>-----Original Message----- >From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] >Sent: 03 June 2005 16:11 >To: Microcontroller discussion list - Public. >Subject: Re: [PIC] 16F88 A/D datasheet contradiction > > >The last time I brought this up to Microchip Tech Support, I >was told that >the figures are 10K for 8-bit A/D inputs and 2K5 for 10-bit A/D >inputs. This is because the input leakage current stayed the >same even >though they improved the resolution. > >Says pretty awful things about their input stages . > >Staying with 10K for 8-bit A/D inputs and 2K5 for 10-bit A/D >inputs keeps >leakage error to less than 1/2 LSb. > Hmm, the old 16F877 had 10k maximum source impedance and 10 bit resolution. I was told (by an FAE!) that the increase in leakage current, and consequent reduction in max source impedance was simply down to the die shrinks, i.e. analog does not shrink as well as digital. It's a real PITA having to buffer everything though, Atmel manages to give the AVR very high input impedances. I moaned to Mchip quite a bit about this as PCB real estate is at a premium in our products, and I was hoping that they had improved the more modern parts...clearly not! Regards Mike ======================================================================= This e-mail is intended for the person it is addressed to only. The information contained in it may be confidential and/or protected by law. If you are not the intended recipient of this message, you must not make any use of this information, or copy or show it to any person. Please contact us immediately to tell us that you have received this e-mail, and return the original to us. Any use, forwarding, printing or copying of this message is strictly prohibited. No part of this message can be considered a request for goods or services. ======================================================================= -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist