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ONET1101L: A high speed driver with enough current

Lai Zhou
Prodigy 50 points
Part Number: ONET1101L
Other Parts Discussed in Thread: LMH6525, LMH6526

I need to use the driver to generate very short pulse, e.g., 1 ns. But the problem is that the modulation current is not enough. Hence, I have to use the bias. However, when driving laser you have to reverse bias them to get them to turn off (optically) fast enough, otherwise the turn off time is of order 10ns or longer (from recombination). So how can I generate the short pulse but with enough current ? Thanks.

  • 0
    TI__Guru* 93670 points
    Hi Lai,

    I thought you can use 500MHz input data then bias the device to meet your extinction ratio. Would this work for you?

    Regards,,nasser
  • 0 in reply to Nasser Mohammadi
    Prodigy 50 points

    Hi Nasser,

    Thank you for your reply.

    I understand that the input data determines the pulse. However, the problem is the current, we do not have enough current to drive the laser or LED with this driver (actually, we want to use it to drive the LED). Firstly, we are using the design from fig.20 in the datasheet of ONET1101L. Secondly,  we only have access to the cathodes of the LEDs. Thirdly, in order to turn off the LEDs as fast as possible, we have to reverse bias. These limited conditions may determine that we can not have enough current. 

    Do you have suggestions to increase the current based on the above condition? We are also finding a kind of driver so that we can use the non-reverse bias when turning on the LED and reverse bias when turning off the LED. And it may help to increase the current. Do you have any recommendations for the similar driver?

    Best regards,

    Lai

  • 0 in reply to Lai Zhou
    TI__Guru* 93670 points
    Hi Lai,

    I checked and all TI ONET DML driver modulation and bias current are in the same range as ONET1101L device. Unfortunately, these are device limitations. I thought LED drivers normally require a higher modulation current. I am thinking perhaps LMH6526 or LMH6525 could be more in-line with what you need. However, this part may not be fast enough. Please note link to this part's data sheet:
    www.ti.com/.../lmh6526.pdf

    Regards,,nasser
  • 0 in reply to Nasser Mohammadi
    Prodigy 50 points
    Hi Nasser,

    Thank you!

    Best regards,

    Lai