Q
What is MLVDS and how is it different from B-LVDS and RS-485?
A
MLVDS Stands for Multi-point LVDS (Low-Voltage-Differential-Signaling). It isstandardized by the Telecommunications Industry Association (TIA) in EIA/
TIA-899. It is an electrical specification for OSI Layer 1, the physical
layer. It was developed to overcome the limitations of LVDS, which is a
multi-point link. MLVDS allows for 32 nodes to be connected together on the
same differential pair of lines as opposed to 32 separate differential pairs in
the case of LVDS.
Bus LVDS or B-LVDS was developed by National Semiconductor. It was never
standardized or is that widely adopted. It can only achieve 20 nodes on the
bus. MLVDS can receive signals from B-LVDS devices.
RS-485 allows up to 32 unit load devices to be connected on the same bus. It
has a higher differential voltage (1.5V) and larger common-mode range (-7V to
+12V), which allow it to operate over long distances, up to 1.2km. These
characteristics however, don’t lend themselves to achieving high speeds. MLVDS
sacrifices distance for speed, with lower differential voltages and common-mode
range allowing speeds of up to 250Mbps over shorter distances.