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TXB0108PWRG4

SOON KIAT RAYMOND QUAH
Prodigy 70 points

Other Parts Discussed in Thread: TXS0108E, TXB0108, SN74LVC8T245

Hi, 

Im using TXB0108PWRG4 to translate 3.3V input signal from FPGA chip to 5V output. The 5V input is used to drive a off the shelf power amp's control signal.

I realised that the output voltage drop from 5V to 1.8V when connected to the power amp. I believe this might be cause by the internal pull up / pull down resistor in the power amp.

Is there any recommendation to solve the issue? Is the any chip I can use to replace TXB0108PWRG4 with similar pin layout and size as my PCB board have been fabricated.

    

  • 0
    Mastermind 7395 points

    Take a look at TXS0108E, maybe it can help you

  • 0
    TI__Expert 4705 points

    Hi,

    Please double check the resistor inside the power amp and find the root cause.

    Based on what you talked, it should be the pull down resitor inside. and if so, when you change the TXS0108, it should have the same problem and only the direction control part can solve this problem.

    any update, please let me know.

    BR
    Junjie

  • 0 in reply to Junjie Mai
    Prodigy 70 points

    Hi Junjie, I'm still checking with the vendor on the internal circuity of the power amp. Im suspecting there an 2.2K pull down resistor which will cse the 5V to down to 1.8V due to voltage divider.

    I have looked at the schematic of TXS0108, since it dont have the 4k resistor at the output (no voltage divider circult will be formed).

    Can you explain why TXSB0108 will not work too?

     

  • 0 in reply to SOON KIAT RAYMOND QUAH
    TI__Expert 4705 points

    Hi,

    if you check the datasheet for TXS0108, you will see it is mainly for open drain application, and it has the internal pull up resistor. when it has the "high" output, the internal pull up resistor is 4Kohms, if you have the internal 2.2Kohms pull down in the receiver side. based on the voltage spliter, you still can not get the high voltage.

    so , if it is confirmed 2.2Kohms pull down inside for the receiver(power amp), the only choice is to change the DIR contorl part.

    BR
    Junjie

  • 0 in reply to Junjie Mai
    Prodigy 70 points

    Hi Junjie, can you explain how can i change the DIR control part?

    Do u mean changing the power amp or change to other Voltage Translator IC?

  • 0 in reply to SOON KIAT RAYMOND QUAH
    TI__Expert 4705 points

    Hi,

    :), I mean to change to another Voltage Translator IC with DIR control pin need, but I don't think you can find the PIN-PIN compatile part with TXB0108. so you may need to change your design.

    Our SN74LVC8T245 is the 8 channel part which may be OK for your application, you can check it if your power amp really has the internal pull down resistor with 2.2K.

    BR
    Junjie