Lpc2000

Joerg

Thanks for info - I'll let you know how I get on

Regards
Dave

>
> Hello Dave,
> 
> > 
> > I don't think the scope is influencing things significantly as 
I've 
> > observed faster & better quality waveforms. However I'm keen to 
try 
> > the coax connector & divider trick you described. I'm not 100% 
clear 
> > of the configuration though. Could you talk me through the setup ?
> > 
> 
> There are several nice instruction sets on the web, like this more
> elaborate probe:
> http://www.emcesd.com/1ghzprob.htm
> 
> I usually forego the resistor to GND and the caps since a well
> terminated coax provides a 50ohm load just by itself. This seems to 
be
> what Maxim described in one of their app notes:
> http://www.maxim-ic.com/appnotes.cfm/appnote_number/3699
> 
> The simplest "probe" would just contain one 450ohm SMT resistor, or
> 453ohms since that is the closest value you can find in the usual 1%
> category. It must be a low-inductance resistor which most of them 
are
> nowadays. When you solder that in series with the center conductor 
of
> a coax you have a 1:10 divider, assuming 50ohm coax which is 
properly
> terminated at the scope. Use a small SMT cap in series if you want 
to
> avoid any DC draw. Make it as neat as you can and as short as 
practical.
> 
> Very important is a short connection to ground. Below 100MHz you can
> get away with 1/2".
> 
> Then place a jar on the counter where people can "donate" a girl 
scout
> cookie or something delicious. Because everyone in the lab will want
> to borrow your new probe at some point.
> 
> Regards, Joerg
> 
> http://www.analogconsultants.com/
>