SN75178B: Inquiry

Part Number: SN75178B
Other Parts Discussed in Thread: THVD1551, THVD1550


Good day.

Our customer working on the SN75178B and they have the following question:

1. I want know what is the baud rate with this device

2. Is it possible to derive TTL output signals from this device? And is this device is full duplex?

Can you please help us provide these information? Thank you.



  • Assuming a propagation delay of 40 ns, up to 25 Mbps is possible.

    The schematic on page 2 shows TTL outputs.

    The datasheet says that this repeater is "designed for one-way data communication"; it is neither full nor half duplex.

  • Hi Cedrick,

    Just to add to Clemens' response a bit, the T pin can be used for a TTL output of the A-B differential input state. 

    For reference, an example of a full-duplex device would be THVD1551 which has a differential driver and receiver (like SN75178B) but also has an independent TTL input for the driver (unlike SN75178B where this is internally tied to the differential receiver state). In contrast, a half duplex device such as THVD1550 has its driver and receiver sharing the same differential lines while also having dedicated TTL input and output pins for the driver and receiver respectively. 
    So while I agree with Clemens that SN75178B is neither full nor half duplex, it is similar to a full-duplex device that has its TTL input for the driver tied to the receiver output. 

    Let us know if you have any more questions. 

    Eric Schott