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SN65LVDT388a Driving Capability

miao meng
Prodigy 70 points
Other Parts Discussed in Thread: SN65LVDT388A, SN65LVDS388A

Hello,

I have some questions about SN65LVDT388a.

1. What is the driving capability of this LVDS Receiver? 

2. Is it able to drive a 50 Ohm resistor? If not, is there any good ways to make it possible?

3. When you test it, what is the load? and what is the DC level voltage of the output?

Many thanks in advance!

Miao

  • 0
    TI__Mastermind 20820 points

    Hi Miao, 

    1. The SN65LVDS388A is a LVDS to LVTTL translator. It is capable of excepting LVDS levels and driving LVTTL levels.

    2. This LVDS receiver is not capable of driving 50ohm loads as the VOH level of 2.4V will not be reached with this amount of load resistance. You can calculate this for yourself by looking at Figures 8 and 9 in the data sheet. Based on my calculations your load will have to be at least 68 ohms in order to meet the minimum requirements for the output driver. I do not recommend only meeting the minimum requirements though because if there is any dip in VCC or a glitch in your system it may cause bit errors.

     3. I am not sure of the test circuit used because it is not detailed in the data sheet but I believe that figures 8 and 9 provide us with enough information to answer your question.

    Please let me know if you have any additional questions and I will be happy to help?

    Regards,

    Mike

  • 0 in reply to Michael Peffers
    Prodigy 70 points

    Hi Mike,

    I have three questions regarding this part:

    1. Can this part be operated from a 2.4 V supply?

    2. If I want the output voltage range to be 0-2.4V(or slightly higher), what should the supply voltage be?

    3. what do VOH "nom" value=3V and "min" value=2.4V mean on the data sheet? 

    Many thanks in advance!

    Miao

  • 0 in reply to miao meng
    TI__Mastermind 20820 points

    Hi Miao,

    1. It is not recommended that you operate the part from a 2.4V supply.

    2. What I would worry about when running the part from a 2.4V supply is weather or not you were actually going to achieve the output Voh because you are getting close to the rail at that point. I would say that you should try to stick with the recommended operating conditions listed in the data sheet to achieve optimal performance from the part.

    3. TTL typically  swings from 0 - 3.3V so the output Voh typ and min values align with the requirements of TTL. Typically the rail on the part is 3.3V so you can expect the output to swing to 3V (typ). As you lower that Vcc rail your output level will change.

    Mike

  • 0 in reply to Michael Peffers
    Prodigy 30 points

    Hi Mike,

    Thank you so much again for your previous answers.

    I have 3 more questions about this receiver,

    1. What is the static output DC current of this lvds receiver?

    2. You stated before that from figure 8 and 9, we can calculate the load will have to be at least 68 Ohms to meet the minimum requirements for the output driver. I am wondering how did you calculate this? Can you help me a bit to interpret the figures?

    3. Do you have anything in mind that can

        a. Drive 50 Ohms load with output voltage range to be 0~2.4 V

        b. With a signaling rate to be at least 200M?

    Millions of thanks!

    Miao