Datasheet AD420 (Analog Devices)

Serial Input 16-Bit 4 mA–20 mA, 0 mA–20 mA DAC Data Sheet AD420 FEATURES FUNCTIONAL BLOCK DIAGRAM V 4 mA–20 mA, 0 mA–20 mA or 0 mA–24 mA CC current output VLL REFERENCE 16-bit resolution and monotonicity 4kΩ 40Ω REF OUT ±0.012% max integral nonlinearity BOOST AD420 ±0.05% max offset (trimmable) REF IN ±0.15% max total output error (trimmable) DATA OUT CLOCK Flexible serial digital interface (3.3 MBPS) I CLEAR OUT DATA I/P LATCH V On-Chip loop fault detection REGISTER OUT CLOCK 16-BIT SWITCHED DAC CURRENT 1.25kΩ On-chip 5 V reference (25 ppm/°C max) DATA IN SOURCES FAULT AND Asynchronous CLEAR function RANGE DETECT SELECT 1 FILTERING Maximum power supply range of 32 V RANGE SELECT 2 Output loop compliance of 0 V to VCC − 2.75 V
1 00 4-
24-Lead SOIC and PDIP packages OFFSET CAP 1 CAP 2 GND
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TRIM
00 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 −40°C to +85°C. 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, 0 V to 10 V, ±5 V, or ±10 V with the addition of a single external 2. The AD420 is specified with a power supply range from buffer amplifier. 12 V to 32 V. Output loop compliance is 0 V to VCC − 2.75 V. The 3.3 M Baud serial input logic design minimizes the cost of 3. The flexible serial input can be used in 3-wire mode galvanic isolation and allows for simple connection to commonly with SPI® or MICROWIRE® microcontrollers, or in used microprocessors. It can be used in 3-wire or asynchronous asynchronous mode, which minimizes the number of mode and a serial-out pin is provided to allow daisy chaining of control signals required. multiple DACs on the current loop side of the isolation barrier. 4. The serial data out pin can be used to daisy chain any The AD420 uses sigma-delta (Σ-Δ) DAC technology to achieve number of AD420s together in 3-wire mode. 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 DETECT pin signals when an open circuit occurs in the loop. 8. The offset of ±0.05% and total output error of ±0.15% can The on-chip voltage reference can be used to supply a precision be trimmed if desired, using two external potentiometers. +5 V to external components in addition to the AD420 or, if the
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Document Outline FEATURES FUNCTIONAL BLOCK DIAGRAM GENERAL DESCRIPTION PRODUCT HIGHLIGHTS TABLE OF CONTENTS REVISION HISTORY SPECIFICATIONS ABSOLUTE MAXIMUM RATINGS ESD CAUTION PIN CONFIGURATION AND FUNCTION DESCRIPTIONS TIMING REQUIREMENTS THREE-WIRE INTERFACE THREE-WIRE INTERFACE FAST EDGES ON DIGITAL INPUT ASYNCHRONOUS INTERFACE TERMINOLOGY THEORY OF OPERATION APPLICATIONS INFORMATION CURRENT OUTPUT DRIVING INDUCTIVE LOADS VOLTAGE-MODE OUTPUT OPTIONAL SPAN AND ZERO TRIM THREE-WIRE INTERFACE USING MULTIPLE DACS WITH FAULT DETECT ASYNCHRONOUS INTERFACE USING OPTOCOUPLERS MICROPROCESSOR INTERFACE AD420-TO-MC68HC11 (SPI BUS) INTERFACE AD420 TO MICROWIRE INTERFACE EXTERNAL BOOST FUNCTION AD420 PROTECTION TRANSIENT VOLTAGE PROTECTION BOARD LAYOUT AND GROUNDING POWER SUPPLIES AND DECOUPLING OUTLINE DIMENSIONS ORDERING GUIDE