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SN65176B: Overshoot and Undershoot parameter of SN65176BDR

Zhanpeng Li
Intellectual 2140 points
Part Number: SN65176B

Hi Team,

This is Brandon, My customer is using the SN65176B as RS485 and during the test, we found there are overshoot and undershoot voltage on D-pin, the waveform is attached below:

From the waveform, we found that the undershoot voltage below to -0.62V and overshoot voltage reach to 5.9v. From the datasheet, we could only found the recommendation below:

could you help check is there any Tolerance on this pins?  and also how could we enhance DI siganl quality?

BR

Brandon

  • 0
    TI__Guru 74282 points

    Brandon,

    In the datasheet Absolute Maximum Ratings table is listed the pin voltage tolerances. These tolerances are meant to indicate at what voltage each pin will be damaged. For the D pin, the maximum is 5.5V, and there is no minimum. In reality, the minimum is likely -0.3V, however, with these absolute maximum ratings, especially on older devices, there is some margin to when damage will actually occur.

    Placing a filter capacitor on the D pin, along with a series resistor to create a low-pass filter would help with undershoot, but since the signal is coming from a controller in the SN device, is it possible to condition the signal a bit better from the controller side?

    Regards,

    Eric Hackett