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ONET4201LD in a 1 Mbps CAN application

Martin Gleich
Prodigy 20 points
Other Parts Discussed in Thread: ONET4201LD

Hi,

I already used the ONET4201LD in data Transmission applications with 100 Mbps.

No I try to transmit a CAN - protocol with a datarate of 1 Mbps max.

According to the datasheet the chip is suitable for 155 Mbps and more. But, there are no further specific Details to find in the datasheet about the behaviour of the chip at lower datarates.

Can I expect any Problems with this application?

Thanks,

Martin

  • 0
    TI__Expert 8915 points

    Martin,

    The datasheet does not contain information about operation at very low data rates because the part was originally designed for 4.25Gbps operation.

    The device should operate at 1Mbps but you will have to optimize the external components. For example, large value AC coupling capacitors if used and large value bias-T inductors if used. I would recommend that you use resistive pull-ups and not inductive pull-ups on the outputs for this case. Also, it may not be possible to use the APC loop. At very low data rates the charge and discharge times of the external CAPC capacitor becomes unequal. Typically the bias current will drift higher and the extinction ratio will decrease as the data rate is decreased. This can be improved by adding an external resistor from the CAPC pin to VCC, which helps to equalize the charge and discharge times of the CAPC capacitor. A value of around 30kohm should initially be tried but it will probably require some optimization. Adding this resistor helped the operation at 155Mbps but I'm not sure at 1Mbps.

    Regards,

    Alex.

  • 0 in reply to Alex Davidson
    Prodigy 100 points

    Hi,

    Using ONET4201LD for FSO application. Attached circuit works for 100Mbps. But When I change the speed to 1Gbps, this never works. Can you advice for any change in the design ? Is AC coupling required for 1Gbps ?

    Note : circuit attached.SCHEMATIC1 _ PAGE22 - LD.pdf

    -Sudarshan2604.SCHEMATIC1 _ PAGE22 - LD.pdf

  • 0 in reply to sudarshan ns1
    Prodigy 100 points

    Hi Alex Davidson,

    Could you let me know for the above problem ?

    Thanks

    Regards

    Sudarshan