DIY Smartwatch: Screen Current Draw

To give a better idea of the power budgeting I’ll be working with, I wrote a small test program to cycle through various percentages of the screen set to white with varying brightness levels.  Since black pixels on OLED displays are completely turned off, they consume no power and so a power saving method is to use darker tones.  That is why I’m testing the screen at various “ON” percentages.  As for the brightness, this display uses a 4 bit value to determine how bright the display will be set to with the brightness being in increments of 1/16.  Below is a table relating current draw to percentage of the screen on and the brightness for a 5V supply.

0/15 1/15 2/15 3/15 4/15 5/15 6/15 7/15 8/15 9/15 10/15 11/15 12/15 13/15 14/15 15/15
0% 6.1 mA 6.4 mA 6.5 mA 6.7 mA 6.8 mA 6.7 mA 6.8 mA 6.8 mA 7.0 mA 7.1 mA 7.1 mA 7.1 mA 7.2 mA 7.4 mA 7.4 mA 7.4 mA
25% 17.1 mA 20.8 mA 24.9 mA 29.1 mA 32.8 mA 36.2 mA 39.9 mA 42.4 mA 44.3 mA 46.2 mA 47.9 mA 49.0 mA 49.7 mA 52.1 mA 52.6 mA 53.4 mA
50% 28.1 mA 35.5 mA 43.5 mA 51.4 mA 58.8 mA 65.7 mA 73.5 mA 79.7 mA 81.9 mA 85.3 mA 89.2 mA 91.2 mA 92.6 mA 97.1 mA 97.8 mA 99.6 mA
75% 39.6 mA 50.7 mA 62.6 mA 74.2 mA 85 mA 95.6 mA 107.5 mA 118.8 mA 121.3 mA 125.4 mA 131.2 mA 134.4 mA 141.5 mA 143.2 mA 144.4 mA 146.7 mA
100% 51.1 mA 66.2 mA 82.2 mA 97.1 mA 111.5 mA 125.5 mA 139.2 mA 152.6 mA 160.8 mA 167.3 mA 174.3 mA 177.7 mA 186.8 mA 189.2 mA 191.5 mA 195.2 mA

That’s quite a lot more than what I originally thought the display would draw.  It looks like I’m going to have to do some serious power budgeting to make up for this.
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