AD7703AN

Analog To Digital Converters (ADC) Overview

The AD7703 is a monolithic 20-bit analog-to-digital converter utilizing sigma-delta conversion techniques. It features a six-pole Gaussian digital low-pass filter with a corner frequency of 0.1 Hz to 10 Hz and an output data rate up to 4 kSPS. The device supports unipolar (0 V to +2.5 V) or bipolar (±2.5 V) analog input ranges with a nominal 2.5 V reference voltage. Power supplies range from 4.5 V to 5.5 V for both analog and digital rails, consuming typically 25 mW in normal operation and 10 µW in standby mode.

Analog To Digital Converters (ADC) Feature Summary

• On-chip self-calibration circuitry eliminates zero and gain errors, ensuring high endpoint accuracy without missing codes.
• Flexible serial interface supports synchronous modes compatible with industry-standard microcontrollers and asynchronous UART modes.
• Ultralow power consumption with a dedicated standby mode reduces idle power dissipation significantly for battery-powered applications.

Analog To Digital Converters (ADC) Applications

• Industrial process control systems requiring high precision
• Weigh scales and force measurement instrumentation
• Portable battery-operated instrumentation
• Remote data acquisition networks

Analog To Digital Converters (ADC) Procurement Notes

Verify the specific suffix designation against the manufacturer's datasheet to confirm temperature range and performance grade. The AD7703ANZ variant corresponds to the industrial temperature range. Ensure compatibility with system clock requirements, as the device relies on an external master clock or internal crystal oscillator for proper sampling rates and filter characteristics.

Analog To Digital Converters (ADC) Selection Notes

Select based on required resolution and input range configuration. The device offers 20-bit resolution with guaranteed no missing codes, suitable for low-frequency signals. Consider the package type availability, such as PDIP-20 or SOIC-20, relative to board space constraints. Verify that the system can accommodate the necessary settling time following input step changes due to the Gaussian filter response.

Analog To Digital Converters (ADC) Part Context

The AD7703 belongs to Analog Devices' family of precision sigma-delta ADCs designed for low-frequency measurements. It integrates a charge-balancing modulator, digital filter, and calibration microcontroller on a single LC2MOS die. This integration simplifies design by removing the need for external programmable gain amplifiers or level-setting circuitry typically required in lower-resolution systems.

Analog To Digital Converters (ADC) Replacement Considerations

Public confirmed substitutes include other 20-bit sigma-delta ADCs from Analog Devices such as the AD7709 for multi-channel applications. When replacing, ensure the new component matches the SPI interface timing and supply voltage requirements. Verify that the replacement maintains the required linearity error specifications and physical footprint if PCB rework is not planned.

Analog To Digital Converters (ADC) FAQ

How does the AD7703 handle input overrange conditions?

The device includes built-in overrange headroom in the modulator and digital filter, allowing excursions of up to 100 mV beyond the reference voltage without introducing errors due to overloading.

What determines the output data rate and filter cutoff frequency?

Both parameters are determined by the master clock frequency applied to the CLKIN pin. The filter cutoff is fCLK/409,600, and the output update rate is fCLK/1024.

Can the AD7703 be used for high-speed multiplexing?

No, it is unsuitable for high-speed multiplexing because the Gaussian digital filter requires a significant settling time after step changes in input voltage before valid data is available.