AD7781CRZ

Overview

The AD7781CRZ is a 20-bit, pin-programmable, low-power Sigma-Delta analog-to-digital converter (ADC) manufactured by Analog Devices Inc. It features an internal programmable gain amplifier (PGA) with selectable gains of 1 or 128 and operates on a single supply voltage ranging from 2.7 V to 5.25 V. The device offers two update rates: 16.7 Hz for fast settling and 10 Hz for high rejection. It includes an internal oscillator, a bridge power-down switch, and a 2-wire SPI-compatible serial interface. The component is housed in a 14-lead narrow body SOIC package and supports simultaneous 50 Hz/60 Hz noise rejection.

Feature Summary

• Pin-programmable filter response allows selection between 10 Hz and 16.7 Hz update rates.
• Integrated bridge power-down switch minimizes current consumption in battery-operated systems.
• On-chip PGA provides selectable gain settings of 1 or 128 for flexible signal conditioning.
• Dedicated control pins simplify configuration without requiring complex digital initialization.

Applications

• Weigh scales
• Pressure measurement
• Industrial process control
• Portable instrumentation

Procurement Notes

Verify the specific suffix CRZ corresponds to the 14-lead SOIC package variant when sourcing. Confirm that the component meets the required temperature range specifications for the intended application environment. Ensure compatibility with the system's digital logic levels before integration.

Selection Notes

Select this component for applications requiring high resolution and low power consumption. Consider the 10 Hz filter option if superior stop-band attenuation is necessary to reject mechanical vibrations. Verify that the external reference voltage source has sufficiently low output impedance to prevent gain errors.

Part Context

The AD7781 series serves as a complete front-end solution for bridge sensor products. It integrates a precision ADC, a low-noise PGA, and an internal clock into a single chip. This integration reduces the external component count and simplifies the design of high-precision measurement systems.

Replacement Considerations

The AD7781BRZ is a documented alternative within the same family, offering different performance grades while maintaining identical pinouts and functionality.

FAQ

How is the gain setting configured?

The gain is set via the dedicated GAIN pin. A low logic level selects a gain of 128, while a high logic level selects a gain of 1.

What is the function of the BPDSW pin?

The BPDSW pin controls an internal switch that disconnects the bridge sensor from the excitation voltage during power-down mode to minimize current consumption.

Does the device support independent analog and digital supplies?

Yes, the AD7781 has separate AVDD and DVDD pins, allowing them to operate at different voltages within the 2.7 V to 5.25 V range.