AD7747:  24-Bit Capacitance-to-Digital Converter with Temperature Sensor

The AD7747 is a high-resolution, Σ-Δ capacitance-to-digital converter (CDC). The capacitance to be measured is connected directly to the device inputs. The architecture features inherent high ...More

AD7747:  24-Bit Capacitance-to-Digital Converter with Temperature Sensor

Product Description

The AD7747 is a high-resolution, Σ-Δ capacitance-to-digital converter (CDC). The capacitance to be measured is connected directly to the device inputs. The architecture features inherent high resolution (24-bit no missing codes, up to 19.5-bit effective resolution), high linearity (±0.01%), and high accuracy (±10 fF factory calibrated). The AD7747 capacitance input range is ±8 pF (changing), and 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 AD7747 is designed for single-ended or differential capacitive sensors with one plate connected to ground. For floating (not grounded) capacitive sensors, the AD7745 or AD7746 are recommended.

The part has 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 part has a standard voltage input that, together with the differential reference input, allows easy interface to an external temperature sensor, such as an RTD, thermistor, or diode.

The AD7747 has a 2-wire, I2C-compatible serial interface. The part can operate with a single power supply of 2.7 V to 5.25 V. It is specified over the automotive temperature range of −40°C to +125°C and is housed in a 16-lead TSSOP package.

Applications

Automotive, industrial, and medical systems for:

  • Pressure measurement
  • Position sensing
  • Proximity sensing
  • Level sensing
  • Flowmeters
  • Impurity detections

Features

Capacitance-to-digital converter

  • New standard in single chip solutions
  • Interfaces to single or differential grounded sensors
  • Resolution down to 20 aF (that is, up to 19.5-bit ENOB)
  • Accuracy: 10 fF
  • Linearity: 0.01%
  • Common-mode (not changing) capacitance up to 17 pF
  • Full-scale (changing) capacitance range ±8 pF
  • Update rate: 5 Hz to 45 Hz
  • Simultaneous 50 Hz and 60 Hz rejection at 8.1 Hz update
  • Active shield for shielding sensor connection
  • 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

Diagrams

AD7747 Diagram
Functional Block Diagram for AD7747

Specifications

Resolution (Bits) 24bit
T-Put Rate 45.5SPS
# Chan 1
Supply V Single(+2.7 to +5.25)
Pwr Diss (max) 4.25mW
Sleep Pwr Diss 10µW
Ain Range ± 8 pF (Delta C) ,(2Vref) p-p
Ref Int/Ext Int/Ext
Product Description 24-bit, Cap-to-Dig Conv w/1 SE/Diff Capacitive Input Ch for interface to Single Electrode Cap Sensor

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AD7156 - Ultralow Power, 1.8 V, 3 mm × 3 mm, 2-Channel Capacitance Converter

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Part# Resolution (Bits) T-Put Rate # Chan Supply V Pwr Diss (max) 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 $1.30 CAPTouch (TM) Programmable Controller w/ SPI or I2C Interface for Single-Electrode Cap Sensors I²C/Ser 2-Wire, Ser, SPI
AD7148 16 4SPS 8 Multi(+3.3Anlg, +3.3Dig) 3.3mW 20 ±8 CSP $1.21 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
AD7156 12 100SPS 2 Single(+1.8), Single(+2.5), Single(+2.7), Single(+3), Single(+3.3), Single(+3.6) 306µW - - 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

* The pricing listed here is provided only for budgetary purposes as recommended list price in U.S. Dollars in the United States ex factor per unit for the stated volume. Pricing displayed for Evaluation Boards and Kits is based on 1-piece pricing.
** Pricing is currently unavailable. Click on the product number to see the Product Page for additional information.

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