16-Bit, Serial Input, Loop-Powered, 4 mA to 20 mA DAC Data Sheet AD5421 FEATURES GENERAL DESCRIPTION 16-bit resolution and monotonicity The AD5421 is a complete, loop-powered, 4 mA to 20 mA Pin selectable NAMUR-compliant ranges digital-to-analog converter (DAC) designed to meet the needs 4 mA to 20 mA of smart transmitter manufacturers in the industrial control 3.8 mA to 21 mA industry. The DAC provides a high precision, fully integrated, 3.2 mA to 24 mA low cost solution in compact TSSOP and LFCSP packages. NAMUR-compliant alarm currents The AD5421 includes a regulated voltage output that is used to Downscale alarm current = 3.2 mA power itself and other devices in the transmitter. This regulator Upscale alarm current = 22.8 mA/24 mA provides a regulated 1.8 V to 12 V output voltage. The AD5421 Total unadjusted error (TUE): 0.05% maximum also contains 1.22 V and 2.5 V references, thus eliminating the INL error: 0.0035% FSR maximum need for a discrete regulator and voltage reference. Output TC: 3 ppm/C typical The AD5421 can be used with standard Highway Addressable Quiescent current: 300 A maximum Remote Transducer (HART) FSK protocol communication Flexible SPI-compatible serial digital interface circuitry without any degradation in specified performance. The with Schmitt triggered inputs high speed serial interface is capable of operating at 30 MHz and On-chip fault alerts via FAULT pin or alarm current allows for simple connection to commonly used microprocessors Automatic readback of fault register on each write cycle and microcontrollers via a SPI-compatible, 3-wire interface. Slew rate control function Gain and offset adjust registers The AD5421 is guaranteed monotonic to 16 bits. It provides On-chip reference TC: 4 ppm/C maximum 0.0015% integral nonlinearity, 0.0012% offset error, and Selectable regulated voltage output 0.0006% gain error under typical conditions. Loop voltage range: 5.5 V to 52 V The AD5421 is available in a 28-lead TSSOP and a 32-lead LFCSP Temperature range: 40C to +105C specified over the extended industrial temperature range of TSSOP and LFCSP packages 40C to +105C. APPLICATIONS COMPANION LOW POWER PRODUCTS Industrial process control HART Modem: AD5700, AD5700-1 4 mA to 20 mA loop-powered transmitters Microcontroller: ADuCM360 Smart transmitters HART network connectivity FUNCTIONAL BLOCK DIAGRAM IODV DV V REG SEL0 REG SEL1 REG SEL2 REG REG DD DD LOOP OUT IN LOOP VOLTAGE FAULT DRIVE VOLTAGE REGULATOR MONITOR SYNC INPUT R SET REGISTER SCLK 24k CONTROL SDIN 16 LOGIC 16-BIT SDO DAC GAIN/OFFSET ADJUSTMENT LDAC REGISTERS COM RANGE0 TEMPERATURE RANGE1 11.5k 52 SENSOR LOOP ALARM CURRENT DIRECTION VREF AD5421 R /R INT EXT REFOUT2 REFOUT1 REFIN C R R IN EXT1 EXT2 Figure 1. Rev. I Document Feedback Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. rights of third parties that may result from its use. Specifications subject to change without notice. No Tel: 781.329.4700 20112018 Analog Devices, Inc. All rights reserved. license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Trademarks and registered trademarks are the property of their respective owners. Technical Support www.analog.com 09128-001AD5421 Data Sheet TABLE OF CONTENTS Features .............................................................................................. 1 On-Chip ADC ............................................................................ 23 Applications ....................................................................................... 1 Voltage Regulator ....................................................................... 23 General Description ......................................................................... 1 Loop Current Slew Rate Control .............................................. 23 Companion Low Power Products .................................................. 1 Power-On Default ...................................................................... 24 Functional Block Diagram .............................................................. 1 HART Communications ........................................................... 24 Revision History ............................................................................... 3 Serial Interface ................................................................................ 26 Specifications ..................................................................................... 4 Input Shift Register .................................................................... 26 AC Performance Characteristics ................................................ 9 Register Readback ...................................................................... 26 Timing Characteristics ................................................................ 9 DAC Register .............................................................................. 27 Absolute Maximum Ratings .......................................................... 11 Control Register ......................................................................... 28 Thermal Resistance .................................................................... 11 Fault Register .............................................................................. 29 ESD Caution ................................................................................ 11 Offset Adjust Register ................................................................ 30 Pin Configurations and Function Descriptions ......................... 12 Gain Adjust Register .................................................................. 30 Typical Performance Characteristics ........................................... 14 Applications Information .............................................................. 32 Terminology .................................................................................... 20 Determining the Expected Total Error ................................... 32 Theory of Operation ...................................................................... 21 Thermal and Supply Considerations ....................................... 34 Fault Alerts .................................................................................. 21 Outline Dimensions ....................................................................... 35 External Current Setting Resistor ............................................ 22 Ordering Guide .......................................................................... 36 Loop Current Range Selection .................................................. 22 Connection to Loop Power Supply .......................................... 22 Rev. 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