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ADS1120: Detect ADS1120 vs ADS1220 / Identify original chips

TI-CSC
Genius 10500 points
Part Number: ADS1120
Other Parts Discussed in Thread: ADS1220,

Hello E2E Experts,

Good day.

1. Can you recommend a method to find out in software if the 16bit ADC "ADS1120" or the pin-compatible 24bit ADC "ADS1220" is installed on a PCB?

2. The ADS1120 is unavailable at my usual distributors (mouser.de, digikey.de, farnell.de and de.rs-online.com). US distributors such as Arrows refuse to ship to a me (freelancer without VAT idenfication number). I therefore bought a few ADS1x20 from China's Aliexpress. They did cost less than TI's pricing, which was strange. Do you know if the masses of cheap "original" ADS1x20 chips on Aliexpress are genuine or is that a chesspit of inferior fakes?

Sincere, Dietmar Eilert (https://www.softwareandcircuits.com)

Regards,

CSC

  • 0
    TI__Mastermind 19077 points

    CSC,

    1. The best way is to do a register write followed by a read.  If the read retrieves back the same information written into the register, you know the device is installed and digital communications is working.  Register 00 is a good choice.  The default value is 0x00, so you should write something other than zero and confirm the readback.  
    2. I do not know if these devices are fakes, but I think you are correct to be suspicions.  We generally recommend only purchasing through the usual distributors.  If you have a device from Aliexpress, can you take a picture and send it to us.  In some cases we can look at the package and top marking and determine the device authenticity.  

    Best regards,

    Art

  • 0 in reply to Art Kay
    TI__Genius 10500 points

    Hello Art,

    Good day.

    > 1. The best way is to do a register write followed by a read.  If the
     read retrieves back the same information written into the register,
     you know the device is installed and digital communications are

    My code does that during initialization but that doesn't allow to detect
    if the installed chip is an ADS1120 or ADS1220. Apparently there is no
    (documented) difference in the registers of these chips. At the moment,
    my plan is to clock 24 bits out of the chip after a RDATA command. I
    assume/hope that the 16bit ADS1120 will clock out zeroes after 16 bits
    and that the ADS1220 will always have some noise in the lowest 8 bits.

     2. We are not aware if these devices are fakes, but I think you are
    correct to be suspicious.  We generally recommend only purchasing
    through the usual distributors.  If you have a device from
    Aliexpress, can you take a picture and send it to us?

    Loose ADS1x20 chips on Aliexpress have no uniform appearance. See
    attached pictures. Some have pin 1 marked by a recessed circle, and some by
    a white dot. They have different TI logos (some solid white, some
    dithered, and some have no logo at all). My guess would be that picture 1
    could be an original chip. I have in the meantime found some
    soon-to-be-available ADS1120 on Digikey.

    Photo.zip

    Regards,

    CSC

  • 0 in reply to TI-CSC
    TI__Mastermind 19077 points

    CSC,

    1. Yes., If the ADS1120 is clocked with 24 clocks, the last 8 bits will be zero.  The ADS1220 should always have some noise so it is extremely unlikely that all 8 LSB are zero.
    2. I believe that item #4 is likely the authentic device.  It is unlikely that items #1 and #2 are authentic.  Typically, a crisp logo is a good sign that the device is authentic.  We can look up the lot codes, but this can be copied as well.  I am glad you found some devices on digikey.  Let me know if you think we should do further investigation.  Of course, we can decapsulate devices (or x-ray) and check the die, but this takes time, and effort.  If you can get the devices from a approved vender (e.g. digikey), that is the best approach.

    best regards,

    Art