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SN65176B: Overshoot and Undershoot parameter of SN65176BDR

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

  • 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