Lpc2000

At 11:34 PM 3/7/2006 +0000, Sutton Mehaffey wrote:
>Since Philips isn't responding / hasn't responded to my ADC leakage
>question, as you said would probably happen, is it safe to say the
>leakage at the AD0 channels is probably 4ua max?  If so, I may put in
>extra circuitry to handle to slop in measuring battery voltage, or I
>may just add another ADC to my board.  I had an ADC on an 8051 project
>and it worked great.  I just thought that an onboard ADC would
>eliminate extra parts.  Maybe not...

Well, if you can afford the cost/space for an external A/D you can 
certainly afford to add an op-amp as an external buffer.  As an example 
consider

http://www.national.com/pf/LP/LPV321.html

SOT-23 case 60nA max input bias current <0.40 qty 1000.  I'm sure there are 
many others, such as the LMC7111 with an even lower input bias current in 
the same size package.

Robert

" 'Freedom' has no meaning of itself.  There are always restrictions,   be 
they legal, genetic, or physical.  If you don't believe me, try to chew a 
radio signal. "  -- Kelvin Throop, III
http://www.aeolusdevelopment.com/