TPA3137D2: About slew rate of SD pin

Part Number: TPA3137D2

Hello,

According to Absolute Maximum Ratings, it is described about SD pin as following.

"(2) The voltage slew rate of these pins must be restricted to no more than 10 V/ms. For higher slew rates, use a 100 kΩ resister in series

with the pins."

My customer is asking about the resister in series with SD pin..

(Question)

1) According to Typical Applications(Figure.18/19), 10 kΩ resister in series with SD pin is used.

In this case ,why is 100 kΩ resister not used? Could you please tell us reason?

2) Is resister value needed to change depending on slew rate of SD pin?

 

Regards,

Tao_2199

  • Hi Tao

        Yes, this resistor value is not fixed. It's purpose is to create a RC filter, with the C inside of this pin, to decrease the slew rate and avoid the glitch happens. The resistor value 10K and 100K should all be fine to use.

  • Hello Shadow,

    Thank you for replay.

     I 'm asking about the point of slew rate just in case.

    >It's purpose is to create a RC filter, with the C inside of this pin, to decrease the slew rate and avoid the glitch happens.

    In this case, where is the point slew rate on SD signal?  Internal shutdown brock or external SD pin?

    They couldnt confirm to change the slew rate with changing external resister(10->100 K) at the point of external SD pin.

    Does the point of slew rate in this case mean at Internal shutdown brock?

      

    Regards,

    Tao_2199

  • Hi Tao

      I do think there won't be any damage happens. The RC filter only want to make sure the device can be correctly shutdown or back to PLAY. Sorry we don't have any slew rate value to define good or not good. But we can say that use resistor from 10K to 100K should all be fine. Maybe we needn't struggle too much about this point.  

  • Hello Shadow,

    Thank you for advice and comments.
    And my question is following.
    >In this case, where is the point of slew rate on SD signal as device? Internal shutdown brock or external SD pin?
    I think that because of the point of slew rate as device mean at Internal shutdown brock and they couldn’t confirm to improve the slew rate at the point of external SD pin with changing external resister(10->100 K). (Please refer below.)


    My understanding is correct?

    Regards,
    Tao_2199

  • Hi Tao,

    You can refer the slew rate requirement on table 7.1 in datasheet.

    And this requirement is on pin side, you should check it on pin.

    Customer can add RC filter on SD pin, if slew rate can meet requirement, it is no problem.

    Regards,

    Derek

  • Hello Derek,
    Thank you for reply.
    I informed to my customer your comments and they understood about it.
    I will close this thread.

    Regards,
    Tao_2199