Which company provides non linear ADCs?

[pradeepkumar481]

hi ppl,

I have tried to search for non linear ADC from TI & AD, but i did not get any.

is there any company that provides us with non linear ADCs ?

please help me in this regard
Thanks in advance
Pradeep

 

[FvM]

Re: Non Linear ADC

You'll find any real ADC less linear than you wish, but I guess that's not, what you mean.
However, what you are exactly trying to achieve? The question seems meaningless without specifying an intended characteristic.

 

[karesz]

Non Linear ADC

Hi pradeepkumar481,
In some DAQ-systems you will find PGA+ADC=nonlinear ADC,
in other systems they apply a log Amp+ADC=nonlinear ADC...
What is your case?
K.

 

[dick_freebird]

Non Linear ADC

You could also just use a linear ADC and "cal-map" the linear
output codes to whatever function you want, by lookup.
This would let you do things that are not strictly logarithmic
(or whatever).

 

[karesz]

Non Linear ADC

The goal of nonlinear idea is to extend the resolution with the same ADC i.e. 8 Bit Flasch ADC with "Input modifications" of 4 Bits`=10-12 Bits, what is not to build with given technology (i.e. 100MHz, 11 Bits, but 15-20 years ago!).
This is not equivalent with a cal-map-ing...
K.

 

[pradeepkumar481]

Re: Non Linear ADC

Thank you all for your valuable input,

our specific requirement is as follows

our application has to sample an analog signal which varies from 0-3.3V, but it is more likely that the signal will be in the range of 0-1V, hence we need a finer resolution in this particualr range and coarse resolution in further range(i.e., 1-3.3V).

so, can you please suggest us a solution to solve this issue.

Thanks again
Pradeep

 

[karesz]

Non Linear ADC

OK,
next time begin pls with so a exactly wroten question!
This is basically similar as a "compander" or switched range/voltage gain amps befor your ADC. Do you have possibility to apply external circuitry?

What are the needed Bits, resolutions, in both ranges pls & you wish an parallel output ADC or som SPI typ?
I remember that sow so an application idea_I will search for that...
K.

 

[pradeepkumar481]

Re: Non Linear ADC

Thanks for your reply,

these are our finer reqirements:

Do you have possibility to apply external circuitry?

Since our application is a hand held device, the size becomes a constraint but we can afford if it is small.

Bits, resolutions

We are looking for 16 bit resolution ADCs(0 to 3.3V). Nature of our input distribution is most likely in 0 to 1V(hence we need more resolution in this range).

parallel output ADC or som SPI typ?

Parallel or SPI is not a real concern since we are interfacing it with DSP which has both.

Thanks again,
Pradeep[/quote]

 

[FvM]

Re: Non Linear ADC

Some decades ago, medium resolution ADC (e.g. 12 bit) have been used for digital audio with automatic switched gain stages
to achieve a dynamic of 16 bit.This was mainly done, because the required higher resolution ADC have been too expensive or not
available at all. But unfortunately, the input signal covers the full dynamic range and and it was very difficult to avoid additional
errors due to gain mismatch and offsets. Even more problematic, you get a nonlinear coded digital signal, that has to
be recoded to a linear representation before performing signal processing. Obviously, nobody uses similar designs
in digital audio today, because ADC resolution is always cheaper than additional gain switching circuits.

I guess, it's same for the requested application.

Apart from gain switching circuits or VGAs, continuous nonlinear characteristics have been used in special applications,
e.g. with the µ-law audio codec. But you can't process the data without applying an inverse characteristic before.

Some ADC operation principles would allow to give it an internal nonlinear characteristic. But as long as there's no
standard application, that demands a respective solution, no company will design and produce it. I'm not aware of such
an application in today's electronic.

As already mentioned, you can't seriously expect a meaningful answer without giving more details.

 

[karesz]

Non Linear ADC

Yes,
as FvM wrote; today is so a solution not the best_but not inpossible & the rest of your design must/will be complexer too...
I would select, in my opinion as the best solution, a "sigma-delta" ADC with 24 Bit resolution_if these speed/bandwidth is right for you.
Otherwise todays you can select from lot of 16/18 Bit ADCs with analog bandwidth up to 10-100KHz " sampling rate; i.e. at 1Msps(AD7984/86_in 4x4 mm QFN 20 package, need only 15mW), on the market...
OK, you need such driver amps too_maybe AD8021, or 2x in SO8 as ADA4841-2 (double in SO8 or MSOP8), but if your bandwith is really lower: check pls. other vendors as Micrel/Maxim too...
Is it not a better solution for your aquisitions problem pls?
K.

 

[karesz]

Non Linear ADC

Hi pradeepkumar481,
I found an "design idea" for your problem, if its yet actuell for you?: "16-bit ADC provides 19-bit Resolution"
Uses an PGA +AD7677...
I will scan it and upolad in short.
K.