自动切换转换通道的A/D转换器AD7938及其应用

AD7938是AD公司推出的新型12位高速8输入通道模数转换器，片内自带顺序管理器，能智能切换转换通道，通道接入方式可设定为8路单端、4路差分、4路或7路准差分等4种方式，支持字和字节模式的并行接口，内置2．5V参考电压源，模拟、数字电源分开供电且可不同，软件设定输入电压范围和输出数据格式，功耗很低并具待机、停机模式，使用非常灵活方便。本文介绍了其功能特性和使用方法，并介绍了其与EZ-USB AN2131QC接口，应用于基于USB接口的数据采集卡中的方法。

Application of Auto-switch Converted Channel ADC AD7938

AD7938 is a kind of 12 b,high speed,successive approximation (SAR) ADC,which is producted by Analog Device.This chip feature with a channel sequencer that allows a preprogrammed selection of channels to be converted sequentially,the part can operate with either single*ended,fully differential,or pseudodifferential analog inputs.The chip offers a parallel interface(word or byte mode),an accurate onchip 2.5 V reference,the analog digital power can be connected respectively and differently.The analog input range and output coding mode can be set by software.The 7938 achieves very low power dissipation, it can be used very flexibly and conveniently.This paper offers its features and ways of using.The connection diagram of AD7938 and EZUSB AN2131QC building a data acquisition card based on USB is also introduced.