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TIDA-01573: some questions about tida-01573

kyeongmin choi
Intellectual 590 points
Part Number: TIDA-01573
Other Parts Discussed in Thread: OPT8241, LMG1020, TPS2559, , CSD16301Q2, SN74LVC2T45

We are developing indirect lidar and Direct lidar. I have some questions in terms of ti  lidar components.

 1. it is possible to get higher peak current  when use gan and gate driver.

   We aready reviewed your lidar evm board using opt8241 , 9221.

   I want to get depth data for long distance. (12Mhz ~ upto 3Mhz , duty 50%)

   So i try to change serveral below patrs . because I think gan is getting higher peak current than FET with gate driver.

     -   Gan(epc2040)  instead of FET ( CSD16301Q2 ) 

     -  gate driver (Lmg1020)  instead of sn74lvc2t45

   Could you plz check  my trial is proper or not  for getting higher peak current .

2. how to get peak current  in higher freqency and long duty using TIDA-01573.

  As you mentioned in datasheet (TIDA-01573 ,figure3.) this driver can get 50A for 2ns.

   But  i need faster frequency and long duty cycle .  ( 2M , 100ns, duty 20%)

  If i lower temperature of laser enough, can i drive laser up to 50Apk ?  what if i caculate peak current ?  it's possible?

  I think laser peak current  is depend on duty cycle .

 You can make any recomandation for our requirement (freq : 2M, pulse width : 100ns, duty 20%).

3. The way measure peak current of laser.

  If i use detector ( thorlabs DET08C)  and optical power meter ( Thorlabs PDA150A) .

  Can i calulate peak power from measured power and proportion of laser.

  Below list  is  light modulation  information

  duty : 20% / freq : 2M / LD Peak power : 40W

thank you.

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

    Thanks for your interest in our products!

    What design using the OPT8241 are you looking at?

    Yes, the combination of LMG1020 plus GaN FET gives better performance than a silicon FET plus driver.

    Two things will constrain your system: keeping the laser output below safety limits, and thermal dissipation of your system.

    Depending on the construction, the laser diode may also be the limiting factor due to its maximum current limitations.

    I'm not familiar with the averaging used in the Thorlabs equipment. You might ask them for their recommendations regarding power measurements.

    Let us know if you have any further questions.
  • 0 in reply to Don Dapkus
    Intellectual 590 points

    Thanks for your recomandation.

    I want to get long distance. So i try to raise peak power of laser. Application is not decided yet.

    As you mentioned , i think it is important to limit laser's maxium peak current.

    What if limit peak current using TPS2559 at power loop(Vbus) . Is it possible?

    Another question about  TIDA-01573 board.

    If power loop is split , two loop makes reduction of inductance in half.( reference :  2.2.5 split power loop and Figure 5  in TIDA-01573 's datasheet )

    There are 3 pads for Laser ( anode cathod anode each)

    But we have a laser which have two pin ( anode cathode).  I don't know how to reduce inductance like this way when i have just one laser.

    I thik it's  work  when i use two laser only. parallel!  Could you plz give me tips to reduce inductance  as spliting power loop when i use one laser .


     thankyou

  • 0 in reply to kyeongmin choi
    TI__Genius 12990 points
    Hi Choi,

    I wanted to take over for Don since this seems to be a duplicate post.

    how far a distance do you want?
    you can limit current by using the gate voltage - a smaller VDD drive will limit peak current at the expense of more conduction loss.
    also by adding Rgate you can slow down Ids overshoot during turn on.
    you can attach the laser as needed, LD are typically 3 terminal devices however provisions have been added to properly position the diode on the EVM. The split power loop is independent of the laser pad terminal number.
    to reduce gate loop inductance make sure to use kelvin connection.
    to reduce power loop inductance make sure the caps are as close as possible to the laser - over/undershoot can get high due to 200A/ns slew rate possibility of driving a 60A laser at 300ps.
    Are you wanting to parallel 2 laser diodes? why?

    Thanks,
  • 0 in reply to Jeffrey Mueller
    Intellectual 590 points
    Hi Jeffrey Mueller

    Distance target is 30m.
    I concern about OCP( over current protection) for safety.
    Your recommendation means OCP also? Do you think my trial is wrong way for OCP? using current limit IC( TPS2559 )

    I want to use VCSEL laser which have 2 teminal.

    I also don't need 2 parallel 2 laser , I just want to conduct this way for using 2 power loop.

    It is possible to reduce inductance in EVM when i just use one laser which has two terminal?
    or you can give me any tips about that.

    thankyou
  • 0 in reply to kyeongmin choi
    TI__Genius 12990 points

    Thanks Choi!

    OCP can be implemented case by case depending on the BW. what are your constraints?

    If you want to reduce inductance then you can use a laser diode with a small parasitic inductance package. however the smaller the L the greater Ipeak. 3 terminal laser diodes can help to reduce inductance seen by the bus caps by splitting the power loop or kinda creating a blanket of bus charge on which to switch on to the diode in a simultaneous parallel sequence, this happens from fine tuned EVM board layout. The most important thing to reduce inductance is layout and small component placement.

    Thanks,

  • 0 in reply to Jeffrey Mueller
    Intellectual 590 points

    Thank you for your reply.

    Could you plz recommend high power pulsed 3 terminal laser. (over peak power 90w)

    If i use this way i need 3 teminal laser  which have common anode. but i can't find that.

    I think it just works for 3 teminal laser .  common anode also !

  • 0 in reply to kyeongmin choi
    TI__Genius 12990 points

    Hi Choi,

    Great question! To get to 90W the laser diode leads need to be small, the layout needs to be tight and the pulse width may need to be longer.

    TI recommends the following laser diodes for Excelitas and Osram for 100W laser pulses:

    Hopefully this helps! Let me know!

    Thanks,

  • 0 in reply to Jeffrey Mueller
    Intellectual 590 points
    thank you.

    But , i think , these laser have not 3 teminal you recommended.

    Is it not possible to use 2 power loop for reducing inductance. ?
  • 0 in reply to kyeongmin choi
    TI__Genius 12990 points

    Any excelitas or osram laser diode is recommended and will work for your application. The split power loop is for three terminals.

  • 0 in reply to Jeffrey Mueller
    TI__Genius 12990 points
    Can you give me some more info about the laser diode you require for tour application?
  • 0 in reply to Jeffrey Mueller
    Intellectual 590 points
    If i use 2 teminal laser you recommended. I don't need to split pattern from Vbus to laser's anode when i design pcb artwork? Is it right?
  • 0 in reply to kyeongmin choi
    TI__Genius 12990 points

    Hi Choi,

    Correct! the SMD 2 terminal laser has such small low inductance leads that having another terminal is unnecessary for some applications. The diode package might be the best way to reduce inductance from the fet to the laser. Another way to reduce inductance is if using gate resistors use 0201 resistors from the driver to the fet. Also Check out the LMG1020 datasheet section 10 on layout. let me know if you have any more layout concerns.

    Thanks,

  • 0 in reply to Jeffrey Mueller
    Intellectual 590 points
    Thank you . excelitas is smd type but osram laser is not possible to mount in smt. that is bare chip.

    so could you plz recommend another laser?
  • 0 in reply to kyeongmin choi
    TI__Genius 12990 points

    Hi Choi,

    The right laser for your application is dependent on many factors since there are many moving parts in a LiDAR system. For example what wavelength laser do you need? can you also tell me the exact package you require? what sensitivity do you need and is cost of concern?

    Check out Excelitas's guide to high power laser diode selection. Let me know what you think or which diode you decide to go with. Can you tell me more about what kida LiDAR your working on? you said direct lidar, whats is that?

    thanks,

  • 0 in reply to Jeffrey Mueller
    Intellectual 590 points
    Actually 800nm laser diode is correct . But i think 905 is no problem. We use C-MOS sensor but GAas.

    We are developing automotive lidar for long distance( over 100m) . So i need source which have short pulse , high peak current.

    I tried to develop laser driver using gate driver (LMG1020) and GAN FET.

    That is not work as maximum peak power . Circuit is not problem I guess.

    I think PCB artwork is problem . I didn't divide GND between POWER and other GND. And i didn't use kelvin GND.

    I used long lead laser diode. I think i din't consider inductance intensively.

    That's why i ask you how to reduce inductance for higher peak power.
  • 0 in reply to kyeongmin choi
    TI__Genius 12990 points
    Hi Choi,

    thanks for your update. Ive seen the hardest part to reduce inductance is between the fet and the laser but the lmg1020 definitely helps with the driver to fet inductance.

    let me know if you have any more questions, you can make a new thread or just reach out to me.

    Thanks,
  • 0 in reply to Jeffrey Mueller
    Intellectual 590 points

    IB circuit.pdfHi mueller

    We want to  get long distance using opt8241 , 9221.

    So i try to change several things compare to previous board .

    Let me attached IB circuit.

    If i have some fault  could you please advise for us?

    1. add laser diode  4 --> 8 (series)

    2. change part

        -   Gan(epc2040)  instead of FET ( CSD16301Q2 )

        -  gate driver (Lmg1020)  instead of sn74lvc2t45

  • 0 in reply to kyeongmin choi
    TI__Genius 12990 points

    Hi Choi,

    thanks for your update! I will advise, if you issue is specific post a new thread.
    can you please send me updated layout for review.
    also I would like to see some waveforms of the gate and drain when possible.
    whats your power dissipation of the module?

    Thanks,