AD9937KCP Analog Devices Inc, AD9937KCP Datasheet - Page 21

• Manufacturer Part Number: AD9937KCP
• Manufacturer: Analog Devices Inc

Specifications of AD9937KCP

• Analog Front End Type: CCD
• Analog Front End Category: Video
• Interface Type: Serial (3-Wire)
• Input Voltage Range: 0.5V
• Operating Supply Voltage (min): 2.7V
• Operating Supply Voltage (typ): 3V
• Operating Supply Voltage (max): 3.6V
• Resolution: 10b
• Number Of Adc's: 1
• Power Supply Type: Analog/Digital
• Operating Temp Range: -25C to 85C
• Operating Temperature Classification: Commercial
• Mounting: Surface Mount
• Pin Count: 56
• Package Type: LFCSP EP
• Number Of Channels: 1
• Lead Free Status / RoHS Status: Not Compliant

ANALOG FRONT END DESCRIPTION AND OPERATION
The AD9937 AFE signal processing chain is shown in Figure 11.
Each processing step is essential in achieving a high quality image
from the raw CCD pixel data.
DC Restore
To reduce the large dc offset of the CCD output signal, a dc
restore circuit is used with an external 0.1 µF series coupling
capacitor. This restores the dc level of the CCD signal to approxi-
mately 1.5 V to be compatible with the 3 V analog supply of
the AD9937.
REV. 0
0.1 F
CCDIN
DC RESTORE
1.5V
SHP
CDS
SHD
SHP
GENERATION
PRECISION
TIMING
Figure 11. AFE Block Diagram
SHD
AD9937
VGA GAIN
REGISTER
6dB TO 40dB
VGA
PHASE
DOUT
10
–21–
8-BIT
DAC
GENERATION
Correlated Double Sampler
The CDS circuit samples each CCD pixel twice to extract the
video information and reject low frequency noise. The timing
diagram in Figure 13 illustrates how the two internally gener-
ated CDS clocks, SHP and SHD, are used to sample the
reference level and the data level, respectively, of the CCD
signal. The placement of the SHP and SHD sampling edges is
determined by the setting of the SHPLOC (addr 0x05) and
SHDLOC (addr 0x05) control registers. Placement of these two
clock edges is critical in achieving the best performance from
the CCD.
CLPOB
TIMING
V-H
DIGITAL
FILTER
REFB
1.0V
OPTICAL BLACK
CLAMP
INTERNAL
ADC
1.0 F
VREF
2V FULL
SCALE
CLAMP LEVEL
REGISTER
REFT
2.0V
1.0 F
8
CLPOB
OUTPUT
LATCH
DATA
PHASE
DOUT
10
DOUT
AD9937