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LM3421: LM3421 Unloaded voltage is unstable.

qixiao xie
Prodigy 30 points
Part Number: LM3421

LM3421 Unloaded voltage is unstable.It will fluctuate back and forth around 5V.How can I stabilize the no-load voltage?

  • 0
    TI__Genius 17640 points
    Hi Xie,

    LM3421 is a current regulator and not a voltage regulator. If there is no load at the output, the voltage will continous to ramp up since there is no current (no load). When the output voltage reaches the over voltage level the regulator will shut down and that is what you are seeing.

    Thanks Tuan
  • 0 in reply to Tuan Tran74
    Prodigy 30 points
    HI Tuan,
    Therefore, when the LM3421 is unloaded, the output voltage cannot be stabilized, right? Can it be controlled by external feedback to control stability?
    Thanks Xie
  • 0 in reply to qixiao xie
    TI__Genius 17640 points

    Hi Xie,

    No the output votlage cannot be controlled to a fixed level if there is no load at the output.  Again, the LM3421 is a current regulator.  The voltage will ramp up until it reaches a the controlled current but being that there is no load there it will never reach the controlled current.  The only thing you can control is the Over-voltage protection level so when the voltage reaches that point it will shut down and restart.

    Thanks Tuan 

  • 0 in reply to Tuan Tran74
    Prodigy 30 points
    HI Tuan,
    Do you have a high-power DC-DC LED driver solution recommended: 300W-600W, input 10-31V, output 25-65V, dimmable, LED output does not shake, and light load or no load can instantly switch to heavy Load, switching time is subtle.
    Thanks Xie
  • 0 in reply to qixiao xie
    TI__Genius 17640 points
    Hi Xie,

    Please use our LED driver web site below to help you choose the right driver for your application. You definition above is quite a range and you'll need to narrow it down some.

    www.ti.com/.../overview.html

    Thanks Tuan