Analog Devices Inc. AD7998BRU-1

Overview

AD7998BRU-1 from Analog Devices is a 12-bit, 8-channel successive approximation ADC with I²C-compatible interface, 2 µs conversion time, 2.7 V to 5.5 V supply range, and −40°C to +85°C operating temperature. It supports up to 188 kSPS throughput in Mode 2 at 5 V and integrates an on-chip 8:1 multiplexer, track-and-hold amplifier, and programmable out-of-range alert for industrial sensor monitoring systems.

For engineers reviewing the AD7998BRU-1 datasheet, AD7998BRU-1 pinout, AD7998BRU-1 application, or AD7998BRU-1 equivalent, key selection considerations include its 12-bit resolution with ±1 LSB INL, I²C high-speed mode support (3.4 MHz), REFIN input range (1.2 V to VDD), open-drain ALERT/BUSY output, and 20-lead TSSOP package compatibility with space-constrained embedded data acquisition designs.

Technical Context

The AD7998BRU-1 implements a successive approximation register (SAR) architecture with integrated 8-channel analog multiplexer and track-and-hold, enabling single-supply operation from 2.7 V to 5.5 V while maintaining 11 MHz full-power bandwidth. Its I²C interface supports standard (100 kHz), fast (400 kHz), and high-speed (3.4 MHz) modes depending on variant-AD7998BRU-1 corresponds to the "-1" version with full high-speed capability.

Conversion control is configurable across three modes: CONVST-triggered (Mode 1), command-mode writes (Mode 2), or automatic cycle interval (Mode 3). On-chip registers-including configuration, limit, hysteresis, and alert status-enable autonomous out-of-range detection without host intervention, with ALERT/BUSY pin configurable as either interrupt or busy indicator.

Key Specifications

Pinout & Package

AD7998BRU-1 is housed in a 20-lead Thin Shrink Small Outline Package (TSSOP) with exposed pad, optimized for thermal performance (θJA = 143°C/W) and PCB area efficiency in compact instrumentation layouts.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar multichannel SAR ADC applications.

Compared with AD7997BRU-1, AD7998BRU-1 delivers 9.5 dB higher SINAD and guaranteed 12-bit no-missed-codes operation; versus ADS1015IDGSR, it offers 60× higher throughput and true SAR speed but requires external reference and lacks programmable gain.

Availability

AD7998BRU-1 is available at Aetrix Electronics and suitable for industrial sensor hubs, motor phase monitoring, smart energy metering, and portable data loggers requiring stable component supply, long-term lifecycle support, and traceable sourcing.

Supply support for AD7998BRU-1 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, serving industrial, automotive, communications, and healthcare markets since 1965.

The AD7998BRU-1 belongs to Analog Devices' I²C-compatible precision SAR ADC product line, designed specifically for space- and power-constrained embedded systems needing multichannel, high-speed, low-latency analog digitization without FPGA or complex interface logic.

FAQ

What is the maximum I²C clock frequency supported by the AD7998BRU-1?

The AD7998BRU-1 supports I²C high-speed mode up to 3.4 MHz with a 100 pF bus load, enabling faster register access and higher throughput than standard (100 kHz) or fast (400 kHz) modes. This specification is confirmed for the "-1" variant in the AD7998 datasheet Rev. 0, Table 3. The AD7998BRU-1 achieves 188 kSPS maximum throughput at 5 V under these conditions, making it suitable for time-critical data acquisition where serial interface latency must be minimized.

Does the AD7998BRU-1 require an external voltage reference?

Yes, the AD7998BRU-1 requires an external reference applied to the REFIN pin, which sets the full-scale input range (0 V to REFIN). The REFIN voltage must be between 1.2 V and VDD, and the datasheet recommends using 0.1 µF and 1 µF capacitors from REFIN to AGND for stability. Unlike some delta-sigma ADCs, the AD7998BRU-1 has no internal reference; its 12-bit accuracy depends directly on reference precision, drift, and noise-so a low-drift, low-noise external source (e.g., ADR4525) is recommended for metrology-grade applications.

How does the ALERT/BUSY pin function on the AD7998BRU-1?

The ALERT/BUSY pin on the AD7998BRU-1 is a multifunctional open-drain output configurable via internal registers. When set as ALERT, it asserts low when any conversion result violates user-programmed high or low limits stored in the DATAHIGH/DATALOW registers-acting as a hardware interrupt to offload host polling. When configured as BUSY, it goes low during conversion and returns high upon completion. The AD7998BRU-1's register-based control allows dynamic reconfiguration, and the pin's hysteresis and software enable/disable provide flexibility in fault-handling architectures.

Can the AD7998BRU-1 operate from a 3.3 V supply?

Yes, the AD7998BRU-1 is fully specified for operation from 2.7 V to 5.5 V, including 3.3 V nominal supplies. At 3.3 V, it maintains 12-bit resolution, ±1 LSB INL, and 2 µs conversion time. Power consumption scales accordingly: typical operating current is 0.7 mA in high-speed I²C Mode 2, and shutdown current remains ≤1 µA. Input logic thresholds (e.g., SDA/SCL VINH = 0.7 × VDD) and analog input range (0 to REFIN) are all VDD-referenced, ensuring robust interoperability with 3.3 V microcontrollers and sensors without level-shifting.

What is the purpose of the AS pin on the AD7998BRU-1?

The AS (Address Select) pin on the AD7998BRU-1 determines the device's 7-bit I²C slave address by selecting among five possible values (0100000 to 0100100 binary), as defined in Table 6 of the datasheet. Connecting AS to AGND, VDD, or leaving it floating configures distinct addresses-enabling up to five AD7998BRU-1 devices on the same I²C bus without address conflict. This eliminates the need for external I²C multiplexers in multi-ADC systems such as modular sensor racks or distributed acquisition nodes, simplifying firmware and reducing component count.