CYII4SM1300AA Datasheet, PDF (11/35 Pages) Cypress Semiconductor – IBIS4-1300 1.3 MPxl Rolling Shutter CMOS Image Sensor

CYII4SM1300AA
Figure 7. Offset Adjustment: Fast Offset Adjustment Mode
min. 500 ns
calib_f
dark
signal
stable input
unitygain
> 100 ns
>0
There are 2 modes of offset calibration for the output amplifier:
slow and fast adjustment. Figure 7. shows the timing and signal
waveforms for fast offset adjustment mode. Closing both 'calib_f'
and 'unitygain' operates it. After 'calib_f' is opened again, the
offset level is adjusted to the desired value in a single cycle. The
signal applied to the output amplifier should be stable just before
and during the adjustment phase. The same is true for the DAC
output.
The signal applied to the output amplifier can be either:
■ The signal generated by the electrical dark reference in the
imager core itself, i.e., the pixels named "dark" in Figure 20.
■ Apply the reference from outside on the pin EXTIN, controlled
by SEL_EXTIN.
If this fast offset adjustment is used, it should be done once each
frame, before the readout of the frame starts, e.g., during the
blanking time of the first line.
Figure 8. Slow Offset Adjustment Mode
min. 100 ns
calib_s
dark
signal
stable input
min 100 ns
Figure 8. shows the timing and signal waveforms for slow offset
adjustment mode. It is operated by pulsing 'calib_s'. The
amplifier input signal must be stable and refer to 'dark' signal at
the moment when calib_s goes low. The offset is slowly adjusted
with a time constant of about 100 of these pulses. One pulse is
then generated during each row blanking time.
The baseline is to use the fast calibration once per image. The
slow calibration is intended as alternative if, for very slow
readout, the offset drifts during the image.
Document Number: 38-05707 Rev. *C
Page 11 of 35
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