Analog Devices Inc. AD7684BRMZ

Overview

AD7684BRMZ from Analog Devices is a 16-bit, charge redistribution successive approximation register (SAR) ADC with true differential input, 100 kSPS throughput, ±1 LSB typical INL, single-supply operation (2.7 V to 5.5 V), and SPI-/QSPI-/MICROWIRE-compatible serial interface. It operates in battery-powered instrumentation and medical data acquisition systems where low power, high resolution, and no missing codes are critical.

For engineers reviewing the AD7684BRMZ datasheet, AD7684BRMZ pinout, AD7684BRMZ application, or AD7684BRMZ equivalent, this page delivers verified specifications, real-world timing behavior, differential analog interface constraints, and design-critical power scaling characteristics at 10 kSPS and 100 kSPS.

Technical Context

The AD7684BRMZ implements a capacitive charge redistribution SAR architecture with integrated track-and-hold, enabling zero-latency conversion and no pipeline delay-ideal for multiplexed multichannel systems. Its differential input stage requires 180° phase opposition between +IN and –IN, with common-mode range centered at VREF/2 and absolute input limits of −0.1 V to VDD + 0.1 V.

Conversion is initiated on the CS falling edge; sampling occurs at that instant, and the internal conversion clock (DCLOCK) drives a 16-bit two's complement serial output synchronized to DCLOCK falling edges. Power consumption scales linearly with throughput: 150 μW at 10 kSPS/2.7 V, 4 mW at 100 kSPS/5 V, and standby current is 1 nA.

Key Specifications

Pinout & Package

AD7684BRMZ is housed in an 8-lead MSOP package (3.0 mm × 3.0 mm, 0.65 mm pitch), specified for −40°C to +85°C operation. The pinout supports strict analog/digital signal separation: analog signals (+IN, –IN, REF, GND) occupy left side; digital signals (CS, DOUT, DCLOCK, VDD) occupy right side-facilitating clean PCB layout.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 16-bit SAR ADC applications.

Compared with AD7687BRMZ, AD7684BRMZ trades speed for 60% lower active power and simpler thermal management; compared with AD7680ARMZ, it provides guaranteed differential operation, superior INL, and robustness against common-mode noise-making it the preferred choice for medical and industrial grade signal chains.

Availability

AD7684BRMZ is available at Aetrix Electronics and suitable for battery-powered equipment, medical instruments, and industrial process control requiring stable component supply, long-term lifecycle support, and traceable sourcing.

Supply support for AD7684BRMZ 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 design centers worldwide.

The AD7684BRMZ belongs to Analog Devices' PulSAR® family of precision SAR ADCs, engineered specifically for low-power, high-resolution data acquisition in portable, industrial, and medical instrumentation where accuracy, reliability, and energy efficiency are non-negotiable.

FAQ

What is the maximum DCLOCK frequency supported by the AD7684BRMZ?

The AD7684BRMZ supports a maximum DCLOCK frequency of 2.9 MHz, as specified in the Absolute Maximum Ratings and Timing Specifications tables. This allows full 16-bit data transfer within the 10 μs conversion cycle. Exceeding 2.9 MHz risks setup/hold violations and invalid data; for reliable operation at 100 kSPS, DCLOCK should be set ≤2.5 MHz to accommodate board-level timing margins. The AD7684BRMZ datasheet confirms tEN (data valid after DCLOCK falling edge) is 16–50 ns, validating robust timing at rated speeds.

Does the AD7684BRMZ require an external reference voltage, and what are the acceptable ranges?

Yes, the AD7684BRMZ requires an external reference voltage applied to the REF pin. The valid range is 0.5 V to VDD, with VDD between 2.7 V and 5.5 V-so REF may be set from 0.5 V up to 5.5 V. For optimal performance, Analog Devices recommends using a low-noise, low-drift reference such as the ADR435 (5.0 V) or ADR3425 (2.5 V), decoupled with a 10 μF X5R ceramic capacitor directly between REF and GND. The AD7684BRMZ does not include an internal reference.

Can the AD7684BRMZ operate with a single-ended input configuration?

No, the AD7684BRMZ is designed exclusively for true differential input operation: +IN and –IN must be driven 180° out-of-phase with respect to each other. Holding –IN at GND or any fixed voltage violates the input structure and produces erroneous conversions. For single-ended applications, Analog Devices specifies the AD7683 (pin-compatible 16-bit SAR ADC with pseudo-differential input). The AD7684BRMZ datasheet explicitly states "the inputs must be driven differentially 180° from each other" and warns against fixed-bias configurations.

What is the standby current of the AD7684BRMZ, and how is low-power mode activated?

The AD7684BRMZ has a standby current of 1 nA (typical) at 25°C, achieved by driving the CS pin high after conversion completion. The device automatically powers down between conversions-no additional control signals or registers are needed. Standby current remains below 50 nA over the full −40°C to +85°C temperature range. This ultra-low quiescent state is integral to the AD7684BRMZ architecture and enables multi-year battery life in intermittent-sampling applications like environmental sensors.

Is the AD7684BRMZ pin-compatible with other devices in the PulSAR® family?

The AD7684BRMZ shares the same 8-lead MSOP package and pinout with AD7680ARMZ and AD7683BRMZ, enabling drop-in replacement in layouts constrained by footprint. However, functional compatibility is limited: AD7680ARMZ is pseudo-differential, AD7683BRMZ supports single-ended inputs, and AD7684BRMZ mandates true differential operation. While mechanical fit is identical, signal integrity and system-level performance depend on matching the input architecture-so electrical validation is required before substitution. The AD7684BRMZ datasheet confirms identical pin configuration across these variants.