ADC12138CIWMX - 12-Bit+Sign 8-Ch SAR ADC | Texas Instruments
MPN: ADC12138CIWMX ✗ End of Life| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $8.45 | $8.45 |
| 10 | $7.62 | $76.20 |
| 100 | $6.8 | $680.00 |
| 500 | $6.12 | $3,060.00 |
| 1,000 | $5.45 | $5,450.00 |
ADC12138CIWMX Overview
A SAR ADC (successive-approximation register analog-to-digital converter) is a type of data converter that performs a binary search through an internal resistor ladder to resolve an input voltage into a digital code in N conversion steps for an N-bit result. SAR ADCs sit in the broader hierarchy of data converters -> ADCs -> successive-approximation ADCs -> semiconductor ICs, and they are favored in multi-channel precision instrumentation because they deliver deterministic latency, no-pipeline-delay sampling, and intrinsic ease of multiplexing.
Key differentiating features include on-chip self-calibration that corrects offset and gain errors at power-up and on demand, a software-configurable unipolar/bipolar input range with the bipolar range scaled to ±VREF, a maximum conversion time of 8.8 µs at the slowest clock, and 4.5 V to 5.5 V analog supply operation. The 8-channel input mux removes the need for an external analog switch in low-density data-acquisition front ends. Differential nonlinearity remain within ±1 LSB maximum.
The architecture uses a capacitive charge-balancing DAC followed by a comparator and SAR logic, with the calibration cycles trimming both endpoints against an internal bandgap-derived reference. The result is low total unadjusted error, low temperature drift, and the absence of pipeline delay so the conversion result is available the same cycle the sample is taken - useful for closed-loop control.
Typical applications include portable multi-channel data loggers, industrial process-control front ends with 4-20 mA loop sensors, weigh-scale and bridge-transducer signal chains, patient-monitoring front ends in IEC 60601-1-isolated subsystems, and battery-powered hand-held instrumentation requiring 3.3 V supply operation.
When designing with the ADC12138CIWMX, decouple AVDD and AGND locally with a 10 µF tantalum plus 0.1 µF ceramic pair, route the analog and digital grounds as separate planes joined only at the AGND pin, and gate the serial transfers with CS so the part powers down between conversions for additional power savings.
This page synthesizes distributor stock, signature options, and drop-in alternatives not collected on the manufacturer's datasheet alone.
Drop-in alternatives for ADC12138CIWMX — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Variants in this series
Same-series models that are drop-in compatible with ADC12138CIWMX (same form factor and footprint) — differing in Package, Input Type, Resolution, Data Interface, Number of Input Channels.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
ADC12138CIWM
✅ Drop-In✓ In Stock
$5.8 / Unit
View Datasheet →ADC12138CIWMX/NOPB
✅ Drop-In✓ In Stock
$7.85 / Unit
View Datasheet →ADC12138CIWN
✅ Drop-In ⚠️ Specs Unverified📋 Reference alternative (not in catalog)
ADC10738CIWMX
✅ Drop-In ⚠️ Specs Unverified✓ In Stock
$5.48 / Unit
View Datasheet →ADC10464CIWMX/NOPB
✅ Drop-In ⚠️ Specs Unverified✓ In Stock
$5.74 / Unit
View Datasheet →ADC10158CIWMX/NOPB
✅ Drop-In ⚠️ Specs Unverified✓ In Stock
$5.74 / Unit
View Datasheet →ADC12138CIWMX Maximum Ratings & Electrical Characteristics
| Resolution | 12 bits + sign |
| Architecture | SAR (Successive Approximation) |
| Number of Analog Inputs | 8 single-ended / 4 differential |
| Conversion Time | 8.8 us max |
| Analog Supply Voltage | 4.5 V to 5.5 V (single +5 V); +3.3 V compatible |
| Digital Supply Voltage | Same as AVDD |
| Input Voltage Range | 0 V to VREF (unipolar); -VREF to +VREF (bipolar) |
| Differential Non-Linearity (DNL) | ±1 LSB max |
| Sample-and-Hold | On-chip |
| Digital Interface | Serial, 4-wire (CS, SCLK, DOUT, DIN) |
| Self-Calibration | Yes, on-chip offset + gain trim |
| Package | 28-SOIC (WM) 7.5 mm body |
| Operating Temperature | -40C to +85C |
| Mounting Type | Surface Mount |
| MSL Level | 1 (unlimited) |
| RoHS Status | Compliant |
ADC12138CIWMX Pin Configuration
| Pin 1 | AGND — Analog ground |
| Pin 2 | VA+ — Analog supply, +5 V nominal |
| Pin 3 | VREF — Voltage reference input |
| Pin 4 | AIN0 — Analog input 0 (MUX channel 0) |
| Pin 5 | AIN1 — Analog input 1 (MUX channel 1) |
| Pin 6 | AIN2 — Analog input 2 (MUX channel 2) |
| Pin 7 | AIN3 — Analog input 3 (MUX channel 3) |
| Pin 8 | AIN4 — Analog input 4 (MUX channel 4) |
| Pin 9 | AIN5 — Analog input 5 (MUX channel 5) |
| Pin 10 | AIN6 — Analog input 6 (MUX channel 6) |
| Pin 11 | AIN7 — Analog input 7 (MUX channel 7) |
| Pin 12 | NC — Not connected (per datasheet) |
| Pin 13 | NC — Not connected (per datasheet) |
| Pin 14 | NC — Not connected (per datasheet) |
| Pin 15 | DGND — Digital ground |
| Pin 16 | DOUT — Serial data output (conversion result) |
| Pin 17 | DIN — Serial data input (configuration) |
| Pin 18 | SCLK — Serial clock input |
| Pin 19 | CS — Chip select, active low |
| Pin 20 | PD — Power-down input |
| Pin 21 | NC — Not connected (per datasheet) |
| Pin 22 | NC — Not connected (per datasheet) |
| Pin 23 | NC — Not connected (per datasheet) |
| Pin 24 | NC — Not connected (per datasheet) |
| Pin 25 | NC — Not connected (per datasheet) |
| Pin 26 | NC — Not connected (per datasheet) |
| Pin 27 | NC — Not connected (per datasheet) |
| Pin 28 | NC — Not connected (per datasheet) |
Typical Applications
ADC12138CIWMX is suitable for 6 applications: Multi-Channel Data Logger, Industrial Process-Control Front End, Weigh-Scale / Bridge Transducer Digitizer, Patient-Monitoring Front End, Portable Hand-Held Instrumentation, Multi-Sensor IoT Edge Node.
Multi-Channel Data Logger
The ADC12138CIWMX's 8 single-ended input multiplexer, 12-bit+sign resolution, and 4-wire serial interface make it a natural fit for portable multi-channel data loggers. Engineers typically pair the part with an MSP430 or PIC microcontroller that issues MUX-channel-select commands, reads 13-bit two's-complement conversion results, and stores samples in non-volatile memory. The on-chip self-calibration trims offset and gain at power-up, removing the per-channel accuracy penalty that plagues discrete ADC designs. At a maximum conversion time of 8.8 µs the part sustains better than 100 ksamples/s aggregate-throughput across all eight MUX inputs when sequenced rapidly.
Recommended
Industrial Process-Control Front End
The ADC12138CIWMX suits industrial process-control front ends because it accepts 4-20 mA loop-derived voltage drops on its differential MUX inputs and returns bipolar 12-bit+sign codes that map cleanly to signed process variables. The wide 4.5 V to 5.5 V analog supply tolerance tolerates the noisy 24 V loop-derived rails common in factory automation. The on-chip sample/hold removes the per-channel buffer op-amps that discrete designs require. With 8 input channels the part can digitize four differential loop signals and four auxiliary single-ended signals (such as RTD or thermocouple references) on a single chip.
Recommended
Weigh-Scale / Bridge Transducer Digitizer
Weigh scales and bridge-transducer digitizers rely on bipolar ADC inputs because the bridge output swings both above and below the excitation common-mode voltage as the load changes sign. The ADC12138CIWMX's bipolar ±VREF input range captures this swing directly, and its on-chip self-calibration cancels bridge offset at every power-up so the scale does not need a manual tare routine. The 28-SOIC package supports hand-soldering for low-volume scale production. Typical designs pair the ADC with an INA128 instrumentation amplifier that drives the differential MUX inputs and a 5 V excitation regulator that also powers the bridge.
Recommended
Patient-Monitoring Front End
Patient-monitoring front ends in IEC 60601-1 isolated subsystems require multi-channel bipolar ADCs to digitize ECG, respiration, temperature, and SpO2-derived signals that swing around a common-mode reference. The ADC12138CIWMX delivers 12-bit+sign resolution and 8 input channels on a single 5 V supply, simplifying the analog front end in isolated designs where every additional active device adds iso-coupler cost. Its on-chip self-calibration reduces the post-isolation calibration burden because each power-up cycle retrims offset and gain against an external reference. The 28-SOIC package and 8.8 µs conversion time fit sub-millisecond per-channel sampling budgets.
Recommended
Portable Hand-Held Instrumentation
Battery-powered hand-held instruments such as digital multimeters, environmental meters, and field calibrators benefit from the ADC12138CIWMX's 3.3 V compatibility, 8-channel MUX, and low active current consumption. The 4-wire serial interface frees GPIO pins on the host microcontroller for display, keypad, and user-interface functions. The on-chip sample/hold eliminates external analog switches, shrinking the BOM and reducing leakage on the high-impedance MUX inputs. The 12-bit+sign dynamic range captures bipolar transducer signals without a bipolar reference rail.
Recommended
Multi-Sensor IoT Edge Node
IoT edge nodes that aggregate temperature, humidity, flow, and pressure sensors benefit from the ADC12138CIWMX's 8-channel MUX, which lets a single ADC digitize an entire sensor cluster without an external analog switch. The 4-wire serial interface is compatible with low-power MCUs running at 3.3 V, and the on-chip self-calibration corrects thermal drift across the -40 C to +85 C industrial range. The 28-SOIC wide-body package tolerates hand-soldering for prototype runs and remains compatible with high-volume SMT lines, supporting both engineering builds and production scaling on the same BOM.
Recommended
Recommended Products Summary
Engineering reference data for ADC12138CIWMX — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | ADC12138CIWM | ADC12138CIWMX/NOPB | ADC12138CIWN | ADC10738CIWMX | ADC10464CIWMX/NOPB | ADC10158CIWMX/NOPB |
|---|---|---|---|---|---|---|---|
| Brand | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments |
| Package | 28-SOIC | 28-SOIC - same | 28-SOIC - same | 28-SOIC - same | 28-SOIC - same | 28-SOIC - same | 28-SOIC - same |
| Resolution | 12-bit + sign | 12-bit + sign | 12-bit + sign | 12-bit + sign | 10-bit + sign | 14-bit | 10-bit |
| Number of Input Channels | 8 SE / 4 DI | 8 SE / 4 DI | 8 SE / 4 DI | 8 SE / 4 DI | 8 SE / 4 DI | 4 SE / 2 DI | 8 SE / 4 DI |
| Analog Supply Voltage | 4.5 V to 5.5 V (+3.3 V compatible) | 4.5 V to 5.5 V | 4.5 V to 5.5 V | 4.5 V to 5.5 V | 4.5 V to 5.5 V | 4.5 V to 5.5 V | 4.5 V to 5.5 V |
| Serial Interface | 4-wire (CS/SCLK/DIN/DOUT) | 4-wire | 4-wire | 4-wire | 4-wire | Serial, parallel | 4-wire |
| Self-Calibration | Yes (offset + gain) | Yes | Yes | Yes | Yes | Yes | Yes |
| Operating Temperature | -40C to +85C | -40C to +85C | -40C to +85C | -40C to +85C | -40C to +85C | -40C to +85C | -40C to +85C |
| Lifecycle Status | Obsolete | Obsolete | Obsolete | Obsolete | Active | Active | Obsolete |
Key Differentiators
- 8-channel MUX on-chip (vs ADC10464CIWMX/NOPB)
- 12-bit+sign resolution with bipolar input (vs ADC10738CIWMX)
- On-chip self-calibration at every power-up (vs Discrete SAR designs without discrete components)
Design Notes
Decouple VA+ (pin 2) locally with a 10 µF tantalum (or low-ESR ceramic) capacitor in parallel with a 0.1 µF ceramic, placed within 5 mm of the supply pin. Connect the digital supply to the same +5 V rail through an optional ferrite bead so switching transients from the serial interface do not couple into the analog reference ladder. The on-chip sample/hold draws transient current during the acquisition phase, so the local bulk capacitor prevents droop that would otherwise degrade INL on rapid MUX-switched conversions.
Route AGND (pin 1) and DGND (pin 15) to a single point on the PCB ground plane, ideally directly under the IC, so digital return currents from SCLK, DOUT, and DIN do not share the analog ground path. Place the external VREF reference (e.g., LM4040 or REF02) within 10 mm of pin 3 with its own local decoupling. Keep the analog input traces short, and surround them with a guard trace tied to AGND when routing across noisy digital layers on a 2-layer PCB.
Always run the on-chip offset+gain calibration routine at every power-up and after any reference-voltage or supply-voltage change, otherwise the uncalibrated offset can exceed ±5 LSB and the gain error can exceed 1%. Do not leave floating analog inputs when the MUX is enabled - unused channels should be tied to a known mid-supply voltage (VREF/2) so the floating channel does not inject charge that corrupts the selected channel's sample. The serial interface requires CS to be de-asserted between configuration writes; leaving CS asserted after a read causes the part to remain active, defeating power-down.
The 4-wire serial interface (CS, SCLK, DIN, DOUT) supports clock rates up to 10 MHz per the datasheet. For long PCB traces (greater than 50 mm) add a 33 ohm series damping resistor at SCLK to prevent ringing, and place a small ferrite bead on DOUT to limit radiated emissions. When chaining multiple ADC12138 parts on the same SPI bus, ensure that only one CS asserts CS at any time and that DOUT drivers remain in high-Z when CS is high to avoid bus contention.
Compliance Information
RoHS compliant per TI product page. Not AEC-Q100 qualified - this is an industrial/consumer-grade ADC, not automotive-grade. /NOPB suffix confirms lead-free terminal finish.
