Analog Devices Inc. AD7703CNZ

Overview

AD7703CNZ from Analog Devices is a monolithic 20-bit charge-balancing sigma-delta ADC with on-chip 6-pole Gaussian digital filter, self-calibration microcontroller, and flexible serial interface. It delivers ±0.0003% FSR integral nonlinearity (C version), 0.1 Hz to 10 Hz programmable filter corner frequency, and 4 kSPS output data rate. It operates from ±5 V analog/digital supplies and supports unipolar (0 V to +2.5 V) or bipolar (±2.5 V) input ranges - ideal for precision weigh scales and industrial process transmitters.

For engineers reviewing the AD7703CNZ datasheet, AD7703CNZ pinout, AD7703CNZ application, or AD7703CNZ equivalent, key selection considerations include its guaranteed no-missing-codes 20-bit dynamic range, ultralow 10 µW standby power, system calibration capability for external gain/offset error removal, and dual serial interface modes (SSC/SEC) compatible with microcontroller UARTs or synchronous peripherals.

Technical Context

The AD7703CNZ employs a second-order sigma-delta modulator with continuous sampling and oversampling at 16 kHz (f_CLKIN/256), feeding a deterministic six-pole Gaussian digital filter that produces 20-bit words at 4 kHz. Its calibration architecture uses on-chip SRAM and a dedicated microcontroller to execute zero/full-scale self-calibration or extend calibration to external front-end components.

It supports two distinct serial protocols: Synchronous Self-Clocking (SSC) mode where SCLK is an output (f_CLKIN/4, 25% duty cycle), and Synchronous External Clocking (SEC) mode where SCLK is an input up to 5 MHz. The device requires strict analog/digital ground separation (AGND/DGND ≤ ±0.3 V) and mandates a 1 nF ceramic capacitor from AIN to AGND to stabilize input impedance.

Key Specifications

Pinout & Package

AD7703CNZ is housed in a 20-pin plastic DIP package (0.300" wide) with through-hole mounting. Pin assignments are fully defined per Analog Devices Rev. F datasheet and validated for thermal and ESD robustness in industrial environments.

Key Features

Applications

Equivalent & Alternatives

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

Compared with AD7703CNZ, AD7714BN trades speed and dual-supply flexibility for higher resolution and integrated gain, while ADS1258IPWR sacrifices industrial-grade 60 Hz rejection and system calibration for throughput and integration - making AD7703CNZ uniquely suited for calibrated, low-noise, loop-powered 4–20 mA systems.

Availability

AD7703CNZ is available at Aetrix Electronics and suitable for industrial process control, precision weigh scales, and portable instrumentation requiring stable component supply, long-lifecycle assurance, and traceable sourcing for safety-critical deployments.

Supply support for AD7703CNZ 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 AD7703CNZ 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 master clock frequency supported by the AD7703CNZ?

The AD7703CNZ supports a maximum master clock frequency of 5 MHz for both internal crystal oscillator and external clock configurations. At 4.096 MHz, it achieves its specified 10 Hz filter corner frequency and 4 kSPS output rate. Operation down to 200 kHz is guaranteed, enabling ultra-low-power configurations where settling time and noise performance remain acceptable.

Does the AD7703CNZ require external analog anti-aliasing filtering?

No - the AD7703CNZ's on-chip 6-pole Gaussian digital filter provides inherent anti-aliasing for input signals within its 0.1 Hz to 10 Hz passband. However, analog filtering remains necessary to prevent saturation from large transient noise spikes exceeding ±100 mV overrange, especially in electrically noisy industrial environments where fast transients could overload the sigma-delta modulator.

How does system calibration work on the AD7703CNZ?

System calibration on the AD7703CNZ extends on-chip self-calibration to external circuitry: by applying known zero and full-scale voltages at the AIN pin (with SC1/SC2 set appropriately), the AD7703CNZ measures and corrects for gain and offset errors introduced by upstream op-amps, resistive networks, or sensor excitation circuits - storing compensation values in on-chip SRAM for automatic application to all subsequent conversions.

Can the AD7703CNZ operate from a single +5 V supply?

No - the AD7703CNZ requires dual ±5 V analog and digital supplies (AVDD/DVDD = +5 V, AVSS/DVSS = –5 V) to support its bipolar ±2.5 V input range and internal charge-balancing architecture. Attempting single-supply operation violates absolute maximum ratings and will result in incorrect conversion or permanent damage. A split-rail supply or isolated DC-DC converter is mandatory.

What is the purpose of the 1 nF capacitor required at the AIN pin?

The 1 nF capacitor from AIN to AGND stabilizes the dynamic input impedance presented by the AD7703CNZ's sigma-delta modulator, which varies with clock frequency. Without it, source resistance >750 Ω causes gain errors and nonlinearity due to incomplete settling before sampling. This capacitor forms a low-pass filter with the source impedance, ensuring accurate charge transfer during each sampling phase.