kac-9637 ETC-unknow, kac-9637 Datasheet - Page 18

• Manufacturer Part Number: kac-9637
• Description: Cmos Image Sensor 648 H X 488 V Vga 68 Fps Monochrome Cis
• Manufacturer: ETC-unknow

IMAGE SENSOR SOLUTIONS
Functional Description
7.0
The KAC-9637 allows for both fine and coarse black level
adjustment. Coarse adjustment is made using the PIXELOFF-
SET register and only needs to be done once at power up. Fine
offset adjustment is done on a row basis and can be accom-
plished either atomically using the on chip black level compen-
sation circuit or manually by disabling the on chip black level
compensation circuit.
7.1
To ensure maximum performance of the CMOS image sensor,
the natural offset of the pixel array needs to be minimized.
Coarse adjustment is made using the PIXELOFFSET register
and only needs to be done once at power up. This procedure is
explained in detail in KAC-9637 Application Note 4.
7.2
The offset channel can provide up to 255 levels of black level
and offset adjustment. To manually adjust the black level and
offset the BlkLevEn bit in the BLKLEVCONFIG register should
be set to a logic 1. Eight bit offset values can then be pro-
grammed to register OFFSET.
Up to 255 levels of black level and offset adjustment are pro-
vided. To manually adjust the black level and offset the
BlkLevEn bit in the BLKLEVCONFIG register should be set to a
logic 0. The eight bit offset value can then be programmed using
the Offset parameter in the OFFSET register.
7.3
Automatic black level and offset adjustment mode is enabled by
setting the BlkLevEn bit in the BLKLEVCONFIG register to a
logic 0.
Figure 21 illustrates the automatic black level and offset com-
pensation circuit contained within the sensor. For every row, the
digitized values of the middle 8 black pixels are acquired and fed
to the compensation level calculator circuit. This circuit is a digi-
tal first order exponential averaging filter. It calculates the com-
pensation level (cmpl) that is required to ensure that for pixels
that are optically black, the black level at the output of the ADC
is equal to the desired black level. The desired black level (Clk-
Target) can be programmed in the BLKTARGET register.
The black level control loop not only controls the black level of
the pixels in the sensor array, but also controls the offset of the
PGA and A/D in the system. The convergence rate of the can-
cellation loop can be set by programming the BlkRate parameter
located in the BLKLEVCONFIG register. Small values of the
BlkRate parameter ensure a fast convergence. High values of
the BlkRate parameter reduce the noise in the calculated com-
pensation level. The optimal setting of the BlkRate parameter is
the result of a compromise between convergence speed after
power up and image quality.
www.kodak.com/go/imagers 585-722-4385
all CHx
Figure 21: Digital Black Level & Offset Adjustment Loop
Pixels
BLACK LEVEL & OFFSET ADJUSTMENT
Coarse Black Level and Offset Adjustment
Manual Black Level and Offset Adjustment
Auto Black Level and Offset Adjustment
+
DAC
8 bit
CHx
cmpl Level Calc
BlkRate
Comp
(continued)
ADC
BlkTraget
Black Pixel
Acquisition
10
Output
Data
18
8.0
8.1
Upon power up an on-chip power on reset block will ensure that
the sensor is initialized to its reset state. After power up the sen-
sor can be reset by asserting a logic 0 on the resetb pin or by
writing to the SenReset bin in the PWD&RESET register.
Furthermore, all state machines contained in the sensors inte-
grated timing and control block can be reset by writing to the
RstzSoft bit in the OPCTRL register.
8.2
The KAC-9637 is equipped with an on-board power manage-
ment system allowing the analog and digital circuitry to be
switched off (power down) and on (power up) at any time.
The sensor can be put into power down mode by asserting a
logic one on the pdwn pin or by writing to the PwDn bit in the
PWD&RST register.
To power up the sensor a logic zero can be asserted on the
pdwn pin or by writing to the PwDn bit in the PWD&RST regis-
ter.
To ensure proper sensor operation the reference ladders must
be intitialized upon power up of the sensor.
To switch on the sensor’s reference resistors, the following
sequence of codes should be written to the sensor via the I
compatible interface at power up.
This must be done for the sensor to operate properly after reset
or when the sensor is powered up.
SYSTEM MANAGMENT
System Reset
Power Up and Down
Address
(Hex)
INITREG2
POWCTRL
Email:[e-mail]
Data
(Hex)
01
81
2
C