about shift register CONSTANT-CURRENT

i am intersting for CONSTANT-CURRENT shift register for example TLC5916 http://focus.ti.com/lit/ds/symlink/tlc5916.pdf

all i want to do is to connect 8 RED LED (1.63 - 2.03v) with the outputs of a shift register without resistors (between of them).

as i saw datasheet it needs a resistor (Rext) to control current

i'll supply IC with 5V i want 20ma current for led led needs 1.63 - 2.03v.

what resistor do i need o add to ic? and how i caclulate it?

If you are wanting a constant current chip then you might want to look at the M5451 chip.

Can control up to 35 LEDs (or similar) and only needs one resistor for the lot of them.

Mowcius

what resistor do i need o add to ic? and how i caclulate it?

It's 2K5 and you calculate according to page 17 of the data sheet you posted a link to.

so i dont need to calculate the forward voltage of led?

No that's the point of constant current, it's constant it doesn't matter what the forward voltage is.

chears!!!!!