Texas Instruments DDC112U

Overview

DDC112U from Texas Instruments is a dual-channel, 20-bit charge-digitizing analog-to-digital converter optimized for low-level current input sensors. 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 from single +5V supplies (AVDD/DVDD). It is used in CT scanner data acquisition systems where high dynamic range and stable offset over temperature are critical.

For engineers reviewing the DDC112U datasheet, DDC112U pinout, DDC112U application, or DDC112U equivalent, key selection considerations include integration time programmability (500 µs nominal), external reference dependency (+4.096 V), cascaded serial output capability, and SO-28 package thermal performance (θJA = 150°C/W).

Technical Context

The DDC112U implements two independent input channels, each with paired switched integrators (A/B) enabling uninterrupted current integration: while one side integrates, the other is digitized by a shared delta-sigma modulator and digital filter. Its front-end topology uses capacitor-based charge integration referenced to VREF, with reset-to-VREF initialization followed by input-current–driven voltage decay.

Conversion control is synchronized via CONV and CLK (10 MHz nominal); digital output is delivered through a synchronous serial interface (DCLK, DXMIT, DOUT, DVALID) supporting daisy-chained configurations. Range selection (RANGE0–RANGE2) configures internal integration capacitors (50 pF to 350 pF) or enables external capacitor use (up to 1000 pC full-scale).

Key Specifications

Pinout & Package

DDC112U is housed in a 28-pin SOIC (SO-28, DW package) with exposed pad not present; thermal resistance θJA = 150°C/W. Pin functions support dual-channel charge integration, serial data chaining, and precise range control.

Key Features

Applications

Equivalent & Alternatives

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

Compared with AD7739BRUZ and ADS1256IPWR, the DDC112U uniquely delivers true dual-channel, zero-dead-time charge integration in a single SO-28 package-eliminating external analog front-end components and synchronization overhead in photonics and medical DAS designs.

Availability

DDC112U is available at Aetrix Electronics and suitable for CT scanner data acquisition, infrared pyrometry, liquid chromatography detection, blood analysis instrumentation, and precision process control requiring stable component supply across extended temperature ranges.

Supply support for DDC112U 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 analog and embedded processing technologies, with decades of heritage in precision data converters and medical-grade ICs.

The DDC112U belongs to TI's high-accuracy charge-digitizing ADC product line, designed specifically for direct photodetector and low-current sensor interfacing in diagnostic imaging, analytical instrumentation, and industrial metrology.

FAQ

What is the maximum integration time supported by the DDC112U in continuous mode?

The DDC112U supports an integration time (TINT) of up to 1,000,000 µs (1 second) in continuous mode per the electrical characteristics table. At the nominal 500 µs setting, it achieves optimal noise performance (3.2 ppm rms). Longer integration times reduce average VREF current draw but increase conversion latency. The DDC112U does not impose hard upper limits beyond datasheet-specified timing constraints and thermal dissipation limits of the SO-28 package.

Can the DDC112U operate with a reference voltage other than +4.096 V?

Yes-the DDC112U accepts VREF from –0.3 V to AVDD + 0.3 V, with specified performance at +4.096 V. Using alternate references (e.g., +2.5 V or +5.0 V) changes full-scale charge range proportionally and affects offset drift and noise floor. For example, halving VREF halves full-scale range and doubles sensitivity to reference drift. The DDC112U datasheet characterizes accuracy and noise only at +4.096 V; deviation requires system-level recalibration and validation.

How does the DDC112U handle crosstalk between its two input channels?

The DDC112U achieves >120 dB crosstalk isolation between IN1 and IN2 across DC to 500 Hz, as verified in typical characteristics plots. This results from fully differential integrator design, separate capacitor networks per channel, and physical pin separation (IN1 at Pin 1, IN2 at Pin 28). No additional shielding or guard traces are required in standard layouts. The DDC112U maintains this isolation even under mismatched external capacitor conditions, provided both sides of each integrator pair remain balanced.

Is the DDC112U pin-compatible with the DDC112UK or DDC112Y variants?

No-the DDC112U (SO-28, –40°C to +85°C) is not pin-compatible with DDC112Y (TQFP-32, –40°C to +85°C) due to different package footprints and pin counts. While DDC112U and DDC112UK share the same SO-28 package and pinout, they differ in temperature grade (industrial vs. commercial) and tested specifications-DDC112UK is characterized only from 0°C to +70°C and may exhibit degraded linearity or drift outside that range. The DDC112U remains the sole choice for full industrial-temperature operation in the SO-28 form factor.

What is the role of the TEST pin on the DDC112U, and how is it used in calibration?

The TEST pin enables on-chip calibration by injecting a precise 13 pC charge packet into both integrator banks (IN1 and IN2) upon a CONV edge. When asserted before CONV, it grounds the analog inputs and transfers fixed charge-allowing verification of gain, linearity, and channel matching without external test equipment. The DDC112U datasheet confirms this function is production-tested and traceable; repeated pulses enable averaging to suppress noise. It is especially valuable for field recalibration of deployed CT scanner DAS modules where sensor access is impractical.