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AD7746:  24-bit, 2 Channel Capacitance to Digital Converter

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 ...More

AD7746:  24-bit, 2 Channel Capacitance to Digital Converter

Product Description

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

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    Capacitance-to-digital converter

  • 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
  • Resolution (Bits): 24bit
  • T-Put Rate: 90SPS
  • # Chan: 2
  • Supply V: Single(+2.7 to +5.25)
  • Pwr Diss: 4.25mW
  • Sleep Pwr Diss: 10µW
  • Ain Range: (2Vref) p-p,± 4 pF (Delta C)
  • Ref Int/Ext: Int/Ext
  • Product Description: 24-bit, Cap-to-Dig Conv. w/ 2 SE/Diff Capacitive Input Ch for interface to Dual Electrode Cap Sensor

Functional Block Diagram for AD7746

Circuits from the Lab

Find more at our Circuits Library.

Similar Products

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Part# Resolution (Bits) T-Put Rate # Chan Supply V Pwr Diss Input Base C (pF Max) Cin Range (pF) Pkg Type Price* (1000-4999) Product Description Interface
AD7142 16 27.8SPS 14 Single(+2.6 to +3.6), Single(+2.7), Single(+3), Single(+3.3) 3.6mW 20 ±2 CSP $1.37 CAPTouch (TM) Programmable Controller for 2-Electrode Capacitance Sensor with SPI or I2C Interface I²C/Ser 2-Wire, Ser, SPI
AD7143 16 43.5SPS 8 Single(+2.6 to +3.6) 3.6mW 20 ±2 CSP $1.25 CAPTouch (TM) Programmable Controller for 2-Electrode Capacitance Sensor with I2C Interface I²C/Ser 2-Wire, Ser
AD7147 16 111SPS 13 Single(+3), Single(+3.3) 3.6mW 20 ±8 CSP $1.28 CAPTouch (TM) Programmable Controller w/ SPI or I2C Interface for Single-Electrode Cap Sensors I²C/Ser 2-Wire, Ser, SPI
AD7147A 16 111SPS 13 Single(+3), Single(+3.3) 3.6mW 20 ±8 CSP $1.25 CapTouch® Programmable Controller for Single-Electrode Capacitance Sensors I²C/Ser 2-Wire, Ser, SPI
AD7148 16 4SPS 8 Multi(+3.3Anlg, +3.3Dig) 3.3mW 20 ±8 CSP $1.21 Octal Input, Programmable-Touch Controller for Single Electrode Capacitance Sensors I²C/Ser 2-Wire, Ser
AD7150 12 100SPS 2 Single(+2.7 to +3.6) 0.43mW 10 ±4 SOP $1.37 Ultra-Lo Pwr, 2-Ch Capacitance Converter for Proximity Sensing Applications I²C/Ser 2-Wire, Ser
AD7151 12 100SPS 1 Single(+2.7 to +3.6) 0.3mW 10 ±4 SOP $1.37 Ultra-Low Power, 1-Ch, Capacitance Converter for Proximity Sensing Applications I²C/Ser 2-Wire, Ser
AD7152 12 200SPS 2 Single(+2.7 to +3.6) 432µW 50 ±0.25 SOP $1.97 12-Bit Capacitance-to-Digital Converter (2 Capacitance Input Channels) I²C/Ser 2-Wire, Ser
AD7153 12 200SPS 1 Single(+2.7 to +3.6) 432µW 50 ±0.25 SOP $1.77 12-Bit Capacitance-to-Digital Converter I²C/Ser 2-Wire, Ser
AD7156 12 100SPS 2 Single(+1.8), Single(+2.5), Single(+2.7), Single(+3), Single(+3.3), Single(+3.6) 306µW 50 ±0.5 CSP $1.25 Ultralow Power, 1.8 V, 3 mm × 3 mm, 2-Channel Capacitance Converter I²C/Ser 2-Wire, Ser
AD7745 24 90SPS 1 Single(+2.7 to +5.25) 4.25mW 17 ±4 SOP $4.66 24-Bit, Cap-to-Dig Conv. w/ 1 SE/Diff Capacitive Input Ch for Interface to Dual Electrode Cap Sensor I²C/Ser 2-Wire, Ser
AD7746 24 90SPS 2 Single(+2.7 to +5.25) 4.25mW 17 ±4 SOP $5.01 24-bit, Cap-to-Dig Conv. w/ 2 SE/Diff Capacitive Input Ch for interface to Dual Electrode Cap Sensor I²C/Ser 2-Wire, Ser
AD7747 24 45.5SPS 1 Single(+2.7 to +5.25) 4.25mW 17 ±8 SOP $4.66 24-bit, Cap-to-Dig Conv w/1 SE/Diff Capacitive Input Ch for interface to Single Electrode Cap Sensor I²C/Ser 2-Wire, Ser
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This is the acceptable operating range of the device. The various ranges specified are as follows:
  • Commercial: 0 to +70 degrees Celsius
  • Military : -55 to +125 degrees Celsius
  • Industrial: Temperature ranges may vary by model. Please consult the datasheet for more information.
  • Automotive: -40 to +125 degrees Celsius
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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.
**Sample availability may be better than production availability. Please enter samples into your cart to check sample availability.