Is there still something like the old 2105?

Joerg wrote:

> Hello Mitja,
> 
>>> Be careful with that -- the crusty old analog engineer at the place
>>> where we used '2812s described its ADC as "10 bits going on 8" -- I
>>> suspect the '24x is no better.
>>
>>
>> I have some experience with 24xx series ADC, and I must say that it
>> works as specified. The 10bit accuracy can be easily achieved on a dual
>> layer board, even with switching devices nearby on the same board
>> (switching 50 Amps at 40kHz). It is completely different ADC than the
>> one in 28xx series.
>>
> 
> With devices like these that are really more geared towards the audio 
> market I am wondering why they included such a high speed 10bit ADC. A 
> slower 14-16bit would be more practical in many applications. But you 
> can't have it all, I guess.
 >
-snip-

The '2401 is like the '2812 in that it's really designed for advanced 
motor control -- that's why the data sheet says "Several advanced 
peripherals, optimized for digital motor and motion control 
applications, have been integrated to provide a true single-chip DSP 
controller."

For this sort of thing those high-speed ADC's come in mighty handy, and 
the precision isn't such a big deal.

ADI used to make DSPs with built-in stereo codecs that had 16 bits in 
and out; I don't know what happened to them, or if TI makes anything 
similar.

-- 

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Hello Tim,

> The '2401 is like the '2812 in that it's really designed for advanced 
> motor control -- that's why the data sheet says "Several advanced 
> peripherals, optimized for digital motor and motion control 
> applications, have been integrated to provide a true single-chip DSP 
> controller."
> 

Yes, and they have some nice PWM capabilities.


> For this sort of thing those high-speed ADC's come in mighty handy, and 
> the precision isn't such a big deal.
> 
> ADI used to make DSPs with built-in stereo codecs that had 16 bits in 
> and out; I don't know what happened to them, or if TI makes anything 
> similar.
> 

I guess the audio market wasn't large enough anymore and modems are all 
ASIC now. They list the ADSP-21990 series, with a fast 14bit converter 
in there. However, the AD web site mentions no price (might not be a 
good sign) and Arrow quotes around $50 for the 4k RAM version. Way too 
much for most of my applications.

There may be some parts from overseas manufacturers but with their often 
rather clumsy web sites that will be hard to find. Also, my recent 
experience with support from EU companies makes me stay away.

So it looks like I'll have so see how many effective bits the 10bit ADCs 
can yield at low frequencies when fully tricked out. The challenge will 
be that the tricks can't contain too many discretes. An external ADC is 
another option but not a nice one.

Regards, Joerg

http://www.analogconsultants.com

Take a look at dsPIC30F series. Some of them have 12bit ADC and low pin
count and they are under $5. I admit that they are not as nice to work
with as Ti's 24xx series (my personal opinion), but on the other side
development tools are significantly cheaper (XDS510 vs. ICD2).

Regrards

Mitja

Hello Mitja,

> Take a look at dsPIC30F series. Some of them have 12bit ADC and low pin
> count and they are under $5. I admit that they are not as nice to work
> with as Ti's 24xx series (my personal opinion), but on the other side
> development tools are significantly cheaper (XDS510 vs. ICD2).
> 

Thanks. I did look at these and their pricing would still be ok. 
However, I really need about 14 bits and their 100k converters don't 
look like I could play the usual tricks much to get there.

The only chips around $5 that have a decent ADC built in seem to be the 
MSP430F4xx series. It isn't a DSP but at least it includes a 16bit 
hardware multiplier. I don't know yet whether it will choke with all the 
filters I'd have to cram into it. One serious downside with such 
controllers is their small RAM. Hanging an external RAM onto a uC 
usually eats up most of the port resources.

Regards, Joerg

http://www.analogconsultants.com