Texas Instruments DDC112UK

Overview

DDC112UK from Texas Instruments is a dual-channel, 20-bit charge-digitizing analog-to-digital converter optimized for low-current photodetector and sensor interfaces. It features continuous dual-switched integrator architecture, ±0.025% reading integral linearity (max), 3.2 ppm rms noise at 250 pC full-scale, and operates with AVDD = DVDD = +5 V, TINT = 333.3 µs, CLK = 15 MHz, and VREF = +4.096 V in continuous mode - enabling high-precision current measurement in CT scanner data acquisition systems.

For engineers reviewing the DDC112UK datasheet, DDC112UK pinout, DDC112UK application, or DDC112UK equivalent, this page delivers verified technical context, SO-28 package mapping, confirmed 28-pin terminal roles, real-world use-value metrics for photodiode digitization and precision process control, and two validated alternative parts with documented functional and thermal differences.

Technical Context

The DDC112UK implements a true continuous-time, dual-input, dual-integrator-per-channel architecture: each input (IN1/IN2) uses two switched integrators (A/B sides) to enable uninterrupted current integration while interleaving digitization via a shared ∆Σ modulator and digital filter. Its internal programmable full-scale ranges (RANGE0–RANGE2) select seven on-chip integration capacitors (e.g., 50 pF for Range 4), supporting up to 250 pC nominal full-scale with external capacitor extension to 1000 pC.

Operation relies on precise timing coordination between CONV (integrator side selection), CLK (15 MHz system clock), and DCLK (serial data clock); conversion completes in ~220 µs per channel at 15 MHz, yielding 2–3 kHz effective throughput. The device uses VREF = +4.096 V both to reset integration capacitors and as the ∆Σ converter reference, making stability and low-noise buffering critical for offset and range accuracy.

Key Specifications

Pinout & Package

DDC112UK is housed in a 28-pin SOIC (SO-28) package with DW suffix, rated for 0°C to +70°C industrial temperature range. Thermal resistance θJA = +150°C/W. Pin layout supports dual independent current inputs, cascaded serial interface, and full-scale range selection via three control bits.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar charge-digitizing ADC applications.

Compared with DDC112UK, AD7739BRUZ offers higher resolution but no native dual-channel continuous integration, while ADS1258IPWR provides channel count and supply flexibility at the cost of added external components and reduced suitability for high-fidelity photodiode pulse capture.

Availability

DDC112UK is available at Aetrix Electronics and suitable for CT scanner DAS, infrared pyrometry, liquid chromatography, and clinical blood analysis requiring stable component supply across extended production lifecycles and industrial temperature operation.

Supply support for DDC112UK includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Texas Instruments is a global semiconductor leader specializing in precision analog, embedded processing, and high-reliability ICs for industrial, medical, and test equipment markets.

The DDC112UK belongs to TI's precision charge-digitizing ADC product line, designed specifically for direct photodiode and low-current sensor interfacing in medical imaging, analytical instrumentation, and scientific measurement systems.

FAQ

What is the maximum full-scale input charge supported by the DDC112UK?

The DDC112UK supports up to 1000 pC full-scale input charge when external integration capacitors are used with RANGE2–RANGE0 = 000. With internal capacitors only, the maximum is 350 pC (Range 7, 87.5 pF). This 1000 pC capability enables direct digitization of high-output photodiodes or transimpedance amplifier outputs without signal attenuation or gain staging - preserving SNR and simplifying front-end design for the DDC112UK.

How does the DDC112UK achieve continuous integration with only one ∆Σ converter?

The DDC112UK achieves continuous integration using two independent switched integrators per input channel (IN1A/IN1B and IN2A/IN2B). While one integrator side (e.g., IN1A) is being digitized by the shared ∆Σ converter, the other (IN1B) simultaneously integrates incoming current - and vice versa. This interleaved operation, controlled by the CONV signal synchronized to CLK, eliminates dead time and ensures uninterrupted signal capture for the DDC112UK.

What is the purpose of the TEST pin on the DDC112UK, and how is it used?

The TEST pin on the DDC112UK enables hardware-calibrated self-test: when asserted HIGH before a CONV edge, it grounds IN1 and IN2 and injects precise 13 pC charge packets into all four integrators. This allows factory or field verification of gain, offset, and linearity without external stimulus - critical for medical and analytical instruments requiring traceable calibration. The DDC112UK test mode is fully documented in SBAS085B Rev. October 2004.

Why does the DDC112UK require a buffered +4.096 V reference on the VREF pin?

The DDC112UK uses VREF for two critical functions: resetting integration capacitors to a known voltage at cycle start, and serving as the reference for the ∆Σ converter during digitization. Any droop or noise on VREF directly introduces offset error and full-scale drift. A buffered source (e.g., REF3040 + OPA350) maintains stability under dynamic current demand (~150 µA at TINT = 333.3 µs), ensuring consistent performance for the DDC112UK across temperature and time.

Can multiple DDC112UK devices be synchronized for simultaneous sampling?

Yes - multiple DDC112UK devices can be synchronized using a common CLK and CONV signal routed with matched trace lengths. Because integration timing is determined by CONV edges aligned to CLK, and digitization is interleaved per device, precise inter-device phase alignment ensures simultaneous integration windows. The DDC112UK's cascaded serial interface (DIN/DOUT) then allows consolidated readout without additional timing control lines.