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DS15BA101 / Adjustable output amplitude

S.Satoshi
Guru 21685 points
Other Parts Discussed in Thread: DS15BA101, DS15EA101, DS30BA101

Hi,


Our customer is evaluating DS15BA101 and then they have question about adjustable output amplitude. Please give your comment for questions below.

- Can customer set the output voltage other than 400mVpp or 800mVpp ?
- How to calcurate the Rvo to set desired voltage if they can adjust it ?
- How much the min/max voltage if they can adjust it other than 400mVpp or 800mVpp ?

Best Regards,

  • 0
    TI__Expert 4400 points

    Can you find out more about the customer's application?  Do you know why they want to change the output amplitude?  Typically, the DS15BA101 buffer is paired with the DS15EA101 cable equalizer in cable extender applications.  The launch amplitude of the signal going into the cable (i.e. the DS15BA101 output amplitude) must be set appropriately for proper equalizer operation.  The DS15BA101 output amplitude should be either 800 mVP-P single-ended for 50 ohm coaxial cable applications, or 800 mVP-P differential (400 mVP-P single-ended) for 100 ohm differential cable applications.

    The DS15BA101 output amplitude may be adjusted by changing the RVO resistor value.  The output amplitude is inversely proportional to the value of RVO and fairly linear.  The RVO resistor may be set between 487 and 1100 ohms, which allows the output amplitude to be adjusted from a maximum of 800 mVP-P (RVO = 487 ohms) to a minimum of 300 mVP-P (RVO = 1100 ohms) single-ended into 50 ohm loads.

    Gary Melchior

  • 0 in reply to Gary Melchior
    Guru 21685 points

    Hi Gray Melchior-san,

    Thank you for your response.

    Unfortunately I can not talk about detailed information about customer's application, but our customer need to handle about 1Gbps of signal with very long and thin cable which has high cable losses. So they are looking to set as high as DS15BA101 can.

    Anyway I understand that the Rvo resister may be set between 487 and 1100 ohms, and can be set up to 800mVpp. I will inform it as the maximum setting for DS15BA101.

    Best Regards,

    Sonoki

  • 0 in reply to S.Satoshi
    Guru 21685 points

    Dear Gray Melchior-san,


    Before I asked about the adjustable range of output, and now I have additional question.

    Our customer tried to set the output level to 100mV by using EVM, then they could confirm the desired output, 100mV. In addition, they attenuated signal from input signal of higher than 100mV.

    Can you recommend to use DS15BA101 with 100mV setting and use with attenuated operation?



    Best Regards,

    Sonoki

  • 0 in reply to S.Satoshi
    TI__Expert 4400 points

    I cannot recommend setting the DS15BA101 for 100 mV output.  The output swing can be set as low as 300-400 mVP-P, but it should not be set lower.  To get the minimum output swing, set the RVO resistor to 1.1 kΩ - this should provide an output amplitude of about 300 mVP-P single-ended into 50Ω.  The RVO resistor value should not be set any higher than 1.1 kΩ.

    Gary Melchior

  • 0 in reply to Gary Melchior
    Guru 21685 points

    Hi Gary-san,


    Sorry for my delayed response.

    Our customer is now requesting following information for DS15BA101. 

    1, Equation to calculate output level by using Rvo

    2, Block diagram for DS15BQ101 like below


    This is very important business for us, so can you contact me via E-mail directly? I will let you know the detail of this business.


    Best Regards,

    Sonoki

  • 0 in reply to S.Satoshi
    TI__Expert 4400 points

    Satoshi-san,

    I have sent you an email with answers to these questions.

    Gary Melchior

  • 0 in reply to Gary Melchior
    Guru 21685 points

    Hi Gary-san,

    Thank you for sending email directly. I'll reply you on email.

    Best Regards,

    Sonoki

  • 0 in reply to Gary Melchior
    Intellectual 270 points
    The datasheet for the device states that the single-ended output voltage for a "25 ohm load" when Rvo is set to 487 ohm is 800 mVpp. Should that a 50 ohm load?
  • 0 in reply to Mark Heh
    TI__Mastermind 29655 points
    Hi Mark,

    I reviewed the datasheet and compared it with the DS30BA101. You are correct, the device is designed to drive a 50-ohm load for each polarity, so the spec should be for 50 ohm load instead of 25 ohm load.

    Thanks,

    Michael