ADI AD7685高性能過程控制模擬前端解決方案

ADI AD7685高性能過程控制模擬前端解決方案關鍵字：工業(yè)控制, 過程控制,ADC,數(shù)據(jù)采集ADI公司的AD7685是16位電荷重新分布逐次逼近模數(shù)轉換器(ADC),單電源2.3V-5.5V工作,包括有不丟失碼的低功耗高速16位取樣ADC,內(nèi)部轉換時鐘,以及多功能串口.吞吐量250kSPS, INL典型為0.6 LSB,最大為2 LSB(0.003% of FSR),20kHz的SINAD為93.5dB,THD為-110dB,假性差分模擬輸入,主要用在手持設備,醫(yī)療儀器,移動通信,PDA,數(shù)據(jù)采集和儀器儀表于過程控制.本文介紹了AD7685主要特性, 多個電源應用電源框圖, 真正16位隔離同時取樣采集系統(tǒng)框圖,EVAL-AD76XXCB 8/10-Pin評估板主要特性,電路圖以及完整的過程控制用高速高CMRR精密模擬前端簡化框圖, EVAL-A-INPUT-1AZ評估板電路圖和材料清單.The AD7685 is a 16-bit, charge redistribution successive approximation, analog-to-digital converter (ADC) that operates from a single power supply, VDD, between 2.3 V to 5.5 V. It contains a low power, high speed, 16-bit sampling ADC with no missing codes, an internal conversion clock, and a versatile serial interface port. The part also contains a low noise, wide bandwidth, short aperture delay, track-and-hold circuit. On the CNV rising edge, it samples an analog input IN+ between 0 V to REF with respect to a ground sense IN. The reference voltage, REF, is applied externally and can be set up to the supply voltage. Power dissipation scales linearly with throughput.The SPI-compatible serial interface also features the ability, using the SDI input, to daisy chain several ADCs on a single 3-wire bus or provides an optional BUSY indicator. It is compatible with 1.8 V, 2.5 V, 3 V, or 5 V logic using the separate supply VIO.The AD7685 is housed in a 10-lead MSOP or a 10-lead QFN (LFCSP) with operation specified from 40C to +85C.AD7685主要特性:16-bit resolution with no missing codesThroughput: 250 kSPSINL: 0.6 LSB typical, 2 LSB maximum (0.003% of FSR)SINAD: 93.5 dB 20 kHzTHD: 110 dB 20 kHzPseudo differential analog input range0 V to VREF with VREF up to VDDNo pipeline delaySingle-supply operation 2.3 V to 5.5 V with1.8 V to 5 V logic interfaceSerial interface SPI-/QSPI-/MICROWIRE-/DSP-compatibleDaisy-chain multiple ADCs, BUSY indicatorPower dissipation1.4 W 2.5 V/100 SPS1.35 mW 2.5 V/100 kSPS, 4 mW 5 V/100 kSPSStandby current: 1 nA10-lead package: MSOP (MSOP-8 size) and3 mm 3 mm QFN (LFCSP) (SOT-23 size)Pin-for-pin-compatible with 10-lead MSOP/QFN PulSAR ADCsAD7685應用:Battery-powered equipmentMedical instrumentsMobile communicationsPersonal digital assistants (PDAs)Data acquisitionInstrumentationProcess controls圖1.ADC簡化電路圖圖2.AD7685 多個電源應用電源框圖圖3.AD7685真正16位隔離同時取樣采集系統(tǒng)框圖EVAL-AD76XXCB 8/10-Pin評估板The EVAL-AD76XXCB 8/10-Pin is an evaluation board for the AD768x/AD769x/AD794x/AD798x 8 and 10-pin PulSAR high resolution ADCs (see the Ordering Guide at the end of this document for a product list).The evaluation board is designed to demonstrate the ADCs performance and to provide an easy to understand interface for a variety of system applications.The evaluation board is ideal for use with either Analog Devices EVAL-CONTROL BRD2/BRD3 (EVAL-CONTROL BRDx), DSP based controller board, to run the Analog devices evaluation software and to develop a specific application using LabVIEW, or as a stand-alone evaluation board.The EVAL-CONTROL BRDx is sold separately from the evaluation board, is required to run the evaluation software, is not required in stand alone mode and can be reused with many Analog Devices ADCs.EVAL-AD76XXCB 8/10-Pin評估板主要特性:Versatile analog signal conditioning circuitryOn-board reference, crystal oscillator and buffers16-bit Parallel Buffered OutputsIdeal for DSP and data acquisition card interfacesAnalog and digital prototyping area for breadbording thetarget systemStand-alone operation or Eval control board compatibilityPC software for control and data analysisLabVIEW1 driver to develop custom application圖4. EVAL-AD76XXCB 8/10-Pin評估板電路圖:模擬部分圖5. EVAL-AD76XXCB 8/10-Pin評估板電路圖:數(shù)字部分圖6. EVAL-AD76XXCB 8/10-Pin評估板電路圖:電源部分圖7. EVAL-AD76XXCB 8/10-Pin評估板電路圖:選擇部分完整的過程控制用高速高CMRR精密模擬前端Complete High Speed, High CMRR Precision Analog Front End for Process ControlSignal levels in industrial process control systems generally fall into one of the following categories: single-ended current (4 mA-to-20 mA), single-ended, differential voltage (0 V to 5V, 0 V to 10 V, 5 V, 10 V), or small signal inputs from sensors such as thermocouples or load cells. Large common-mode voltage swings are also typical, especially for small signal differential inputs; therefore good common-mode rejection is an important specification in the analog signal processing system.The analog front-end circuit shown in Figure 1 is optimized for high precision and high common-mode rejection ratio (CMRR) when processing these types of industrial-level signals.圖8.高性能過程控制的模