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SN65MLVD201: STAR NETWORK Configuration

Part Number: SN65MLVD201

THE 14  MLVDS (sn65mlvd201) are connected in Star network. where 7 act as transmitter and 7 act as receiver. the parallel termination of 100E is provided across all the 14MLVDS

Method1:

When the one transmitter send the data 7 receiver are receiving the same. But the load impedance is around 7.15ohm (100ohm divided by 14). But the datasheet prefers 30-55ohm load

Method2.

1. Then removed the 100ohm from 7 transmitter and replaced 100E to 220E in all the receiver. Then the load impedance was 31 ohm.

2. Out of 7, one MLVDS made as transmitter, the data transmitted from transmitter are not received at the 7 receiver side.


Query?

  1. Why for method 1 the MLVDS is working why not method 2?
  2. When one is transmitting rest 6 are floating will there be impact on the network (with parallel termination 100E on transmitter)
  3. When one is transmitting rest 6 are floating will there be impact on the network (without parallel termination 100E on transmitter i.e no termination )

  • MLVDS requires two 100ohm termination only

    please refer to this video.

    1. Why for method 1 the MLVDS is working why not method 2?

      Most likely method 2 is not working due to reflections.

    2. When one is transmitting rest 6 are floating will there be impact on the network (with parallel termination 100E on transmitter)
      1. you will want two 100ohms one for tx one for rx
    3. When one is transmitting rest 6 are floating will there be impact on the network (without parallel termination 100E on transmitter i.e no termination )
      1. no termination will not produce a voltage

  • Beyond the DC loading, both of these configurations are full of transmission line segments.  The MLVDS transmit waveform will react to the transmission line impedances and the DC load of the termination resistor.  To help debug this type of application a more detailed description of the topology would be helpful.  Any oscilloscope waveforms with information about the measurement location is also a benefit.

    Regards,

    Lee