RDR290 output current

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Dear All,

 

I'm working on a project based on RDR290 (IC - lnk420) desing. I'm searching for a best solution to change output current without using any kind of dimming. I only need 2 values of output current - 100%(2.1A)  and ~50%(~1.1A). Easiest way, i think, is to change one of  FB resistors value, but i cant find any info about how to recalculate this value. Any ideas? 

 

Thanks.

You can utilize PIXLS Designer so you can estimate the FB resistor to transition from 100% to 50%.

However, please note that the recommended range of IFB is 90uA to 210uA. I suggest you adjust the design at 100% such that IFB is around 190 to 200 uA so that at 50% load, IFB is still > 100uA. 

 

After you set the IFB to the recommended value, you can either just trim the FB resistor until you reach the 50% load or use PIXLS Designer to give you a starting value.