• State TI Thinks Resolved
  • Locked Locked
  • Replies 8 replies
  • Answers 1 answer
  • Subscribers 49 subscribers
  • Views 320 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

Original question:

TL072: technical tests of our products

TL072: difference in value and consequently not functioning properly

DEFECTIVE RMA TEAM
Prodigy 40 points
Part Number: TL072

It was identified in the technical tests of our products, the component TL072 of the manufacturer Texas of the lot 1621012MY1, giving a difference in
value and consequently not functioning properly for the products. It was identified in the tests, that from 4KHz, the product has a significant drop in
response. At 18KHz the result is -8dB on the product.
2,500 pieces were used, and they are also being sent, but outside their encapsulation and with traces of solder.

  • 0
    Prodigy 40 points

    Arrow Ref: RMA-2022-04254

  • 0 in reply to DEFECTIVE RMA TEAM
    TI__Mastermind 31576 points

    Hello,

    Per the previous thread, could you please provide the schematic of the circuit that the devices were tested in?

    This was asked for multiple time in the previous thread. This is necessary information to help answer your question and we cannot provide a comment without it. The previous thread you have linked was locked because of inactivity.

    Best,
    Jerry

  • 0 in reply to Gerasimos Madalvanos
    Prodigy 40 points

    SCH_HL800.4-TPT1000.4_2ohms_R4A.pdf 

    Hello, Above is the schematic that they finally have provided. Please let us know if you are or aren't able to access the link above. 

    Thankyou, 

    Josheil 

  • 0 in reply to DEFECTIVE RMA TEAM
    Guru 140200 points

    Hi Joshell,

    the 90Hz low pass filter looks strange. R109 and R137 present a strong load to the output of OPAmp and cause a high load current. At low frequencies and 1Vpeak 10mA peak is flowing. Is this wished?

    Also, C90 goes to the connection point of these two resistors. This looks very unusual. Looks like a mix of a Sallen Key filter without gain and a Sallen Key filter with gain. Is this planned?

    Also, if this low pass filter shall have a precise performance, no X7R caps should be used in this low pass filter because they show a huge capacitance drift with frequency, voltage and temperature. You should use plastic foil caps or at least NP0.

    DEFECTIVE RMA TEAM said:
    It was identified in the tests, that from 4KHz, the product has a significant drop in
    response. At 18KHz the result is -8dB on the product.

    Are you sure that C47 and C52 are 15pF and not 150pF?

    Many cap meters allow the measurement of capacitance even if the cap is still soldered in the circuit. Remove the supply voltage of OPAmps and measure the capacitance of C47. If the cap meter gives a strange reading, carefully desolder C47 and measure its capacitance afterwards. I wouldn't be surprised, if the caps are 150pF instead of 15pF.

    Kai

  • 0 in reply to kai klaas69
    TI__Mastermind 31576 points

    Hello Josheil,

    I would like to let you know that this is a public forum. I have downloaded your schematic and will remove the post with the link. In future cases you may add me as a friend on E2E and message a schematic directly if you do not wish to share a schematic publicly.

    Supplementing Kai's comments with simulation: if the value of C47 and 52 are 15pF, your cutoff is 33.87k

    If they are 150pF your 3dB cutoff is at 4.6kHz

    Best,
    Jerry

  • 0 in reply to Gerasimos Madalvanos
    Prodigy 40 points

    Hello team, 

    Here is the customer's response: 

    the 90Hz low pass filter looks strange. R109 and R137 present a strong load to the output of OPAmp and cause a high load current. At low frequencies and 1Vpeak 10mA peak is flowing. Is this wished?

    Also, C90 goes to the connection point of these two resistors. This looks very unusual. Looks like a mix of a Sallen Key filter without gain and a Sallen Key filter with gain. Is this planned?

     

    ------ Yes, this circuit has been used for a long time. TI in Brazil is aware of it

     

    Also, if this low pass filter shall have a precise performance, no X7R caps should be used in this low pass filter because they show a huge capacitance drift with frequency, voltage and temperature. You should use plastic foil caps or at least NP0.

     

    DEFECTIVE RMA TEAM said:

    It was identified in the tests, that from 4KHz, the product has a significant drop in
    response. At 18KHz the result is -8dB on the product.

    Are you sure that C47 and C52 are 15pF and not 150pF?

    ------------------Yes, we are sure

    Many cap meters allow the measurement of capacitance even if the cap is still soldered in the circuit. Remove the supply voltage of OPAmps and measure the capacitance of C47. If the cap meter gives a strange reading, carefully desolder C47 and measure its capacitance afterwards. I wouldn't be surprised, if the caps are 150pF instead of 15pF.

    Arrow Ref: RMA-2022-04254

    thankyou, 

    Josheil 

  • 0 in reply to DEFECTIVE RMA TEAM
    TI__Mastermind 21172 points

    Hello Josheil, 

    I will continue support from here as Jerry is currently out of office. 

    What is the failure rate on this lot? What about other lots of the same device? 

    All the best,
    Carolina