Here is another one : a paper of Samsung, presented by dr. Choi. His paper can be seen as a kind of continuation of his work he did for his PhD at Univ. of Michigan : having a sensor ALWAYS TURNED ON in a kind of hibernation mode (= ultra-low power, low resolution, low quality), but waking up as soon as there is any movement in the scene and switching to a normal mode (= higher resolution, higher quality). Classical ways to lower power is reducing speed, reducing resolution, reducing number of bits, etc. But what I appreciated very much in this work were two additional techniques to lower the power :
– using a classical PPD pixel in the normal mode at 3.3 V, and using the same pixel (with TG always switched ON) in a kind of 3T pixel mode operating at 0.9 V (with reduced performance),
– turning the circuitry of two adjacent PGA’s (of 2 adjacent columns in the normal mode) into an 8-bit SAR ADC for the low-power, low quality mode.
In this way the power of the ALWAYS ON mode was reduced by a factor of 500 compared to the normal mode. Final power consumption was 45.5 uW.
Some more numbers (Numbers add up to Nothing ! Neil Young in “Powderfinger”) : reduced resolution (/4), same fps (30 fps), supply voltage reduced from 3.3 V analog/1.8 V digital to 0.9 V for all, sensitivity down by a factor of 4, FPN went up 20 x (but still less than 1 %)and random noise went up by 4x (expressed in DN, but is 1 DN in the high-quality mode equal to 1 DN in the low-quality mode ???). But power goes down by 500 times !
Albert, 26-02-2015.