Overview
The AD694BRZ, produced by Analog Devices Inc., is a monolithic current transmitter designed for noise-immune 4–20 mA signal transmission. It is an ideal building block for systems that require the control of valves, actuators, and other devices commonly used in industrial process control, factory automation, and system monitoring. The AD694BRZ accepts high-level signal inputs and drives a standard 4–20 mA current loop, making it suitable for transmitting process parameters such as pressure, temperature, or flow.
Key Specifications
| Parameter | Min | Typ | Max | Unit |
|---|---|---|---|---|
| Input Voltage Range | -0.2 VS | - | -2.5 V | V |
| Input Bias Current | 1.5 | 51 | 51 | nA |
| Offset Current | ±0.1 | ±11 | ±11 | nA |
| Offset Current Drift | ±1.0 | ±5.0 | ±5.0 | pA/°C |
| Input Impedance | 5 | - | - | MΩ |
| Operating Current Range | 0 | - | 23 | mA |
| Output Voltage Compliance | VS – 36 V | - | VS – 2 V | V |
| Output Impedance (4–20 mA) | 40.0 | 50.0 | 50.0 | MΩ |
| Current Limit (@ 2 × FS Overdrive) | 241 | - | 441 | mA |
| Slew Rate | 1.3 | - | - | mA/µs |
| Operating Temperature | -40°C | - | +85°C | °C |
Key Features
- Precalibrated input ranges: 0 V to 2 V and 0 V to 10 V, selectable by simple pin strapping
- Programmable to other input spans using external resistors
- Wide power supply range: 4.5 V to 36 V
- Wide output compliance: extends to within 2 V of the positive supply and below common in dual supply operation
- Input buffer amplifier that can scale the input signal or buffer the output from a current mode DAC
- Open-loop alarm for loop failure or noncompliance of the output stage
- Optional external pass transistor to reduce self-heating errors and extend the temperature range of operation
- 0–20 mA operation capability by shutting off the 4 mA offset current
- High accuracy due to active laser trimming of thin film resistors
Applications
- Industrial process control: transmission of process parameters such as pressure, temperature, or flow
- Factory automation: control of valves, actuators, and other control devices
- System monitoring: noise-immune signal transmission for reliable system monitoring
Q & A
- What is the primary function of the AD694BRZ?
The AD694BRZ is a monolithic current transmitter designed to convert high-level signal inputs into a 4–20 mA current loop for controlling valves, actuators, and other devices in industrial process control and factory automation.
- What are the precalibrated input ranges of the AD694BRZ?
The precalibrated input ranges are 0 V to 2 V and 0 V to 10 V, selectable by simple pin strapping.
- What is the operating temperature range of the AD694BRZ?
The operating temperature range is –40°C to +85°C for the industrial temperature range and 0°C to +70°C for the commercial temperature range.
- Can the AD694BRZ operate with different power supply voltages?
Yes, the AD694BRZ has a wide power supply range of 4.5 V to 36 V.
- What is the purpose of the open-loop alarm in the AD694BRZ?
The open-loop alarm warns of loop failure due to open wires or noncompliance of the output stage.
- How can the AD694BRZ be configured for 0–20 mA operation?
The 4 mA offset current can be shut off completely by lifting Pin 9 to 3.0 V or more, allowing 0 to 20 mA operation.
- Can the AD694BRZ be used with an external pass transistor?
Yes, an external pass transistor can be used to reduce self-heating errors and extend the temperature range of operation.
- What is the significance of the input buffer amplifier in the AD694BRZ?
The input buffer amplifier can be used to scale the input signal or buffer the output from a current mode DAC.
- How accurate is the AD694BRZ in terms of current transmission?
The AD694BRZ achieves high accuracy due to active laser trimming of its thin film resistors, resulting in a nonlinearity of 0.002% typical.
- What are some common applications of the AD694BRZ?
Common applications include industrial process control, factory automation, and system monitoring for transmitting process parameters such as pressure, temperature, or flow.
