Analog Devices Inc. AD7703CR

Overview

AD7703CR from Analog Devices is a monolithic 20-bit charge-balancing sigma-delta ADC with integrated six-pole Gaussian digital filter, on-chip self-calibration microcontroller, and flexible serial interface. It delivers ±0.0003% integral nonlinearity (C grade), 4 kSPS output data rate, and 0.1 Hz to 10 Hz programmable low-pass filter corner frequency. It is used in high-precision industrial weigh scales and remote data acquisition systems requiring stable DC measurement of low-frequency analog signals.

For engineers reviewing the AD7703CR datasheet, AD7703CR pinout, AD7703CR application, or AD7703CR equivalent, key selection considerations include its 20-bit no-missing-codes resolution, ultralow 10 µW standby power, bipolar/unipolar input mode selection via BP/UP pin, system calibration capability for external gain/offset error removal, and compatibility with both synchronous (SEC) and self-clocked (SSC) serial interfaces.

Technical Context

The AD7703CR employs a second-order sigma-delta modulator with continuous analog sampling and a six-pole Gaussian digital filter that provides 55 dB rejection at 60 Hz (10 Hz cutoff) and settles to ±0.0007% FS in 125 ms. Its calibration architecture uses an embedded microcontroller and SRAM to perform zero/full-scale self-calibration or extend calibration to external signal conditioning circuitry.

It supports dual supply operation (±5 V analog, +5 V/–5 V digital), features separate analog/digital grounds (AGND/DGND), and offers three serial interface modes controlled by MODE and CAL pins - including SCLK-as-input (SEC) and SCLK-as-output (SSC) configurations - enabling direct connection to UARTs, microcontrollers, and DSPs without external logic.

Key Specifications

Pinout & Package

AD7703CR is available in 20-pin SOIC and DIP packages. Pin functions are electrically identical across packages; mechanical dimensions differ per JEDEC MS-012 (SOIC) and MS-001 (DIP) standards.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 20-bit sigma-delta ADC applications.

Compared with AD7714BRU and LTC2418CGN#PBF, the AD7703CR uniquely balances 20-bit no-missing-codes performance, 4 kSPS throughput, on-chip system calibration, and 10 µW standby power - making it optimal for industrial field instruments where power, accuracy, and calibration flexibility are co-constrained.

Availability

AD7703CR is available at Aetrix Electronics and suitable for industrial process control, weigh scale manufacturing, and portable instrumentation requiring stable component supply across extended temperature ranges (–40°C to +85°C).

Supply support for AD7703CR 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 Wilmington, MA.

The AD7703CR belongs to Analog Devices' precision sigma-delta ADC product line, designed specifically for high-resolution, low-frequency measurement of physical, chemical, and biological signals in harsh industrial environments.

FAQ

What is the maximum master clock frequency supported by the AD7703CR?

AD7703CR supports a maximum master clock frequency of 5 MHz, whether supplied externally to CLKIN or generated internally using a crystal between CLKIN and CLKOUT. At 4.096 MHz, it achieves 10 Hz filter corner frequency and 4 kSPS output data rate. Operation down to 200 kHz is guaranteed, enabling ultra-low-power configurations with reduced throughput.

Does the AD7703CR require external analog anti-aliasing filtering?

AD7703CR incorporates a six-pole Gaussian digital low-pass filter with 55 dB rejection at 60 Hz (10 Hz cutoff), which suppresses out-of-band noise after conversion. However, analog input signals with large-amplitude noise peaks (>100 mV overrange) can saturate the sigma-delta modulator. Therefore, a simple RC filter (e.g., 1 kΩ + 100 nF) is recommended at AIN to limit slew-induced aliasing and protect against transient overvoltage.

How does system calibration work on the AD7703CR?

System calibration on AD7703CR uses SC1 and SC2 pins to configure CAL-triggered cycles that calibrate both the AD7703CR itself and external front-end circuitry. When SC2 is low, the device calibrates its own offset; when SC1 and SC2 are set appropriately, it performs full-scale calibration using applied reference voltages. This allows removal of gain/offset errors introduced by external op-amps, RTDs, or long sensor cables - all stored in on-chip SRAM.

What is the purpose of the BP/UP pin on the AD7703CR?

The BP/UP pin on AD7703CR selects analog input configuration: logic high configures bipolar mode (±2.5 V input range referenced to AGND), while logic low selects unipolar mode (0 V to +2.5 V). This hardware-selectable range eliminates need for external level-shifting circuitry and allows single-device support of both sensor types - e.g., differential bridge outputs (bipolar) and single-ended thermocouple amplifiers (unipolar).

Can the AD7703CR interface directly to a microcontroller's SPI port?

AD7703CR does not implement standard SPI protocol but supports two synchronous serial modes compatible with microcontroller peripherals: Synchronous External Clocking (SEC) mode uses SCLK as input and outputs unformatted 20-bit MSB-first data, while Synchronous Self-Clocking (SSC) mode drives SCLK at fCLKIN/4 and outputs formatted data. Both modes require minimal firmware handling - no SPI mode bits or frame synchronization - and are widely used with MSP430, PIC, and ARM Cortex-M MCUs.