DDC114| Datasheet

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DDC114
SBAS255B - JUNE 2004 - REVISED JUNE 2005

Quad Current Input 20-Bit Analog-To-Digital Converter
FEATURES
D D D D D D D D D D D D
SINGLE-CHIP SOLUTION TO DIRECTLY MEASURE FOUR LOW-LEVEL CURRENTS HIGH PRECISION, TRUE INTEGRATING FUNCTION INTEGRAL LINEARITY: 0.01% of Reading 0.5ppm of FSR VERY LOW NOISE: 5.2ppm of FSR LOW POWER: 13.5mW/channel ADJUSTABLE DATA RATE: Up to 3.125kSPS PROGRAMMABLE FULL SCALE DAISY-CHAINABLE SERIAL INTERFACE

DESCRIPTION
The DDC114 is a 20-bit quad channel, current-input analog-to-digital (A/D) converter. It combines both current-to-voltage and A/D conversion so that four low-level current output devices, such as photodiodes, can be directly connected to its inputs and digitized. For each of the four inputs, the DDC114 provides a dual-switched integrator front-end. This design allows for continuous current integration: while one integrator is being digitized by the onboard A/D converter, the other is integrating the input current. Adjustable full-scale ranges from 12pC to 350pC and adjustable integration times from 50us to 1s allow currents from fAs to uAs to be measured with outstanding precision. Low-level linearity is 0.5ppm of the full-scale range and noise is 5.2ppm of the full-scale range. Two modes of operation are provided. In Low-Power mode, total power dissipation is only 13.5mW per channel with a maximum data rate of 2.5kSPS. High-Speed mode supports data rates up to 3.125kSPS with a corresponding dissipation of
18mW per channel.
CLK

APPLICATIONS
CT SCANNER DAS PHOTODIODE SENSORS INFRARED PYROMETER LIQUID/GAS CHROMATOGRAPHY

Protected by US Patent #5841310
AVDD VREF DVDD

IN1 Dual Switched Integrator IN3 Dual Switched Integrator Modulator

CONV RANGE0 Digital Filter RANGE1 Control RANGE2 TEST CLK_4X HISPD/LOPWR RESET FORMAT DCLK

The DDC114 has a serial interface designed for daisy-chaining in multi-device systems. Simply connect the output of one device to the input of the next to create the chain. Common clocking feeds all the devices in the chain so that the digital overhead in a multi-DDC114 system is minimal. The DDC114 is a single-supply device using a +5V analog supply and supporting a +2.7V to +5.25V digital supply. Operating over the industrial temperature range of -40 C to 85 C, the DDC114 is offered in a QFN-48 package.

IN2 DCLK Dual Switched Integrator IN4 Dual Switched Integrator AGND DGND Modulator Digital Filter Digital Input/Output DVALID DOUT DOUT DIN DIN

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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.

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