AD9898KCP-20 Analog Devices Inc, AD9898KCP-20 Datasheet - Page 19

• Manufacturer Part Number: AD9898KCP-20
• Description: IC CCD SIGNAL PROC/GEN 48-LFCSP
• Manufacturer: Analog Devices Inc
• Type: CCD Signal Processor, 10-Bitr

Specifications of AD9898KCP-20

• Rohs Status: RoHS non-compliant
• Input Type: Logic
• Output Type: Logic
• Interface: 3-Wire Serial
• Mounting Type: Surface Mount
• Package / Case: 48-LFCSP
• 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: -20C to 85C
• Operating Temperature Classification: Commercial
• Mounting: Surface Mount
• Pin Count: 48
• Package Type: LFCSP EP
• Number Of Channels: 3
• Current - Supply: -
• Lead Free Status / RoHS Status: Not Compliant

ANALOG FRONT END (AFE) DESCRIPTION AND
OPERATION
The AD9898 AFE signal processing chain is shown in Figure 10.
Each processing step is essential to achieving a high quality image
from the raw CCD pixel data. Registers for the AD9898 AFE
section are listed in Table VII.
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, which is compatible with the 3 V analog supply of
the AD9898.
Correlated Double Sampler
To extract the video information and reject low frequency noise,
the CDS circuit samples each CCD pixel twice. The timing
shown in Figure 12 illustrates how the two internally generated
CDS clocks, SHP and SHD, are used to sample the reference
level and the data level of the CCD signal, respectively. The
placement of the SHP and SHD sampling edges is determined
by the setting of the SHPLOC (Addr 0x02) and SHDLOC
(Addr 0x02) registers. Placement of these two clock edges is criti-
cal to achieving the best performance from the CCD.
Register
Name
VGAGAIN
REFBLACK 6
AFESTBY
REV. 0
0.1 F
Bit
Width Register Type
10
1
Table VII. AFE Registers
CCDIN
Control (Addr 0x0E) VGA Gain
Control (Addr 0x04) Blk Clamp Level
Control (Addr 0x05) AFE Standby
DC RESTORE
1.5V
SHP
CDS
SHD
SHP
Description
GENERATION
PRECISION
TIMING
Figure 10. AFE Block Diagram
SHD
VGA GAIN
REGISTER
6dB TO 40dB
AD9898
VGA
PHASE
DOUT
10
–19–
8-BIT
DAC
GENERATION
PRECISION TIMING HIGH SPEED TIMING GENERATION
The AD9898 generates flexible high speed timing signals using
the Precision Timing core. This core is the foundation for gen-
erating the timing used for both the CCD and the AFE signals,
including the reset gate RG, the horizontal drivers H1–H2, and
the CDS sample clocks. By providing precise control over the
horizontal CCD readout and the AFE correlated double sampling,
the unique architecture of the AD9898 makes optimizing image
quality a routine task for a system designer.
Timing Resolution
The Precision Timing core uses a 1× master clock input (CLI)
as a reference. This clock should be the same as the CCD pixel
clock frequency. Figure 11 illustrates how the internal timing
core divides the master clock period into 48 steps or edge posi-
tions. Using a 20 MHz CLI frequency for the AD9898, the
edge resolution of the Precision Timing core is 1 ns. A 40 MHz
CLI frequency can be applied where the AD9898 will inter-
nally divide the CLI frequency by two. Division by one-third
and one-fourth is also provided. CLI frequency division is con-
trolled using the CLKDIV (Addr 0xD5) register.
High Speed Clock Programmability
Figure 13 shows how the high speed clocks RG, H1–H2, SHP,
and SHD are generated. The RG pulse has a fixed rising edge
and a programmable falling edge. The horizontal clock H1
has a programmable rising and a fixed falling edge occurring at
H1POSLOC + 24 steps. The H2 clock is always the inverse of
H1. Table VIII summarizes the high speed timing registers and
the parameters for the high speed clocks. Each register is six bits
wide with the 2 MSB used to select the quadrant region as
outlined in Table VIII. Figure 13 shows the range and de-
fault locations of the high speed clock signals.
CLPOB
TIMING
V-H
DIGITAL
FILTER
REFB
1.0V
OPTICAL BLACK
CLAMP
INTERNAL
ADC
1.0 F
V
REF
2V FULL
SCALE
CLAMP LEVEL
REGISTER
REFT
2.0V
1.0 F
6
CLPOB
OUTPUT
LATCH
DATA
PHASE
DOUT
10
DOUT
AD9898