Re: tiny inductor with every bypass cap?

Joel Koltner wrote:

> "Vladimir Vassilevsky" <antispam_bogus@[EMAIL PROTECTED]
> wrote:

>>Despite of the popular beliefs, many
>>analog or digital designs can be built in two layers just fine. It takes
>>care, understanding and attention to details.
> 
> For many companies, coming up with that "care, understanding, and
attention to 
> detail" requires both significant time and often money -- so I think
MK's 
> point is valid, since those are not always available!

Classic question of the development cost vs production cost; it depends.

> But I think that all of us would be interested to hear your advice on 
> designing high-speed/low-noise circuitry on two-layer PCBs; it's not the
sort 
> of material that's commonly discussed.

There is no magic to it; just understanding which way the current flows 
and distingui****ng a ground and a signal return path.

> Do you recommend any microcontrollers or DSPs with decent references
on-board? 

Analog Devices ADUCxxxx series.

> We use a number of Atmel AVR microcontrollers and most often it's with
an 
> external reference, as the internal one is pretty bad; about +/-10% (!).

The good thing about AVR is that it is possible to use the external 
reference, and that the ADC input range is from 0 to Vcc. The ADC of TMS 
28xx can't do that.

> Being charitable, I want to believe that you just can't build a
reference 
> that's much better using whatever process they have available to them,
but 
> perhaps it is just a lack of better circuit designers (e.g., someone
like Jim 
> could easily build them 1% references using the same process).

Perhaps there is a limitation of the high speed CMOS process which 
doesn't allow making reasonable on-chip ADCs. May be Jim can explain us
why.

> 
> ---Joel
> 

Vladimir Vassilevsky
DSP and Mixed Signal Design Consultant
http://www.abvolt.com