AD7745

24位电容至数字转换器，温度传感器 24-Bit Capacitance-to-Digital Converter with Temperature Sensor

Product Details

The /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:

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Pressure Measurement

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Position Sensors

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Level Sensors

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Flowmeters

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Humidity Sensors

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Impurity Detection

### Features and Benefits

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New standard in single chip solutions

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Interfaces to single or differential floating sensors

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Resolution down to 4 aF that is, up to 21 ENOB

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Accuracy: 4 fF

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Linearity: 0.01%

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Common-mode not changing capacitance up to 17 pF

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Full-scale changing capacitance range: ±4 pF

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Tolerant of parasitic capacitance to ground up to 60 pF

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Update rate: 10 Hz to 90 Hz

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Simultaneous 50 Hz and 60 Hz rejection at 16 Hz >

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Temperature sensor on-chip

▪ Resolution: 0.1°C, accuracy: ±2°C

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Voltage input channel

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Internal clock oscillator

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2-wire serial interface I2C®-compatible

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Power

▪ 2.7 V to 5.25 V single-supply operation

▪ 0.7 mA current consumption

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Operating temperature: –40°C to +125°C

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16-lead TSSOP package

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