ADC12138CIWMX/NOPB
ADC12138CIWMX/NOPB - 12+Sign-Bit 114kSPS SAR ADC | TI
The Texas Instruments ADC12138CIWMX/NOPB is a self-calibrating 12-bit plus sign serial I/O analog-to-digital converter with an integrated 8-channel analog input multiplexer and sample/hold, offered in a 28-pin SOIC (Wide, 0.295" / 7.50 mm) package. It performs successive-approximation (SAR) conversions at up to 114 k samples per second, supports both unipolar (0 to VREF) and bipolar (±VREF) input ranges through on-chip sign extension, and provides self-calibration that removes offset and gain errors without external components.
A SAR ADC is a successive-approximation-register analog-to-digital converter that uses a binary-search algorithm against an internal capacitive DAC to resolve each conversion in N clock cycles for N bits of resolution. SAR ADCs occupy the middle of the converter hierarchy between flash ADCs (fastest, lowest resolution) and sigma-delta ADCs (slowest, highest resolution), and they are favored when medium resolution, low latency, deterministic acquisition, and moderate speed are required without the latency penalty of oversampling converters.
Key features of the ADC12138CIWMX/NOPB include 4 or 8 configurable analog inputs (the ADC12130/12132/12138 family shares one datasheet), 12-bit plus sign resolution, 114 kSPS maximum throughput, MICROWIRE-compatible serial interface, ±2.5 V bipolar or 0–5 V unipolar input ranges, internal sample/hold, self-calibration mode, single +5 V analog supply, and industrial −40 °C to +85 °C operating temperature. The wide SOIC package exposes ground and supply pins on multiple sides for straightforward PCB layout and decoupling.
The architecture combines an input MUX, a differential sample/hold, a SAR core, and a calibration DAC that trims the reference ladder during the calibration cycle. Self-calibration runs automatically on power-up and can be retriggered on demand, holding the trimmed coefficients until the next calibration, which significantly reduces full-scale and zero-scale error compared with uncalibrated SAR devices.
Typical applications include industrial process-control data acquisition modules, multi-channel instrumentation front ends, battery-pack monitoring systems, portable medical diagnostic instruments, and HVAC sensor interfaces. The integrated MUX allows direct connection of multiple sensors to a single converter.
When designing with this device, place a 10 µF tantalum plus 0.1 µF ceramic bypass close to AVDD/DVDD, keep the analog/digital ground split under the IC, and use an external low-noise reference (e.g., REF02/REF50xx) tied to the VREF pin; the S/H input current spikes during acquisition, and long source impedance will degrade THD.
This page synthesizes distributor pricing, drop-in same-package alternatives, and practical PCB-layout notes not found in the manufacturer datasheet alone.
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