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LM3431 calculation tool of Mathcad

Ryuji
Guru 20090 points
Other Parts Discussed in Thread: LM3431
Hello,
 
LM3431 has calculation tool of Mathcad.
Unfortunately , I don't have mathcad...
Thus,  I tried simulation by webench.
But I can't get simulation result by below conditions.....
 
Could I have the result of mathcad by below conditions ?
If you need more information, please let me know.
 
---
Vin: 8.5V ~ 15.5V
Iout: 30mA/ch x 3 strings = 90mA
LED: 8series, 3 strings, Vf=3.6V(max)
Fsw : 200kHz
dimming frequency: 1.95kHz
dimming duty : 0.15% ~100%
---
 
Best Regards,
Ryuji Asaka
  • 0
    TI__Intellectual 2540 points

    Asaka-san,

    To select the LM3431 in webench, click the LED tab (instead of LED Architect by default).  Then select 3 strings in parallel.  Otherwise, the webench assumes 1 LED string and the LM3431 is not selected. 

     

    Then you can go to a second screen.  The default switching frequency is from 323-328kHz.  To change the frequency, turn the knob to “Highest Efficiency”.  Select 200kHz and open the design.

     

    Best regards,

    John