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TLC555: Regarding propagation delay

Daisuke Higa
Genius 5035 points

Part Number: TLC555

Hello support team all.

I found the following post.

[FAQ] TLC555: What are the performance differences expected for TLC555 PCN 20231130002.1? - Clock & timing forum - Clock & timing - TI E2E support forums

It seems that the propagation delay time is controlled very small in the products of the new process, but there seems to be a big gap with the data of propagation delay time in the data sheet.
Is the measurement condition different?
Or is the data in the data sheet wrong?

image.png

image.png

Also, regarding the calculation tool in the following site, could you tell me the details of the calculation formula of H period and L period with diode?
I think the delay time is substituted in the calculation formula, but since there is no specific information, I cannot verify whether the result is correct.

www.ti.com/.../TLC555CALC

The process is new and many problems occur. I would like to organize the correct information, so please cooperate.

Best regards,

DH

 

  • 0
    TI__Guru**** 174826 points

    Hello DH,

    That PCN did result in delay being much shorter as described in FAQ.  A later PCN 20260217004 changes design to make delays closer to original. The current data sheet is updated for this new PCN.

    Daisuke Higa said:
    I cannot verify whether the result is correct.

    What is the desired frequency and duty cycle and what value were chosen?

  • 0 in reply to Ron Michallick
    Genius 5035 points

    Hi Michallick-san

    Is the Rev in the datasheet I->J because the die was changed to Rev. A in the first PCN?

    I did not see any data on the Rev. J datasheet showing a significant reduction in delay time.

    I am asking because the frequency and duty are set in a wide range, which has a significant impact on the system we are currently using.

    Could you also answer the other question below?

    Also, regarding the calculation tool in the following site, could you tell me the details of the calculation formula of H period and L period with diode?
    I think the delay time is substituted in the calculation formula, but since there is no specific information, I cannot verify whether the result is correct.

    www.ti.com/.../TLC555CALC

    Best regards,

    DH

  • 0 in reply to Daisuke Higa
    TI__Guru**** 174826 points

    DH,

    The importance of propagation delay being the same wasn't fully understood when rev was changed to A. 

    Shorter delays are better except when existing application designs were tuned for original being worse.

    Daisuke Higa said:
    could you tell me the details of the calculation formula of H period and L period with diode?

    Discharge (L period) is unchanged. Set by RB and C 

    Charge (H period) is likely simplified. Charge voltage reduced by diode forward voltage. Set by RA and C

      

    Two diode is better for less duty cycle variability.

    Now both high and low period have mostly matching reduced charge/discharge voltage 

  • 0 in reply to Ron Michallick
    Genius 5035 points

    Hi Michallick-san

    Thank you for your information.

    I understand that with one diode, only the H period is affected by diode fluctuations, so it is appropriate to use two diodes.

    TLC555CALC uses a formula with two diodes, right?

    Best regards,

    DH

  • 0 in reply to Daisuke Higa
    TI__Guru**** 174826 points

    DH,

    This tool uses one Diode