基于AD5421设计的回路供电工业过程控制技术

本文介绍了AD5421主要特性, 功能方框图,和HART调制解调器连接框图以及应用框图.

ADI公司的AD5421是完整的16位4mA-20mA转换器,包括用来给自身和发送器中其它器件供电的稳压器,输出电压从1.8V到12V,漂移为5ppm/℃.器件还包括精密的1.25V和2.5V基准电压源. AD5421采用标准的HART FSK协议通信,串口速率高达20Mbps,主要应用在工业过程控制,4-20mA回路供电发送器以及智能发送器.
16-Bit, Serial Input, Loop-Powered, 4mA to 20mA DAC

The AD5421 is a complete, loop powered, digital to 4mA-to-20mA converter, designed to meet the needs of smart transmitter manufacturers in the Industrial Control industry.It provides a high precision, fully integrated, low cost solution in a compact TSSOP package.

The AD5421 includes a regulated voltage output that is used to power itself and other devices in the transmitter. This regulator provides a regulated 1.8V to 12V output voltage. The device also contains precision 1.25V and 2.5V references, The AD5421 thus eliminates the need for a discrete regulator and voltage reference.

The AD5421 can be used with standard HART FSK protocol communication circuitry without any degradation in specified performance. The high speed serial interface is capable of operating at 20 Mbps and allows for simple connection to commonly-used microprocessors and microcontrollers via a SPI compatible three-wire interface.

The AD5421 is guaranteed monotonic to 16-bits, offers 0.0015% integral nonlinearity, 0.03% offset error and 0.03 % gain error.

The AD5421 is available in a 28 lead TSSOP package and is specified over the extended industrial temperature range of –40℃ to +105℃.

AD5421主要特性:

16-Bit Resolution and Monotonicity

Pin selectable NAMUR Compliant Ranges

4mA to 20mA

3.8mA to 21mA

3.2mA to 24mA

NAMUR Compliant ALARM Currents

Downscale ALARM current = 3.2mA

Upscale ALARM Current = 22.8mA/24mA

0.05% maximum Total Unadjusted Error (TUE)

0.0015% maximum INL Error (15 Bits minimum)

5ppm/℃ typ Output Drift

350uA maximum Quiescent Current

Flexible SPI Compatible Serial Digital Interface

Schmitt Triggered Inputs

On-Chip Fault Alerts via FAULT pin or ALARM Current

Loss of SPI Interface Control

SPI Communication Error (Packet Error Check)

Programmed Loop Current out of Range

Insufficient Loop Voltage

Over Temperature

Automatic Readback of Fault Register on each write cycle

Slew Rate Control Function

Gain and Offset Adjust Registers

On-Chip Reference (10 ppm/℃ Max)

Selectable Regulated Voltage Output

Loop Voltage Range

5.5V to 52V

Temperature Range: -40℃ to +105℃

TSSOP Package

HART Compatible

AD5421应用:

Industrial Process Control

4-20mA Loop Powered Transmitter

Smart Transmitter

图1.AD5421功能方框图

图2.AD5421和HART调制解调器连接框图

图3.AD5421应用框图