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Data Sheet
16-Bit, Serial Input, Loop-Powered, 4 mA to 20 mA DAC AD5421
FEATURES
GENERAL DESCRIPTION
16-bit resolution and monotonicity Pin selectable NAMUR-compliant ranges
4 mA to 20 mA 3.8 mA to 21 mA 3.2 mA to 24 mA NAMUR-compliant alarm currents Downscale alarm current = 3.2 mA Upscale alarm current = 22.8 mA/24 mA Total unadjusted error (TUE): 0.05% maximum INL error: 0.0035% FSR maximum Output TC: 3 ppm/°C typical Quiescent current: 300 μA maximum Flexible SPI-compatible serial digital interface with Schmitt triggered inputs On-chip fault alerts via FAULT pin or alarm current Automatic readback of fault register on each write cycle Slew rate control function Gain and offset adjust registers On-chip reference TC: 4 ppm/°C maximum Selectable regulated voltage output Loop voltage range: 5.5 V to 52 V Temperature range: −40°C to +105°C TSSOP and LFCSP packages
APPLICATIONS
Industrial process control 4 mA to 20 mA loop-powered transmitters Smart transmitters HART network connectivity
The AD5421 is a complete, loop-powered, 4 mA to 20 mA digital-to-analog converter (DAC) designed to meet the needs of smart transmitter manufacturers in the industrial control industry. The DAC provides a high precision, fully integrated, low cost solution in compact TSSOP and LFCSP packages.
The AD5421 includes a regulated voltage output that is used to power itself and other devices in the transmitter. This regulator provides a regulated 1.8 V to 12 V output voltage. The AD5421 also contains 1.22 V and 2.5 V references, thus eliminating the need for a discrete regulator and voltage reference.
The AD5421 can be used with standard Highway Addressable Remote Transducer (HART®) FSK protocol communication circuitry without any degradation in specified performance. The high speed serial interface is capable of operating at 30 MHz and allows for simple connection to commonly used microprocessors and microcontrollers via a SPI-compatible, 3-wire interface.
The AD5421 is guaranteed monotonic to 16 bits. It provides 0.0015% integral nonlinearity, 0.0012% offset error, and 0.0006% gain error under typical conditions.
The AD5421 is available in a 28-lead TSSOP and a 32-lead LFCSP specified over the extended industrial temperature range of −40°C to +105°C.
COMPANION LOW POWER PRODUCTS
HART Modem: AD5700, AD5700-1 Microcontroller: ADuCM360
FUNCTIONAL BLOCK DIAGRAM
IODVDD DVDD
VLOOP REG_SEL0 REG_SEL1 REG_SEL2 REGOUT REGIN
FAULT
SYNC SCLK SDIN
SDO LDAC
RANGE0 RANGE1
ALARM_CURRENT_DIRECTION
RINT/REXT
INPUT REGISTER CONTROL
LOGIC GAIN/OFFSET ADJUSTMENT REGISTERS
LOOP VOLTAGE MONITOR
16
16-BIT
DAC
TEMPERATURE SENSOR VREF
RSET 24kΩ
VOLTAGE REGULATOR
DRIVE
11.5kΩ 52Ω
AD5421
COM LOOP–
09128-001
REFOUT2 REFOUT1
REFIN
Figure 1.
CIN REXT1 REXT2
Rev. I
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