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THVD1550: RS485 Transceiver

venkat reddy chinthapalli
Prodigy 20 points
Part Number: THVD1550

Hi Team,

I am using THVD1550 RS485 Transceiver in my design.

Please help me out for below queries.

1. How much of overshoot and undershoot is allowed for this IC. We have connected VCC to +5VDC.

2. We have probed on Pin no. 6 (A) & Pin no.7 (B) of the IC while RS485 communication to individual probe channels and done Math Calculation (A-B). Captures of A signal, B signal and A-B is attached.

3.  We are seeing some overshoots and ringing. I would like to know how much is acceptable.

THVD1550.xlsx

  • 0
    TI__Mastermind 46447 points

    Hi Venkat,

    For your questions please see comments below:

    1. So it depends what pins you are referring to different pins have different voltage ratings:

    For Differential Pins (A and B)

    For the A/B pins we recommend that the application keeps A or B pins between -15V to 15 w.r.t. ground with a max rating of -18V to 18V (but we recommend typical operating between -15 to 15V). If the ringing overshoot/undershoot doesn't violate the conditions it will not damage the device - if there is ringing as long as its voltage is in a fully defined logic range (above VTH+ or below VTH- during ringing will keep logic consistent). 

    For Single Ended Inputs and Output (D,R, /RE, DE)·

    We recommend operating these pins from 0V to VCC (R is an output - but if attaching a pull-up resistor on this pin make sure it is connected to VCC not higher) The max rating is up to 5.7V and min is -0.3V. 
    2.  Nothing looks like there would be problems with that signal - there is some ringing but it doesn't seem to violate any spec. 
    3. As mentioned in the response the first question - essentially as long as the logic is defined (which in your example it looks like it is) and there isn't voltage violations (which by your example there is not) - You should be okay and I don't see issue with the amount of ringing seen. 
    Please let me know if you have any other questions!
    Best,
    Parker Dodson