I am now designing M-LVDS circuit in my design.
I have two questions.
1. PCB Trace impedance
I will use 100 ohm termination resistor at both ends of M-LVDS lines. What shoudl be the trace impedance?
-Differential impedance : 50ohm (Line to Ground impedance : 100 ohm)
Am I correct?
2. Input threshold of Type 2 M-LVDS receiver
I am considerign M-LVDS as a drop replacement of RS485 communication. Do I need bias resistor for fail-safe?
RS485 Receiver (like SN75176) has input threshold ( < -0.2V, or >0.2V) but, Type 2 M-LVDS Receiver( like SN65MLVD204) has input threshold (<0.05V, >0.15V), so in case there is no node to transmit, the receiver output of RS485 with bias resistor will be high, but the receiver output of M-LVDS without bias resistor will be low.
the output of receiver is connected to UART RX in MCU. so, low input in idle bus will cause wrong UART function.
Do I need same bias resistor in M-LVDS bus (as replacement of RS485), and if yes, what resistor value shoud be used?
Thank you for your help and advice in advance.
Best Regards
Hak-Jin Jeong