Lpc2000

----- Original Message ----- 
From: "David Willmore" <willmore@...>
To: <lpc2100@yahoogroups.com>
Sent: Wednesday, January 07, 2004 11:51 PM
Subject: Re: [lpc2100] MAX3232 problems?


> > Oops! You are right. It could cause a problem with a polarised cap. Try
> > putting it the other way round.
> >
> > I'll correct the schematic and fix the problem if I get some more boards
> > made. I'll modify
> > any more boards I send out.
> >
> > 100 nF ceramic caps are really all that is needed. The older MAX232
needs 1
> > uF.
>
> I put in a 100nF chip cap for the problematic V+ cap and put in a new
> MAX3232.  No joy.  Same results.  150mA current draw and a warm chip.
> Could both of my chips be bad?  I've never had this bad of luck since
> I put a chip in backwards.  PICs hate that.
>
> I've got more coming in a few days.  Maybe I'll proto a good old MAX232
> and trust the tolerance of the lpc2106. :)

I can't really see both chips being faulty. You must have something else
wrong. Have you checked that all the capacitors are OK?

I get +6 V on pin 2 and -5.6 V on pin 6, checked on two boards. I'd expect
about +/- (2 x 3.3 V)
less a diode drop or two as the charge pump circuit inside the chip is
essentially a voltage doubler on the output of an oscillator.

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