Analog Devices Inc. AD7738BRU

Overview

AD7738BRU from Analog Devices is a high-precision, 24-bit sigma-delta analog front end with eight single-ended or four fully differential input channels, 0.0015% INL, 18-bit p-p resolution at 500 Hz, and 16-bit p-p resolution at 8.5 kHz - designed for high-throughput multiplexed industrial data acquisition in PLCs and process control systems.

For engineers reviewing the AD7738BRU datasheet, AD7738BRU pinout, AD7738BRU application, or AD7738BRU equivalent, key selection criteria include per-channel system calibration support, configurable unipolar/bipolar input ranges (±0.625 V to ±2.5 V), 3-wire SPI/QSPI/MICROWIRE interface compatibility, and operation across –40°C to +105°C.

Technical Context

The AD7738BRU implements a chopping-enabled sigma-delta ADC architecture with on-chip programmable gain multiplexer output (MUXOUT±) and differential reference input with "No-Reference" detection. Its digital filter supports user-configurable conversion time via 7-bit Filter Word register (FW), enabling trade-offs between noise (e.g., 18.4-bit p-p resolution at 372 Hz) and throughput (up to 15.4 kHz).

It features dual-supply operation (5 V AVDD, 3 V or 5 V DVDD), Schmitt-triggered logic inputs, and internal buffer selectable per channel. The MUXOUT pins allow external signal conditioning before ADCIN(±), while SYNC/P1 and AINCOM/P0 provide configurable I/O port functionality for system synchronization and common-mode referencing.

Key Specifications

Pinout & Package

AD7738BRU is housed in a 28-lead Thin Shrink Small Outline Package (TSSOP), RU-28 footprint, with exposed pad not electrically connected. Pin pitch is 0.65 mm; body dimensions are 9.7 mm × 4.4 mm × 1.2 mm (max).

Key Features

Applications

Equivalent & Alternatives

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

Compared with AD7734BRU and AD7732BRU, the AD7738BRU uniquely balances 8-channel flexibility, MUXOUT accessibility, and per-channel range/calibration - making it the only option supporting both high-density scanning and external signal conditioning in a single IC.

Availability

AD7738BRU is available at Aetrix Electronics and suitable for PLC analog input modules, multi-sensor industrial monitors, and process control DCS nodes requiring stable component supply across extended temperature and long production lifecycles.

Supply support for AD7738BRU 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 AD7738BRU belongs to Analog Devices' precision sigma-delta ADC family, engineered specifically for high-accuracy, high-throughput industrial data acquisition where channel density, calibration autonomy, and noise resilience are critical.

FAQ

What is the maximum channel switching rate supported by the AD7738BRU?

The AD7738BRU achieves a maximum channel switching rate of 8.5 kHz with 16-bit p-p resolution (19-bit effective) when chopping is disabled and conversion time is set to 117 µs (FW = 0x08). At this rate, the device maintains true 16-bit performance without missing codes, making it suitable for fast-scanning multiplexed systems. This specification is verified under AVDD = 5 V, DVDD = 5 V, and fMCLK = 6.144 MHz conditions.

Does the AD7738BRU support both unipolar and bipolar input configurations?

Yes, the AD7738BRU supports six configurable input ranges per channel: ±0.625 V, ±1.25 V, ±2.5 V, and their unipolar equivalents (0–0.625 V, 0–1.25 V, 0–2.5 V), selected via RNG[2:0] bits in the Channel Setup register. Each channel can be independently configured, and the common-mode voltage range spans 0.2 V above AGND to AVDD – 0.3 V - enabling flexible interfacing with sensors, transmitters, and signal conditioning circuits.

How does the "No-Reference" detection feature work on the AD7738BRU?

The AD7738BRU monitors the differential reference voltage (REFIN+ minus REFIN–) and asserts the NOREF bit in the Channel Status register when the voltage falls below 0.5 V. This flag is latched until cleared by reading the status register, providing fail-safe indication of reference loss. The feature operates independently of conversion mode and requires no host intervention - ensuring robust operation in safety-critical industrial systems where reference integrity is mandatory.

Can the AD7738BRU operate with a 3 V digital supply while using a 5 V analog supply?

Yes, the AD7738BRU supports mixed-supply operation: AVDD = 4.75–5.25 V (analog) and DVDD = 2.7–3.6 V (digital). Logic inputs (SCLK, DIN, CS, RESET) are Schmitt-triggered and specified down to DVDD = 3 V, with VINL = 0.4 V and VINH = 2.5 V. Digital outputs (DOUT, RDY, MCLKOUT) drive to DVDD – 0.6 V high and 0.4 V low at 100 µA - enabling direct interface with 3 V microcontrollers without level shifters.

What is the purpose of the MUXOUT(+) and MUXOUT(–) pins on the AD7738BRU?

The MUXOUT(+) and MUXOUT(–) pins expose the analog signal after channel selection but before the ADC core - allowing external circuitry (e.g., programmable gain amplifiers, anti-alias filters, or isolation stages) to be inserted between multiplexing and conversion. This architecture decouples signal routing from digitization, enabling custom front-end optimization per channel without modifying the ADC's internal signal path or timing behavior.