Analog Devices Inc. AD7701BNZ

Overview

AD7701BNZ from Analog Devices is a monolithic 16-bit sigma-delta ADC with on-chip 6-pole Gaussian digital filter, self-calibration circuitry, and flexible serial interface. It delivers 0.0015% linearity error, 4 kSPS output data rate, and supports unipolar (0 V to +2.5 V) or bipolar (±2.5 V) analog input ranges. It is used in high-accuracy industrial weigh scales requiring stable low-drift conversion of slow-varying sensor signals.

For engineers reviewing the AD7701BNZ datasheet, AD7701BNZ pinout, AD7701BNZ application, or AD7701BNZ equivalent, key selection considerations include its programmable 0.1 Hz–10 Hz low-pass filter corner frequency, ultralow 10 µW standby power, ±0.0015% FSR integral nonlinearity (max), and support for system-level offset/gain calibration via SC1/SC2 pins.

Technical Context

The AD7701BNZ employs a second-order sigma-delta modulator with charge-balancing architecture, continuously sampling at f_CLKIN/256 and feeding a six-pole Gaussian digital filter that updates the 16-bit output register at f_CLKIN/1024. Its clock generator accepts either external 200 kHz–5 MHz CLKIN or crystal-based internal oscillation via CLKOUT–CLKIN connection.

Calibration is performed by an on-chip microcontroller with SRAM storage, supporting zero/full-scale self-calibration and extended system calibration modes where external front-end errors are nulled. The serial interface operates in three modes-Asynchronous Communications (AC), Synchronous External Clocking (SEC), or Synchronous Self-Clocking (SSC)-determined by MODE pin voltage level.

Key Specifications

Pinout & Package

AD7701BNZ is packaged in a 20-lead PDIP (Plastic Dual In-line Package) with 0.3-inch body width and through-hole mounting. Pin 1 is located at the top-left corner adjacent to the notch or dot marking.

Key Features

Applications

Equivalent & Alternatives

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

Compared with AD7705BRUZ and LTC2400CGN#PBF, the AD7701BNZ uniquely combines bipolar/unipolar configurability, dual ±5 V supply tolerance, on-chip system calibration support, and 10 µW standby-making it optimal for ruggedized, recalibratable industrial transmitters.

Availability

AD7701BNZ is available at Aetrix Electronics and suitable for industrial process control, weigh scale manufacturing, and portable instrumentation requiring stable component supply with long-term lifecycle assurance.

Supply support for AD7701BNZ 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 AD7701BNZ belongs to Analog Devices' precision sigma-delta ADC product line, engineered specifically for high-accuracy, low-frequency measurement of physical, chemical, and biological signals in harsh industrial environments.

FAQ

What is the maximum clock frequency supported by the AD7701BNZ?

The AD7701BNZ supports a master clock (CLKIN) frequency from 200 kHz to 5 MHz. At the maximum 5 MHz, the output data rate reaches 4.88 kSPS and the digital filter corner frequency is 12.2 Hz. Operation at 4.096 MHz is production-tested and yields exactly 4 kSPS and 10 Hz cutoff - the most commonly used configuration for 50/60 Hz rejection. The AD7701BNZ must have CLKIN active during normal operation; absence of clock in non-SLEEP mode may cause excessive current draw or calibration loss.

Does the AD7701BNZ support true bipolar input operation?

Yes, the AD7701BNZ supports true bipolar input operation via the BP/UP pin (Pin 12). When BP/UP is logic high, the device configures for ±2.5 V input range with midscale transition at 0 V, enabling direct digitization of AC-coupled or centered sensor outputs. The bipolar mode uses internal offset alignment and guarantees ±0.5 LSB bipolar zero error (max), ensuring accurate zero-crossing detection critical in motor control feedback and vibration analysis. This functionality is intrinsic to the AD7701BNZ silicon design and requires no external components.

How does the AD7701BNZ perform system-level calibration?

The AD7701BNZ performs system-level calibration using SC1 and SC2 pins in conjunction with CAL. With SC1 low and SC2 low, applying a CAL pulse initiates system offset calibration; with SC1 high and SC2 low, it performs system full-scale calibration. This allows the AD7701BNZ to null gain and offset errors introduced by external front-end circuitry (e.g., instrumentation amplifiers or RTD excitation networks). The AD7701BNZ stores calibrated coefficients in on-chip SRAM, and the process is repeatable at any time - a core capability distinguishing it from basic self-calibrating ADCs.

What is the purpose of the SLEEP pin on the AD7701BNZ?

The SLEEP pin (Pin 11) places the AD7701BNZ into ultralow-power standby mode when driven logic low, reducing total supply current to 10 µW typical. In this state, the analog modulator, digital filter, and clock circuitry halt, but calibration memory retention is guaranteed down to 2.0 V supply. Wake-up occurs on SLEEP high, followed by automatic reinitialization and settling - no external reset required. This feature makes the AD7701BNZ suitable for duty-cycled remote sensors where measurement occurs intermittently, maximizing battery service life without sacrificing accuracy.

Can the AD7701BNZ interface directly to a microcontroller's SPI port?

Yes, the AD7701BNZ can interface directly to a microcontroller's SPI port using its Synchronous External Clocking (SEC) mode. When MODE (Pin 1) is grounded, SCLK becomes an input, SDATA outputs raw 16-bit MSB-first data without start/stop bits, and DRDY serves as a ready flag. No level-shifting or protocol translation is needed - the AD7701BNZ's CMOS-compatible logic thresholds (VINH ≥ 2.0 V, VINL ≤ 0.8 V) match standard 5 V microcontrollers. CS (Pin 16) enables frame synchronization, and timing parameters (e.g., t13 = 160 ns access time) ensure reliable capture even at 5 MHz SCLK.