Breadboard Power 3.3V for ICs

[GT]

Hi -

I want to experiment with 3.3 Volt IC chips (LVTTL and LVCMOS33) on my
breadboard. I need to power the chips and I was wondering if it is OK to
just have a 5VDC (1.5Amp rated) wall transformer and then use LM317 to make
a 3.3Volt source for my chips?

Thanks for any advice or info!

 

[John Fields]

On Mon, 9 May 2005 16:07:39 -0400, "GT" <no@spam.com> wrote:

Hi -

I want to experiment with 3.3 Volt IC chips (LVTTL and LVCMOS33) on my
breadboard. I need to power the chips and I was wondering if it is OK to
just have a 5VDC (1.5Amp rated) wall transformer and then use LM317 to make
a 3.3Volt source for my chips?

---
Frayed knot. According to Nationals's data sheet:

http://www.national.com/ds/LM/LM117.pdf

You need at least 3 Volts of headroom, which mean that for 3.3V out
you need at least 6.3V in.

What you need is a regulator with a low droput voltge, something like
an LM3940:

http://www.national.com/ds/LM/LM3940.pdf

--
John Fields
Professional Circuit Designer

 

[petrus bitbyter]

"GT" <no@spam.com> schreef in bericht
news:117vgr03a0bai9c@corp.supernews.com...

Hi -

I want to experiment with 3.3 Volt IC chips (LVTTL and LVCMOS33) on my
breadboard. I need to power the chips and I was wondering if it is OK to
just have a 5VDC (1.5Amp rated) wall transformer and then use LM317 to
make
a 3.3Volt source for my chips?

Thanks for any advice or info!

The LM117-317s specifications include a minimum of 3V between in- and
output. It may work a little below that voltage or not. The 1.7V however for
sure is to low to make an LM317 work well. Look for an LM1117-3.3. It works
well from an 5V input and can provide up to 800mA at 3.3V.

petrus bitbyter

 

[Paul Jones]

The lower the voltage the wore the loss in the diodes ....hmmmm
But who wants to do syncr' rectification using a POWER FET !!
The N-ch FET works both ways , Drain neg or pos !

But you want simple .....

The simple is buck regulator . It's the simplist switcher out there
..
A 10 amp PNP then a diode to gnd then a coil 30 microhen or
bigger. LM431 to control it . But remember 431 don't start
til .001 amp !! So put a PNP and a 400 ohm base to emm then to
LM431 to make LM431 snap in at exactly 2.5 vdc .

 

GT wrote:

Hi -

I want to experiment with 3.3 Volt IC chips (LVTTL and LVCMOS33) on
my
breadboard. I need to power the chips and I was wondering if it is OK
to
just have a 5VDC (1.5Amp rated) wall transformer and then use LM317
to make
a 3.3Volt source for my chips?

Thanks for any advice or info!

OK idea, just the wrong chip. Try an LM3940 from National.
GG