AD9840AJST Analog Devices Inc, AD9840AJST Datasheet - Page 14

• Manufacturer Part Number: AD9840AJST
• Description: IC CCD SIGNAL PROC 10BIT 48-LQFP
• Manufacturer: Analog Devices Inc
• Type: CCD Signal Processor, 10-Bitr

Specifications of AD9840AJST

• Rohs Status: RoHS non-compliant
• Input Type: Logic
• Output Type: Logic
• Interface: 3-Wire Serial
• Mounting Type: Surface Mount
• Package / Case: 48-LQFP
• Analog Front End Type: CCD
• Analog Front End Category: Video
• Interface Type: Serial (3-Wire)
• Sample Rate: 40MSPS
• Input Voltage Range: 0.8V
• 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: LQFP
• Number Of Channels: 1
• Current - Supply: -
• Lead Free Status / RoHS Status: Compliant

AD9840A
APPLICATIONS INFORMATION
The AD9840A is a complete Analog Front End (AFE) product
for digital still camera and camcorder applications. As shown in
Figure 16, the CCD image (pixel) data is buffered and sent to
the AD9840A analog input through a series input capacitor. The
AD9840A performs the dc restoration, CDS, gain adjustment,
black level correction, and analog-to-digital conversion. The
AD9840A’s digital output data is then processed by the image
processing ASIC. The internal registers of the AD9840A—used
to control gain, offset level, and other functions—are programmed
by the ASIC or microprocessor through a 3-wire serial digital
interface. A system timing generator provides the clock signals
for both the CCD and the AFE.
Internal Power-On Reset Circuitry
After power-on, the AD9840A will automatically reset all internal
registers and perform internal calibration procedures. This takes
approximately 1 ms to complete. During this time, normal clock
signals and serial write operations may occur. However, serial
register writes will be ignored until the internal reset operation is
completed. Pin 43 (formerly RSTB on the AD9843 non-A) is no
longer used for the reset operation. Toggling Pin 43 in the
AD9840A will have no effect.
V-DRIVE
CCD
V
OUT
BUFFER
0.1 F
TIMING
CCD
CCDIN
GENERATOR
AD9840A
TIMING
REGISTER
CDS/CLAMP
TIMING
ADC
Grounding and Decoupling Recommendations
As shown in Figure 17, a single ground plane is recommended
for the AD9840A. This ground plane should be as continuous
as possible, particularly around Pins 25 through 39. This will
ensure that all analog decoupling capacitors provide the lowest
possible impedance path between the power and bypass pins
and their respective ground pins. All decoupling capacitors
should be located as close as possible to the package pins. A
single clean power supply is recommended for the AD9840A,
but a separate digital driver supply may be used for DRVDD
(Pin 13). DRVDD should always be decoupled to DRVSS (Pin
14), which should be connected to the analog ground plane.
Advantages of using a separate digital driver supply include
using a lower voltage (2.7 V) to match levels with a 2.7 V ASIC,
reducing digital power dissipation, and reducing potential noise
coupling. If the digital outputs (Pins 3–12) must drive a load
larger than 20 pF, buffering is recommended to reduce digital
code transition noise. Alternatively, placing series resistors
close to the digital output pins may help reduce noise.
DATA
OUT
OUTPUTS
INTERFACE
DIGITAL
SERIAL
DIGITAL IMAGE
PROCESSING
ASIC