IBIS4-A-6600 Datasheet, PDF (18/40 Pages) Cypress Semiconductor – 6.6 MP CMOS Image Sensor

ADVANCE
INFORMATION
IBIS4-A-6600
CYII4SM6600AB
Electronic Shutter
A curtain-like (rolling) electronic shutter has been
implemented on-chip. As can be seen in Figure 14., there are
two Y shift registers. One of them points to the row that is
currently being read out. The other shift register points to the
row that is currently being reset. Both pointers are shifted by
the same Y-clock and move over the focal plane. The
integration time is set by the delay between both pointers.
In case of a mechanical shutter, the two shift registers can be
combined to apply the pulses from both sides of the pixel array
simultaneously. This is to halve the influence of the parasitic
RC times of the reset and select lines in the pixel array (which
can result in a reduction of the row blanking time). This is the
case when FAST_RESET in the SEQUENCER register is set
to 1 or in the non-destructive readout modes 1 and 2.
Readout
pointer
Reset
pointer
Line number
Figure 14. Electronic Rolling Shutter Operation
Reset sequence
Frame time
Time axis
Integration time
High Dynamic Range Modes
Double Slope Integration
The IBIS4-6600 has a feature to increase the optical dynamic
range of the sensor; called double slope integration. The pixel
response can be extended over a larger range of light
intensities by using a "dual slope integration" (patents
pending). This is obtained by the addition of charge packets
from a long and a short integration time in the pixel during the
same exposure time. Figure 15. shows the response curve of
a pixel in dual slope integration mode. The curve also shows
the response of the same pixel in linear integration mode, with
a long and short integration time, at the same light levels.
Dual slope integration is obtained by:
Feeding a lower supply voltage to VDD_RESET_DS (e.g.,
apply 2.0V to 2.5V). Note that for normal (single slope
operation VDD_RESET_DS should have the same value as
VDD_RESET. The difference between VDD_RESET_DS and
VDD_RESET determines the range of the high sensitivity, thus
the output signal level at which the transition between high and
low sensitivity occurs.
Put the amplifier gain to the lowest value where the analog
output swing covers the ADC's digital input swing. Increasing
the amplification too much will likely boost the high sensitivity
part over the whole ADC range.
The electronic shutter determines the ratio of integration times
of the two slopes. The high sensitivity ramp corresponds to "no
electronic shutter", thus maximal integration time (frame read
out time). The low sensitivity ramp corresponds to the
electronic shutter value that would have been obtained in
normal operation.
Document Number: 001-02366 Rev. *D
Page 18 of 40
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