Overview
The AD694BQ, produced by Analog Devices Inc., is a monolithic current transmitter designed for high-level signal inputs to drive a standard 4–20 mA current loop. This component is ideal for systems requiring noise-immune signal transmission to control valves, actuators, and other control devices, as well as for transmitting process parameters such as pressure, temperature, or flow. It is recommended as a replacement for discrete designs in various applications including industrial process control, factory automation, and system monitoring.
Key Specifications
| Parameter | Min | Typ | Max | Unit |
|---|---|---|---|---|
| Input Voltage Range | -0.2 VS | -2.0 V | -2.5 V | V |
| Input Bias Current | 1.5 | 5 | 5 | nA |
| Offset Current | ±0.1 | ±1 | ±1 | nA |
| Offset Current Drift | ±1.0 | ±5.0 | ±5.0 | pA/°C |
| Input Impedance | 5 | 5 | 5 | MΩ |
| Operating Current Range | 0 | 23 | 23 | mA |
| Output Voltage Compliance | VS – 36 V | VS – 2 V | VS – 2 V | V |
| Output Impedance, 4–20 mA | 40.0 | 50.0 | 50.0 | MΩ |
| Current Limit (@ 2 × FS Overdrive) | 241 | 441 | 441 | mA |
| Slew Rate | 1.3 | 1.3 | 1.3 | mA/µs |
Key Features
- Complete voltage-to-current transmitter with pin-programmable input ranges (0 V to 2 V and 0 V to 10 V).
- The input amplifier can be configured to buffer and scale the input voltage or serve as an output amplifier for current output DACs.
- Output voltage compliance extends to within 2 V of the positive supply and below common, with up to 30 V below common when operated with a 5 V supply.
- Interfaces directly with 8-, 10-, and 12-bit single supply CMOS and bipolar DACs.
- The 4 mA zero current can be switched on and off with a TTL control pin, allowing 0–20 mA operation.
- An open collector alarm warns of loop failure due to open wires or noncompliance of the output stage.
- A monitored output is provided to drive an external pass transistor, off-loading power dissipation to extend the temperature range of operation and minimize self-heating error.
Applications
- Industrial process control: For transmitting process parameters such as pressure, temperature, or flow.
- Factory automation: To control valves, actuators, and other control devices.
- System monitoring: For noise-immune signal transmission in monitoring systems.
Q & A
- What is the primary function of the AD694BQ?
The AD694BQ is a monolithic current transmitter that converts high-level signal inputs into a standard 4–20 mA current loop.
- What are the available input voltage ranges for the AD694BQ?
The input voltage ranges are precalibrated at 0 V to 2 V and 0 V to 10 V.
- How can the 4 mA zero current be controlled?
The 4 mA zero current can be switched on and off with a TTL control pin, allowing 0–20 mA operation.
- What is the purpose of the monitored output in the AD694BQ?
The monitored output is provided to drive an external pass transistor, which helps in off-loading power dissipation to extend the temperature range of operation and minimize self-heating error.
- What types of DACs does the AD694BQ interface with?
The AD694BQ interfaces directly with 8-, 10-, and 12-bit single supply CMOS and bipolar DACs.
- What is the temperature range for the AD694BQ?
The AD694BQ is specified over the –40°C to +85°C industrial temperature range for CERDIP and SOIC packages, and 0°C to +70°C for plastic DIP packages.
- How does the AD694BQ handle loop failure?
An open collector alarm warns of loop failure due to open wires or noncompliance of the output stage.
- What is the output voltage compliance of the AD694BQ?
The output voltage compliance extends to within 2 V of the positive supply and below common, with up to 30 V below common when operated with a 5 V supply.
- Can the AD694BQ be used with different types of packages?
Yes, the AD694BQ is available in hermetically sealed 16-pin CERDIP, plastic SOIC, and plastic DIP packages.
- What is the slew rate of the AD694BQ?
The slew rate of the AD694BQ is 1.3 mA/µs.
