Hi,
How does ppm of temperature coefficient of ZTC resistor impact VCSEL driver's output current granularity? Is there any quantifiable data around? The reference design suggests an external ZTC resistor.
+/- 0.2ppm/C as well as +/- 2ppm/C 30Kohm resistor from Vishay are incredibly expensive (~$6 for a single resistor in high volume). +/- 5ppm/C resistor pricing is not bad for a single resistor though still very expensive.
I'm trying to see what is the trade-off if I choose 5ppm/C resistor. My specific application using this VCSEL driver runs at, relatively, very low speed (in couple of 100's of MHz). So I'm willing to sacrifice some inaccuracy to lower cost.
Thanks,
Satish Acharya