I don't agree to this reasoning,
A sigma delta converter is different to how one might expect that they work.
The sigma part is an intergration point of the converter. This is used to
only reduce the delta of the incomming signal so that a simple comparator
can be used in the desission process (Have a look at stuff on one bit DSP).
The great thing about this style of converter is that the noise is high pass
filtered by nature of design. The basic concept of sigma (intregation) delta
(Change in) has been around since the 1950's but only in recent times has it
been of use.


Dennis





> -----Original Message-----
> From: Wagner Lipnharski [SMTP:wagner@USTR.NET]
> Sent: Thursday, 13 April 2000 2:11
> To:   PICLIST@MITVMA.MIT.EDU
> Subject:      Re: [OT] What is a Sigma-Delta AtoD converter? [EE]
>
> All ADCs for high bit counting (bigger than 14 bits) use Sigma-Delta
> conversion for a lower cost production. Sigma Delta use a capacitor ramp
> measurement based on voltage comparison. They use integration, discharge
> and other techniques to get great precision and accuracy. Actually they
> are quire precise, and much cheaper than the regular instantaneous
> multiple voltage comparison technique used in lower bit count.
>
> Personal experiences about ADC's point the latest Linear Technologies
> LT2400 and LT2408 one of the easier to use, with a low cost. They run at
> 24 bits !!! in just 8 pin DIP package for the 2400.  The 2408 has an
> embebed input mux at the chip.
>
> Wagner.
>
> Mark Skeels wrote:
> >
> > Hi, folks.
> >
> > TelCom has a new AtoD part, a TC3401. It claims to be a 16 bit AtoD
> > converter and it's cost at 1000 pcs is $4.63 US.
> >
> > I never heard of a Sigma-Delta AtoD converter before. Can anyone tell me
> how
> > it works, and has anyone had experience with this new part?
> >
> > Thanks on advance,
> >
> > Mark