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| ADS8688 八路数据采集系统开发方案 |
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| 文章来源： 更新时间：2014/11/8 9:25:00 |
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TI公司的ADS8688是基于16位逐次逼近(SAR)模数转换器(ADC)的八路数据采集系统,工作在500kSPs的吞吐量.双极工作电源±10.24 V,±5.12 V和±2.56 V,单极工作电源0 V 到 10.24 V和0 V到5.12 V,输出保护电压高达成±20 V,低功耗65mW,具有极好的性能: SNR: 92 dB;THD:–102 dB.主要用于工业控制,PLC和数据采集系统.本文介绍了ADS8688主要特性,框图,以及在电源自动化和PLC的数据采集系统框图, ADS8688EVM-PDK 评估模块主要特性和GUI主要特性,电路图,材料清单和六层PCB设计图.
The ADS8684 and ADS8688 are 4- and 8-channel, integrated data acquisition systems based on a 16-bit successive approximation (SAR) analog-to-digital converter (ADC), operating at a throughput of 500 kSPS. The devices feature integrated analog front-end circuitry for each input channel with overvoltage protection up to ±20 V, a 4- or 8-channel multiplexer with automatic and manual scanning modes, and an on-chip, 4.096-V reference with low temperature drift. Operating on a single 5-V analog supply, each input channel on the devices can support true bipolar input ranges of ±10.24 V, ±5.12 V, and ±2.56 V, as well as unipolar input ranges of 0 V to 10.24 V and 0 V to 5.12 V. The gain of the analog front-end for all input ranges is accurately trimmed to ensure a high dc precision. The input range selection is software-programmable and independent for each channel. The devices offer a 1-MΩ constant resistive input impedance irrespective of the selected input range.
The ADS8684 and ADS8688 offer a simple SPI-compatible serial interface to the digital host and also support daisy-chaining of multiple devices. The digital supply operates from 1.65 V to 5.25 V, enabling direct interface to a wide range of host controllers.
ADS8688主要特性:
16-Bit ADC with Integrated Analog Front-End
4-, 8-Channel MUX with Auto and Manual Scan
Channel-Independent Programmable Input Ranges:
Bipolar: ±10.24 V, ±5.12 V, and ±2.56 V
Unipolar: 0 V to 10.24 V and 0 V to 5.12 V
5-V Analog Supply: 1.65-V to 5-V I/O Supply
Constant Resistive Input Impedance: 1 MΩ
Input Overvoltage Protection: Up to ±20 V
On-Chip, 4.096-V Reference with Low Drift
Excellent Performance:
500-kSPS Aggregate Throughput
DNL: ±0.5 LSB; INL: ±0.75 LSB
Low Drift for Gain Error and Offset
SNR: 92 dB; THD: –102 dB
Low Power: 65 mW
AUX Input → Direct Connection to ADC Inputs
SPI™-Compatible Interface with Daisy-Chain
–40℃ to 125℃ Industrial Temperature Range
TSSOP-38 Package (9.7 mm × 4.4 mm)
图1. ADS8688功能框图
图2. 用于电源自动化的ADS8688八路复用数据采集系统框图
图3. 用于PLC的ADS8688 16位八路综合模拟输出模块框图
ADS8688EVM-PDK 评估模块
The ADS8688EVM-PDK is a platform for evaluating the ADS8688 device. The ADS8688EVM-PDK consists of an ADS8688EVM board and an SDCC controller card. The SDCC is an FPGA-based controller card that functions as an serial peripheral interface (SPI™) host and transfers data to the ADS8688EVM graphical user interface (GUI) via a USB interface. The ADS8688EVM GUI collects, analyzes, and records data from the ADS8688EVM board. The ADS8688EVM GUI is capable of collecting data from the ADS8688EVM in auto and manual modes, configuring the ADC program registers, and performing FFT analysis of data captured from the ADC.
ADS8688EVM-PDK 评估模块主要特性:
• Includes support circuitry as a design example to match ADC performance.
• 3.3-V slave SPI.
• Serial interface header for easy connection to the SDCC controller card.
• Designed for a 5-V analog supply.
• Integrated 4.096-V voltage reference.
• Bipolar (±10.24 V, ±5,12 V, ±2.56 V )or unipolar(0 V to 10.24 V, 0 V to 5.12 V) input ranges for each channel.
• Onboard, second-order, Butterworth, low-pass filters for four channels.
• Onboard regulator for generating a ±15-V bipolar supply for second-order, Butterworth, low-pass filters.
• Capable of accepting a ±100-mV signal on the negative analog inputs (AIN_xGND).
ADS8688EVM-PDK 评估模块GUI特性:
• Captures data from the ADS8688EVM in auto and manual modes.
• Configures the ADS8688 device program registers.
• Enables and disables channels in auto mode.
• FFT analysis and calculates the SNR, THD, and SINAD ac performance parameters.
• Single and multiple graph views for captured data.
• Includes a dc histogram for dc inputs.
• Logs ADC data.
图4.ADS8688EVM-PDK 评估模块外形图: microSD存储卡和SDCC控制板
The ADS8688EVM-PDK includes microSD memory cards that contain the EVM software and SDCC controller board firmware required for the EVM operation
图5.ADS8688EVM-PDK 评估模块电路图(1)
图6.ADS8688EVM-PDK 评估模块电路图(2)
ADS8688EVM材料清单:
图7.ADS8688EVM-PDK 评估模块PCB设计图:顶层(L1)
图8.ADS8688EVM-PDK 评估模块PCB设计图:地层(L2)
图9.ADS8688EVM-PDK 评估模块PCB设计图:模拟电源层(L3)
图10.ADS8688EVM-PDK 评估模块PCB设计图:数字电源层(L4)
图11.ADS8688EVM-PDK 评估模块PCB设计图:地层(L5)
图12.ADS8688EVM-PDK 评估模块PCB设计图:底层(L6)
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