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Topic: A question about TLC5940 (Read 942 times) previous topic - next topic

mttgwh

:)HI!

I would like to use TLC5940 with Arduino to create something,
but I don't understand the following figure:
http://students.washington.edu/acleone/codes/tlc5940arduino/img/breadboard-arduino-tlc5940.png
from(http://www.arduino.cc/playground/Learning/TLC5940)
Why It's 39.06???
Where 39.06 come from?

Thanks a lot!!!

MarkT

Since the accuracy is only +/-13% or so anyway, that figure should be 40, 4 digits of precision is utterly unwarranted!

The way the chip works is that the output current is set by a current mirror with a nominal gain of 31.5, and the reference current is set by the resistor from an on-chip 1.24V voltage reference. 31.5 x 1.24 ~= 39

The 31.5 figure probably represents linear proportions of the relevant transistors' channel width on the silicon of 63:2
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