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SN74LVTH16244A: Input transition rise or fall rate requirement

Johnny Guo
Expert 4910 points
Part Number: SN74LVTH16244A

Hi, team,

I have one question about SN74LVTH16244A Input transition rise or fall rate.

In datasheet, the input transition rise or fall rate is 10ns/V maximum as shown below. But in customer's test, the result is 3.36us/V shown in below waveform.

My questions:

1. What is the minimum value of input transition rise or fall rate?

2. How is the risk for customer's test rate?

Thanks.

Johnny

  • 0
    TI__Guru 62060 points
    Hi Johnny ,

    It could be a potential problem for the customer with such slow rising inputs.
    www.ti.com.cn/.../slla364a.pdf

    Please refer to this white paper which talks about implications of having slow rising edge inputs in general.
    However, in case of bus hold inputs it may be different if the feedback circuit internally holds a value until switched. In any case , i would suggest using a schmitt trigger device ahead to square up the signal.
  • 0 in reply to ShreyasRao
    TI__Expert 4910 points

    Hi, Shreyas,

    In customer's application, this slow rising edge only occurs once or twice when the system first starts up. After startup, the input of SN74LVTH16244A will be a constant high or low voltage, no pulse signal any more.

    So how about the risk of this?

    Thanks.

    Johnny

  • 0 in reply to Johnny Guo
    TI__Guru 62060 points
    Hi Johnny ,

    The risk is not with the device but for the system performance. The slow rising edge can cause some oscillations or signal integrity issues and if the customer is fine to accept it then there is no concerns w.r.t the device.
    also , to note that if the Vcc is also ramping along with input signal at startup(slow or fast) , it wont cause issues.
  • 0 in reply to ShreyasRao
    TI__Expert 4910 points

    Shreyas,

    Thanks for your reply.

    I have another question, for SN74LVTH16244A, is there any requirement of Bushold Input Over-Drive Current to Change State?

    Thanks.

    Johnny

  • 0 in reply to Johnny Guo
    TI__Guru 62060 points

    johnny ,

    The bus hold current is defined in the electrical spec as Ii(hold) which is the over drive current required to change state of the inputs.