• State Resolved
  • Locked Locked
  • Replies 4 replies
  • Subscribers 34 subscribers
  • Views 1378 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

DP83620: Optical Media Converter Transceiver

Benjamin Stuart
Prodigy 40 points
Part Number: DP83620

Hi all,

I am trying to make sure that the DP83620 can be used as a media converter from an RJ 45 with magnetics. I think it is capable of output NRZI or NRZ also known as PECL output or FX output to drive an LED but I need to make sure.  Essentially I am hoping it can connect from an RJ 45 and act as the PHY layer which can be used as an optical media converter, and receiver of an FX electrical signal from a photodiode and maintain the auto negotiation for the different 10 mb/s and 100 mb/s. Does there have to be software embedded on to this device?  Would there be FX output be able to modulate an LED if I amplified it (in theory)? Would the connections to the RX signal be differential from or can it take a direct signal from a photodiode? 

After I get out a FX signal the signal needs to be amplified to drive a high power LED.  The FX signal would come out at what current and voltage? Can i use something like a wide band transconductance amplifier (OPA 861) and a high speed high power mosfet capable of ~32 mhz at ~600-750 ma and 11.2 V to modulate the LED?

Can I use something like the OPA 694 to receive the photodiode and then into High Speed Differential Driver such as the analog's AD8131 or some TI equivalent. 

I realize there are several questions in this thread, the main priority is the function of the DP 83620.

  • 0
    TI__Mastermind 18425 points
    Hello Benjamin,

    I would like to confirm if I understand your final objective correctly. It looks like you are trying to make a media convertor from standard RJ-45 to optical but not use a SFP optical transceiver. Instead you wish to use the FX output to drive a high power LED. Please correct me if I have missed something.

    DP83620 does support Fiber and Copper Ethernet but the pins are multiplexed. In other words, DP83620 will work for standard ethernet or fiber ethernet at a time. For media conversion, you would have to use 2 DP83620 in back to back configuration. If a single PHY solution is needed then I would recommend DP83849. When the PHY is configured to operate in Fiber mode then it will generate signals in compliance with IEEE 802.3u standard for 100BASE-FX. The output voltage will be between 0.3V-0.93V. The input signals will have to be differential. Auto-negotiation will not work in 100BASE-FX mode because there is no Fiber mode for 10Mbps speed.

    Lastly, could you elaborate on the use of a high power LED? Usually a SFP fiber optic transceiver is used for 100BASE-FX mode.

    -Regards,
    Aniruddha
  • 0 in reply to Aniruddha Khadye
    TI__Mastermind 26320 points

    Further, you may want to refer to TI Design "Media Converter - RJ45 to Fiber Converter Reference Design" .

    Regards,

    Geet

  • 0 in reply to Geet Modi
    Prodigy 40 points

    You are right in your analysis however if Ti had a SFP driver that would be great. We are trying to impose the FX signal on a linear part of the IV curve for the LED for a small signal change which can create the data out. From what i understand the FX signal can be interpreted as the transformation of an MLT-3 singal into a signal able to be used for an LED. The problem was i couldnt find an LED driver such as a Maxim 3967A in a dip form, so I've been looking for other solutions. We are just going to make our own dip out of the device for prototyping. The high power LED needs to be able to illuminate a room so a high power RF mosfet would need to be used to create a queiscent point for the LED, from what I understand about electronics the incoming signal will oscilate in the same form as the FX at a desired point of reference on an IV curve which then translates into an power vs current curve. Correct me if I am wrong, and if you know of a SFP chip which outputs 32 MHz which is the bandwidth of the LED that would help.

    Thanks
    Ben

  • 0 in reply to Benjamin Stuart
    Prodigy 185 points
    Dear Benjamin,
    I understand what you are trying to achieve. You need to use either 2 single Port PHY IC's or a media converter IC. The RJ45 interface is 100BaseTX, you need to convert this to 100BaseFX. To make this conversion with the DP83620 you need to use 2 of these PHY's back to back connecting over the Mii interface. So you need to start with your RJ45, take this into the 1st PHY (configured for 100BaseTX), then out across the Mii interface into the 2nd PHY configured for 100BaseFX. Now, lets look at your LED lighting that you want to modulate with Ethernet. The 100Base-FX signal from the PHY is a differential signal, this cannot drive an LED as it cannot source the current necessary. Therefore, your first step is to convert this to a TTL signal and then use the TTL to switch voltage through the LED's. Your biggest problem is the speed of your LED's. In general LED's used in lighting are slow and will not support the 125 MBd ( 62.5 MHZ ) required for fast Ethernet. In-order to get the fast rising and fall edges from your LED's you will need to provide a strong peaking circuit. Therefore, you need to feed your TTL signal into an LED drive circuit which has a high peaking current.
    Good luck with your design / Michael