Yes, LTC2400 is  a very nice product indeed but not suitable for my
application due to the need for ultimate low cost. The processor is
set due to other considerations and I must live withing its
constraints while costing approx nothing at all. What I have achieved
(see separate post) will do what I want (9 or 10 bits accuracy - 8
probably OK) using an LM324, 9 resistors (including an amplifier and
"reference", zener and 3 capacitors. Assembly costs and board space
costs all add up but still far below LTC2400 cost I imagine - I
couldn't find a price at Digikey, Pioneer or Netbuy. How much are you
buying them for?


RM



-----Original Message-----
From: Tom Handley <        >
To: PICLIST@MITVMA.MIT.EDU <PICLIST@MITVMA.MIT.EDU>
Date: Thursday, July 15, 1999 12:22 AM
Subject: Re: Sigma Delta Converter


>re: LTC2400 24-Bit ADC
>
>   Ditto Marcos and Wagner's comments. I use two of them with a
>precision external reference hooked up to a PIC. Very easy to
program.
>The results have been excellent. These are ideal for precision
>voltmeters which is what I'm doing (2-channel with differential
inputs).
>Two status Bits provide Sign and Extended Range information which
make
>it easy to implement an auto-ranging DVM. There are other features
such
>as an internal oscillator, 110db 50/60Hz rejection, Auto Shutdown,
12.5%
>Overrange and Underrange, reference voltage range of 0.1V to 0.9 x
VCC,
>and a 3-wire SPI interface. All this in a SO-8 package.
>
>   - Tom
>
>At 09:53 PM 7/13/99 -0400, Wagner Lipnharski wrote:
>>Pretty one, already tested.
>>DIP 8 small package... without nasty programming.
>>Some small problems with grounding, but works nice.
>>Wagner.
>>
>>Marcos Migliorini wrote:
>>>
>>> If you want a good sigma delta converter take a look at
>www.linear-tech.com
>>> (LTC2400 24 bits sigma delta a/d).
>>>
>>> Marcos
>