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Output Impedance Value of Logic translators

Mhark Anoyo
Prodigy 100 points
Other Parts Discussed in Thread: SN74AVC32T245, TXS0102, SN74AVCA164245, SN74LVC1G125

Hi,

How could we determine the output impedance values of logic  translators SN74AVCA164245, SN74AVC32T245 and TXS0102?

Thanks.

Mhark

  • 0
    TI__Genius 9085 points

    Hello Mhark,

    Using the VOH and VOL voltage and current from the electrical characteristics section of the datasheet, you can calculate the output impedance of the sn74avc32t245 and sn74avca164245 (at 3V VCC) is about 60 Ohm.

    The TXS0102 has some internal 10kOhm pull-up resistors. This means that when the signal is high, the input impedance is around 10kOhm. When the signal is low, the impedance is going to be roughly equivalent to the RON of the TXS0102 internal FET (maximum 250 Ohm.)  

    Are there any other questions I can answer with regards to these devices? How are you going to use the information on the output impedance?

  • 0 in reply to Hattie
    Prodigy 100 points

    Thanks Hattie.

    The output impedance is for computation of compensation resistor to match with transmission line impedance.

  • 0 in reply to Mhark Anoyo
    Prodigy 190 points

    I am using SN74lvc1g125 two communicate between two micro controller on UART on long cable(CAT5) by putting this buffer on Tx of both side .now i find few problems in this:

    1. Burning of either  Rx and tx  in few cases(this happens even if i use to connect it on small cable).

    2. Noise on he output of the buffer on both side(not on input of buffer).

    Can u please tell me what will be output impedance in case of sn74lvc1g125 so that  i can choose a damping resistor to connect on the output of buffers.

     

     

  • 0 in reply to sadatan vashistha
    TI__Mastermind 46480 points

    I have attached the Voh/Ioh plots so you can calculate output impedance at the Vcc you are using.

    LVC1G125 vohioh.docx