Overview

Features and Benefits

  • New standard in single chip solutions
  • Interfaces to single or differential floating sensors
  • Resolution down to 4 aF (that is, up to 21 ENOB)
  • Accuracy: 4 fF
  • Linearity: 0.01%
  • Common-mode (not changing) capacitance up to 17 pF
  • Full-scale (changing) capacitance range: ±4 pF
  • Tolerant of parasitic capacitance to ground up to 60 pF
  • Update rate: 10 Hz to 90 Hz
  • Simultaneous 50 Hz and 60 Hz rejection at 16 Hz
  • Temperature sensor on-chip
    Resolution: 0.1°C, accuracy: ±2°C
  • Voltage input channel
  • Internal clock oscillator
  • 2-wire serial interface (I2C®-compatible)
  • Power
    2.7 V to 5.25 V single-supply operation
    0.7 mA current consumption
  • Operating temperature: –40°C to +125°C
  • 16-lead TSSOP package

Product Details

The AD7745/AD7746 are a high resolution, Σ-Δ capacitance-to-digital converter (CDC). The capacitance to be measured is connected directly to the device inputs. The architecture fea-tures inherent high resolution (24-bit no missing codes, up to 21-bit effective resolution), high linearity (±0.01%), and high accuracy (±4 fF factory calibrated). The AD7745/AD7746 capacitance input range is ±4 pF (changing), while it can accept up to 17 pF common-mode capacitance (not changing), which can be balanced by a programmable on-chip, digital-to-capacitance converter (CAPDAC).

The AD7745 has one capacitance input channel, while the AD7746 has two channels. Each channel can be configured as single-ended or differential. The AD7745/AD7746 are designed for floating capacitive sensors. For capacitive sensors with one plate connected to ground, the AD7747 is recommended.

The parts have an on-chip temperature sensor with a resolution of 0.1°C and accuracy of ±2°C. The on-chip voltage reference and the on-chip clock generator eliminate the need for any external components in capacitive sensor applications. The parts have a standard voltage input, which together with the differential reference input allows easy interface to an external temperature sensor, such as an RTD, thermistor, or diode.

The AD7745/AD7746 have a 2-wire, I2C-compatible serial interface. Both parts can operate with a single power supply from 2.7 V to 5.25 V. They are specified over the automotive temperature range of –40°C to +125°C and are housed in a 16-lead TSSOP package.

Applications

Automotive, Industrial and Medical Systems for:

  • Pressure Measurement
  • Position Sensors
  • Level Sensors
  • Flowmeters
  • Humidity Sensors
  • Impurity Detection

Product Lifecycle icon-recommended Production

At least one model within this product family is in production and available for purchase. The product is appropriate for new designs but newer alternatives may exist.

Evaluation Kits (1)

Reference Designs (1)

Design Resources

ADI has always placed the highest emphasis on delivering products that meet the maximum levels of quality and reliability. We achieve this by incorporating quality and reliability checks in every scope of product and process design, and in the manufacturing process as well.  "Zero defects" for shipped products is always our goal.

PCN-PDN Information

Discussions

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The USA list pricing shown is for BUDGETARY USE ONLY, shown in United States dollars (FOB USA per unit for the stated volume), and is subject to change. International prices may differ due to local duties, taxes, fees and exchange rates. For volume-specific price or delivery quotes, please contact your local Analog Devices, Inc. sales office or authorized distributor. Pricing displayed for Evaluation Boards and Kits is based on 1-piece pricing.


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Evaluation Boards Pricing displayed is based on 1-piece.
Pricing displayed is based on 1-piece. The USA list pricing shown is for budgetary use only, shown in United States dollars (FOB USA per unit), and is subject to change. International prices may vary due to local duties, taxes, fees and exchange rates.