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AD7745 Datasheet PDF

Part Series:AD7745 Series
Description:24Bit, 1Channel Capacitance to Digital Converter
Document:AD7745ARUZ-REEL7 Datasheet PDF (29 Pages)

AD7745 - ADI Function Overview

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 features 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
### 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
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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
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