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TLK1501: TLK1501-Correct value of RREF value

Mehmet Nazim Batur
Prodigy 20 points
Part Number: TLK1501


Hi all,

We would like to use TLK1501 in 50 ohm environment. Could you please answer the questions given below?

  1. RREF is given as 200 ohm in the datasheet. However, 100 ohm resistor is used in the EVM circuitry.  (Please see attached.) Which one is correct?
  2. We will use two TLK1501 ICs on seperate PCBS, one of them will be transmitter and the other one will be receiver. We'll use 50 ohm cables for connection. Which one is the best choice for our application, AC coupled or DC coupled circuitry? What is the difference between them?
  3.   Could you please share min/max values for VOD(p) for AC coupled circuitry? (It is given as DC coupled version in the datasheet page 18.)

Regards,

 

 

TLK1501_EVB_screenshot.jpg

 

  • +1
    TI__Mastermind 39033 points

    Hi Mehmet,

    1. I would recommend following the data sheet recommended value of 200 Ohms.

    2. AC coupling is common with high speed interfaces.  This allows for devices with different termination bias voltages to be connected together.  Also, this helps eliminate the data lines as a path for DC current that might occur in a ground imbalance.  I would recommend AC coupling.

    3. Unfortunately I don't have this data available.

    Thanks,

    Drew

  • 0 in reply to Mehmet Nazim Batur
    Prodigy 20 points

    Hi again Drew,

    As you recommended we use AC coupling option with 200 ohm RRFEF. However, there is a communication error. If we use 100 ohm instead, communication is OK.

    We're measuring output voltage waveform wih oscilloscope and VOD(pp_p) is around 300mV for 200 ohm RREF. It is around 800 mV for 100 ohm RREF. I think this error comes from the inappropriate value of VOD(pp_p). 


    What should be the VOD(pp_p) value? (min or max)

    Do we need to see similiar waveform on oscilloscope for reliable communication?(for AC coupling) 

    P.s: Internal loop-back test is OK for both version, 200 ohm and 100 ohm.