CYIL1SM4000AA-GWCES Cypress Semiconductor Corp., CYIL1SM4000AA-GWCES Datasheet - Page 15

• Manufacturer Part Number: CYIL1SM4000AA-GWCES
• Description: 4 Megapixel CMOS Image Sensor
• Manufacturer: Cypress Semiconductor Corp.

The timing of the pixel array is straightforward. Before the frame
is read, the information on the photodiode must be stored onto
the memory element inside the pixels. This is done with 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 starts. The frame blanking time or frame
overhead time is thus the time that Mem_hl is low, which is about
5 μs. After 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 μs.
The readout of an image consists of the FOT (Frame overhead
time) and the sequential selection of all pixels. The FOT is the
overhead time between two frames to transfer the information on
the photodiode to the memory elements.
this time Mem_hl is low (typically 5 μs). After the FOT, the
information is stored into the memory elements and a sequential
selection of rows and columns makes sure the frame is read.
X and Y Addressing
To readout a frame the lines are selected sequentially.
gives the timing to select the lines sequentially. This is done with
Document Number: 38-05712 Rev. *C
(F.O.T: Frame Overhead Time. R.O.T: Row Overhead Time. L: Selection of Line, C: Selection of Column)
R.O.T
F.O.T
Read frame I
Figure 15
C1
L1
Figure 16. Readout of Image Sensor
C2
shows that at
Figure 17
L2
Readout pixels
Readout Lines
L3
An additional reset pulse of minimum 2 μs can be given during
integration by asserting Reset_ds to implement the double slope
integration mode.
Readout of Image Sensor
As soon as the information of the pixels is stored in to the
memory element of each pixel, it can be readout sequentially.
Integration and readout can also be done in parallel.
The readout timing is straightforward and is basically controlled
by sync and clock pulses.
Figure 16
of a frame consists of the frame overhead time, the selection of
the lines sequentially, and the readout of the pixels of the
selected line.
a Clock_y and Sync_y signal. The Sync_y signals synchronises
the y-addressing and initialises the y-address selection registers.
The start address is the address downloaded in the SPI
multiplied by two.
On the rising edge of Clock_y the next line is selected. The
Sync_y signal is dominant and from the moment it occurs the
y-address registers are initialised. If a Sync_y pulse is given
before the end of the frame is reached, only a part of the frame
is read. To obtain a correct initialisation, Sync_y must contain at
least one rising edge of Clock_y when it is active.
Integration I + 2
shows the top level concept of this timing. The readout
L2048
C2048
CYIL1SM4000AA
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