REF6241: Voltage References for more than one adc

hi Vahid

do you have the p/n of the ADCs, so I could be more precise?
on the spot I would say THS4281 or OPA835 / OPA836...

KR
Vincenzo

the ADC i am going to use is AD7693

As  I said I want to  use  four  of  it,

regrads

hello

thank  you for recommendation. i read the ads8319 specification.  all  thing is right but I  need to  convert true differential  signal.

thank  you for  the point

I will check the  specifications and let you know,

by the way ,   when  both  ADC  is similar  why there is a big difference in price.

I  think there must be a difference in quality  too since  big companies always check their competitors price . particularity in   similar products

hi Vahid,

that is not necessarily true...

everything comes from the technology / process in place to produce the parts: the better / newer the technology, the lower the cost of the part and then, as consequence, the price on the market...

anyway it is the "web" price (only for volumes < 1K), while if we talk about interesting volumes we can provide specific offer, just let me know and I will put you in contact to the right channel...

KR

Vincenzo

Hi Vincenzo
I read the both datasheet carefully and there is only  a  bit  better quality (in term of accuracy)  in ad7693, but it dose not deserve to pay that much for.

 I also think about utilizing ADS8885 , but I  need more accurate driver ,
the problem is I am looking for something like AD8475, AD8251 not only a simple driver,

I planing  to apply some gain (both manual or digital ) to be able to work with several level of signal inputs,

Do you have some thing like that in TI products that be appropriate for working with ADS8885 or ADS8865

Another question is about ADC packaging, it is VSSOP . Is this compatible with MSSOP(AD7693), i saw there is a small difference

I am going to use 4.096 as voltage reference
And why TI dosnot recommend REF6241 as voltage reference on ADS8885 datasheet? dose REF6x41 release after ADS8885 last revision .


thank you

hi Vahid,

you might consider a PGAxxx -like device for the AD/8475 / AD8251 replacement.

details at  

at a quick look the PGA280 should work, but yeah have a look filtering out the options you are looking for (# of channels, supply, rating, price, etc.)

and yes, the two packages you mentioned are actually the same (any company uses its own fancy name)...

last but not least, yes you are right also about the references: REF6241 was released on 2016, while the ADS8885 was released on 2013

KR

Vincenzo

Hi Vincenzo

How are you?hope you are doing well

As you may  remember we have talked about using ADS8865 instead of AD7693 , I got your advice and one again thank you fro that

Now  I want to use ADS8865 but my  input signal is singlended (0v -4.096).but still want to use this ADC in diff mode.

Base on  my requirement  there is a schematic on device datasheet(figure 73) . I am going to set  Vref to 4.096v  , AVDD=3.3V   and THS4521  VCOM_OUT=Vref/2  THS4521 positive supply to 3.3V just like datasheet

I want to know  that  can I apply  0-4.096 V to ADC analog input(VIN)? 

AND  is  there  any specific simulation software that I can evaluate Ths4521 behavior ? I cant find ths4521 on Orcad spice

thank  you

OK.

Thank you. You’re so helpful.

hi Vahid,

I just got back from my long absence...

I talked with the BU folks and actually you may want to consider the ADS8864 (instead of ADS8865).

The ADS8864 supports single-ended input and you don't need to use a single-ended to differential circuit like the THS4521.

The ADS8864 is also pin and software compatible to ADS8865.

KR

Vincenzo

Hi

well comeback

how are  you.

As we talk later , I already have ADS8865 , ( However   I  prefer    to use  diff  ADC to get more SNR).

I use ADS8865  both whit  singlended and differential  input   , because of that   in  need  to know how to use it in both mode
.

thank  you

Hi Vahid

I'm fine tks

Yes you can do it as any input of the adc can go from 0 to vref (se) and from -vref to +vref (diff).

No problem then with your setup.

The challenge is with the ths, as the signal will be limited by the supply, so in order to get +/-4v out you should use 5v supply instead of 3.3v

KR

Vincenzo

thank   you  so much

wouldn't it make a possibility of error when ADC  power and its driver Op Amp power  are not  the same level .

Don't we need   to make  a protection  for  ADC  inputs  ?

no you don't need (see page 3, top of the table, the session ANALOG INPUT of the ADS8865)...
but if it makes you feel more confortable, you can align everything @ 5V

KR
Vincenzo