●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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