AD7781 :20位、引脚可编程的超低功耗Σ−Δ型ADC
AD7781是一款完整的低功耗前端解决方案，适用于桥式传感器产品，包括电子秤、应变计和压力传感器。它内置一个精密、低功耗、20位Σ-Δ型ADC，一个片内低噪声可编程增益放大器(PGA)，以及一个片内振荡器。AD7781功耗仅为330 μA，因此特别适合要求极低功耗的便携式或电池供电产品。该器件还提供省电模式，不执行转换时，用户可以切断对桥式传感器的供电，并使该器件进入省电模式，从而延长产品的电池使用时间。为便于使用，AD7781的所有特性均由专用引脚控制。每次发生数据读取操作时，8个状态位便会附加到20位转换结果上。这些状态位含有一个码序列，可用来确认串行传输的有效性。片内PGA的增益为1或128，支持±5 V或±39 mV的满量程差分输入。这款器件提供两种滤波器响应选项。当更新速率为16.7 Hz时，滤波器响应可提供出色的动态性能，建立时间为120 ms。当更新速率为10 Hz时，滤波器响应可提供优于-45 dB的阻带衰减。在称重传感器应用中，此阻带抑制性能可有效抑制称重传感器的低频机械振动。此时的建立时间为300 ms。在10 Hz和16.7 Hz更新速率时，均可实现50 Hz/60 Hz同时抑制。AD7781采用2.7 V至5.25 V电源供电，提供窄体、14引脚SOIC和16引脚TSSOP两种封装。
The AD7781 is a complete low power front-end solution for bridge sensor products, including weigh scales, strain gages, and pressure sensors. It contains a precision low power 20-bit sigma-delta (Σ-Δ) ADC, an on-chip, low noise programmable gain amplifier (PGA), and an on-chip oscillator.
Consuming only 330 μA, the AD7781 is particularly suitable for portable or battery-operated products where very low power is required. The AD7781 also has a power-down mode that allows the user to switch off the power to the bridge sensor and power down the AD7781 when not converting, thus increasing the battery life of the product.
For ease of use, all the features of the AD7781 are controlled by dedicated pins. Each time that a data read occurs, eight status bits are appended to the 20-bit conversion. These status bits contain a pattern sequence that can be used to confirm the validity of the serial transfer.
The on-chip PGA has a gain of 1 or 128, supporting a full-scale differential input of ±5 V or ±39 mV. The device has two filter response options. The filter response at the 16.7 Hz update rate provides superior dynamic performance. The settling time is 120 ms at this update rate. At the 10 Hz update rate, the filter response provides better than -45 dB of stop-band attenuation. In load cell applications, this stop-band rejection is useful to reject low frequency mechanical vibrations of the load cell. The settling time is 300 ms at this update rate. Simultaneous 50 Hz/60 Hz rejection occurs at both the 10 Hz and 16.7 Hz update rates.
The AD7781 operates with a power supply from 2.7 V to 5.25 V. It is available in a narrow body, 14-lead SOIC package and in a 16-lead TSSOP package.
AD7781 特点
- 引脚可编程的滤波器响应更新速率：10 Hz或16.7 Hz
- 引脚可编程的仪表放大器增益
- 引脚可编程省电和复位功能
- 状态功能
- 内部时钟振荡器
- 内部电桥关断开关
- 电流:
115 μA（典型值，G = 1）
330 μA（典型值，G = 128） - 50 Hz/60 Hz同时抑制
- 欲了解更多特性，请参考数据手册
AD7781 功能框图
AD7781 应用领域
- 电子秤
- 压力测量
- 工业过程控制
- 便携式仪器仪表
AD7781 芯片订购指南
| 产品型号 | 产品状态 | 封装 | 引脚 | 温度范围 |
|---|---|---|---|---|
| AD7781BRUZ | 量产 | 16 ld TSSOP | 16 | 工业 |
| AD7781BRUZ-REEL | 量产 | 16 ld TSSOP | 16 | 工业 |
| AD7781BRZ | 量产 | 14 ld SOIC | 14 | 工业 |
| AD7781BRZ-REEL | 量产 | 14 ld SOIC | 14 | 工业 |
| AD7781CRUZ | 量产 | 16 ld TSSOP | 16 | 工业 |
| AD7781CRUZ-REEL | 量产 | 16 ld TSSOP | 16 | 工业 |
| AD7781CRZ | 量产 | 14 ld SOIC | 14 | 工业 |
| AD7781CRZ-REEL | 量产 | 14 ld SOIC | 14 | 工业 |
| EVAL-AD7781EBZ | 量产 | 评估板 |
