AD9891KBC Analog Devices Inc, AD9891KBC Datasheet - Page 33

• Manufacturer Part Number: AD9891KBC
• Description: IC CCD SIGNAL PROC/GEN 64-CSPBGA
• Manufacturer: Analog Devices Inc
• Type: CCD Signal Processor, 10-Bitr

Specifications of AD9891KBC

• Rohs Status: RoHS non-compliant
• Input Type: Logic
• Output Type: Logic
• Interface: 3-Wire Serial
• Mounting Type: Surface Mount
• Package / Case: 64-CSPBGA
• Analog Front End Type: CCD
• Analog Front End Category: Video
• Interface Type: Serial (3-Wire)
• Operating Supply Voltage (min): 2.7/3V
• Resolution: 10b
• Number Of Adc's: 1
• Power Supply Type: Analog/Digital
• Operating Temp Range: -20C to 85C
• Operating Temperature Classification: Commercial
• Mounting: Surface Mount
• Pin Count: 64
• Package Type: CSPBGA
• Number Of Channels: 1
• Current - Supply: -
• Lead Free Status / RoHS Status: Not Compliant

Variable Gain Amplifier
The VGA stage provides a gain range of 2 dB to 36 dB, pro-
grammable with 10-bit resolution through the serial digital
interface. Combined with approximately 4 dB from the PxGA
stage, the total gain range for the AD9891/AD9895 is 6 dB to
40 dB. The minimum gain of 6 dB is needed to match a 1 V
input signal with the ADC full-scale range of 2 V. When com-
pared to 1 V full-scale systems (such as ADI’s AD9803), the
equivalent gain range is 0 dB to 34 dB.
REV. A
Figure 41. VGA Gain Curve (PxGA not included)
PxGA GAIN
NOTES
1. VD FALLING EDGE WILL RESET THE PxGA GAIN REGISTER STEERING TO “01230123” LINE.
2. HD FALLING EDGES WILL ALTERNATE THE PxGA GAIN REGISTER STEERING BETWEEN “01230123” AND “23012301” LINES.
3. FLD STATUS IS IGNORED.
(100000)
REGISTER
10
–2
–4
36
30
24
18
12
8
6
4
2
0
6
0
32
0
FLD
HD
VD
127
40
Figure 40. PxGA Gain Curve
X
255
X
48
PxGA GAIN REGISTER CODE
VGA GAIN REGISTER CODE
0
58
383
1
511
2
0
3
639
8
2
Figure 39g. 4-Color 2-Color Steering Mode
767
ODD FIELD
16
3
0
24
895
1
(011111)
1023
31
0
1
2
–33–
3
The VGA gain curve follows a “linear-in-dB” characteristic.
The exact VGA gain can be calculated for any gain register
value by using the equation:
where the code range is 0 to 1023. PxGA default gain is included.
The gain accuracy specifications include the PxGA gain of
approximately 4 dB, for a total gain range of 6 dB to 40 dB.
Optical Black Clamp
The optical black clamp loop is used to remove residual offsets
in the signal chain and to track low frequency variations in the
CCD’s black level. During the optical black (shielded) pixel
interval on each line, the ADC output is compared with a fixed
black level reference selected by the user in the Clamp Level
Register. The clamp level is programmable in 256 steps, with a
range between 0 LSB and 63.75 LSB in the AD9891 and be-
tween 0 LSB and 255 LSB in the AD9895. The resulting error
signal is filtered to reduce noise, and the correction value is
applied to the ADC input through a D/A converter. Normally,
the optical black clamp loop is turned on once per horizontal
line, but this loop can be updated more slowly to suit a particu-
lar application. If external digital clamping is used during
the post- processing, the AD9891/AD9895 optical black
clamping may be disabled using Bit D5 in the Operation Regis-
ter (see Serial Interface Timing and Register Listing sections).
When the loop is disabled, the Clamp Level Register may still
be used to provide programmable offset adjustment.
The optical black clamp is controlled by the CLPOB signal,
which is fully programmable (see Horizontal Clamping and
Blanking section). System timing examples are shown in the
Horizontal Timing Sequence Example section. The CLPOB
pulse should be placed during the CCD’s optical black pixels. It
is recommended that the CLPOB pulse duration be at least
20 pixels wide. Shorter pulsewidths may be used, but the ability
to track low frequency variations in the black level will be
reduced.
A/D Converter
The AD9891 uses a high a performance 10-bit ADC archi-
tecture, optimized for high speed and low power, while the
AD9895 uses a 12-bit ADC architecture. Differential
nonlinearity (DNL) performance is typically better than
0.5 LSB for both products. The ADC uses a 2 V input range.
Better noise performance results from using a larger ADC full-
scale range.
0
1
2
3
Gain
2
=
EVEN FIELD
3
( .
0 035
0
×
1
Code
AD9891/AD9895
0
)
1
+
3 55
.
2
3
0