AD7711A: 内置RTD电流源的CMOS、24位Σ-Δ型信号调理ADC
AD7711A是一款适合低频测量应用的完整模拟前端,可直接接受来自传感器的低电平信号,并产生串行数字输出。它采用Σ-Δ转换技术,可实现最高24位无失码性能。输入信号加在一个以模拟调制器为基础的专有可编程增益前端。调制器输出由片内数字滤波器处理。此数字滤波器的第一个陷波可通过片内控制寄存器进行编程,以便对滤波器截止和建立时间进行调整。该器件具有两个差分模拟输入和一个差分基准电压输入。一般而言,其中一个通道将用作主通道,而另一个通道将用作辅助输入,用来定期检测第二电压输入。如果模拟输入上的输入信号高于-30 mV,则该器件可采用单电源供电（将VSS引脚与AGND相连）。将VSS引脚接负电压时,该器件可转换低至-VREF的输入信号。该器件还提供一个400 uA电流源,可用来为RTD传感器提供激励。因此,AD7711A能处理单通道或双通道系统所有的信号调节和转换。AD7711A非常适合基于微控制器的智能系统应用。利用双向串行端口,可在软件中进行输入通道选择、增益设置和信号极性配置。AD7711A包含自校准、系统校准和后台校准选项,同时允许用户读取和写入片内校准寄存器。CMOS构造可确保低功耗,软件可编程省电模式则将待机功耗降至仅7 mW（典型值）。该器件提供两种封装：24引脚、0.3英寸宽、密封双列直插式封装（Cerdip）和24引脚小形集成封装（SOIC）。
The AD7711A is a complete analog front end for low-frequency measurement applications. The device accepts low level signals directly from a transducer and outputs a serial digital word. It employs a sigma-delta conversion technique to realize up to 24 bits of no missing codes performance. The input signal is applied to a proprietary programmable gain front end based around an analog modulator. The modulator output is processed by an on-chip digital filter. The first notch of this digital filter can be programmed via the on-chip control register allowing adjustment of the filter cutoff and settling time.The part features two differential analog inputs and a differential reference input. Normally, one of the channels will be used as the main channel with the second channel used as an auxiliary input to periodically measure a second voltage. It can be operated from a single supply (by tying the VSS pin to AGND) provided that the input signals on the analog inputs are more positive than -30 mV. By taking the VSS pin negative, the part can convert signals down to -VREF on its inputs. The part also provides a 400 uA current source that can be used to provide excitation for RTD transducers. The AD7711A thus performs all signal conditioning and conversion for a single or dual channel system.The AD7711A is ideal for use in smart, microcontroller based systems. Input channel selection, gain settings and signal polarity can be configured in software using the bidirectional serial port. The AD7711A contains self-calibration, system calibration and background calibration options and also allows the user to read and write the on-chip calibration registers.CMOS construction ensures low power dissipation, and a software programmable power-down mode reduces the standby power consumption to only 7 mW typical. The part is available in a 24-pin, 0.3 inch-wide, hermetic dual-in-line package (Cerdip) as well as a 24-lead small outline (SOIC) package.
AD7711A 特点
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AD7711A 技术指标
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