be good or if a switching regulator should be avoided all together.

thanks

Owen

Phil Pilgrim (PhiPi)
03-23-2007, 01:55 PM
Linear Technology has a low-noise switching regulator chip that might work for you. Here's an app note (http://www.linear.com/pc/downloadDocument.do?navId=H0,C1,C1003,C1042,C1034, D4422).

-Phil

stamptrol
03-23-2007, 10:17 PM
I use Linear Tech's PT5101 sw. regs. They are rock solid, don't need heat sinks, don't heat up, and with the recommended output cap don't generate any harmful noise. Also available in a range of output voltages.

Digikey has over 6000 in stock as we speak.

Cheers,

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Tom Sisk

http://www.siskconsult.com

Owen
03-24-2007, 01:43 AM
the pt 5101 looks good and simple given it is a three terminal unit with all its components on board I think I'll give it a try. have you sed the srface mount version? I'm wondering how it would hold up to being reflow soldered? thanks for the sujestion.

owen

stamptrol
03-24-2007, 03:23 AM
I use mostly through-hole components. Note that you can get both a vertical arrangement and one that hugs the board.

But, if they're selling surface mount, I'm sure they can take process heat.

Cheers,

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Tom Sisk

http://www.siskconsult.com