DDC112

Dual Current Input 20-Bit

ANALOG-TO-DIGITAL CONVERTER

FEATURES

q MONOLITHIC CHARGE MEASUREMENT A/D

CONVERTER

q DIGITAL FILTER NOISE REDUCTION:

3.2ppm, rms

q INTEGRAL LINEARITY:

q HIGH PRECISION, TRUE INTEGRATING FUNC-

TION

q PROGRAMMABLE FULL-SCALE

q SINGLE SUPPLY

q CASCADABLE OUTPUT

APPLICATIONS

q DIRECT PHOTOSENSOR DIGITIZATION

q CT SCANNER DAS

q INFRARED PYROMETER

q PRECISION PROCESS CONTROL

q LIQUID/GAS CHROMATOGRAPHY

q BLOOD ANALYSIS

DESCRIPTION

The DDC112 is a dual input, wide dynamic range, charge-

digitizing analog-to-digital (A/D) converter with 20-bit resolu-

tion. Low-level current output devices, such as photosensors,

can be directly connected to its inputs. Charge integration is

continuous as each input uses two integrators; while one is

being digitized, the other is integrating.

For each of its two inputs, the DDC112 combines current-to-

voltage conversion, continuous integration, programmable

full-scale range, A/D conversion, and digital filtering to achieve

a precision, wide dynamic range digital result. In addition to

the internal programmable full-scale ranges, external integrat-

ing capacitors allow an additional user-settable full-scale

range of up to 1000pC.

To provide single-supply operation, the internal A/D converter

When the integration capacitor is reset at the beginning of

charge is removed in proportion to the input current. At the

end of the integration cycle, the remaining voltage is com-

The high-speed serial shift register which holds the result of

the last conversion can be configured to allow multiple DDC112

units to be cascaded, minimizing interconnections. The

DDC112 is available in an SO-28 or TQFP-32 package and is

offered in two performance grades.

Protected by US Patent #5841310

Dual

Switched

Integrator

Dual

Switched

Integrator

∆Σ

Modulator

Digital

Filter

Control

Digital

Input/Output

DVALID

DXMIT

DOUT

DIN

DCLK

RANGE2

RANGE1

RANGE0

TEST

CONV

CLK

CAP1A

CAP1A

CAP1B

CAP1B

CAP2A

CAP2A

CAP2B

CAP2B

IN2

IN1

DGND

AGND

CHANNEL 1

CHANNEL 2

SBAS085B – JANUARY 2000 – REVISED OCTOBER 2004

DDC1

12

®

DDC

112

®

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PRODUCTION DATA information is current as of publication date.

Products conform to specifications per the terms of Texas Instruments

standard warranty. Production processing does not necessarily include

testing of all parameters.

Copyright © 2000-2004, Texas Instruments Incorporated

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