CYIL1SM0300AA CYPRESS [Cypress Semiconductor], CYIL1SM0300AA Datasheet - Page 12

• Manufacturer Part Number: CYIL1SM0300AA
• Description: LUPA-300 CMOS Image Sensor
• Manufacturer: CYPRESS [Cypress Semiconductor]

Document Number: 001-00371 Rev. *D
1.45V and a swing of 100 mV. With this swing it fits in the input
range of the ADC, but a large part of the range of the ADC is
not used in this case. For this reason an offset will be added
first, to align the black level with the input range of the ADC. In
the first step an offset of 200 mV is added with the default
settings of VBLACK and VOFFSET. This results in the red
histogram with a average black level of 1.65V. This means that
the spread on the black level falls completely inside the range
of the ADC. In a second step, explained in section 2.4.2, the
signal will be amplified to use the full range of the ADC.
Programmable Gain
The amplification inside the PGA is controlled by three SPI
settings:
The PGA gain selection: 16 gain steps are selectable by
means of the GAIN_PGA<3:0> register. Selection word 0000
corresponds with gain 1.32 and selection word 1111
corresponds with gain 15.5. Table 9 gives the 16 gain settings
The unity gain selection of the PGA is done by the
UNITY_PGA setting. If this bit is high, the GAIN_PGA settings
are ignored.
The SEL_UNI setting can be used to have more gain steps. If
this bit is low, the signal is divided by two before entering the
PGA. GAIN_PGA and UNITY_PGA settings are applied
afterwards. If the SEL_UNI bit is high, there is a unity feed
through to the PGA. This allows having a total gain range of
0.5 to 16 in 32 steps.
Figure 6. Offset Regulation
1.45V
1.65V
1.75V
VADC_HIGH
Volts
Table 9. Gain Settings
The amplification in the PGA is done around a pivoting point,
set by Vcal. See Figure 7 for an illustration of this. The
VCAL<7:0> setting is used to apply the Vcal voltage through
an on chip DAC
Figure 7. Effect on Histogram of PGA (gain=4); Vcal is the
Figure 8 continues on the example of section 2.4.1. The blue
histogram is the histogram of the image after the column
amplifiers. With offset regulation an offset of 200 mV is added
to bring the signal in range of the ADC. The black level of
1.45V is shifted to 1.65V.
The red and blue histograms have a swing of 100 mV. This
means the input range of the ADC is not completely used. By
0001
0010
0011
0100
0101
0110
0111
1000
1001
1010
1011
1100
1101
1110
1111
GAIN_PGA<3.0>
0000
Vcal
green line.
1.56
1.85
2.18
2.58
3.05
3.59
4.22
4.9
5.84
6.84
8.02
9.38
11.2
13.12
15.38
CYIL1SM0300AA
Gain
1.32
Page 12 of 36
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