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LM358A: Counterfeit LM358A? Because of never seen problems in functional testing

Stefan Hunziker
Prodigy 100 points
Part Number: LM358A

Hello

Because of problems in functional testing and checking assembly I have seen there is a different device marking on LM358A.
In production lot 1  we did not have such functional testing problems.


Below you see the device marking of lot 1 (with TI label) and lot 2 (without label) and the reel label from production lot 2.

Device marking lot 1:

Device marking lot 2:

Reel label of lot 2:

Please could you check if these amplifiers from lot 2 are really origin ware from TI.

Thanking you in anticipation.

Stefan

  • 0
    Guru 140200 points
    Hi Stefan,

    were the LM358A purchased from an authorized TI's distributor?

    What are the functional testing problems?

    Kai
  • 0 in reply to kai klaas69
    Prodigy 100 points
    Hi Kai

    they were purchased from Arrow Central (labeled on reel).

    The functional testing problems are the followed:
    Basicallly two Opamps are used in application. The first Opamp is used to amplify current sensing and second Opamp as a comparator for delayed overcurrent shutdown. So after 5..9 second with overcurrent the circuit should be shutted down.
    When I test this function in first time the time the shut down takes about 11 seconds, when I test this function a second time (Power off time appr. 30 sec) the time out is normal between 6..8 seconds.

    Stefan
  • 0 in reply to Stefan Hunziker
    Guru 54087 points
    Hi Stefan,

    Would you suspect a capacitor value has more to do with RC time constant for those delay periods? Do you have a capacitance checker to verify the odd delay time constants are not due to temperature changes effecting cap values? Several values we tested from AVX/TDK were not holding the datasheet tolerance. Most the Samsung caps were the closest to the actual NF values @25-32*C. Tenma DMM starts cap check at 9.34NF so we have to subtract that from the final digital display value.
  • 0 in reply to Genatco
    TI__Guru*** 140146 points
    Stefan,

    Both device symbols are correct based on assembly site used. The timing differences are likely based on capacitance value and the remaining voltage charge from the previous power on.
  • 0 in reply to Genatco
    Guru 140200 points
    Hi BP101,

    good point! And ceramic caps can show a huge DC bias effect as well...

    Kai
  • 0 in reply to kai klaas69
    Guru 54087 points
    Hi Kai,

    Never knew that bias effect part. Only recently discovered issue can exist after I was personally assembling custom PCB & 1st checking the caps tolerance. Several expected values were no were close to 20% and some 10% were even worse. Wonder how many retailers actually check the reels are in tolerance before they pay the bill?
  • 0 in reply to Genatco
    Guru 140200 points

    Hi BP101,

    this is a 100µF/10V/X5R/1210 cap which we have to use in a product to decouple a 5V supply:

    -----------------------------------------------------------------------------------------------------------------------------

    -----------------------------------------------------------------------------------------------------------------------------

    As you can see in figure 3) the capacitance at 10V bias voltage is only 20% of the capacitance at 0V bias voltage! So, 80% of the capacitance is lost!!

    Kai