AD421 Analog Devices, AD421 Datasheet
AD421
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AD421 Summary of contents
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... RESET COM PRODUCT HIGHLIGHTS 1. The AD421 is a single chip, high performance, low cost solution for generating signals for smart industrial control transmitters. 2. The AD421’s regulated supply voltage can be used to power any additional circuits in the transmitter. The regulated output value is pin selectable as either + The AD421’ ...
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... V, the transfer function shifts negative by typically 0.25 kΩ resistor connected between COM and LOOPRTN will approximately compensate for the V CC supply sensitivity in moving from skewing the gain of the AD421. 5 100 kΩ resistor only required if this reference is being used in application circuits. ...
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... Figure 2. Serial Interface Timing Diagram –3– AD421 unless otherwise noted) Conditions/Comments Data Clock Period Data Clock Low Time Data Clock High Time Data Stable Width Data Setup Time Data Hold Time Latch Delay Time ...
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... LATCH CLOCK DATA LOOP RTN ORDERING GUIDE Temperature Model Range AD421BN –40°C to +85°C AD421BR –40°C to +85°C AD421BRRL –40°C to +85°C EVAL-AD421EB Evaluation Board *N = Plastic DIP SOIC. –4– DIP and SOIC BOOST 3 14 ...
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... If more than 16 clock cycles are provided between LATCH pulses, the data is assumed to be alarm current data (see Digital Interface section). 7 DATA Data Input. The data to be loaded to the AD421 input shift register is applied to this input. Data should be valid on the rising edge of the CLOCK input. 8 LOOP RTN Loop Return Output ...
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... NPN transistor which acts as a current amplifier to set the current flowing through the LOOP RTN pin. Figure 4 shows the current amplifier section of the AD421 kΩ resistor connected between the DAC output and loop return is used as a sampling resistor to determine current. The base drive to the NPN transistor servos the voltage across the 40 Ω ...
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... V reference voltage which can supply external current. The REF OUT2 pin provides LOOP RTN a +2.5 V reference voltage which is also capable of providing 0 external current. To use the AD421 with its own reference, simply connect the REF OUT2 pin to the REF IN pin. As the DAC CC pin of the device ...
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... Table III. Figure 7 shows a timing diagram for loading an alarm cur- rent of 3. the AD421 with an 8-bit microcontroller using three 8-bit writes. The output current values shown assume a REF IN voltage of +2 ...
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... V devices in the system. If the AD421 is operated with V the transfer function shifts negative. To correct for this a 16 kΩ resistor connected between COM and LOOPRTN will approxi- mately compensate for the adjusting the gain of the AD421 EXTERNAL CC CIRCUITRY 2 ...
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... Figure 12. External NPN Transistor Reduces Power Load on FET Smart Transmitter The AD421 is intended for use smart trans- mitters. A smart transmitter is a system that incorporates a microprocessor system which is used for linearization and communication. Figure 13 shows a block diagram of a typical smart transmitter ...
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... HART protocol is an example of a smart intelligent transmitter. SENSORS Figure 16. Smart and Intelligent Transmitter Figure 17 shows an example of the AD421 in a HART transmit- ter application. Most of the circuit is as outlined in the smart transmitter as shown in Figure 14. The HART data transmitted on the loop is received by the transmitter using a bandpass filter and modem and the HART data is transferred to the micro- controller’ ...
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... Figure 17. AD421 in HART Transmitter Application Current Source Figure 18 shows an application circuit for the AD421 being used as a current source. The current programmed to the AD421 ( mA) will develop a voltage across R1. This same voltage due to negative feedback will be generated 10k 10k DATA ...
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... Battery Backup Figure 19 shows an application circuit for the AD421 where the micro and memory sections of the circuitry are protected against losing data if the loop is broken. The backup circuit switches from V to battery voltage without a glitch when V CC lost. The IRFF9113 acts as a current source during normal operation and provides a constant charging current to the supercap or Nicad ...
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... AD421 0.210 (5.33) 0.160 (4.06) 0.115 (2.93) 0.0118 (0.30) 0.0040 (0.10) OUTLINE DIMENSIONS Dimensions shown in inches and (mm). 16-Lead Plastic DIP (N-16) 0.840 (21.34) 0.745 (18.92 0.280 (7.11) 0.240 (6.10 0.325 (8.26) 0.300 (7.62) PIN 1 0.060 (1.52) 0.015 (0.38) MAX 0.130 (3.30) MIN 0.100 0.070 (1.77) SEATING 0.022 (0.558) PLANE (2.54) 0.045 (1.15) 0.014 (0.356) BSC 16-Lead (Wide Body) Small Outline Package (R-16) 0 ...