原标题：ADI AD5780 18位精度低噪音±10 V DC电压源解决方案

　　ADI公司的AD5780是真正18位线性低噪音精密的±10 V DC电压源,工作电压双极电压高达33V,采用正基准输入电压从5V到VDD-2.5V,而负基准输入电压从VSS+2.5V到0V,输出噪音8 nV/√Hz,长期稳定性为0.025 LSB,增益误差±0.018 ppm/℃,输出电压设定时间2.5 μs, 施密特触发器数字接口35MHz,1.8V兼容数字接口,主要用在医疗仪器,测试测量,工业控制,数据采集系统,数字增益和失调调整,电源控制等.本文介绍了AD57801产品亮点和主要特性, 功能框图和典型工作电路图以及评估板EVAL-AD5780主要特性,电路图,材料清单和PCB布局图.

　　The AD57801 is a true 18-bit, unbuffered voltage output DAC that operates from a bipolar supply of up to 33 V. The AD5780 accepts a positive reference input range of 5 V to VDD − 2.5 V and a negative reference input range of VSS + 2.5 V to 0 V. Both reference inputs are buffered on chip and external buffers are not required. The AD5780 offers a relative accuracy specifica-tion of ±1 LSB maximum range, and operation is guaranteed monotonic with a ±1 LSB DNL maximum range specification.

　　The part uses a versatile 3-wire serial interface that operates at clock rates of up to 35 MHz and is compatible with standard SPI, QSPI™, MICROWIRE™, and DSP interface standards. The part incorporates a power-on reset circuit that ensures that the DAC output powers up to 0 V in a known output impedance state and remains in this state until a valid write to the device takes place. The part provides an output clamp feature that places the output in a defined load state.

　　AD57801产品亮点:

　　True 18-bit accuracy.

　　Wide power supply range of up to ±16.5 V.

　　−40℃ to +125℃ operating temperature range.

　　Low 8 nV/√Hz noise.

　　Low ±0.018 ppm/℃ gain error temperature coefficient

　　AD57801主要特性:

　　True 18-bit voltage output DAC, ±1 LSB INL

　　8 nV/√Hz output noise spectral density

　　0.025 LSB long-term linearity error stability

　　±0.018 ppm/°C gain error temperature coefficient

　　2.5 μs output voltage settling time

　　3.5 nV-sec midscale glitch impulse

　　Integrated precision reference buffers

　　Operating temperature range: −40℃ to +125℃

　　4 mm × 5 mm LFCSP package

　　Wide power supply range of up to ±16.5 V

　　35 MHz Schmitt triggered digital interface

　　1.8 V-compatible digital interface

　　AD57801应用:

　　Medical instrumentation

　　Test and measurement

　　Industrial control

　　Scientific and aerospace instrumentation

　　Data acquisition systems

　　Digital gain and offset adjustment

　　Power supply control

　　图1.AD57801功能框图

　　图2.AD57801典型工作电路图

　　AD57801评估板EVAL-AD5780

　　Evaluation Board for a 18-Bit Serial Input, Voltage Output DAC with Integrated Precision Reference Buffer Amplifiers

　　The EVAL-AD5780 is a full-featured evaluation board, designed to allow the user to easily evaluate all features of the AD5780 voltage output, 18-bit digital-to-analog converter (DAC). The AD5780 pins are accessible at on-board connectors for external connection. The board can be controlled by two means: via the on-board connector (J3), or via the system development platform connector (J4). The SDP board allows the evaluation board to be controlled through the USB port of a Windows® XP- (SP2 or later) or Vista-based (32-bit) PC using the AD5780 evaluation software.

　　评估板EVAL-AD5780主要特性:

　　Full-featured evaluation board for the AD5780

　　Link options

　　PC control in conjunction with Analog Devices, Inc., system development platform

　　PC software for control

　　图3.评估板EVAL-AD5780框图

　　图4.评估板EVAL-AD5780电路图:AD5780

　　图5.评估板EVAL-AD5780电路图:电压参考电路

　　图6.评估板EVAL-AD5780电路图:SDP板连接器

　　图7. 18位精度±10V电压源简化电路图

　　评估板EVAL-AD5780材料清单: