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100Mbps Ethernet Transceiver Chip for E/O/E Media Converter

Nasri Naim
Prodigy 70 points
Other Parts Discussed in Thread: DS15BR400, DP83620, DP83620-EVK, DP83849IF, DP83849IFVS-EVK

Hi everyone,

I have an in-house built optical transmitter (LED) and ROSA (PIN & TIA) that we are developing as our optical link. I would like to demo this link by building a prototype 100Mbps Ethernet - Optical and Optical - 100Mbps Ethernet media converter. 

My question is, what kind of 100Mbps Ethernet Transceiver chip is suitable for this purpose based on my transmitter and receiver specification below.

Transmitter - Input Signal : Works best with LVDS. But it will be able to take low voltage differential in the region of 200mVpp to 500 mVpp differential. The common move voltage is not important as I will AC-couple the signal before entering the device.

Receiver - Output signal is SLVS, which is Vcm = 200mV and Vswing = 200mV (single ended). I will use the output in differential mode

My Tx-Rx link can achieve up to 700Mbps using LVDS input signal to my transmitter (I used TI DS15BR400). However, the target of this demo is only at 100Mbps using 100Base-T configuration. Based on my transmitter requirement and receiver output, I think it works best if there is an Ethernet - LVDS transceiver chip, but I'm not sure if TI has such a thing.

I realize that there are many 100Base-T to SFP media converters out there. However, our current transceiver product is still in prototype form and are not in the SFP module form. Thus, I'm looking to purchase the transceiver chip (or its Eval board) and try to tap the signal direct to my transmitter, and also take my receiver's signal to the chip for media conversion.

Thanks in advance!

 

  • 0
    TI__Mastermind 31600 points

    As I understand it, the proposed configuration would be:

    100Mbps Ethernet - DS15BR400 - Optical

    The DP83620 supports 100Mbps via Copper or Fiber.  The EVM page is:

    http://www.ti.com/tool/dp83620-evk

    The EVM is populated with an RJ-45 that includes integrated magnetics and has a footprint for a fiber transceiver.  Does this look like a possible starting point for your implementation?

    Patrick

  • 0 in reply to Patrick OFarrell
    Prodigy 70 points

    Hi Patrick,

    The proposed configuration is actually:

    100Mbps Ethernet - Optical and Optical - 100Mbps

    It is just that our particular type of transmitter works best with LVDS input signal. The DS1BR400 was only used to simulate an LVDS input signal in the Tx-Rx link test. In this prototype build, the signal would come from the Ethernet PHY, so it would be best if the signal is near LVDS. What is the typical output to the transmitter by the Ethernet PHY?

    And also, our optical receiver has a single ended output of VCM = 200mV and Vswing = 200mV. Does the Ethernet PHY receiver input requirement meets this spec? 

    Thanks,

    Nasri

  • 0 in reply to Nasri Naim
    Prodigy 70 points

    Hi Patrick,

    Just to add, I would like to design my transceiver board to meet the SFP interface requirements. So I'm looking for a chip that possible comes with an eval board that has the SFP connector ready.

    On a side note, for the DP83620 you showed me, what is actually the pins that would drive my transmitter and which pins would receiver my receiver output? I'm sorry but this is the first time i'm dealing with an Ethernet PHY so I'm quite confused. 

    Thanks.

  • 0 in reply to Nasri Naim
    TI__Mastermind 31600 points

    You can see the connections to the fiber transceiver in the schematic for the DP83620 eval board (http://www.ti.com/lit/pdf/snlr004).  The fiber interface for the DP83620 operates differentially at LVPECL levels so it will not be directly compatible with your requirement for a single ended signal with 200mV swing.

    Patrick

  • 0 in reply to Patrick OFarrell
    Prodigy 70 points

    Hi Patrick,

    Thanks for your feedback. There are three things that I'd like to ask.

    1. Correct me if I'm wrong, but the DP83620 does not seem to  permit the copper-optical (BASE-T to BASE-x) or optical-copper on a single chip, does it? It looks to me that it requires me to have two back-to-back DP83620 to convert optical-copper or copper-optical.
    2. I've also realized that many Ethernet PHY with BASE-X support commonly makes use LVPECL levels. If i have a receiver output of VCM = 0.2V and Vswing = 0.2V (single ended), would you recommend that I use a limiting amp to make it compatible with LVPECL? If so, what type of limiting amp would you recommend?
    3. Lastly, I'd like to find a PHY that can do BASE-T to BASE-X (and conversely) conversion on a single chip, is there any from TI that you would recommend?

    Thanks and I really appreciate your response.

    Nasri

  • 0 in reply to Nasri Naim
    TI__Mastermind 31600 points

    A single DP83620 device cannot convert Copper to Optical by itself.  As you note, it would require two DP83620 devices back to back.

    TI does offer a device that can perform this conversion on a single chip.  The DP83849IF is a two port PHY that supports this functionality. 

    We have an application note for the DP83849IF that describes the configuration options for this functionality (http://www.ti.com/lit/pdf/snla086).  In the application note, conversion between copper and optical is referred to as media conversion.

    The DP83848IF evaluation board (http://www.ti.com/tool/dp83849ifvs-evk) supports media conversion.  It comes populated with one optical transceiver and one transformer / RJ-45.  The connections are the same as those for the DP83620 and can be seen in the evaluation board schematic (http://www.ti.com/lit/pdf/snlr002).

    I will discuss possibilities for adapting the signal swing to LVPECL levels with my colleagues and see if we can make a suggestion.

    Patrick

  • 0 in reply to Patrick OFarrell
    Prodigy 70 points

    Hi Patrick,

    Going back to my previous post about the Ethernet PHY for media converter application. I have renewed my interest in using the DP83849IF as a one-chip solution for media converter. For now, I have the following questions:

    1. I have read the datasheet that stated that the chip can be used in media converter mode (no connection to MAC) with only the strap options, which means no registry configuration is necessary. Can you confirm this?
    2. For the fiber interface, the input requirements into the chip (which is the output from my TIA) is 200mVpp minimum to 1000mVpp maximum as stated in Datasheet-Page 15-PMD Input Pair. Is this correct?
    3. For the fiber interface, what is the pk-pk output of the chip (which will be the input in my transmitter)? Is it the one labelled as 'VFXTD_100' where the value is 0.5V typical? If it is, is this value configurable? 

    Thank you.

    Nasri

  • 0 in reply to Nasri Naim
    TI__Mastermind 31600 points

    Nasri,

    Yes, the device can be strapped to media converter mode without any register configuration.  This is described in the application note.

    The fiber receive inputs are LVPECL levels.  The 200mVpp and 1000mVpp levels in the datasheet DC specifications refers to the 100Base-TX (Copper) rather than 100Base-FX (Fiber).

    Yes, the VFXTD_100 value indicates the fiber transmit levels.  No, this is not configurable. 

    Patrick

  • 0 in reply to Patrick OFarrell
    Prodigy 70 points

    Hi Patrick,

    Thanks for the clarification.

    Out of curiosity, is there any other TI Ethernet PHY product that offers media conversion mode on one single chip, other than the DP83849IF? I'm looking at the 100BASE conversion, so it can be either with/without 10BASE & 1000BASE. 

    Thanks,

    Nasri

  • 0 in reply to Nasri Naim
    TI__Mastermind 31600 points

    Nasri,

    The DP83849IF is the only device in the Ethernet portfolio that supports media conversion in a single chip. 

    Patrick

  • 0 in reply to Patrick OFarrell
    Prodigy 140 points
    Greetings!

    Is there any provision for support of Infiniband (IB), Internet Wide Area,RDMA Protocol (iWARP), and RDMA over Converged Ethernet (RoCE),NIC - Remote Direct Memory Access (RDMA) together with the SMB Direct and SMB Multichannel features of SMB 3.0. RDMA
    with TI's Copper-to-Fiber Ethernet Media Converter-Copper-to-Fiber (Media Converter with TI DP83849).

    Thank you.
    Maneesh