V/I converter, 4 ... 20 mA, 300 kHz, SOIC-16

4-20 mA measuring transducer

Description
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 to buffer the output of a current mode DAC. Pre-calibrated input voltages from 0 V to 2 V and 0 V to 10 V are selected by simple pin-banding; other voltages can 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 be extended below the voltage commonly used in dual-supply operation. An alarm warns of an open 4-20 mA loop or output stage non-compliance. Active laser trimming of the AD694's thin film resistors results in a high degree of accuracy without the need for additional adjustments and calibrations. An external pass transistor can be used with the AD694 to relieve power dissipation, extending the temperature range of operation. The AD694 is the ideal device for systems that require noise-immune 4-20 mA signal transmission to operate valves, actuators and other control devices as well as to transmit process parameters such as pressure, temperature or flow. It is recommended as a replacement for discrete designs in a variety of industrial process control, factory automation and system monitoring applications. The AD694 is available in hermetically sealed, 16-pin CERDIP and plastic SOIC, specified over the industrial temperature range of -40°C to +85°C, and in a 16-pin plastic DIP, specified over the temperature range of 0°C to +70°C.

PRODUCT HIGHLIGHTS
1. the AD694 is a full voltage input to 4-20 mA output current transmitter.
2. pin-programmable input ranges are pre-calibrated to 0 V to 2 V and 0 V to 10 V.
3. the input amplifier can be used for buffering and scaling the input voltage, or as an output amplifier for current DACs.
4. the conformity of the output voltage extends to 2 V of the positive supply and below the common. When operating with a 5 V supply, the output voltage compliance extends to 30 V below common.
5. the AD694 can supply directly to 8-, 10- and 12-bit single CMOS and bipolar DACs.
6. 4 mA zero current can be turned on and off with a TTL control pin, allowing 0-20 mA operation.
7. an open collector alarm warns of loop failure due to open wires or non-compliance with the output stage.
8. a monitored output is provided to drive an external pass transistor. The function turns off power dissipation to extend the operating temperature range and minimize self-heating error.

Parameter
- 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
- Operation with single or dual supply
- Wide power supply range: 4.5 V to 36 V
- Wide output compatibility
- Input buffer amplifier
- Open loop alarm
- Optional external pass transistor to reduce self-heating errors
- 0.002% type non-linearity