DS34LV86T: Are external termination resistors required across receiver input pins?

Figure 8 does not show an internal termination resistor. And if there were one, its value would have been mentioned in the datasheet.

Figure 6 shows external termination resistors. It says that "R_T is optional although highly recommended to reduce reflection".

Hi Brian,

This part is RS-422 - so based on the protocol - the last receiver on the line should be terminated from A - B with a 100 Ohm resistor with a cable/trace characteristic impedance appx. 100 Ohms (the termination resistor can be higher, say 120 Ohms, if it makes it easier to match characteristic impedances - you just shouldn't go below 100 Ohms)  to help reduce reflections that can cause signal integrity issues. So if you have 1 driver and 5 receivers on the bus - only the last one (farthest from driver) needs to be terminated. However this is assuming that the other receivers on the line have a stub length (the length between the main bus and the unterminated receiver) is < 1/10 * tr * c * v - where tr is the transition time, c is the speed of light, and V is the velocity of the signal in the transmission medium (usually ~70% to 75% but on trace / cable construction) . The Tr is specifically going to be for the driver of the system (since these are receivers there won't be info on this part of the application). This also assuming that a Daisy-Chain or Junction Box topology is used (which is recommended).

Please let me know if you have any other questions!

Best,

Parker Dodson