ADI AD8275电平转换16位ADC驱动方案

ADI 公司的AD8275是增益为0.2的电平转换16位ADC驱动器,能把+/-10V的信号转换成+ 4V的信号,它能和两种信号接口,解决了工业和测量中+/-10V信号必须要和4V或5V ADC接口的问题,从而简化了设计. AD8275能驱动16位SAR的ADC,VS=5V时的输入过载电压为+40V到-35V,到0.001%的设定时间为450ns,轨到轨输出,工作电压从3.3V到15V,CMRR为80dB,可广泛用在电平转换器,ADC驱动器,自动测试设备(ATE)和仪表放大器模块.本文介绍了AD8275的主要特性, 简化电路图和把±10 V转换成4.096 V的电路图, 驱动单端ADC电路图, 驱动差分ADC电路图以及数据采集系统中的电平转换电路图与AC耦合的电平转换器.

AD8275: G = 0.2, Level Translation, 16-Bit ADC Driver
The AD8275 is a G=0.2 difference amplifier that can be used to translate +/-10V signals to a +4V level. It solves the problem typically encountered in industrial and instrumentation where +/-10V signals must be interfaced to a single supply 4V or 5V ADC. The AD8275 interfaces the two signal levels, simplifying design.

The AD8275 has fast settle time and low distortion making it suitable for driving fast, successive approximation (SAR) ADCs. Its wide input voltage range and rail to rail outputs make it an easy to use building block. Single-supply operation reduces the power consumption of the amplifier and helps to protect the ADC from overdrive conditions.

Internal, matched, precision laser-trimmed resistors ensure low gain error, low gain drift of 1 ppm/°C (maximum), and high common-mode rejection of 80 dB. Low offset and low offset drift, combined with its fast settling time, make the AD8275 suitable for a variety of data acquisition applications where accurate and quick capture is required.

The AD8275 can be used as an analog front end, or it can follow buffers to level translate high voltages to a voltage range accepted by the ADC. In addition, the AD8275 can be configured for diff-erential outputs if used with a differential ADC. The AD8275 is available in a space-saving, 8-lead MSOP and is specified for performance over the −40°C to +85°C temperature range.

AD8275主要特性:
Translates ±10 V to +4 V
Drives 16-bit SAR ADCs
Small MSOP package
Input overvoltage: +40 V to −35 V (VS = 5 V)
Fast settling time: 450 ns to 0.001%
Rail-to-rail output
Wide supply operation: +3.3 V to +15 V
High CMRR: 80 dB
Low gain drift: 1 ppm/°C
Low offset drift: 2.5 μV/°C

AD8275应用:
Level Translator
ADC Driver
Automated test equipment
Instrumentation Amplifier Building Block



图1. AD8275简化电路图



图2.转换±10 V到4.096 V ADC满刻度



图3.AD8275基本连接图(共享基准电压)



图4.AD8275基本连接图(单独基准电压)



图5.AD8275驱动单端ADC电路图



图6.AD8275驱动差分ADC电路图



图7.增加运放缓冲器,提高输入阻抗



图8.数据采集系统中的电平转换



图9.AC耦合的电平转换器