Analog Devices Inc. AD7701BN

Overview

AD7701BN from Analog Devices is a monolithic 16-bit sigma-delta ADC with on-chip 6-pole Gaussian digital filtering, self-calibration circuitry, and flexible serial interface. It delivers 0.0015% linearity error (max), 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, low-frequency measurement systems such as industrial weigh scales and remote data acquisition nodes.

For engineers reviewing the AD7701BN datasheet, AD7701BN pinout, AD7701BN application, or AD7701BN equivalent, key selection criteria include its guaranteed no-missing-codes performance, ultralow 10 µW standby power, programmable 0.1 Hz–10 Hz filter corner frequency, system calibration capability for external offset/gain errors, and compatibility with UARTs or microcontroller serial ports via MODE-selectable AC/SEC/SSC protocols.

Technical Context

The AD7701BN employs a second-order sigma-delta modulator with charge-balancing architecture and an oversampling ratio of 256× (f_CLKIN/256), feeding a deterministic six-pole Gaussian digital filter that provides 55 dB rejection at 60 Hz when f_CLKIN = 4.096 MHz. Its output register updates synchronously at f_CLKIN/1024, yielding up to 4 kHz word rate.

Calibration is executed by an embedded microcontroller with SRAM storage, supporting zero/full-scale self-calibration or system-level calibration where SC1/SC2 configure external sensor channel compensation. The MODE pin selects among asynchronous (UART-compatible), synchronous external clocking, or synchronous self-clocking serial modes - each defining SCLK direction, framing, and MSB-first timing.

Key Specifications

Pinout & Package

AD7701BN is supplied in a 20-pin plastic DIP (N-20) package with 0.3-inch width, through-hole mounting, and industry-standard pin spacing. Pin functions are electrically and mechanically defined per Analog Devices Rev. E datasheet.

Key Features

Applications

Equivalent & Alternatives

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

Compared with AD7701BN, AD7714BN offers greater channel density and resolution but consumes >250× more standby power and lacks dedicated sleep control; ADS1211U adds PGA and SPI simplicity but removes asynchronous UART support and system calibration flexibility critical for field-deployed sensors.

Availability

AD7701BN is available at Aetrix Electronics and suitable for industrial process control, weigh scale manufacturing, and portable instrumentation requiring stable component supply across extended product lifecycles.

Supply support for AD7701BN 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 AD7701BN belongs to Analog Devices' precision sigma-delta ADC product line, designed specifically for high-accuracy, low-frequency measurement of physical, chemical, and biological signals in harsh industrial and portable environments.

FAQ

What is the maximum clock frequency supported by the AD7701BN?

The AD7701BN supports a master clock (CLKIN) frequency up to 5 MHz, with typical operation at 4.096 MHz. At this frequency, the device achieves a 4 kHz output data rate and 10 Hz digital filter corner frequency. Operation down to 200 kHz is guaranteed, enabling ultra-low-power configurations where reduced throughput is acceptable. The AD7701BN datasheet specifies strict timing margins for CLKIN duty cycle (20–80%) and rise/fall times to ensure reliable modulation and filtering performance.

Does the AD7701BN require an external voltage reference?

No - the AD7701BN accepts an external 2.5 V reference at the VREF pin, but it does not integrate a reference. Users must supply a stable, low-noise 2.5 V reference (e.g., ADR291 or REF192) to achieve specified linearity and drift performance. The AD7701BN datasheet defines VREF tolerance, temperature coefficient, and noise sensitivity requirements; deviation beyond ±0.1 V or excessive noise degrades full-scale accuracy and system calibration validity.

How does the AD7701BN handle system-level offset and gain calibration?

The AD7701BN supports system calibration via SC1 and SC2 pins, allowing users to include external front-end components (e.g., instrumentation amplifiers, sensor bridges) in the calibration loop. When CAL is asserted with specific SC1/SC2 states, the AD7701BN measures actual system zero and full-scale points and stores correction coefficients in on-chip SRAM. This eliminates errors introduced by PCB traces, connectors, and external gain stages - a capability confirmed in the AD7701BN datasheet's "SYSTEM CALIBRATION" section and functional block diagram.

Can the AD7701BN interface directly with a UART without additional logic?

Yes - when the MODE pin is tied to –5 V, the AD7701BN operates in Asynchronous Communications (AC) mode, outputting framed 16-bit data with one start bit and two stop bits on SDATA, synchronized to internally generated SCLK edges. This UART-compatible format allows direct connection to standard RS-232 or TTL-level UART receivers without protocol translation or bit-banging firmware. The AD7701BN datasheet confirms AC mode timing, voltage levels, and framing in Figures 6 and Table of Timing Characteristics.

What is the purpose of the BP/UP pin on the AD7701BN?

The BP/UP (Pin 12) configures the AD7701BN's analog input range: logic high selects bipolar mode (±2.5 V), logic low selects unipolar mode (0 V to +2.5 V). This hardware-selectable range eliminates software configuration overhead and ensures deterministic behavior at power-up. The AD7701BN datasheet specifies distinct offset, full-scale, and overrange limits for each mode, and the pin's voltage threshold (DGND or +5 V) is compatible with standard logic families driving AVSS/AVDD rails.