Arduino Forum

Using Arduino => General Electronics => Topic started by: bratan on Jan 02, 2013, 05:53 pm

Title: 3.3 V regulator recommendation?
Post by: bratan on Jan 02, 2013, 05:53 pm
Which voltage regulator would you recommend for SD/MicroSD card VCC power? My input is 5 Volts which powers ATMega644p, so I need to down-convert it to 3.3 Volts to supply power to MicroSD card.  Again this is just to VCC card, I already purchased CD4050BE HEX converter data voltage lines.
SMD or Thru the hole are both ok :) Looking for most efficient one...
Title: Re: 3.3 V regulator recommendation?
Post by: ivanseidel on Jan 02, 2013, 06:03 pm
I always use the "LM1117". Can output a maximum current of 800mA.
It's really easy to find in stores, exists in DIP and SMD models, and is really cheap.
http://www.ti.com/lit/ds/symlink/lm1117-n.pdf
Title: Re: 3.3 V regulator recommendation?
Post by: bratan on Jan 02, 2013, 06:07 pm

I always use the "LM1117". Can output a maximum current of 800mA.
It's really easy to find in stores, exists in DIP and SMD models, and is really cheap.
http://www.ti.com/lit/ds/symlink/lm1117-n.pdf

Thanks! :)  Looks like just what I need
Title: Re: 3.3 V regulator recommendation?
Post by: oric_dan on Jan 02, 2013, 06:33 pm
The LM1117 v.reg is a good choice, and I use them too. They say 800 mA, but you need to
also take into account power dissipation relative to actual load current for your app.

Take note of the Thermal Resistance, Junction to Case values shown on page 5 of the d/s.
Eg, the SOT-223 devices get almost 2X as hot as the others for the same load currents.
Title: Re: 3.3 V regulator recommendation?
Post by: bratan on Jan 02, 2013, 06:35 pm

The LM1117 v.reg is a good choice, and I use them too. They say 800 mA, but you need to
also take into account power dissipation relative to actual load current for your app.

Take note of the Thermal Resistance, Junction to Case values shown on page 5 of the d/s.
Eg, the SOT-223 devices get almost 2X as hot as the others for the same load currents.


Thanks, that's good to know! I just ordered TO-220 package, so it should stay cooler...
Title: Re: 3.3 V regulator recommendation?
Post by: oric_dan on Jan 02, 2013, 07:02 pm
Power dissipation of the v.regs is the one thing most often understated when people
"advertise" their boards. Almost all of the Arduino boards use the tiny SOT-223 v.regs
for 5V, and claim 1-Amp, but they'll get very hot with loads over 200 mA or so, for
Vin > 6V or so.

TO-220 is the monster package, and will handle probably full current loads when using
a heatsink, and run off Vin up to 9-12V or so. On my own pcbs, I usually use the
D-PAK [TO-252] to bootstrap the 3.3V v.reg off the 5V v.reg. It helps to include some
extra copper area on the pcb under the v.reg to act as a heatsink for such parts.