LUPA-4000_07 Datasheet, PDF (12/38 Pages) Cypress Semiconductor – 4M Pixel CMOS Image Sensor

LUPA-4000
Figure 8 shows the integration and read out sequence for the
synchronous shutter. All pixels are light sensitive at the same
period of time. The whole pixel core is reset simultaneously
and after the integration time all pixel values are sampled
together on the storage node inside each pixel. The pixel core
is read out line by line after integration. Note that the
integration and read out cycle can occur in parallel or in
sequential mode. (ref. 4. Timing and read out of the image
sensor)
Non-destructive readout (NDR)
The sensor can also be read out in a non-destructive way. After
a pixel is initially reset, it can be read multiple times, without
resetting. The initial reset level and all intermediate signals can
be recorded. High light levels will saturate the pixels quickly,
but a useful signal is obtained from the early samples. For low
light levels, one has to use the later or latest samples.
Figure 9. Principle of non-destructive readout
time
Essentially an active pixel array is read multiple times, and
reset only once. The external system intelligence takes care
of the interpretation of the data. Table 7 summarizes the
advantages and disadvantages of non-destructive readout.
Table 7. Advantages and disadvantages of non-destruc-
tive readout.
Advantages
Low noise - as it is true CDS.
Disadvantages
System memory required
to record the reset level and
the intermediate samples.
High sensitivity - as the
Requires multiples
conversion capacitance is kept readings of each pixel, thus
rather low.
higher data throughput.
High dynamic range - as the Requires system level
results includes signal for short digital calculations.
and long integrations times.
Operation and signalling
One can distinguish the different signals into different groups:
• Power supplies and grounds
• Biasing and Analog signals
• Pixel array signals
• Digital signals
• Test signals
Power supplies and ground
Every module on chip, as there are: column amplifiers, output
stages, digital modules, drivers has its own power supply and
ground. Off chip the grounds can be combined, but not all
power supplies may be combined. This results in several
different power supplies, but this is required to reduce
electrical cross-talk and to improve shielding, dynamic range
and output swing.
On chip we have the ground lines of every module which are
kept separately to improve shielding and electrical cross talk
between them.
An overview of the supplies is given in Table 8 and Table 9.
Table 9 summarizes the supplies related to the pixel array
signals, where Table 8 summarizes the supplies related with
all other modules
Table 8. Power supplies
Name
Vaa
DC Current
7 mA
Va3
10 mA
Max.current
50 mA
50 mA
Typ.
2.5V
3.3V
Vdd
Voo
Vdda
Vddd
1 mA
20 mA
1 mA
1 mA
200 mA
20 mA
200 mA
200 mA
2.5V
2.5V
2.5V
2.5V
Max.
3.3V
Description
Power supply column readout module.
Power supply column readout module.
Should be tuneable to 3.3V max.
Power supply digital modules
Power supply output stages
Analog supply of ADC circuitry
Digital supply of ADC circuitry
Document Number: 38-05712 Rev. *B
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