LUPA-4000 Datasheet, PDF (28/49 Pages) Cypress Semiconductor – 4M Pixel CMOS Image Sensor

LUPA-4000
Data Sheet
The timing of the pixel array is straightforward. Before the frame is read, the
information on the photodiode needs to be stored onto the memory element inside the
pixels. This is done by means of the signals Mem_hl, Precharge and Sample. When
precharge is activated it serves as a load for the first source follower in the pixel.
Sample stores the photodiode information onto the memory element. Mem_hl pumps
up this value to reduce the loss of signal in the pixel and this signal must be the
envelop of Precharge and Sample. After Mem_hl is high again, the readout of the
pixel array can start. The frame blanking time or frame overhead time is thus the time
that Mem_hl is low, which is about 5µsec. Once the readout starts, the photodiodes
can all be initialised by reset for the next integration time. The minimal integration
time is the minimal time between the falling edge of reset and the rising edge of
sample. Keeping the slow fall times of the corresponding internal generated signals in
mind, the minimal integration time is about 2 µsec.
An additional reset pulse of minimum 2 µsec can be given during integration by
asserting Reset_ds to implement the double slope integration mode.
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