AD7746ARUZ

ADCs/DACs - Special Purpose Overview

The AD7746ARUZ is a dual-channel, 24-bit Sigma-Delta capacitance-to-digital converter (CDC) manufactured by Analog Devices Inc. It features an automotive temperature range of –40°C to +125°C and operates on a single supply from 2.7 V to 5.25 V with typical current consumption of 0.7 mA. The device provides high resolution down to 4 aF (up to 21 ENOB), ±0.01% linearity, and ±4 fF accuracy. Key specifications include a full-scale changing capacitance range of ±4 pF, tolerance for up to 17 pF common-mode capacitance, and support for parasitic capacitance to ground up to 60 pF. It integrates an internal clock oscillator, voltage reference, and a 2-wire I²C-compatible serial interface.

ADCs/DACs - Special Purpose Feature Summary

• Dual-channel architecture supporting independent single-ended or differential capacitive inputs.
• Integrated programmable digital-to-capacitance converter (CAPDAC) balances common-mode capacitance up to 17 pF.
• On-chip temperature sensor with 0.1°C resolution and ±2°C accuracy.
• Internal excitation source at 32 kHz eliminates external components for floating capacitive sensors.

ADCs/DACs - Special Purpose Applications

• Pressure measurement systems
• Position sensing applications
• Level sensing and flowmeters
• Humidity sensing devices

ADCs/DACs - Special Purpose Procurement Notes

Verify the specific ordering suffix against the manufacturer's official documentation to confirm package type and reel specifications. Confirm that the component meets the required automotive temperature grade (-40°C to +125°C) for the intended deployment environment. Ensure compatibility with the system's I²C bus voltage levels and pull-up requirements before integration.

ADCs/DACs - Special Purpose Selection Notes

Select the AD7746ARUZ over the AD7745 when dual-channel simultaneous or sequential capacitance measurement is required. This model is optimized for floating capacitive sensors; for sensors with one plate grounded, the AD7747 is recommended. Consider the 16-lead TSSOP package constraints and the need for decoupling capacitors near the VDD pin to maintain signal integrity.

ADCs/DACs - Special Purpose Part Context

The AD7746ARUZ belongs to the AD7745/AD7746 family of high-resolution capacitance-to-digital converters. While the AD7745 offers a single channel, the AD7746 provides two channels within the same 16-lead TSSOP footprint. Both share identical core performance metrics, including the 24-bit Sigma-Delta modulation architecture and integrated calibration capabilities.

ADCs/DACs - Special Purpose Replacement Considerations

The AD7745ARUZ serves as a functional substitute if only a single capacitive channel is needed, sharing the same package and electrical characteristics. No other direct cross-model replacements are documented in the provided datasheet.

ADCs/DACs - Special Purpose FAQ

How does the AD7746 handle large common-mode capacitance?

The device accepts up to 17 pF of common-mode (unchanging) capacitance, which can be balanced using the programmable on-chip digital-to-capacitance converter (CAPDAC).

What is the maximum allowable parasitic capacitance to ground?

The AD7746 is tolerant of parasitic capacitance to ground up to 60 pF on the capacitive input pins without significant performance degradation.

Can the AD7746 measure both capacitance and temperature simultaneously?

Yes, the device includes an on-chip temperature sensor and a voltage input channel alongside the dual capacitive channels, allowing for multi-parameter acquisition.