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TINA/Spice/LM3424: LM3424 Pspice and Driving capability

Manju CV
Prodigy 30 points
Part Number: LM3424
Other Parts Discussed in Thread: TINA-TI,

Tool/software: TINA-TI or Spice Models

Hi,

Part 1)

I'm trying to import LM3424 Pspice model and have not been successful. Tried to import macro and its throwing error "  Invalid device : CDNENCSTART. Line #41". Please suggest how to import the Pspice , this was downloaded from TI - LM3424 part webpage 

Part 2)

Can one LM3424  drive 4 (in series)  X 5 (in parallel )  LEDs  combination  ? the Work bench simulation suggests 4 Series X 2 Parallel combination with one LM3424 .

Part 3) 

I'm hearing acoustic noise when driving 4 Series X 2 Parallel combination with one LM3424, any suggestion what could be the cause ?

Regards,

C V

  • 0
    TI__Mastermind 25500 points

    Hello CV,

    To answer your questions:

    1. Most people that monitor this forum are from a product line and do not have knowledge of pspice or TINA-TI coding or importing. You would probably have better luck posting this question in the "Development Tools" forum.

    2. Yes, it can. You can do as many parallel strings as you would like. Simulations will still give the same results as long as you have the same total LED output current.

    3. Is this while PWM dimming or just normal continuous operation? What is your input voltage, LED string voltage, and LED current you are driving? What topology are you using?

    Regards,

    Clint

  • 0 in reply to Clinton Jensen
    Prodigy 30 points

    Hi Clint,

    Thank you for a very quick reply

    The LEDs are driven in a continuous operation .

    the Input Voltage range is 8 to 20 V 

    LED string voltage is 33.6V, I'm using Cree XP G2 LED (12 in Series) in a Boost topology.

    The Audible noise is heard at  a voltage point only between 11V and 12V 

    could this acoustic noise be due to singing capacitors / Inductors , Please suggest 

    Thanks,

    CV

  • 0 in reply to Manju CV
    TI__Mastermind 25500 points

    Hello CV,

    Usually audible noise is only present during PWM dimming and could be the inductor or ceramic capacitors. There should be no audible noise during normal continuous operation. If there is it is still usually the inductor/ceramics, but it shouldn't be.

    It could make noise if it is kicking in and out of OVP or UVLO but that doesn't make sense in this case if it is ok at other input voltages. That leaves the most likely scenario either layout or instability. Either could cause oscillations that could produce audible noise. The first would require doing another layout, but it also probably wouldn't work at 8V either. Instability can be tested by increasing the COMP capacitor value and/or increasing the output capacitance. At that conversion ratio it is quite possible the right half plane zero is at too low a frequency so you need to cut down the bandwidth to eliminate its effects.

    Regards,

    Clint