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sn65hvd96: Creating Power-Over-Data with Polarity Immunity

Majdi Richa
Prodigy 10 points

Part Number: SN65HVD96

Hello,

Based on this application note "slla336" we're willing to design power over data communication bus with maximum number of nodes.

Known parameters: +12V DC bus, 20kbps maximum bitrate

Unknown parameters:

- Maximum number of allowed nodes on the same terminated bus

- Maximum number of allowed nodes on an un-terminated bus

The latter application note dos not show the maximum number of nodes; however the datasheet mentions something about 32 and 200 nodes (respectively)

What are the design considerations in order to allow a maximum number of nodes on that specific power over data bus (coil value, capacitors values, etc...)? We have also checked this document "tidu993"

Any support would be much appreciated.

  • 0
    TI__Mastermind 25705 points

    Majdi,

    The number of nodes in the data sheet comes from input impedance of the receiver. In other words, the more nodes we have on a bus, the more current they take from the bus. But in power over RS485 application, it's different. The DC impedance is less a concern, while the AC parameter - cut off frequency is the limit here. More nodes on the bus have less input impedance, therefore the cutoff frequency of high pass filter becomes higher. But we want to make sure it's low enough comparing to the data rate. So overall, the LC value and data rate all contribute to the nodes the system can support.

    Regards,

    Hao

    .