Pixel circuit for an ultra-low power image sensor

A pixel circuit for a ultra-low power image sensor, comprising:

• a photodiode for receiving a light beam representing a visual scene and for generating a photodiode current,
• an integration node, on which said photodiode current is integrated during an integration phase,
• a comparator arranged to compare a voltage at said integration node with a reference voltage, and to generate a comparator output voltage, said comparator comprising a current source arranged for generating a current,
• a memory element comprising a memory node,
• a writing pulse signal generator arranged to generate a writing pulse signal, on the basis of said comparator output voltage and on the voltage at said memory node, said writing pulse signal comprising a pulse having a start and an end,
• characterised in that
• said comparator further comprises a switch in series with said current source,
• said switch being arranged to be commanded by the voltage at said memory node so that said switch is open at the end of said pulse, so as to limit the consumption of static power of the pixel circuit during said integration phase.