Analog Devices Inc. AD7785BRUZ-REEL

Overview

AD7785BRUZ-REEL from Analog Devices is a 20-bit Σ-Δ analog-to-digital converter with integrated instrumentation amplifier, on-chip band gap reference (4 ppm/°C drift), and three differential input channels. It delivers 40 nV RMS noise at 4.17 Hz update rate with gain = 64, consumes 400 μA typical supply current, and operates from 2.7 V to 5.25 V over –40°C to +105°C - enabling high-precision thermocouple and RTD measurements in portable industrial sensors.

For engineers reviewing the AD7785BRUZ-REEL datasheet, AD7785BRUZ-REEL pinout, AD7785BRUZ-REEL application, or AD7785BRUZ-REEL equivalent, key selection criteria include its simultaneous 50/60 Hz rejection capability, programmable excitation currents (10/210/1000 μA), independent DVDD interface supply, Schmitt-triggered SCLK for noise immunity, and TSSOP-16 package compatibility with space-constrained PCB layouts.

Technical Context

The AD7785BRUZ-REEL integrates a low-noise, programmable-gain instrumentation amplifier (gain = 1–128) directly preceding its 20-bit Σ-Δ modulator, eliminating external signal conditioning for microvolt-level sensor outputs. Its internal clock oscillator (64 kHz ±3%) supports software-configurable output data rates from 4.17 Hz to 470 Hz, with built-in digital filtering enabling simultaneous 50 Hz and 60 Hz line-frequency rejection via register-selectable filter settings (FS[3:0]).

It features dual programmable current sources (IOUT1/IOUT2), on-chip bias voltage generator (AVDD/2), burnout detection currents, and flexible reference support - accepting either its internal 1.17 V band gap reference or external differential references from 0.1 V to AVDD. All digital interface pins (SCLK, DIN, DOUT/RDY, CS) are referenced to DVDD, decoupling logic levels from analog supply AVDD.

Key Specifications

Pinout & Package

AD7785BRUZ-REEL is housed in a 16-lead TSSOP package (4.4 mm × 5.0 mm, 0.65 mm pitch), optimized for automated assembly and thermal performance (θJA = 150.4°C/W).

Key Features

Applications

Equivalent & Alternatives

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

Compared with AD7785BRUZ-REEL, AD7124-4BRUZ offers higher resolution but increased power and complexity, while LTC2440CGN#PBF demands external components to match AD7785BRUZ-REEL's integrated signal chain - making AD7785BRUZ-REEL the most balanced solution for compact, low-power, self-contained 20-bit sensor digitization.

Availability

AD7785BRUZ-REEL is available at Aetrix Electronics and suitable for thermocouple measurement systems, RTD-based temperature transmitters, and portable medical analyzers requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for AD7785BRUZ-REEL 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 and a legacy of precision data conversion innovation.

The AD7785BRUZ-REEL belongs to Analog Devices' precision Σ-Δ ADC product line, engineered specifically for low-power, low-noise industrial and medical sensor front ends where integrated signal conditioning, reference, and diagnostics reduce system complexity and improve measurement reliability.

FAQ

What is the maximum achievable effective resolution of the AD7785BRUZ-REEL under optimal conditions?

The AD7785BRUZ-REEL achieves up to 20 bits effective resolution with no missing codes, verified across all gain settings and update rates. At 4.17 Hz with gain = 64 and internal reference, it delivers 40 nV RMS noise - translating to ~19.5 bits peak-to-peak resolution with zero code flicker. This performance is maintained over the full –40°C to +105°C operating range without recalibration.

Does the AD7785BRUZ-REEL support true simultaneous 50 Hz and 60 Hz line-frequency rejection?

Yes, the AD7785BRUZ-REEL implements digital filtering that provides simultaneous 50 Hz and 60 Hz rejection - achieving ≥65 dB attenuation at both frequencies using a single FS[3:0] = 1010 configuration. With external clock and optimized register settings, rejection exceeds 90 dB at each frequency independently, eliminating need for dual external notch filters.

Can the AD7785BRUZ-REEL operate with separate analog and digital supply voltages?

Yes, the AD7785BRUZ-REEL features independent AVDD (2.7 V–5.25 V) and DVDD (2.7 V–5.25 V) supplies. This allows interfacing with 3 V microcontrollers while powering the analog section at 5 V for improved dynamic range - a key advantage in mixed-voltage industrial systems where logic and analog domains are isolated.

How does the on-chip bias voltage generator (VBIAS) function in the AD7785BRUZ-REEL?

The AD7785BRUZ-REEL's VBIAS pin outputs AVDD/2 to set the common-mode voltage of selected analog input channels. It starts up with timing dependent on external capacitance (e.g., 1 ms for 100 nF load), eliminating need for external resistor dividers. This feature ensures proper input stage biasing in differential configurations and improves CMRR performance across gain settings.

What are the valid excitation current values supported by the AD7785BRUZ-REEL's IOUT1 and IOUT2 pins?

The AD7785BRUZ-REEL supports three programmable excitation current levels per output: 10 μA, 210 μA, and 1000 μA, with ±5% initial tolerance at 25°C and 200 ppm/°C drift. Current matching between IOUT1 and IOUT2 is ±0.5% typical, enabling accurate 3-/4-wire RTD measurements and reliable burnout detection in sensor fault scenarios.