原标题：Linear LTC2373-18 18位8路SAR ADC解决方案

　　Linear公司的LTC2373-18是18位取样频率1Msps的8路SAR低噪音高速模数转换器(ADC),SNR为100dB,工作电压单源5V,具有高度可配置低串扰8路输入复接器,支持全差分,假差分单极和假差分双极信号输入,典型功耗40mW,主要用在可编逻辑控制器(PLC),工业过程控制,高速数据采集,手持仪表和自动测试设备(ATE).本文介绍了LTC2373-18主要特性,框图,几种应用电路,以及演示板DC2071A主要特性,电路图,材料清单和PCB元件布局图.

　　The LTCR2373-18 is a low noise, high speed, 8-channel18-bit successive approximation register (SAR) ADC. Operatingfrom a single 5V supply, the LTC2373-18 has a highlyconfigurable, low crosstalk 8-channel input multiplexer,supporting fully differential, pseudo-differential unipolar and pseudo-differential bipolar analog input ranges. TheLTC2373-18 achieves ±2.75LSB INL (maximum) in allinput ranges, no missing codes at 18-bits and 100dB (fullydifferential)/ 95dB (pseudo-differential) SNR (typical).

　　The LTC2373-18 has an onboard low drift (20ppm/°C max)2.048V temperature-compensated reference and a singleshotcapable reference buffer. The LTC2373-18 also has ahigh speed SPI-compatible serial interface that supports1.8V, 2.5V, 3.3V and 5V logic through which a sequencerwith a depth of 16 may be programmed. An internal oscillatorsets the conversion time, easing external timingconsiderations. The LTC2373-18 dissipates only 40mWand automatically naps between conversions, leading toreduced power dissipation that scales with the samplingrate. A sleep mode is also provided to reduce the powerconsumption of the LTC2373-18 to 300μW for furtherpower savings during inactive periods.

　　LTC2373-18主要特性:

　　1Msps Throughput Rate

　　18-Bit Resolution with No Missing Codes

　　8-Channel Multiplexer with Selectable Input Range

　　Fully Differential (±4.096V)

　　Pseudo-Differential Unipolar (0V to 4.096V)

　　Pseudo-Differential Bipolar (±2.048V)

　　INL: ±2.75LSB (Maximum)

　　SNR: 100dB (Fully Differential)/95dB (Pseudo-Differential) (Typical) at fIN = 1kHz

　　THD: –110dB (Typical) at fIN = 1kHz

　　Programmable Sequencer

　　Selectable Digital Gain Compression

　　Single 5V Supply with 1.8V to 5V I/O Voltages

　　SPI-Compatible Serial I/O

　　Onboard 2.048V Reference and Reference Buffer

　　No Pipeline Delay, No Cycle Latency

　　Power Dissipation 40mW (Typical)

　　Guaranteed Operation to 125°C

　　32-Lead 5mm × 5mm QFN Package

　　LTC2373-18应用:

　　Programmable Logic Controllers

　　Industrial Process Control

　　High Speed Data Acquisition

　　Portable or Compact Instrumentation

　　ATE

　　图1.LTC2373-18框图

　　图2.LTC2373-18典型应用电路图

　　图3.LTC2373-18输入信件链

　　图4.LTC2373-18和LTC6362应用框图

　　演示板DC2071A

　　Demonstration circuit 2071A features the LTC®2373 family.The LTC2374/LTC2373/LTC2372 are low noise, highspeed, 8-channel, 16/18-bit successive approximationregister (SAR) ADCs. The following text refers to theLTC2373-18 but applies to all parts in the family, the onlydifferences being the number of bits and the maximumsample rate. Operating from a single 5V supply, the LTC2373-18 has a highly configurable, low crosstalk,8-channel input multiplexer, supporting fully differential,pseudo-differential unipolar and pseudo-differential bipolaranalog input ranges.

　　The DC2071 demonstrates the DC and AC performance ofthe LTC2373-18 in conjunction with the DC590 and DC890data collection boards. Use the DC590 to demonstrate DCperformance such as peak-to-peak noise and DC linearity.

　　Use the DC890 if precise sampling rates are required or todemonstrate AC performance such as SNR, THD, SINADand SFDR. The demonstration circuit 2071 is intended todemonstrate recommended grounding, component placementand selection, routing and bypassing for this ADC.

　　Several suggested driver circuits for the analog inputswill be presented.

　　图5.演示板DC2071A外形图

　　演示板DC2071A材料清单: