# Reading the DotStar datasheet - power requirements

I'm trying to figure out my power requirements for a strand of Adafruit DotStar LEDs - APA102 Cool White, not the RGB. I'm not sure how to interpret the datasheet.

In the middle of the product spec table on page 1, under Power Consumption, it says `0.2W (MAX: 1W)`. Which would mean at 5V, MAX would be 0.2A, or 200mA.

Then on page 3 in the electrical characteristics table under the symbol/Parameter "LOL/Sink Current Voltage" it says `typ. 24.5mA; max. 26.5mA`.

I plan on having the strand on full brightness most of the time.

So which is it? 200mA? or 26.5mA?

I expect you will have to run an experiment and measure how much current each unit draws at full brightness.

The APA102C spec sheet seems to mix together data about the whole unit (controller chip plus three LEDs) and the controller chip itself. The “LOL/Sink Current Voltage (RGB)” line that shows “min. 22.5, typ. 24.5, and max. 26.5 mA” appears to apply to the controller, and probably to single outputs on that controller, which anyway would give a 3X multiplier. (The Cool White strips have three white LED chips per unit, instead of 1 each R, G, B.)

Note, the Adafruit DotStar LED Strip - APA102 Cool White webpage suggests using their 5V 4A power supply to drive “a half meter or meter” and their 5V 10A supply to drive “a couple meters”, which at 30 units per meter works out at 2/3 to 5/6 W of power supply capacity per unit.

You have correctly worked out:

``````I(A) = P(W) / V(V)

I = 0.2 / 5
I = 0.04A

MAX:
I = 1 / 5
I = 0.2A
``````

From that it seems it will use between 40 - 200mA depending on brightness.

Sink current refers to the current required to drive the led's digital input from your MCU's digital output.