• Resolved

Digital UART TTL Signal Conditioning in range of 1-50 MHz: Inverters, Buffers, Repeaters?


I have a simple UART communication signal coming from a µC, in the rangeof 1-50 MHz (not decided yet). Theoretically, the signal could originate from a MCU's GPIO as well. 

The signal is transmitted to several other µCs. In the transmission line, there are several switches and connectors and bifurcations that cannot be avoided and deteriorate the signal. What looked perfectly square and steep flank in the beginning is not recognizable when arriving at some of the destination MCUs, because the switches round the flanks, and there are reflections in the line and some signal attenuation.

We are talking about unidirectional traffic at the moment as a simplification. Later, half-duplex operation will be used too.

Even if I use buses (I2C, RS-485, CAN...), similar problems arise through the above mentioned issues in the transmission path.

What I am looking for is the following:

I guess that components exist that simply take an input signal (ideally with help of sub-sampling), detect if it is 0 and 1, and output a new, nice, "perfectly" square output signal. Of course, there will be a little propagation delay, but I expect this to be only a bit longer than the duration of one bit (right?). The transmission speed is constant and known. However, I would like to avoid sending a clock signal, as that signal would deteriorate as well and would need an additional connection.

What type of components, and possibly which concrete choice for a TTL +5V signal against GND could you recommend? I was looking for repeaters, but could not find one for a "simple" UART signal. Or do I need a 1-bit buffer?

It seems that I could pass the signal through 2 inverters such as SN7414? But this would waste PCB space, connections and probably propagation delay.

Any help would be appreciated.

Thank you,


  • Hi Christoph,

    We are looking into this one and will get back to you soon.


  • In reply to Max Robertson:

    Hi Max,

    in the meantime, I believe to have understood that I simply need a buffer / line driver, which is essentially the same or quite similar to two inverters in a row. The question now is rather if there is a good selection tool for such buffers, and if I forgot about anything. I am working with 5V signals in the range of 1-12 Mbps. 



  • Hello Christoph,

    Do you want auto direction sensing buffer (TXB0101) or would you rather have a direction controlled buffer (SN74LVC1T45).  The auto direction buffers generally have lower drive strengths but might be able to support 50MHz but that depends on the bus loading, the data rates in the datasheet are at 15pF.  I doubt your bus is that lightly loaded, but it could save you one pin on your micro. 

    Direction control (SN74LVC1T45) is more likely the best choice for heavy loading. 


    Let me know if you have any questions. 

    -Francis Houde