AD694 Analog Devices, AD694 Datasheet
AD694
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AD694 Summary of contents
Page 1
... Analog Devices. 4–20 mA Transmitter FUNCTIONAL BLOCK DIAGRAM PRODUCT HIGHLIGHTS 1. The AD694 is a complete voltage in to 4–20 mA out current transmitter. 2. Pin programmable input ranges are pre-calibrated and The input amplifier may be configured to buffer and scale the input voltage serve as an output amplifier for current output DACs ...
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... POWER REQUIREMENTS Specified Performance Operating Range REF FS REF Quiescent Current Off TEMPERATURE RANGE 5 Specified Performance AD694AQ/BQ/AR/BR –40 AD694JN Operating AD694AQ/BQ/AR/BR –55 AD694JN (@ + 250 and V = +24 V, unless otherwise noted AD694JN/AQ/AR Min ...
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... Reference Short Circuit to Common . . . . . . . . . . . . Indefinite Alarm Voltage, Pin + Adj, Pin On/Off, Pin Storage Temperature Range AD694Q . . . . . . . . . . . . . . . . . . . . . . . . . – +150 C AD694N – +125 C Lead Temperature, 10 sec Soldering . . . . . . . . . . . . . . +300 C Maximum Junction Temperature . . . . . . . . . . . . . . . . . +150 C Maximum Case Temperature Plastic Package (N, R) ...
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... Voltage Compliance vs. Temperature OUT FUNCTIONAL DESCRIPTION The operation of the AD694 can best be understood by dividing the circuit into three functional parts (see Figure 1). First, a single supply input amplifier buffers the high level, single-ended input signal. The buffer amplifier drives the second section, a voltage to current (V/I) converter, that makes sig- nal dependent current ...
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... Adj (Pin 6) allows the offset current to be adjusted to any cur- rent in the range 4.8 mA. Pin On/Off) can shut off the offset current completely lifted to 3 more, allowing operation of the AD694. In normal 4-20 mA operation, Pin 9 is connected to ground. VOLTAGE REFERENCE voltage reference is available for user applications, selectable by pin-strapping ...
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... NPN transistor is used, the capacitor and diodes should connect to the NPN emitter instead of Pin 11. 0-20 mA OPERATION A 0-20 mA output range is available with the AD694 by remov- ing the 4 mA offset current with the 4 mA On/Off pin. In nor- mal 4-20 mA operation 4 mA On/Off (Pin 9) is tied to ground, enabling the 4 mA offset current. Tying Pin potential greater turns off the 4 mA offset current ...
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... V + (24 V – (24 V – C/Watt and of 70 C/Watt, (from spec page 542 mW ( 104 through the use of air flow or heat sinks re the AD694 through the use of an external pass TOT AD694 20 mA ...
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... Figure 6. Optional 4 mA Zero Adjustment ADJUSTING SPAN FOR When the AD694 is configured with input full-scale the span maybe adjusted using the network shown in Figure 7. This scheme allows an approximately linear adjustment of the span above or below the nominal value. The span adjustment does not interact with the 4 mA offset ...
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... V. The first decreases the input span by programming a non- inverting gain into the buffer amplifier. For example, to achieve an input span of 0–5 V, the AD694 is set in its 10 V full-scale mode and the buffer amplifier is configured with a noninverting gain adding 2 resistors. Now signal at +Sig results full-scale signal at FB (Pin 1), the input to the V/I ...
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... The 10 V reference of the AD694 supplies reference input of the AD566. The buffer amplifier converts the full-scale current to +10 V utilizing the internal resistors in the DAC; therefore the AD694 is configured for full-scale input capaci- tor compensates for the 25 pF output capacitance of the DAC. An optional 100 ...
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... REV. A LOW COST SENSOR TRANSMITTER Sensor bridges typically output differential signals in the 100 mV full-scale range. With an AD694, a dual op amp, and S some resistors, an instrumentation amplifier front end can be added which easily handles these types of low level signals. The traditional 3 op amp instrumentation amplifier is built us- ing an AD708, dual op amp for the front end, and the AD694’ ...
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... AD694 The AD694 will now output a 4-20 mA output current for differential swing across V . The gain of the in amp front A end is adjusted so that the desired full-scale input signal at V results For example a sensor that has a 100 mV A full scale will require a gain the front end. The gain is ...