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Lm5021

rui Duarte
Prodigy 80 points
Other Parts Discussed in Thread: LM5021

Hi,

I am using LM5021 to do a AD-DC voltage
converter, with an output of 5 Volts. My circuit in the beginning has 5.025
Volts in the output, but after 2 seconds (more and less) he starts oscillating,
like 2.4 Volts, then 4.5Volts and 5.025V, and he keeps like that all the time.
I am using a 65 ohm resistance, which means about 70mA. The problem must be the
transformer? In Cs pin, or comp?

 

Regards,

Rui Duarte

 

  • 0
    TI__Intellectual 940 points

    Rui,

    With this little information I really don't know what to tell you.  Did you do a volt-second calculation on the transformer to make sure it doesn't saturate?  If the transformer moved toward saturation, currents would increase causing heating and the LM5021 would go into current limit and would most likely appear unstable.  Or, you control loop could be marginally stable, or it could be several other things.  I need a schematic with values of components including the transformer you are using.  You can send them to me directly at ron.crews@ti.com. 

    Regards,

    Ron