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LM34922: LM34922 as current source

Norbert Nestler
Intellectual 340 points

Part Number: LM34922

Hi to all,

i want to do a new project,where i need a power supply 12V => 4V, with adjustable output current (current has to be 1Amp)

I'm thinking of using the LM34922 as a current source.

The LM34922 should supply a LED (3.3V) with a current of 1Amp. Therefore i would like to set the output voltage of the LM34922 to appr. 4V. Input voltage is 12V. The output must be open load save, since the LED is connected/disconnected continuous. Do you think that the LM34922 would work for this?

I don't want to use a special LED driver, since i don't need features as dimming, e.g.

Kind regards

Norbert

  • 0
    TI__Mastermind 49470 points

    Hi Norbert,

    I am not sure if I understand your application correctly. Vin=12V, Vout=4V, Iout could switch from 0A (disconnected) to 1A (connected). Iout behavior is same as load transient. Am I correct? If Yes, what is the output voltage regulation requirement? What is the load change slew rate? It should be ok.

    Thanks,

    Nancy 

  • 0 in reply to Nancy Zhang
    Intellectual 340 points

    Hi Nancy,

    yes, you are right. The switching time from 0A to 1A should be 1...2µs if possible. Output voltage at 1A is about 3.3V. But thats not critical. Important is a stable current of 1A (+/-5% or so) and that the output is open load save.

    Kind regards

    Norbert

  • 0 in reply to Norbert Nestler
    TI__Mastermind 49470 points

    Hi Norbert,

    Understand, but this is not exact same as load transient. You need to control LED to be disconnected with the output of LM34922 when LED is off. Because the output 4V is still there to turn on LED if the LED is not disconnect from the output.

    Thanks,

    Nancy