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Original question:

UCC27424: Questions about new datasheet.

UCC27424: Question about UCC27424 new datasheet.

Kazuya Nakai59
Guru 21505 points
Part Number: UCC27424

Hello guys,

Two of my customers use UCC27424 for their mass-production.

The device datasheet was changed recently.

At this moment, they have the following questions about the datasheet.
Could you please give me your reply?

Q1.
The following are deferent points of output resistance between UCC27424 new and old datasheet.

Datasheet Version                 :        SLUS545E(OLD)                          SLUS545F(New)

Output resistance high(ohm) :     Min/Typ/Max --> 18/--/45                Min/Typ/Max --> --/1.2/2.5
Output resistance low(ohm) :     Min/Typ/Max --> 1.2/--/4.0                Min/Typ/Max --> --/0.7/1.2

Output resistances of UCC27424 new chip are improved very much from old chip.
Is measurement method and condition of the output resistance same in new chip and old chip?

Q2.
If Q1 answer is yes, what is the cause of this improvement?
Is it the switch elements (PMOS, NMOS, Bipolar NPN transistor) drivability improvement at new process?  
Or the switch element size was changed bigger to be reduced output resistances?  

Q3.
Why didn't TI design the output resistance value to be the similar with the old chip?

Your reply would be much appreciated.

Best regards,
Kazuya.

  • 0
    TI__Expert 8460 points

    Hi Kazuya,

    The PCN describes the reason for the changes. This device was qualified for a new manufacturing flow and part of that qualification process was re-characterizing the device to ensure performance expectations. During this testing, it was found that certain specs were better than the original datasheet and then the latest datasheet was updated to match those specs and performance of the device.

    Thanks,
    Rubas

  • 0 in reply to Rubas Khalid
    Guru 21505 points

    Hi Rubas,

    Thank you very much for your reply.

    Could I ask you one question as the below?

    Q.
    Are these output resistance improvement intentional?

    Thank you again and best regards,
    Kazuya.

  • 0 in reply to Kazuya Nakai59
    TI__Expert 8460 points

    Hi Kazuya,

    When moving to the new manufacturing flow, we expected improvements. During testing we found certain characteristics to be heavily improved, like the output resistance in this case. Please review the PCN, as it explains the manufacturing process changes and resulting characterization changes.

    Thanks,
    Rubas

  • 0 in reply to Rubas Khalid
    Guru 21505 points

    Hi Rubas,

    Thank you very much for your reply.

    In the result, I couldn't understand why TI changed the Ron of output driver.
    Is there any your customer who are in trouble with UCC27424 of new fab because lower Ron causes switching noise increasing?

    Thank you again and best regards,
    Kazuya.

  • 0 in reply to Kazuya Nakai59
    TI__Expert 8460 points

    Hi Kazuya,

    Typically, it is not the output resistance that creates switching noise. Switching losses are circuit/application dependent, and thus they vary between different applications. Improvements were expected when moving to the new manufacturing flow, and the characteristics that were improved are reflected on the PCN and updated datasheet.

    Thanks,
    Rubas