Analog Devices Inc. AD7787BRM

Overview

AD7787BRM from Analog Devices is a low-power, 24-bit sigma-delta ADC with dual analog inputs (one differential AIN1±, one single-ended AIN2), rail-to-rail input buffer, internal clock oscillator, and VDD monitor channel - delivering 1.1 µV rms noise at 9.5 Hz update rate for precision sensor measurement in battery-powered industrial transmitters.

For engineers reviewing the AD7787BRM datasheet, AD7787BRM pinout, AD7787BRM application, or AD7787BRM equivalent, key selection considerations include simultaneous 50/60 Hz rejection, software-programmable update rate (9.5–120 Hz), buffered/unbuffered mode configuration, 3-wire SPI-compatible interface, and operation from 2.5 V to 5.25 V supply with ≤75 µA normal-mode current.

Technical Context

The AD7787BRM integrates a Σ-Δ modulator with programmable digital filter, internal 1 MHz clock oscillator, and configurable input mux selecting between AIN1(±), AIN2, internal short, or VDD monitor. Its filter register supports clock division (×1/2/4/8) to scale update rate and reduce current consumption.

It implements offset binary coding, supports unipolar/bipolar output formats via U/B bit, enables burnout current (100 nA) only in buffered mode, and provides simultaneous 50 Hz and 60 Hz rejection through selectable filter settings (FS[2:0] = 100, 101, or 011) - all controlled via three on-chip 8-bit registers (Mode, Filter, Status) accessed over a 3-wire serial interface.

Key Specifications

Pinout & Package

AD7787BRM is housed in a 10-lead MSOP package (3.0 mm × 3.0 mm, 0.5 mm pitch), optimized for space-constrained PCB layouts in handheld and loop-powered devices.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 24-bit sigma-delta ADC applications.

Compared with AD7787BRM, AD7170BRMZ offers lower quiescent current but sacrifices dual-input flexibility and VDD monitoring, while ADS124S08IPW adds PGA and higher throughput at the cost of current and external clock dependency - making AD7787BRM optimal for compact, self-contained, dual-channel sensor nodes where supply awareness and mains-noise immunity are critical.

Availability

AD7787BRM is available at Aetrix Electronics and suitable for smart transmitters, battery-powered instrumentation, and portable sensor measurement systems requiring stable component supply, long-term lifecycle support, and guaranteed traceable sourcing.

Supply support for AD7787BRM 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 AD7787BRM belongs to Analog Devices' precision sigma-delta ADC product line, engineered specifically for low-power, high-accuracy measurement in space- and energy-constrained applications such as loop-powered transmitters and portable test equipment.

FAQ

What is the maximum update rate supported by the AD7787BRM?

The AD7787BRM supports a maximum output update rate of 120 Hz, achieved when the internal clock operates at full frequency (no division) and the filter register's FS[2:0] bits are set to 000. At this rate, rms noise increases to approximately 3.5 µV, trading resolution for speed - a setting commonly used in dynamic pressure or flow measurement where response time is prioritized over absolute precision.

Does the AD7787BRM require an external crystal or clock source?

No, the AD7787BRM does not require an external crystal or clock source. It contains a fully integrated internal clock oscillator operating at approximately 1 MHz, which drives the sigma-delta modulator and digital filter. This eliminates external timing components, reduces system cost and board area, and improves reliability in vibration-prone or high-EMI environments where crystal stability could be compromised.

Can the AD7787BRM measure its own supply voltage?

Yes, the AD7787BRM includes a dedicated VDD monitor channel. When CH1/CH0 bits are set to 11 in the communications register, the device internally divides VDD by 5 and applies the result to the modulator using a 1.17 V ±5% on-chip reference. This enables real-time supply monitoring without external resistive dividers, supporting brown-out detection and self-calibration routines in the AD7787BRM-based system.

What are the input voltage limits for AIN2 in buffered versus unbuffered mode?

In buffered mode, AIN2 accepts voltages from GND + 100 mV to VDD – 100 mV. In unbuffered mode, the absolute input range expands to GND – 100 mV to VDD + 30 mV, though leakage current rises significantly outside the buffered range. This extended unbuffered range allows direct interfacing with certain thermocouple cold-junction compensation circuits or bipolar sensor outputs, provided layout minimizes leakage paths.

How does the AD7787BRM achieve simultaneous 50 Hz and 60 Hz rejection?

The AD7787BRM achieves simultaneous 50 Hz and 60 Hz rejection through its programmable digital filter architecture. By setting FS[2:0] = 100 in the filter register, the device configures a notch response centered at both frequencies with ≥73 dB attenuation. This is implemented via sinc³ filter coefficients synchronized to the internal clock - eliminating the need for external analog filters or firmware-based digital post-processing in globally deployed AD7787BRM systems.