ADC121S101CISD - 12-Bit 1Msps SAR ADC | Texas Instruments
MPN: ADC121S101CISD ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $3.45 | $3.45 |
| 10 | $3.1 | $31.00 |
| 100 | $2.65 | $265.00 |
| 500 | $2.3 | $1,150.00 |
| 1,000 | $2.05 | $2,050.00 |
| 3,000 | $1.85 | $5,550.00 |
ADC121S101CISD Overview
A SAR ADC is a successive-approximation analog-to-digital converter that uses a binary-search algorithm and an internal capacitive DAC to convert an analog input to a digital code in N clock cycles for N bits of resolution. SAR ADCs sit at the bottom of the high-resolution ADC taxonomy (SAR -> ADC -> data converter -> signal-chain IC) and are prized for low latency, deterministic conversion time, no-pipeline delay, and excellent DC accuracy, which is why they dominate multiplexed multi-channel precision instrumentation, sensor read-out, and process-control front-ends.
Key specifications include 12-bit resolution, 0.5 Msps to 1 Msps sampling rate, ±0.65 LSB INL (typical), ±0.5 LSB DNL (typical), no missing codes, a 71 dB SINAD at 100 kHz input, and an SPI-compatible serial data output with a 3-wire (SCLK, /CS, DOUT) interface. The 6-WSON package enables very compact PCB layouts suitable for space-constrained sensor modules and portable instrumentation.
The converter is built on a CMOS process and integrates a sample-and-hold amplifier, precision reference input (VAIN with respect to AGND), and an on-chip conversion clock, eliminating the need for an external clock. The /CS falling edge initiates conversion, and the SCLK drives the serial data out, simplifying firmware on microcontrollers without a dedicated ADC peripheral.
Typical applications include portable data acquisition, factory automation sensor read-out, optical modules, battery monitoring, handheld instruments, and consumer audio/video signal level measurement where a small-footprint 12-bit ADC with deterministic latency is required.
When designing with this device, observe the layout guidance in the TI datasheet: keep the analog input trace short, place a 0.1 uF bypass capacitor close to VAIN, and ensure a clean low-impedance AGND return. The reference voltage on VAIN is the analog supply; for best linearity decouple VAIN to AGND with at least 1 uF of effective capacitance.
This page synthesizes distributor pricing, drop-in alternatives, and practical design notes not found on stock aggregator pages, helping engineers choose between the ADC121S101 and pin-compatible 10/12-bit SAR alternatives.
Drop-in alternatives for ADC121S101CISD — 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 ADC121S101CISD (same form factor and footprint) — differing in Package, Architecture, Resolution, Operating Temperature, RoHS Status.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
ADC121S101CISD/NOPB
✅ Drop-In📋 Reference alternative (not in catalog)
ADC121S101CISDX
✅ Drop-In📋 Reference alternative (not in catalog)
ADC121S021CISD
✅ Drop-In✓ In Stock
$1.79 / Unit
View Datasheet →ADC121S021CISDX
✅ Drop-In✓ In Stock
$1.85 / Unit
View Datasheet →ADC121S101CIMFX
✅ Drop-In✓ In Stock
$1.85 / Unit
View Datasheet →ADC121S051CIMFX
✅ Drop-In✓ In Stock
$1.95 / Unit
View Datasheet →ADC121S101CISD Maximum Ratings & Electrical Characteristics
| Resolution | 12 bit |
| Number of Channels | 1 |
| Sample Rate | 0.5 Msps to 1 Msps |
| Architecture | SAR (Successive Approximation Register) |
| Input Type | Single-ended |
| Analog Supply Voltage (VAIN) | 2.7 V to 5.25 V |
| Digital Supply Voltage (VD) | 2.7 V to 5.25 V |
| SINAD | 71 dB (typ) at 100 kHz input |
| Power Consumption | 1.5 mW (typ) at VAIN = VD = 3.3 V |
| Operating Temperature Range | -40 C to +125 C |
| Package | 6-WSON (2.2 mm x 2.5 mm, NGF) |
| Interface | SPI / QSPI / MICROWIRE compatible, 3-wire |
| Mounting Type | Surface Mount |
| RoHS Status | Compliant |
ADC121S101CISD Pin Configuration
| Pin 1 | VAIN — Analog input and analog supply voltage (2.7 V to 5.25 V) |
| Pin 2 | AGND — Analog ground reference |
| Pin 3 | VD — Digital supply voltage (2.7 V to 5.25 V) |
| Pin 4 | DGND — Digital ground reference |
| Pin 5 | DOUT — Serial data output (SPI MOSI from ADC) |
| Pin 6 | /CS — Chip select input (active low), also SCLK clock input |
Typical Applications
ADC121S101CISD is suitable for 7 applications: Portable Data Acquisition Modules, Factory Automation Sensor Read-Out, Optical Module Power Monitoring, Battery Monitoring and Energy Metering, Handheld Test and Measurement, Consumer Audio/Video Level Metering, Industrial Sensor Front-Ends.
Portable Data Acquisition Modules
The ADC121S101CISD's 1 Msps sample rate, 12-bit resolution, and 1.5 mW typical power consumption make it a strong fit for battery-powered portable data-acquisition modules that digitize multi-megahertz-bandwidth sensor signals. With a single 2.7-5.25 V supply and a 3-wire SPI interface, the part integrates easily with low-power MCUs without a dedicated analog front end. The 6-WSON package fits inside handheld enclosures where every square millimeter matters.
Recommended
Factory Automation Sensor Read-Out
For factory-automation analog sensor read-out (4-20 mA bridges, strain gauges, RTDs), the ADC121S101CISD's SAR architecture provides deterministic single-cycle conversion with no pipeline delay, which is essential when multiplexing multiple sensors and reacting to over-current or over-temperature events within one control loop. The -40 C to +125 C operating range and SPI isolation-friendly interface simplify integration with industrial PLC backplanes.
Recommended
Optical Module Power Monitoring
In optical transceiver modules (SFP, QSFP, XFP), the ADC121S101CISD is commonly used to digitize the receive-power monitor photodiode current via a transimpedance amplifier, providing feedback to the host for loss-of-signal alarms and AGC loops. Its 1 Msps sample rate comfortably exceeds the 4 kHz update rate demanded by typical optical diagnostics, while its small 6-WSON footprint fits inside the cramped module housing alongside the laser driver and TIA.
Recommended
Battery Monitoring and Energy Metering
The ADC121S101CISD's wide 2.7-5.25 V supply range and 1.5 mW power draw suit multi-cell battery-monitoring ICs where stack voltages of 12-48 V must be scaled and digitized. Its SAR conversion gives a single-cycle, deterministic latency that aligns well with coulomb-counting and protection-IC algorithms, and its 12-bit resolution is sufficient to detect cell imbalance in Li-ion packs above 1% state-of-charge granularity.
Recommended
Handheld Test and Measurement
Handheld DMMs, oscilloscope probes, and field-strength meters leverage the ADC121S101CISD's combination of 12-bit resolution, 1 Msps burst sample rate, and tiny 6-WSON footprint to digitize slowly varying process signals with high DC accuracy. The SPI output streams directly into a low-cost Cortex-M0 MCU, eliminating the need for an analog front-end ASIC. The -40 C to +125 C range supports outdoor and industrial field use.
Recommended
Consumer Audio/Video Level Metering
The ADC121S101CISD's 71 dB SINAD and 1 Msps sample rate enable VU/PPM metering for consumer audio mixers, set-top box AGC loops, and video level-monitoring applications. SPI output simplifies integration with DSP processors that lack a built-in ADC; the 6-WSON package supports dense PCB layouts in HDMI switchers and AV receivers. Drop-in compatibility with the 10-bit ADC101S021CISD lets designers right-size the ADC to the channel.
Recommended
Industrial Sensor Front-Ends
In multi-channel industrial sensor front-ends the ADC121S101CISD provides a deterministic SAR conversion that multiplexes well with external analog switches, allowing 4-8 channels to be scanned sequentially without the pipeline-delay artifacts of pipeline ADCs. Its wide operating temperature and small footprint suit remote terminal units (RTUs) and industrial IoT edge nodes. Pin-compatible 12-bit and 10-bit siblings (ADC121S021CISD, ADC101S021CISD) support cost-engineered variants.
Recommended
Recommended Products Summary
Engineering reference data for ADC121S101CISD — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | ADC121S101CISD/NOPB | ADC121S101CISDX | ADC121S021CISD | ADC121S021CISDX | ADC121S101CIMFX | ADC121S051CIMFX |
|---|---|---|---|---|---|---|---|
| Package | 6-WSON (2.2x2.5 mm, NGF) | 6-WSON (2.2x2.5 mm) - same | 6-WSON (2.2x2.5 mm) - same | 6-WSON (2.2x2.5 mm) - same | 6-WSON (2.2x2.5 mm) - same | 6-WSON (2.2x2.5 mm) - same | 6-WSON (2.2x2.5 mm) - same |
| Brand | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments |
| Resolution | 12 bit | 12 bit | 12 bit | 12 bit | 12 bit | 12 bit | 12 bit |
| Sample Rate | 1 Msps | 1 Msps | 1 Msps | 200 ksps | 200 ksps | 1 Msps | 500 ksps |
| Supply Voltage | 2.7 V to 5.25 V | 2.7 V to 5.25 V | 2.7 V to 5.25 V | 2.7 V to 5.25 V | 2.7 V to 5.25 V | 2.7 V to 5.25 V | 2.7 V to 5.25 V |
| Interface | SPI / 3-wire serial | SPI / 3-wire serial | SPI / 3-wire serial | SPI / 3-wire serial | SPI / 3-wire serial | SPI / 3-wire serial | SPI / 3-wire serial |
| Operating Temperature | -40 C to +125 C | -40 C to +125 C | -40 C to +125 C | -40 C to +125 C | -40 C to +125 C | -40 C to +125 C | -40 C to +125 C |
| Power Consumption (typ) | 1.5 mW at 3.3 V | 1.5 mW at 3.3 V | 1.5 mW at 3.3 V | lower (200 ksps) | lower (200 ksps) | 1.5 mW at 3.3 V | lower (500 ksps) |
| Qty-1 Price (USD, approx) | 3.45 | 3.30 | 3.40 | 2.80 | 2.75 | 3.40 | 3.10 |
Key Differentiators
- Industry-standard 12-bit 1 Msps SAR with guaranteed no-missing-codes and 71 dB SINAD (vs ADC121S021CISD)
- Smallest 1 Msps 12-bit SAR footprint in TI's WSON family (vs ADC121S051CIMFX)
- Wide 2.7 V to 5.25 V single-supply operation simplifies power-tree design (vs ADC101S021CISD)
Design Notes
Decouple VAIN and VD locally with a 0.1 uF ceramic capacitor placed within 2 mm of each supply pin, and add a 10 uF bulk capacitor on the analog rail. Although the ADC121S101CISD draws only 1.5 mW at 3.3 V, the SAR architecture injects transient current spikes on VAIN at each conversion edge - poor decoupling couples these into the analog input and degrades SINAD. Tie VAIN and VD to the same 3.3 V rail when possible to minimize ground-loop noise.
Route the analog input trace on the top layer directly to pin 1 (VAIN) with a guard trace tied to AGND on both sides; avoid routing digital SCLK, /CS, or DOUT traces parallel to or beneath the analog input. Place the WSON exposed thermal pad on a continuous AGND pour with at least 4 thermal vias to the inner ground plane to reduce thermal-gradient-induced offset drift. Keep the digital ground return path (DGND) star-connected to AGND at one point near the ADC.
A common pitfall is assuming the analog input pin VAIN doubles as a separate reference voltage; per the TI datasheet, the analog input signal is referenced to the AGND pin, and VAIN is the supply rail, not an independent reference. When digitizing small bipolar signals, bias the input mid-rail with a resistor divider buffered by an op-amp, otherwise the SAR conversion range is truncated. Also note that /CS falling edge starts conversion - do not toggle /CS during SCLK activity or the conversion aborts.
For best 71 dB SINAD at 1 Msps, the SCLK frequency should be held below 20 MHz to limit digital feedthrough into the analog input. Place a small series resistor (22-33 ohm) at the DOUT pin if the trace exceeds 25 mm to dampen ringing on the SPI bus. Use a low-impedance AGND return path directly beneath the DOUT trace to minimize crosstalk onto the analog input.
Compliance Information
RoHS and REACH compliance confirmed on TI product page; for AEC-Q100 automotive grade use the -Q1 suffix variants. Standard variant is not AEC-Q100 qualified.
