AD9822JRS Analog Devices Inc, AD9822JRS Datasheet - Page 16

• Manufacturer Part Number: AD9822JRS
• Description: IC CCD SIGNAL PROC 14BIT 28-SSOP
• Manufacturer: Analog Devices Inc
• Type: CCD Signal Processor, 14-Bitr

Specifications of AD9822JRS

• Rohs Status: RoHS non-compliant
• Input Type: Logic
• Output Type: Logic
• Interface: 3-Wire Serial
• Current - Supply: 73mA
• Mounting Type: Surface Mount
• Package / Case: 28-SSOP
• Analog Front End Type: CCD/CIS
• Analog Front End Category: Video
• Interface Type: Serial (3-Wire)
• Sample Rate: 15MSPS
• Input Voltage Range: 1V
• Operating Supply Voltage (min): 3/4.75V
• Operating Supply Voltage (typ): 5V
• Operating Supply Voltage (max): 5.25V
• Resolution: 14b
• Supply Current: 4/73mA
• Number Of Adc's: 1
• Power Supply Type: Analog/Digital
• Operating Temp Range: 0C to 70C
• Operating Temperature Classification: Commercial
• Mounting: Surface Mount
• Pin Count: 28
• Package Type: SSOP
• Number Of Channels: 3
• Lead Free Status / RoHS Status: Not Compliant

AD9822
ANALOG INPUTS—SHA MODE
Figure 12 shows the analog input configuration for the SHA
mode of operation. Figure 13 shows the internal timing for the
sampling switches. The input signal is sampled when CDSCLK2
transitions from high to low, opening S1. The voltage on the
OFFSET pin is also sampled on the falling edge of CDSCLK2,
when S2 opens. S3 is then closed, generating a differential
output voltage representing the difference between the sampled
input voltage and the OFFSET voltage. The input clamp is
disabled during SHA mode operation.
Figure 14 shows how the OFFSET pin may be used in a CIS
application for coarse offset adjustment. Many CIS signals have
dc offsets ranging from several hundred millivolts to more than
1 V. By connecting the appropriate dc voltage to the OFFSET
pin, the CIS signal is restored to 0. After the large dc offset is
removed, the signal can be scaled using the PGA to maximize
the ADC’s dynamic range.
(OR CONNECT TO GND)
(INTERNAL)
Figure 12. SHA Mode Input Configuration (All Three Channels are Identical)
OPTIONAL DC OFFSET
CDSCLK2
Q3
INPUT SIGNAL
S1, S2 OPEN
S3 OPEN
Figure 13. SHA Mode Internal Switch Timing
S1, S2 CLOSED
OFFSET
VING
VINR
VINB
S3 CLOSED
AD9822
S2
S1
S3
S1, S2 CLOSED
2pF
2pF
S3 CLOSED
CML
RED
CML
GREEN
BLUE
Rev. B | Page 16 of 20
CIS MODULE
PROGRAMMABLE GAIN AMPLIFIERS (PGA)
The AD9822 uses one PGA for each channel. Each PGA has a
gain range from 1× (0 dB) to 5.8× (15.5 dB), adjustable in
64 steps. Figure 15 shows the PGA gain as a function of the
PGA register code. Although the gain curve is approximately
linear-in-dB, the gain in V/V varies nonlinearly with register
code, following the equation
where G is the decimal value of the gain register contents and
varies from 0 to 63.
VREF FROM
DC OFFSET
Gain
15
12
9
6
3
0
R1
R2
AVDD
0
=
Figure 14. SHA Mode Used with External DC Offset
4
1
+
8
4.7
Figure 15. PGA Gain Transfer Function
12 16 20 24 28 32 36 40 44 48 52 56 60
5.7
GREEN
⎡
⎢
⎣
PGA REGISTER VALUE (Decimal)
BLUE
63
RED
63
0.1µF
−
OFFSET
G
VING
VINR
VINB
⎤
⎥
⎦
AD9822
SHA
SHA
SHA
RED-OFFSET
GREEN-OFFSET
BLUE-OFFSET
63
5.7
5.0
4.0
3.0
2.0
1.0