Analog Devices Inc. AD7691BRMZ

Overview

AD7691BRMZ from Analog Devices is an 18-bit, charge redistribution successive approximation register (SAR) analog-to-digital converter with true differential input, ±1.5 LSB INL max, 250 kSPS throughput, and no pipeline delay-designed for high-precision data acquisition in battery-powered instrumentation and seismic systems.

For engineers reviewing the AD7691BRMZ datasheet, AD7691BRMZ pinout, AD7691BRMZ application, or AD7691BRMZ equivalent, this page delivers verified specifications, validated package mapping (10-lead MSOP/LFCSP), confirmed SPI/QSPI/MICROWIRE-compatible serial interface behavior, and real-world design implications for low-power, high-dynamic-range signal digitization.

Technical Context

The AD7691BRMZ employs a single-supply SAR architecture with integrated track-and-hold, enabling zero-latency conversion and full-scale step acquisition in 1.8 µs. It supports true differential analog inputs spanning ±VREF with common-mode range centered at VREF/2, and features proprietary serial interface modes including daisy-chainable chain mode and CS-selectable 3-/4-wire SPI-compatible operation.

Its power scaling is linear with throughput: 1.35 mW at 2.5 V/100 kSPS and 12.5 mW at 5 V/250 kSPS, while standby current remains at 1 nA. The device uses external reference (0.5 V to VDD) and separate VIO (1.8 V to VDD) for logic-level flexibility across host systems.

Key Specifications

Pinout & Package

AD7691BRMZ is available in two 10-lead packages: MSOP (3 mm × 3 mm, 0.5 mm pitch) and LFCSP (3 mm × 3 mm, 0.5 mm pitch), both rated for −40°C to +85°C operation. The exposed pad (EPAD) must be soldered to ground for thermal and reliability performance.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar high-resolution SAR ADC applications.

Compared with AD7690BRMZ and AD7687BRMZ, the AD7691BRMZ uniquely delivers 18-bit resolution at 250 kSPS with 102 dB dynamic range-making it the only option among the three for battery-powered, high-fidelity data acquisition demanding both speed and precision without compromise.

Availability

AD7691BRMZ is available at Aetrix Electronics and suitable for seismic data acquisition, portable medical instrumentation, and battery-powered test equipment requiring stable component supply, long-term lifecycle support, and guaranteed authentic sourcing.

Supply support for AD7691BRMZ 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, Inc. is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, headquartered in Norwood, MA, with R&D and manufacturing infrastructure spanning North America, Europe, and Asia.

The AD7691BRMZ belongs to Analog Devices' PulSAR® family of precision SAR ADCs-engineered specifically for high-speed, low-power, high-linearity data acquisition in portable, industrial, and medical instrumentation where accuracy and energy efficiency are co-critical.

FAQ

What is the maximum sample rate supported by the AD7691BRMZ?

The AD7691BRMZ supports up to 250 kSPS when operated with VDD ≥ 4.5 V. At lower supply voltages (2.3 V to 4.5 V), the maximum throughput reduces to 180 kSPS. This variation is specified in Table 2 of the AD7691BRMZ datasheet and reflects internal clock scaling to maintain accuracy and power efficiency across the full supply range.

Does the AD7691BRMZ require an external reference voltage?

Yes, the AD7691BRMZ requires an external reference voltage applied to the REF pin, with a valid range of 0.5 V to VDD. The device does not include an internal reference; reference stability and noise directly impact INL, SNR, and overall measurement accuracy. A low-noise, high-precision external reference such as the ADR4550 is recommended for optimal AD7691BRMZ performance.

Can the AD7691BRMZ interface with a 1.8 V microcontroller?

Yes, the AD7691BRMZ supports 1.8 V logic levels via its dedicated VIO supply pin. When VIO = 1.8 V, all digital inputs (CNV, SCK, SDI) accept 0.3 × VIO to 0.7 × VIO thresholds, and the SDO output swings between 0.4 V and VIO − 0.3 V-ensuring reliable communication with 1.8 V hosts without level-shifting circuitry.

Is the AD7691BRMZ pin-compatible with other PulSAR ADCs?

Yes, the AD7691BRMZ is pin-for-pin compatible with the AD7690 (18-bit, 100 kSPS), AD7693 (16-bit, 250 kSPS), AD7688 (16-bit, 250 kSPS), and AD7687 (16-bit, 250 kSPS). This allows drop-in replacement or resolution scaling on the same PCB layout, provided the host firmware accommodates differing bit widths and timing parameters.

What is the significance of the "no pipeline delay" specification for the AD7691BRMZ?

No pipeline delay means the AD7691BRMZ delivers conversion results immediately after completion-without intermediate storage or latency cycles. This enables deterministic timing for time-critical applications such as real-time control loops, synchronized multi-channel sampling, and burst-mode acquisition where output alignment with the CNV edge is essential for system-level timing integrity.