Analog Devices Inc. AD7708BRUZ-REEL7

Overview

AD7708BRUZ-REEL7 from Analog Devices is a 16-bit, 8-/10-channel Σ-Δ analog-to-digital converter optimized for low-frequency industrial measurement. It features on-chip programmable gain amplifier (PGA), simultaneous 50 Hz/60 Hz rejection, rail-to-rail input buffering, and operates from single 3 V or 5 V supplies with typical power dissipation of 3.84 mW at 3 V. It is used in smart transmitters and portable instrumentation where high resolution and noise immunity are critical.

For engineers reviewing the AD7708BRUZ-REEL7 datasheet, AD7708BRUZ-REEL7 pinout, AD7708BRUZ-REEL7 application, or AD7708BRUZ-REEL7 equivalent, key selection considerations include its 16-bit no-missing-codes performance, CHOP mode vs. non-CHOP trade-offs in throughput versus noise, ±20 mV to ±2.56 V input range support via PGA gain 1–128, and compatibility with SPI/QSPI/MICROWIRE interfaces.

Technical Context

The AD7708BRUZ-REEL7 integrates a 16-bit Σ-Δ ADC core with a 2-bit digital I/O port, on-chip oscillator (32.768 kHz crystal), PLL, and serial interface logic. Its signal chain supports both pseudo-differential (8/10 channels) and fully-differential (4/5 channels) configurations, with two pins (REFIN2+/AIN9 and REFIN2−/AIN10) configurable as analog inputs or reference inputs.

It implements dual operating modes: CHOP = 0 (optimized for analog performance, up to 105 Hz update rate, 13–16 bits peak-to-peak resolution) and CHOP = 1 (optimized for channel throughput, up to 1.365 kHz, with 13–16 bits p-p resolution depending on gain and range). Calibration is factory-performed and supports self-calibration for offset and full-scale correction.

Key Specifications

Pinout & Package

The AD7708BRUZ-REEL7 is housed in a 28-lead TSSOP package (RU-28), RoHS-compliant and tape-and-reel packaged (REEL7).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar ADC applications.

Compared with AD7718BRUZ, AD7708BRUZ-REEL7 delivers lower resolution but reduced cost and power; compared with ADS124S08IPWR, it offers proven CHOP-mode line-frequency rejection and direct pin compatibility within the AD77xx family, simplifying migration from existing designs.

Availability

AD7708BRUZ-REEL7 is available at Aetrix Electronics and suitable for industrial process control, smart transmitter design, and portable instrumentation requiring stable component supply, long-term manufacturability, and RoHS-compliant TSSOP packaging.

Supply support for AD7708BRUZ-REEL7 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.

The AD7708 is part of Analog Devices' precision sigma-delta ADC product line, designed specifically for low-frequency, high-accuracy industrial measurement applications including sensor conditioning, weigh scales, and analytical instrumentation.

FAQ

What is the maximum update rate of the AD7708BRUZ-REEL7 in non-CHOP mode?

The AD7708BRUZ-REEL7 achieves a maximum output update rate of 1.365 kHz in non-CHOP mode (CHOP = 1), enabling faster channel scanning in multiplexed systems. This mode trades some noise performance for throughput, delivering 13–16 bits peak-to-peak resolution depending on gain setting and input range. The AD7708BRUZ-REEL7 maintains simultaneous 50 Hz and 60 Hz rejection even at this rate.

Does the AD7708BRUZ-REEL7 require an external crystal?

Yes, the AD7708BRUZ-REEL7 requires a 32.768 kHz crystal connected between XTAL1 and XTAL2 pins to operate its on-chip oscillator and PLL. The crystal input buffer is enabled by default, and the device does not support external clock input - only crystal-based timing. The AD7708BRUZ-REEL7 uses this frequency to generate all internal clocks necessary for Σ-Δ modulation and digital filtering.

Can the AD7708BRUZ-REEL7 measure both ratiometric and absolute signals?

Yes, the AD7708BRUZ-REEL7 supports both ratiometric and absolute measurements via its VREF Select™ feature. When configured for ratiometric mode, the ADC uses the same reference that excites the sensor (e.g., bridge), rejecting supply variations. In absolute mode, it uses an independent precision reference (e.g., 2.5 V on REFIN1). The AD7708BRUZ-REEL7 handles both seamlessly through register configuration without hardware changes.

What is the purpose of the P1 and P2 pins on the AD7708BRUZ-REEL7?

The P1 and P2 pins on the AD7708BRUZ-REEL7 form a 2-bit general-purpose digital I/O port, configurable as inputs or outputs via the I/O Control Register. They operate with logic levels referenced to AVDD and AGND, enabling functions such as status indication, external multiplexer control, or simple system handshaking. These pins reduce the need for additional GPIOs on the host microcontroller and are fully integrated into the AD7708BRUZ-REEL7's serial interface protocol.

How does the CHOP mode affect noise performance in the AD7708BRUZ-REEL7?

In CHOP mode (CHOP = 0), the AD7708BRUZ-REEL7 applies chopping to the PGA and modulator to cancel 1/f noise and offset drift, improving effective resolution - e.g., 13–16 bits peak-to-peak at 20 Hz update rate. This mode enhances DC accuracy and long-term stability but reduces maximum update rate to 105 Hz. The AD7708BRUZ-REEL7's CHOP implementation is fully transparent and requires no external timing control.