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TIDA-01573: luminescent intensity uniformity on TIDA-01573

miao wang
Prodigy 30 points
Part Number: TIDA-01573
Other Parts Discussed in Thread: LM5000, LMG1020

Hello!

       Thanks for  the Gerber and BOM given by TI website,I have the chance to test the performance of the TIDA-01573  myself. It is a wonderful design that be able to solving most problems I met,but still some questions unsolved, I will be appreciate to your help.

      1. what is the  resisitors R5,R6,R7,R8  used for? In my test, amostly not find the difference  between removing the four resistors and placing. Are the resisitors R5,R6,R7,R8 and diode D1 a loop when the GaN FET Q1 is turned off?

      2. In my test, the luminescent intensity and luminescent pulse wide of LD is not stable, this will have a strong impact on our Lidar  measurement accuracy.  LD is OSRAM SPL_PL90_(peak current 40A). The output GATE signal wide of XLMG1020  is 20ns  or 10 ns , both having the same result. Will you please give me some advice to improve it ? The Vbus is DC 35V,0.2A offered by LM5000, the Vbus is not serious affected by  oscilloscope when LD drivered.The Capacitance capacity value of C2(0.01uf)，C3(0.01uf)，C6、C7、C8、C9(0.1uf) is the same to BOM. Does the pulse wide  accuracy of  driving signal to XLMG1020  have obvious implication to the luminescent intensity?

     3. It seems to be difficult to buy LMG1020 in a large number now, it is a huge risk for me.

Thanks to help and best wishes!

  • 0
    TI__Guru**** 189399 points
    Hi Miao,

    Welcome to e2e, and thanks for your interest in our LMG1020!

    Let me study this and get back to you tomorrow.
  • 0
    TI__Genius 12990 points

    Hi Miao,

    Welcome to e2e! thanks for your interest in LMG1020 EVM. Im an apps engineer and will help out.

    1) see post below
    2) Since your measurement doesnt change from 10ns to 20ns the peak current is reached therefore the intensity is not affected by this pulse width. There will be at some point a minimum pulse width where the current wont reach its peak and the intensity will degrade. If VBUS is OK then check the voltage on the LD (further down the line of parasitic inductance) to see if its getting what it needs. You also should make sure to reduce any resistances and inductances in the LD path to not limit the peak current as little as possible. This might mean choosing a diode without long leads. Are you also asking what might be limiting the peak current seen on the EVM?
    3) what amount are you trying to order? I can see if I can reach out to the right person to help you out with this.

    Thanks,

  • 0 in reply to Jeffrey Mueller
    Prodigy 30 points
    Hi Jeff,

    Thanks so much. I will try.
  • 0 in reply to miao wang
    TI__Genius 12990 points
    Hi Miao,

    I have an update, the resistors from 1) are actually not supposed to be used with an LD and they are to be considered a dummy load so the EVM can be used right out of the box. The four 4ohm resistors are in parallel to increase current capability and equal 1 ohm so its possible to see high peak current.

    Sorry about this wrong information before. However if you did use the resistors with the LD we should also be correct.
    Thanks,
  • 0 in reply to Jeffrey Mueller
    Prodigy 30 points

    Hi Jeff !

       Thanks  your  help!