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SN65LVDS1: optical transceivers AFBR-5805ATZ

Ilia Hadzhiev
Prodigy 200 points
Part Number: SN65LVDS1
Other Parts Discussed in Thread: SN65LVDS2, SN65ELT20, SN65ELT21, SN65ELT22, SN65LVELT23

Hello, I am trying to use AFBR-5805ATZ in custom application where no high speed communication is needed. 
I just want to send pulses to the transmitter and read them back from the receiver. 
Since AFBR-5805ATZ has differential input and output I decided to use SN65LVDS1 and LVDS2 . 
I have attached oscillographs. 

1. Can I drive the optical transceiver using custom protocol instead of ethernet ? 
2. What are the logic levels the optical transmitter needs to emit light ? ( cause with those logic levels it doesn't work) 
3. Why SN65LVDS2 doesn't generate output signal ? 



1.  Transmit 10kHz 
Yellow SN65LVDS1 input 
Green SN65LVDS2 output differential


2. Receive from external beam 
Green SN65LVDS2 diff input ( Common mode voltage 1.8V)
Yellow SN65LVDS2 output

  • 0
    TI__Genius 14791 points

    Hi Ilia,

    The AFBR-5805ATZ indicates in the transmitter and receiver sections (page 2), that the signals are differential PECL. 

    The differential output of a PECL driver is greater than what is expected for an LVDS receiver.

    Please refer to this TI application note, in the section "PECL - LVDS Interoperation" for reference: LVDS, CML, ECL-differential interfaces with odd voltages

    An option is to use to a driver / receiver / translator that accepts PECL. I did a search on the TI page using this criteria:

    LVDS, M-LVDS & PECL ICs product selection | TI.com

    Additionally, if you can share your schematic that may be helpful as well.

    Regards, Amy

  • 0 in reply to Amy
    Prodigy 200 points

    Hi Amy, 

    Thank you I will purchase SN65ELT20 and SN65ELT21 since I will have TTL logic. 
    I don't have schematic yet its concept prove stage. 
    If I connect SN65ELT20/21 to the termination scheme shown in the AFBR-5905ATZ it should work, yes ? 

  • +1 in reply to Ilia Hadzhiev
    TI__Genius 14791 points

    Hi Ilia,

    I am not an expert on the AFBR-5905ATZ as this is not a TI device, but I believe that the SN65ELT20 / SN65ELT21 will work for what you have described. 

    Note that the SN65ELT20 / SN65ELT21 will require 5V. It appears the AFBR-5905ATZ has the option to run on 3.3V. If you would like to explore 3.3V options, you can consider the SN65ELT22 / SN65LVELT23 (these devices are dual channel).

    It is also recommended to check that all minimum VIH / VOL levels can be met per datasheet specifications for your application.

    Regards, Amy