• State
  • Locked Locked
  • Replies 7 replies
  • Subscribers 63 subscribers
  • Views 961 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

LM3406 WEBENCH simulation issues

HPB
Expert 1350 points
Other Parts Discussed in Thread: TINA-TI

Hi, I built an LED driver using the WEBENCH tools and the design is attached here. When I try and simulate this design in TINA-TI, I dont get the outputs I'm looking for. What am I missing here? Both are attached here.

LM3406 webench_design_3851011_27_524973120.pdf

LM3406 v2.TSC

  • 0
    TI__Mastermind 25500 points
    I'm not sure exactly what you are looking at or expecting. Could you be more specific? In either case upon first glance I see you are using a resistor load for the TINA model. An LED load will behave very different than a resistive load during any transient or startup events. Perhaps that explains the discrepancies.
  • 0 in reply to Clinton Jensen
    Expert 1350 points

    OK. How do I then simulate a custom LED? I tried editing the LED configurations in the steady state schematic but it says its encrypted. The Vf of my LED is 2.6V and If is about 250mA. I wanted to connect 6 parallel chains with each chain containing 2 of these in series giving me 5.2V and 1.5A at the output.

  • 0 in reply to HPB
    TI__Mastermind 25500 points
    I would have no idea how to make a custom LED, but you could use a zener and it would behave much more like an LED than a resistor. An EVM with a real LED load would be better than any simulation though.
  • 0 in reply to Clinton Jensen
    Prodigy 30 points

    I've attached the schematic with the Zener as the load and it does not seem to be working. I still see the full Vin at Vo and the load current is barely about 300mA. Ron, Cin, Cout and duty cycle are all calculated using the formulas given in the datasheet. Any help would really help. 

    LM3406 v3.TSC

  • 0 in reply to CBP
    TI__Mastermind 25500 points
    That is odd. Maybe there is an error in the TINA model. The output voltage looks right as does the switching. But for some reason it is regulating to a lower value than it should. I will see if somebody that works with the models can take a look at it, but the circuit itself in real life should work great.
  • 0 in reply to Clinton Jensen
    Expert 1350 points
    Awesome, I'd really appreciate that. Here are the values I had calculated from the datasheet.

    Vin = 12V
    Vo = 5.5V
    Iout = 1.4A
    Fsw = 450KHz

    Calculated values:
    Duty cycle: 52.4%
    Ron = 169K
    Cout = 1uF x 2
    Cin = 10uF x 1
    Ton = 1.157 us
  • 0 in reply to HPB
    TI__Mastermind 25500 points

    I have no idea when they can get around to looking at it, they are very busy and it may take a long time. But your circuit should work well as long as you follow good layout guidelines.