Lpc2000

Hello, all.

All of the power usage comments I've seem never mention
which supply the current draw is for.  This got me
thinking what kind of power supply curcuits everyone
is using.  That lead to a few questions:

What is the current draw at max/sleep for each (3.3 and
1.8V) supply?

Does anyone know of a simple chip that does two channels
of buck mode switching step down?

Is anyone using anything but linear regulation?

I don't remember seeing them, but there have to be power
supply sequencing requirements.  Does anyone know what
they are?  (page numbers in the manual where I failed to
read them)

Happy holidays!

Cheers,
David

>Does anyone know of a simple chip that does two channels
>of buck mode switching step down?

I'm no expert on SMPS design, but wouldn't this normally be done with a 
multitap transformer, rather than two entirely separate SMPSs?

>Is anyone using anything but linear regulation?

I'm not designing anything around an LPC right now, but if I was, I'd be 
using a boilerplate circuit based around the MC34063, because it's 
childishly simple to use, and dirt cheap. If space was a consideration, I'd 
look at one of the more modern, higher-frequency parts.

Linear regulation is feasible for these low-power parts, and it's certainly 
the no-brainer solution for a development board, *but* I wouldn't choose it 
for a new design unless there was some special consideration (e.g. noise 
requirements).

A good switcher is not much more expensive, certainly not difficult to 
build, and it's potentially much more efficient. It also gets you much 
better operation off batteries (esp. with a buck-boost, you could run your 
LPC off a couple of AAA cells and get pretty decent life).

-- Lewin A.R.W. Edwards (http://www.zws.com/)
Learn how to develop high-end embedded systems on a tight budget!
http://www.amazon.com/exec/obidos/ASIN/0750676094/zws-20

----- Original Message ----- 

From: "David Willmore" <willmore@...>
To: <lpc2100@yahoogroups.com>
Sent: Tuesday, December 23, 2003 4:56 PM
Subject: [lpc2100] power question


>
> Hello, all.
>
> All of the power usage comments I've seem never mention
> which supply the current draw is for.  This got me
> thinking what kind of power supply curcuits everyone
> is using.  That lead to a few questions:
>
> What is the current draw at max/sleep for each (3.3 and
> 1.8V) supply?

The 3.3 V supply current will mainly depend on the current taken by the
I/Os.

>
> Does anyone know of a simple chip that does two channels
> of buck mode switching step down?

I think that TI makes this sort of thing.

>
> Is anyone using anything but linear regulation?
>
> I don't remember seeing them, but there have to be power
> supply sequencing requirements.  Does anyone know what
> they are?  (page numbers in the manual where I failed to
> read them)


Leon Heller, G1HSM
Email: aqzf13@...
My low-cost Philips LPC210x ARM development system:
http://www.geocities.com/leon_heller/lpc2104.html

At 11:56 AM 12/23/03 -0500, you wrote:
>Is anyone using anything but linear regulation?

If you have a good low voltage supply (like 5V) already I can't see why you 
would use anything other than a linear (other than running off of a 
battery).  Less noise, fewer components, lower cost in small qtys, no 
magnetics.  Of course if you already have a switcher a few extra winding on 
the transformer may not be an issue (other than sourcing the transformer)


>I don't remember seeing them, but there have to be power
>supply sequencing requirements.  Does anyone know what
>they are?  (page numbers in the manual where I failed to
>read them)

Apparently there are none. I asked the question on Philips forum, their answer

"                 The only thing you have to take care is to keep RST low 
until power supply reaches level specified by the data sheet, X1 signal is 
present and stable, and requested 10 ms expire. 10 ms window is chosen 
based on measurements
                  when even in the worst case, LPC2106/05/04's oscillator 
using external crystal would start to operate properly (measured from the 
moment when specified power supply is applied, till stable signal on X1 is 
detected). "

http://forums.semiconductors.philips.com/forums/viewtopic.php?t=3576

That's the most complete answer I've managed to get out of them so far.

Robert