/均为高分辨率、Σ-Δ电容数字转换器（CDC）,可直接与电容传感器的电容连接进行测量。该芯片还具有高分辨率（24位无失码、{zg}21位有效分辨率）、高线性度（±0.01%）和高精度（±4 fF工厂校准）等固有特性。AD7745/AD7746的电容输入范围是±4 pF（可变）,同时可接受{zd0}17 pF共模电容（不可变）,后者可以通过一个可编程片内数字电容转换器（CAPDAC）来平衡。AD7745拥有一个电容输入通道,AD7746则拥有两个通道。每个通道均可配置为单端输入或差分输入方式。AD7745/AD7746针对浮动式电容传感器而设计。若需一块极板接地的电容传感器,推荐使用AD7747。

这些器件内置一个片内温度传感器,其分辨率为0.1°C,精度为±2°C；还集成片内基准电压源和片内时钟发生器,因此在电容传感器应用中无需任何额外外部元件。两款器件都有一个标准电压输入,当与差分基准电压输入结合使用时,可方便地与一个外部温度传感器（如RTD、热敏电阻或二极管等）接口。AD7745/AD7746均有一个双线式I?C兼容串行接口,二者均可采用2.7 V至5.25 V单电源供电,额定温度范围为–40°C至+125°C汽车电子温度范围,采用16引脚TSSOP封装。

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, I?C-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.

应用

汽车电子、工业和医疗系统,用于：

Applications

Automotive, Industrial and Medical Systems for:

EVAL-AD7746LDZ 特点

电容数字转换器

采用单芯片解决方案的新标准
可与单一或差分浮动式传感器接口
分辨率：{zd1}4 aF（即{zg}21 ENOB）
精度：4 fF
线性度：0.01%
共模（不可变）电容{zd0}可达17 pF
满量程（可变）电容范围：±4 pF
耐受对地寄生电容：{zd0}60 pF
更新速率：10 Hz～90 Hz
16 Hz时,50 Hz、60 Hz同时抑制
片内温度传感器

分辨率：0.1°C,精度：±2°C

2.7 V至5.25 V单电源工作

功耗：0.7 mA

2.7 V to 5.25 V single-supply operation

0.7 mA current consumption

EVAL-AD7746LDZ 功能框图

AD7746 芯片订购指南

EVAL-AD7746LDZ 应用技术支持与电子电路设计开发资源下载

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