®
DDC112
DDC112
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information, visit www.burr-brown.com
Dual Current Input 20-Bit
ANALOG-TO-DIGITAL CONVERTER
FEATURES
DESCRIPTION
● MONOLITHIC CHARGE MEASUREMENT ADC
The DDC112 is a dual input, wide dynamic range,
charge-digitizing analog-to-digital converter (ADC) with
20-bit resolution. 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.
● DIGITAL FILTER NOISE REDUCTION:
3.2ppm, rms
● INTEGRAL LINEARITY:
±0.005% Reading ±0.5ppm FSR
● HIGH PRECISION, TRUE 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 program-
mable full-scale ranges, external integrating capacitors
allow an additional user-settable full-scale range of up
to 1000pC.
FUNCTION
● PROGRAMMABLE FULL SCALE
● SINGLE SUPPLY
● CASCADABLE OUTPUT
APPLICATIONS
● DIRECT PHOTOSENSOR DIGITIZATION
To provide single-supply operation, the internal ADC
utilizes a differential input, with the positive input tied
to VREF. When the integration capacitor is reset at the
beginning of each integration cycle, the capacitor
charges to VREF. This charge is removed in proportion
to the input current. At the end of the integration cycle,
● CT SCANNER DAS
● INFRARED PYROMETER
● PRECISION PROCESS CONTROL
● LIQUID/GAS CHROMATOGRAPHY
● BLOOD ANALYSIS
the remaining voltage is compared to VREF
.
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 a SO-28
package and is offered in two performance grades.
Protected by US Patent #5841310
AVDD
AGND
VREF
DVDD DGND
CAP1A
CAP1A
CHANNEL 1
DCLK
IN1
Dual
Switched
Integrator
DVALID
CAP1B
CAP1B
∆Σ
Modulator
DXMIT
DOUT
DIN
Digital
Filter
Digital
Input/Output
CAP2A
CAP2A
CHANNEL 2
RANGE2
RANGE1
RANGE0
IN2
Control
Dual
Switched
Integrator
CAP2B
CAP2B
TEST
CLK
CONV
International Airport Industrial Park
•
Mailing Address: PO Box 11400, Tucson, AZ 85734
•
Street Address: 6730 S. Tucson Blvd., Tucson, AZ 85706
• Tel: (520) 746-1111
Twx: 910-952-1111
•
Internet: http://www.burr-brown.com/
•
Cable: BBRCORP Telex: 066-6491
•
•
FAX: (520) 889-1510 Immediate Product Info: (800) 548-6132
•
®
©1997 Burr-Brown Corporation
PDS-1421D
Printed in U.S.A. January, 2000
DDC112
1