AD7862同时采样双250kSPS的12位模数转换器

　　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 0–2.5 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.