Complete 14-Bit

CCD/CIS Signal Processor

AD9822

Rev. B

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FEATURES

14-bit 15 MSPS ADC

No missing codes guaranteed

3-channel operation up to 15 MSPS

1-channel operation up to 12.5 MSPS

Correlated double sampling

1–6× programmable gain

±350 mV programmable offset

Input clamp circuitry

Internal voltage reference

Multiplexed byte-wide output (8 + 6 format)

3-wire serial digital interface

3 V/5 V digital I/O compatibility

28-Lead SOIC or SSOP

Low power CMOS: 385 mW (typ)

Power-down mode: <1 mW

APPLICATIONS

Flatbed document scanners

Film scanners

Digital color copiers

Multifunction peripherals

GENERAL DESCRIPTION

The AD9822 is a complete analog signal processor for CCD

imaging applications. It features a 3-channel architecture designed

to sample and condition the outputs of trilinear color CCD

arrays. Each channel consists of an input clamp, correlated double

sampler (CDS), offset DAC, and programmable gain amplifier

(PGA) multiplexed to a high performance 14-bit ADC.

The CDS amplifiers may be disabled for use with sensors such

as contact image sensors (CIS) and CMOS active pixel sensors,

which do not require CDS.

The 14-bit digital output is multiplexed into an 8-bit output

word that is accessed using two read cycles. The internal

registers are programmed through a 3-wire serial interface and

provide adjustment of the gain, offset, and operating mode.

The AD9822 operates from a single 5 V power supply,

consumes 385 mW of power typically, and is packaged in a

28-lead SOIC or SSOP.

FUNCTIONAL BLOCK DIAGRAM

14

8

BAND GAP

REFERENCE

CONFIGURATION

REGISTER

MUX

REGISTER

6

6

9

9

GAIN

REGISTERS

OFFSET

REGISTERS

DIGITAL

CONTROL

INTERFACE

INPUT

CLAMP

BIAS

AD9822

DRVDD

DRVSS

AVDD

AVSS

CAPT

CAPB

AVDD

AVSS

CML

OEB

DOUT

ADCCLK

CDSCLK2

CDSCLK1

OFFSET

VINB

VING

VINR

9-BIT

DAC

SCLK

SLOAD

SDATA

9-BIT

DAC

9-BIT

DAC

CDS

PGA

PGA

PGA

CDS

CDS

3:1

MUX

14-BIT

ADC

14:8

MUX

BLUE

GREEN

RED

BLUE

GREEN

RED

Figure 1.