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DP83849I: Fiber_port_PECL

Ganesh V
Prodigy 120 points
Part Number: DP83849I

Tool/software:

Hi,

I am referring the "DP83849 DUAL PHYTER DEMO BOARD" schematic. we are planning to use this PHY for Copper and Fiber port.

I would like to know about the PECL voltage standard,

From the below Image the "HFBR-5308" device accept the VIL Min -1.81 and VIH -1.16V

I am confusing will the DP83849 device will give the negative voltage to the Fiber transceiver?

Can you clarify how the DP83849 voltage standard meeting the  VIL Min -1.81 and VIH -1.16V requirement? how to measure this ?

  

From HFBR5308 datasheet.

Thanks

Ganesh V

  • 0
    TI__Mastermind 39785 points

    Hello,

    In your provided table, it appears that VIL/VIH is dependent on the VCC. So if VCC = 3.3V, the VIL would be [1.49V, 1.825V] while VIH would be [2.135V, 2.42V]. 

    Sincerely,

    Gerome

  • 0 in reply to Gerome Cacho
    Prodigy 120 points

    Hi,

    "if VCC = 3.3V, the VIL would be [1.49V, 1.825V] while VIH would be [2.135V, 2.42V]."

    VIL and VIH of which device was it "DP83849 " then even the Fiber transceiver VOL and VOH also mentioned the same thing, my doubt is how the Negative voltage coming here , we are not providing any negative voltage to the  'DP83849 " and "HFBR-5308" this case how this is working.

    thanks

    Ganesh V

  • 0 in reply to Ganesh V
    Prodigy 120 points

    Hi,

    Now I understand, They mentioned in Data input Low as (VIL-VCC)= -1.81  this case VIL is equal to [1.49V, 1.825V] so this depends the VCC.

    Correct me if I am wrong.

    The below 130 and 80 Ohms termination used to shift the Voltage to ~2V from the Ethernet data? I assume DP83849  Ethernet output for 100Mbps +/- 1V.

    So that this will meet the VIL and VIH standard of Fiber transceiver. 

     

    Please provide the clarification on this.

    Thanks

    Ganesh V

  • 0 in reply to Ganesh V
    TI__Mastermind 39785 points

    Hello Ganesh,

    This guidance looks to be present on the datasheet recommendation for FX circuitry, Figure 8-2 of SNOSAX8D. Please note that support for this device is limited only to datasheet.

    Sincerely,

    Gerome