Analog Devices Inc. AD7921ARMZ

Overview

AD7921ARMZ from Analog Devices is a 12-bit, dual-channel successive approximation ADC with 250 kSPS throughput, operating from a single 2.35 V to 5.25 V supply and delivering 71 dB minimum SNR at 100 kHz input frequency. It features internal VDD-referenced conversion, no pipeline delay, and SPI/QSPI/MICROWIRE/DSP-compatible serial interface - used in portable medical instruments and battery-powered data acquisition systems.

For engineers reviewing the AD7921ARMZ datasheet, AD7921ARMZ pinout, AD7921ARMZ application, or AD7921ARMZ equivalent, key selection considerations include its 12-bit resolution, channel-to-channel isolation (−90 dB typ), 290 ns track-and-hold acquisition time, standby current of 1 μA max, and compatibility with low-voltage microprocessor interfaces requiring minimal power and board space.

Technical Context

The AD7921ARMZ implements a true successive approximation register (SAR) architecture with a wide-bandwidth track-and-hold amplifier supporting >6 MHz input frequencies. Conversion is initiated on the falling edge of CS, with sampling synchronized to that edge and no latency between command and sample capture.

It uses VDD as the internal reference source, enabling full-scale analog input range of 0 V to VDD. Channel selection is performed via DIN pin during CS assertion, and the serial output includes a channel identifier bit followed by 12 MSB-first data bits - ensuring unambiguous dual-channel operation without external multiplexing.

Key Specifications

Pinout & Package

AD7921ARMZ is housed in an 8-lead TSOT package (3 mm × 3 mm × 0.8 mm), optimized for space-constrained portable designs. Thermal resistance θ_JA is 207°C/W.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar dual-channel SAR ADC applications.

Compared with AD7921ARMZ, AD7911ARMZ trades 2 bits of resolution and ~10 dB SNR for lower cost and identical footprint, while ADS7822U offers comparable resolution but sacrifices throughput, supply flexibility, and embedded channel awareness - making AD7921ARMZ optimal for precision, dual-channel, battery-aware systems.

Availability

AD7921ARMZ is available at Aetrix Electronics and suitable for portable medical instrumentation, battery-powered data acquisition, optical sensor interface, and industrial control loop monitoring requiring stable component supply across production lifecycles.

Supply support for AD7921ARMZ 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

Analog Devices is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, headquartered in Norwood, MA, with R&D and manufacturing operations worldwide.

The AD79xx family - including AD7921ARMZ - was designed specifically for low-power, high-speed, dual-channel data acquisition in space- and energy-constrained applications such as handheld test equipment and remote sensing nodes.

FAQ

What is the maximum sampling rate supported by the AD7921ARMZ?

The AD7921ARMZ supports a maximum throughput rate of 250 kSPS under specified conditions (VDD = 2.35 V to 5.25 V, fSCLK = 5 MHz). This rate is achieved using 16 SCLK cycles per conversion, with conversion time limited to 3.2 μs max. The actual achievable rate depends on SCLK frequency and system-level timing margins, but 250 kSPS is the guaranteed maximum performance point documented in the AD7921ARMZ datasheet.

Does the AD7921ARMZ require an external voltage reference?

No, the AD7921ARMZ does not require an external voltage reference. It uses the VDD supply rail as its internal reference source, enabling a full-scale analog input range of 0 V to VDD. This eliminates the need for external reference components, reduces PCB area, and simplifies power domain design - a key advantage in compact, battery-powered systems where the AD7921ARMZ is commonly deployed.

How is channel selection implemented on the AD7921ARMZ?

Channel selection on the AD7921ARMZ is controlled via the DIN pin during the CS assertion cycle. A logic level applied to DIN on the falling edge of SCLK determines whether VIN0 or VIN1 is sampled in the subsequent conversion. The DOUT stream includes a dedicated channel identifier bit, allowing unambiguous identification of the source channel without additional control lines or external multiplexers - a feature integral to the AD7921ARMZ's dual-channel architecture.

What is the meaning of "no pipeline delay" for the AD7921ARMZ?

"No pipeline delay" means the AD7921ARMZ completes sampling and conversion in a single, deterministic CS cycle with zero latency between command and result availability. Unlike pipelined or sigma-delta ADCs, it delivers the conversion result corresponding to the most recent CS-initiated sample immediately after the serial frame ends - critical for real-time control, trigger-based acquisition, and applications where timing predictability is mandatory, such as in the AD7921ARMZ's target use cases.

Can the AD7921ARMZ operate from a 2.5 V supply?

Yes, the AD7921ARMZ is fully specified to operate from 2.35 V to 5.25 V, so a 2.5 V supply falls within its valid VDD range. At 2.5 V, typical operational current is 2 mA max at 250 kSPS, yielding ~5 mW power dissipation. Input range becomes 0–2.5 V, and logic thresholds scale accordingly (e.g., VINH ≥ 0.7 × VDD = 1.75 V). All AC and DC specifications - including SNR, INL, and throughput - remain guaranteed across this range, as confirmed in the AD7921ARMZ datasheet.