Lpc2000

----- Original Message ----- 
From: "Aalt Lokhorst" <lokhorst@...>
To: <lpc2000@yahoogroups.com>
Sent: Friday, April 08, 2005 12:57 PM
Subject: Re: [lpc2000] Re: Wiggler with LPC2124


>
> Hello Leon,
>
> In first instance I used a HC244 and it was working fine in combination
> with the KEIL MCB2100 board. After several days I connected some extra
> hardware to the board and I was debugging the circuit with the
> oscilloscope. A 'led blink' program was running and I saw the 3.3V
> supply 'bouncing' between 3.3V and 3.6V. If the leds were 'on' then
> circuit was sinking more current than the LPT port could deliver and the
> result was 3.3V. If the leds were 'off' then the circuit was powered by
> the LPT-port instead of the 3.3V regulator. If I didn't measure the
> voltage in the circuit then I probably never discovered this because the
> software was running as expected.
>
> BTW there is another power issue but this is related to the MCB2100
> board. On my MCB2100 board the 3.3V supply had a ripple. I read the
> datasheets from the LD1117S33 regulator, which is used on the MCB2100,
> and found that all the specs were based on a circuit whit a 10uF output
> capacitor on the regulator. As far as I know this capacitor is not
> present on the MCB2100 board. I soldered one at the bottom of the board
> and now the ripple is gone and the voltage is a stable 3.3V.

I thought everyone put a 10 uF capacitor on regulator outputs feeding high 
speed circuits. 8-)

Leon
--
Leon Heller, G1HSM
http://www.geocities.com/leon_heller