The AD7862 is a high speed, low power, dual 12-bit A/D converter that operates from a single +5 V supply. The part contains two 4 µs successive approximation ADCs, two track/ hold amplifiers, an internal +2.5 V reference and a high speed parallel interface. There are four analog inputs that are grouped into two channels (A & B) selected by the A0 input. Each channel has two inputs (VA1 & VA2 or VB1 & VB2) that can be sampled and converted simultaneously thus preserving the relative phase information of the signals on both analog inputs. The part accepts an analog input range of ±10 V (AD7862-10), ±2.5 V (AD7862-3) and 02.5 V (AD7862-2). Overvoltage protection on the analog inputs for the part allows the input voltage to go to ±17 V, ±7 V or +7 V, respectively, without causing damage.
A single conversion start signal (CONVST) places both track/ holds into hold simultaneously and initiates conversion on both inputs. The BUSY signal indicates the end of conversion, and at this time the conversion results for both channels are available to be read. The first read after a conversion accesses the result from VA1 or VB1, while the second read accesses the result from VA2 or VB2, depending on whether the multiplexer select A0 is low or high, respectively. Data is read from the part via a 12-bit parallel data bus with standard CS and RD signals.
In addition to the traditional dc accuracy specifications such as linearity, full-scale and offset errors, the part is also specified for dynamic performance parameters including harmonic distortion and signal-to-noise ratio.
The AD7862 is fabricated in Analog Devices' Linear Compatible CMOS (LC2MOS) process, a mixed technology process that combines precision bipolar circuits with low power CMOS logic. It is available in 28-lead SSOP, SOIC and DIP.
AD7862是一款高速、低功耗、双核12位模数转换器（ADC）,采用+5 V单电源供电。该器件内置两个4 微秒（µs）逐次逼近型ADC、两个采样保持放大器、一个+2.5 V内部基准电压源和一个高速并行接口。4个模拟输入组成两个通道（A和B）,通过A0输入选择通道。每个通道的两个输入（VA1与VA2或VB1与VB2）可同时进行采样和转换,从而保留这两个模拟输入上的信号相对相位信息。该器件可接受的模拟输入范围为±10 V （AD7862-10）、±2.5 V （AD7862-3）和0至2.5 V （AD7862-2）。模拟输入均具有过压保护,允许输入电压分别达到±17 V、±7 V或+7 V而不会造成损坏。
单一转换开始信号（CONVST）同时将两个采样保持放大器置于保持状态,并启动两个输入上的转换操作。BUSY信号表示转换结束,此时便可读取两个通道的转换结果。转换结束后的第一次读取操作访问VA1或VB1的结果,而第二次读取操作访问VA2或VB2的结果,具体取决于多路复用器选择A0是低电平还是高电平。该器件的读取数据通过具有标准CS和RD信号的12位并行数据总线进行。
除线性度、满量程和失调误差等传统直流精度规格外,该器件的动态性能参数也做了详细规定,包括谐波失真和信噪比。
AD7862采用ADI公司的线性兼容CMOS （LC2MOS）工艺制造,这是一种将精密的双极性电路与低功耗CMOS逻辑结合在一起的混合工艺技术。它提供28引脚SSOP、SOIC和DIP三种封装
