LM3429 sepic circuit frequncy instability

Hello , I met a problem that i used lm3429 for sepic circuit ,the frequency is not stable  , when  change output current , frequency would became bigger .

and i used formula  frequency = 25/Rct *Crct ) =25/(47000*0.000000001)=531K,but measured frequency is 230K . I  cant figure it out  why frequency is strange..

Input voltage is 9 to 16v ,output is 12V,1A.  thanks for you help in advance . 

Hello John,

Could you help to post your schematic & SW waveform for reference? BTW the description of testing setup(Eload_xx mode/LED?) also will be helpful.(Just for change output current, not sure whether you means changed Rsns on board or others).