What Is Dosage Of L Tyrosine To Produce Melanin?

I know that L-tyrosine is a precursor for dopamine, and then I also found out that L-tyrosine is also responsible for production of melanin. My skin is at the perfect shade and don't want to get any darker, just exactly how much of L-tyrosine will be used to produce melanin? and wil my skin get darker because of it?