Texas Instruments ADC121S021CISDX/NOPB

Overview

ADC121S021CISDX/NOPB from Texas Instruments is a single-channel, 12-bit successive-approximation register (SAR) analog-to-digital converter with internal track-and-hold, serial SPI-compatible interface, 50–200 ksps sample rate range, and operation from 2.7 V to 5.25 V supply. It delivers 72.3 dB SNR and supports portable instrumentation, remote data acquisition, and industrial control systems.

For engineers reviewing the ADC121S021CISDX/NOPB datasheet, ADC121S021CISDX/NOPB pinout, ADC121S021CISDX/NOPB application, or ADC121S021CISDX/NOPB equivalent, key selection considerations include guaranteed performance across full 50–200 ksps range, ultra-low 2.6 µW shutdown power, SOT-23/WSON 6-pin packaging, SPI/QSPI/MICROWIRE compatibility, and industrial –40°C to +85°C temperature rating.

Technical Context

The ADC121S021CISDX/NOPB implements a charge-redistribution SAR architecture with integrated track-and-hold, enabling precise sampling of DC to 100 kHz analog inputs. Its conversion timing is fully synchronized to the external SCLK signal, with acquisition time (tACQ) specified at 350 ns and aperture jitter at 30 ps.

Functional mode control is achieved solely via the CS pin: pulling CS low initiates conversion and normal operation; asserting CS high between the 2nd and 10th SCLK falling edge forces shutdown mode, disabling analog circuitry and reducing supply current to 500 nA. Output data is straight binary, clocked out on SDATA on SCLK falling edges, with three leading zero bits followed by 12 data bits (MSB first).

Key Specifications

Pinout & Package

ADC121S021CISDX/NOPB is available in a 6-pin WSON package (NGF0006A) with 2.50 mm × 2.20 mm body size and exposed thermal pad (recommended to be connected to GND). The center pad improves thermal dissipation and reduces junction-to-board resistance to 24.8 °C/W.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 12-bit SAR ADC applications.

Compared with ADS7822U and ADS8320EB, ADC121S021CISDX/NOPB uniquely balances 12-bit accuracy, 200 ksps throughput, ultra-low shutdown power, and compact WSON packaging-making it optimal for space-constrained, battery-aware industrial and portable measurement systems where 8-bit is insufficient and 16-bit is over-specified.

Availability

ADC121S021CISDX/NOPB is available at Aetrix Electronics and suitable for portable instrumentation, remote data acquisition, and industrial control systems requiring stable component supply, long-term lifecycle support, and consistent parametric performance across production batches.

Supply support for ADC121S021CISDX/NOPB 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, embedded processing, and connectivity technologies, with decades of expertise in precision data converters and industrial-grade IC design.

The ADC121S021CISDX/NOPB belongs to TI's precision SAR ADC product line, engineered specifically for low-power, high-accuracy measurement applications in portable, remote, and industrial environments where reliability, small footprint, and guaranteed specifications across voltage and temperature are critical.

FAQ

What is the minimum acquisition time (tACQ) requirement for ADC121S021CISDX/NOPB?

The ADC121S021CISDX/NOPB specifies a minimum acquisition time (tACQ) of 350 ns, measured from the 13th rising edge of SCLK. This parameter defines the shortest interval allowed between the end of one conversion and the start of the next when operating at maximum throughput. Meeting tACQ ensures proper settling of the internal sampling capacitor before the next conversion begins, preserving linearity and accuracy. The value is guaranteed across the full –40°C to +85°C temperature range and all supported supply voltages.

Does ADC121S021CISDX/NOPB support true SPI mode 0 (CPOL = 0, CPHA = 0)?

Yes, ADC121S021CISDX/NOPB supports SPI mode 0. Its SDATA output is valid on the falling edge of SCLK and is sampled by the host on the subsequent rising edge - matching CPOL = 0 (clock idle low) and CPHA = 0 (data sampled on first clock edge). The device does not require clock inversion or phase adjustment, making it directly compatible with standard SPI controllers in microcontrollers such as MSP430, TM4C, and STM32 families without software workarounds.

How does the power-down mode function in ADC121S021CISDX/NOPB?

In ADC121S021CISDX/NOPB, power-down mode is entered by driving CS high between the 2nd and 10th falling edge of SCLK after CS was pulled low. This action aborts the current conversion and disables all analog circuitry, reducing supply current to 500 nA and power consumption to 2.6 µW at 5.25 V. To resume operation, CS must be pulled low again; the first conversion after wake-up is invalid due to power-up delay (~1 µs), but the second is fully specified and usable. This behavior enables deterministic low-power cycling in battery-operated systems.

What is the absolute maximum input voltage range for VIN on ADC121S021CISDX/NOPB?

The absolute maximum input voltage on VIN for ADC121S021CISDX/NOPB is –0.3 V to (VA + 0.3 V), per the Absolute Maximum Ratings table. However, the recommended operating range is strictly 0 V to VA. Exceeding VA or going below GND risks forward-biasing internal ESD diodes (D1/D2), causing leakage currents up to ±1 µA and potential measurement errors. For robust design, VIN must remain within 0–VA under all conditions, with VA itself limited to 2.7–5.25 V.

Is ADC121S021CISDX/NOPB pin-compatible with other members of the ADC121Sxx1 family?

Yes, ADC121S021CISDX/NOPB is fully pin- and function-compatible with ADC121S051 and ADC121S101, as confirmed in the Device Comparison Table and Pin Functions section of the datasheet. All three share identical 6-pin SOT-23/WSON footprints, identical pin assignments (VA, GND, VIN, CS, SDATA, SCLK), and identical SPI timing and control protocols. The only differences are guaranteed sample rate ranges (50–200 ksps, 200–500 ksps, and 500 ksps–1 Msps respectively), allowing drop-in upgrades based on throughput requirements without PCB changes.