AD7746
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AD7746

24-bit, 2 Channel Capacitance to Digital Converter

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Part Details
Part Models 3
1ku List Price Starting From $7.40
Features
  • 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
Additional Details
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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
Part Models 3
1ku List Price Starting From $7.40

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Documentation

Documentation

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Part Model Pin/Package Drawing Documentation CAD Symbols, Footprints, and 3D Models
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Product Lifecycle

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Jan 20, 2012

- 11_0218

Halogen Free Material Change for Certain TSSOP Products at Carsem

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PRODUCTION

AD7746ARUZ-REEL

PRODUCTION

AD7746ARUZ-REEL7

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Product Lifecycle

PCN

Jan 20, 2012

- 11_0218

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Halogen Free Material Change for Certain TSSOP Products at Carsem

AD7746ARUZ

PRODUCTION

AD7746ARUZ-REEL

PRODUCTION

AD7746ARUZ-REEL7

PRODUCTION

Evaluation Kit

Evaluation Kits 1

EVAL-AD7746

AD7746 Evaluation Kit

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EVAL-AD7746

AD7746 Evaluation Kit

Product Detail

The EVAL-AD7746EBZ is a fully featured evaluation board for the AD7746. The evaluation board is operated with a PC via a standard USB connection with software provided enabling the user to perform detailed analysis of the CDC's performance. This software includes the technical note describing the operation and set up of the evaluation board.

Reference Designs

Reference Designs 1

Figure 1. CN0552 Block Diagram

Capacitance to Digital Converter with Extended Range

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cn0552

Capacitance to Digital Converter with Extended Range

cn0552

Circuits from the lab

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Capacitance to Digital Converter with Extended Range

Features and Benefits

  • ±4.096 pF input range suits a wide array sensors.
  • Extended input range circuit provides ±50pF input range
  • 4.2 aF RMS resolution @ 9.1sps conversion rate
  • Auxiliary temperature sensor and voltage input for system-level calibration
View Detailed Reference Design external link

Part Used 2

Design & Integration Tools

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Videos

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Mar 02, 2022

00:59

CN0552 Capacitance-Digital Conversion w/ Extended Range Circuitry

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