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OPA2137: About device marking

Part Number: OPA2137
Other Parts Discussed in Thread: OPA4191, , OPA2990, TLV9002, LM358LV, TLV2170, TLV9302
We are investigating the operational amplifier oscillating on the board that has started mass production.
There was a difference in device marking between the mass-produced board and the prototype board.
Please tell me what the "K" means.
■Part marking lookup on the WEB:
 OPA
 2137U
■Prototype:
 OPA
 2137U K   ← Difference
■Mass production:
 OPA
 2137U
Best regards,
K.Suzuki
  • Hello Suzuki-san,

    Please provide the full part number and all lines of symbolization on the devices.

    Can you share the amplifier circuit so we can review it?

  • Hello Mr.Ron Michallick,

    The part I chose is "OPA2137U".
    All Lines of symbolization on the device are:
    ■Prototype:
       BB  OPA
     ^  2137U   K   ← Difference "K"
     ●  77CGQ1
    ■Mass production:
         BB  OPA
         2 1 3 7 U
     ●     8516V
    The Circuit Sch cannot be disclosed, but the part created by ti-na can be attached after being encrypted.
    As known information, I am using OPA2173U with a voltage follower, but the input voltage seems to be out of the Vcm range.
     [Vcc: 5V single supply, IN+: 2.5V, Vcm: (V–) + 3 ~ (V +) = 3 ~ 5V]
    Moreover, OPA4191 and LM2903D are used in the peripheral circuit.
    I am ready to send the TI-NA file, but is there a way to send it with my password?
    Best regards,
    K.Suzuki
  • The common mode could be a big factor. The margin below the V- +3V is not certain or always the same. It may work on one lot of devices and not on another.

    The missing character doesn't have to be a "K" but it should be there. The bottom line appears to be one character short.

    Where did you purchase the "mass production" devices?

  • Thank you very much for the valuable information.
    I should have sent the device marking from the beginning.
    I will attach a photo of the IC without "K".

    The supplier is currently under investigation.
    Is there a possibility of an old IC in the BB era?
  • Suzuki-san,

    The first 2 characters in the bottom row are [year] and [month]. 

    Due to the missing characters on rows 2 and 3 it can not be 2018 May. However the number of characters in rows 2 and 3 is consistent with 2008 May. I suspect this is old stock. I will confirm with quality team to make sure I am correct.

    Regardless there is risk in using any OPA2137 due to the input common mode voltage. The unity gain function of application and the light loads means that many other op amps could drop into this application. Most have better offset voltage for better accuracy. Would you be interest in a few alternate part suggestions.

  • Hello Mr.Ron Michallick,
    Thank you for checking despite my purchase.
    It seems that it was made in 2018 according to the information of the purchaser, but I feel that I also misunderstand it as 2008.
    When the OPA2137U on the prototype board and the mass-produced board was replaced, the oscillation state moved with the parts, so it was due to the dependence of the parts.
    Raising the Vcm input of the oscillating OPA2137U to 3.1V did not solve the problem, but the oscillation was reduced.
    For example, I'm considering a Rail to Rail OPamp like OPA2990.
    Can you tell me a candidate?
  • Suzuki-san,

    Because power supply is 5V, I suggest LM358LV or TLV9002 as the low cost solutions. To support more supply voltages, I suggest TLV9302 or TLV2170. The  OPA2990 should also work well.

  • Hi Mr.Ron Michallick,

    We will prepare and verify some of the proposed IC.
    We would like to resolve this issue once we receive the answers from the quality team.
    Thank you for your help.

    Best regards,
    K.Suzuki

  • Suzuki-san,

    The top side marking by itself was not enough to determine if this was a real TI 2008 device. Please give the STC or batch# for the affected reel? 

    I can say this is not a 2018 OPA2137U.

  • Hi Mr.Ron Michallick,

    I checked the purchase route, but the answer was that I don't know the batch number now because I wasn't an authorized distributor.
    We apologize for the inconvenience, but it seems that we have no choice but to give up tracking because of what we have found now.
    In addition, when I got a part that matches TI marking via DIGIKEY, I found that it works normally, and even an old part works by adding a filter, so I would like to apply this content to jumper clean.

    Best regards,
    K.Suzuki