Serial Input 16-Bit 4 mA20 mA, 0 mA20 mA DAC Data Sheet AD420 FEATURES FUNCTIONAL BLOCK DIAGRAM V CC 4 mA20 mA, 0 mA20 mA or 0 mA24 mA current output V REFERENCE LL 16-bit resolution and monotonicity 4k 40 REF OUT BOOST 0.012% max integral nonlinearity AD420 0.05% max offset (trimmable) REF IN 0.15% max total output error (trimmable) CLOCK DATA OUT I CLEAR OUT Flexible serial digital interface (3.3 MBPS) DATA I/P LATCH V REGISTER OUT 16-BIT SWITCHED On-Chip loop fault detection CLOCK DAC CURRENT 1.25k DATA IN On-chip 5 V reference (25 ppm/C max) SOURCES FAULT RANGE AND Asynchronous CLEAR function DETECT SELECT 1 FILTERING RANGE Maximum power supply range of 32 V SELECT 2 Output loop compliance of 0 V to V 2.75 V CC OFFSET CAP 1 CAP 2 GND 24-Lead SOIC and PDIP packages TRIM Figure 1. GENERAL DESCRIPTION The AD420 is a complete digital to current loop output user desires temperature stability exceeding 25 ppm/C, an converter, designed to meet the needs of the industrial control external precision reference such as the AD586 can be used as market. It provides a high precision, fully integrated, low cost the reference. The AD420 is available in a 24-lead SOIC and single-chip solution for generating current loop signals in a PDIP over the industrial temperature range of 40C to +85C. compact 24-lead SOIC or PDIP package. PRODUCT HIGHLIGHTS The output current range can be programmed to 4 mA to 1. The AD420 is a single chip solution for generating 4 mA to 20 mA, 0 mA to 20 mA or to an overrange function of 0 mA to 20 mA or 0 mA to 20 mA signals at the controller end of 24 mA. The AD420 can alternatively provide a voltage output the current loop. from a separate pin that can be configured to provide 0 V to 5 V, 2. The AD420 is specified with a power supply range from 0 V to 10 V, 5 V, or 10 V with the addition of a single external 12 V to 32 V. Output loop compliance is 0 V to V 2.75 V. CC buffer amplifier. 3. The flexible serial input can be used in 3-wire mode The 3.3 M Baud serial input logic design minimizes the cost of with SPI or MICROWIRE microcontrollers, or in galvanic isolation and allows for simple connection to commonly asynchronous mode, which minimizes the number of used microprocessors. It can be used in 3-wire or asynchronous control signals required. mode and a serial-out pin is provided to allow daisy chaining of multiple DACs on the current loop side of the isolation barrier. 4. The serial data out pin can be used to daisy chain any number of AD420s together in 3-wire mode. The AD420 uses sigma-delta (-) DAC technology to achieve 16-bit monotonicity at very low cost. Full-scale settling to 0.1% 5. At power-up, the AD420 initializes its output to the low occurs within 3 ms. The only external components that are end of the selected range. required (in addition to normal transient protection circuitry) 6. The AD420 has an asynchronous CLEAR pin, which sends are two low cost capacitors which are used in the DAC out- the output to the low end of the selected range (0 mA, 4 mA, put filter. or 0 V). If the AD420 is used at extreme temperatures and supply 7. The AD420 BOOST pin accommodates an external voltages, an external output transistor can be used to minimize transistor to off-load power dissipation from the chip. power dissipation on the chip via the BOOST pin. The FAULT 8. The offset of 0.05% and total output error of 0.15% can DETECT pin signals when an open circuit occurs in the loop. be trimmed if desired, using two external potentiometers. The on-chip voltage reference can be used to supply a precision +5 V to external components in addition to the AD420 or, if the Rev. 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Technical Support www.analog.com Trademarks and registered trademarks are the property of their respective owners. 00494-001AD420 Data Sheet TABLE OF CONTENTS Features .............................................................................................. 1 Driving Inductive Loads ............................................................ 10 Functional Block Diagram .............................................................. 1 Voltage-Mode Output ................................................................ 10 General Description ......................................................................... 1 Optional Span and Zero Trim .................................................. 10 Product Highlights ........................................................................... 1 Three-Wire Interface ................................................................. 11 Revision History ............................................................................... 2 Using Multiple DACS with Fault Detect ................................. 11 Specifications ..................................................................................... 3 Asynchronous Interface Using Optocouplers ........................ 11 Absolute Maximum Ratings ............................................................ 5 Microprocessor Interface............................................................... 12 ESD Caution .................................................................................. 5 AD420-To-MC68HC11 (SPI Bus) Interface ........................... 12 Pin Configuration and Function Descriptions ............................. 6 AD420 to Microwire Interface ................................................. 12 Timing Requirements ...................................................................... 7 External Boost Function............................................................ 13 Three-Wire Interface ................................................................... 7 AD420 Protection ........................................................................... 14 Three-Wire Interface Fast Edges on Digital Input ................... 7 Transient Voltage Protection .................................................... 14 Asynchronous Interface ............................................................... 7 Board Layout And Grounding ................................................. 14 Terminology ...................................................................................... 8 Power Supplies and Decoupling ............................................... 14 Theory of Operation ........................................................................ 9 Outline Dimensions ....................................................................... 15 Applications Information .............................................................. 10 Ordering Guide .......................................................................... 15 Current Output ........................................................................... 10 REVISION HISTORY 3/15Rev. H to Rev. I Changes to Three-Wire Interface Fast Edges on Digital Input Section ................................................................................................ 7 1/11Rev. G to Rev. H Changes to Figure 13 ...................................................................... 13 Changes to Ordering Guide .......................................................... 15 11/09Rev. F to Rev. G Updated Format .................................................................. Universal Changes to Table 2 ............................................................................ 5 Updated Outline Dimensions ....................................................... 15 Changes to Ordering Guide .......................................................... 15 9/99Rev. E to Rev. F Rev. I Page 2 of 16