Other Parts Discussed in Thread: SN65LBC173A, TB5D1M, SN65LBC172A
I found this app note:
https://www.ti.com/lit/an/snla041a/snla041a.pdf
It mentions:
Differential ECL or even Pseudo ECL (PECL) will typically directly inter-operate with a RS-422 receiver.
Is it possible to use TB5D2H as Driver, and a device like SN65LBC173A as Receiver?
I have a use-case where there are two boards directly connected together (no cabling) and the trace-length is <0.5m maximum.
Receiver-side has 100Ω termination resistor between differential signal lines. There is no pullup or pulldown.
I am a little worried about using the TB5D2H or TB5D1M driver as-is, because the output stage, as far as I can tell, is just a high-side transistor.
The receiver has good common-mode capability, but I'm not sure how the device would work...
Figure 15 ~ Figure 17 in the Datasheet show some examples. Figure 15 would be closest to customer use-case (100Ω termination resistor on Receiver-side), but they can't add pulldown resistors to the design.
Are the pull-down resistors necessary? I think they are used to "pull the voltage low" when that transistor is off.
This way, if one transistor is conducting, then that line is "high"
And if the other transistor is "off", then that line is pulled "low" and this creates the necessary voltage differential.
Is there anyway to use the device without these Rs resistors? What kind of behavior would we see?
