Applies To These Products

WLD3343

Question

I am designing a laser driver circuit using the WLD3343. On page 10 of the data sheet there is a discussion about choosing RLIM. Apparently, RSENSE sets the allowable current range of the laser driver, and RLIM then limits the actual current limit to something less than what RSENSE allows. The first paragraph says “Divide the maximum laser diode current (determined in Section 1) into the desired maximum operating current for the laser diode.” Following the interpretation above, that means dividing a larger number into a smaller number, which is greater than 1. Following example 1, I believe that I want the reciprocal of that number. Are these correct interpretations?

Answer

Your interpretation is correct. Dividing 1.5/2.5 gives you a normalized percentage, then this is used on the table on page 11 to provide the RLIM resistance.

Another way to calculate this is to use Equation 3 on page 10 of the WLD3343 Datasheet to calculate the current limit which is slightly more precise.

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