AD694 IC – 4-20mA Monolithic Current Transmitter IC

The AD694 is a monolithic current transmitter that accepts high level signal inputs to drive a standard 4–20 mA current loop for the control of valves, actuators, and other devices commonly used in process control. The input signal is buffered by an input amplifier that can be used to scale the input signal or buffer the output from a current mode DAC. Pre-calibrated input spans of 0 V to 2 V and 0 V to 10 V are selected by simple pin strapping; other spans may be programmed with external resistors. The output stage compliance extends to within 2 V of VS and its special design allows the output voltage to extend below common in dual supply operation. An alarm warns of an open 4–20 mA loop or noncompliance of the output stage. Active laser trimming of the AD694’s thin film resistors results in high levels of accuracy without the need for additional adjustments and calibration. An external pass transistor may be used with the AD694 to off-load power dissipation, extending the temperature range of operation. The AD694 is the ideal building block for systems requiring noise immune 4–20 mA signal transmission to operate valves, actuators, and other control devices, as well as for the transmission of process parameters such as pressure, temperature, or flow. It is recommended as a replacement for discrete designs in a variety of applications in industrial process control, factory automation, and system monitoring. The AD694 is available in hermetically sealed, 16-pin CERDIP and plastic SOIC, specified over the –40°C to +85°C industrial temperature range, and in a 16-pin plastic DIP, specified over the 0°C to +70°C temperature range. The AD654 is a monolithic V/F converter consisting of an input amplifier, a precision oscillator system, and a high current output stage. A single RC network is all that is required to set up any full scale (FS) frequency up to 500 kHz and any FS input voltage up to ± 30 V. Linearity error is only 0.03% for a 250 kHz FS, and operation is guaranteed over an 80 dB dynamic range.

The overall temperature coefficient (excluding the effects of external components) is typically ±50 ppm/°C. The AD654 operates from a single supply of 5 V to 36 V and consumes only 2.0 mA quiescent current. The low drift (4 µV/°C typ) input amplifier allows operation directly from small signals such as thermocouples or strain gauges while offering a high (250 MΩ) input resistance. Unlike most V/F converters, the AD654 provides a square-wave output, and can drive up to 12 TTL loads, optocouplers, long cables, or similar loads.

Features:-

• 4–20 mA, 0–20 mA Output Ranges

• Pre-calibrated Input Ranges:

0 V to 2 V, 0 V to 10 V

• Precision Voltage Reference

• Programmable to 2.000 V or 10.000 V

• Single or Dual Supply Operation

• Wide Power Supply Range: 4.5 V to 36 V

• Wide Output Compliance

• Input Buffer Amplifier

• Open-Loop Alarm

• Optional External Pass Transistor to Reduce

Self-Heating Errors

0.002% Typ Nonlinearity

Specification:-

* product image for illustration purposes only. actual product may vary.