Overview
The AD693AQ, produced by Analog Devices Inc., is a monolithic signal conditioning circuit designed to accept low-level inputs from various transducers and control a standard 4-20 mA, two-wire current loop. This device is particularly useful for transmitting signals from RTDs, bridges, and pressure transducers. It features an on-chip voltage reference and an auxiliary amplifier, providing up to 3.5 mA of excitation current in loop-powered mode. The AD693AQ is known for its high accuracy, achieved through active laser trimming of its thin-film resistors, and is suitable for applications in process control, factory automation, and system monitoring.
Key Specifications
| Parameter | Min | Typ | Max | Units |
|---|---|---|---|---|
| Total Unadjusted Error (at +25°C) | ±0.25 | ±0.5 | % Full Scale | |
| Total Unadjusted Error (over industrial temperature range) | ±0.4 | ±0.75 | % Full Scale | |
| Input Offset Voltage | ±40 | µV | ||
| Common Mode Rejection Ratio | 90 | dB | ||
| Operating Supply Voltage | 12 | 36 | V | |
| Supply Current | 500 | µA | ||
| Maximum Operating Temperature | +85 | °C | ||
| Minimum Operating Temperature | -40 | °C | ||
| Package/Case | CERDIP-20, CDIP-20, LCCC-20 |
Key Features
- Instrumentation Amplifier Front End
- Loop-Powered Operation with up to 3.5 mA of excitation current
- Independently Adjustable Output Span and Zero
- Precalibrated Output Spans: 4-20 mA, 0-20 mA, 12 ± 8 mA
- Precalibrated 30 mV and 60 mV Input Spans, with options for other spans using external resistors
- Precalibrated 100 Ω RTD Interface with six precalibrated temperature ranges
- 6.2 V Reference with up to 3.5 mA of Current Available
- Uncommitted Auxiliary Amplifier for Extra Flexibility
- Optional External Pass Transistor to Reduce Self-Heating Errors
Applications
The AD693AQ is recommended for use in various applications including:
- Process Control
- Factory Automation
- System Monitoring
- Transmission of low-level signals from RTDs, bridges, and pressure transducers
It serves as a cost-effective signal conditioning solution and is often used as a replacement for discrete designs.
Q & A
- Q: What is the primary function of the AD693AQ?
A: The AD693AQ is a monolithic signal conditioning circuit that accepts low-level inputs from various transducers to control a standard 4-20 mA, two-wire current loop.
- Q: What are the precalibrated output spans available for the AD693AQ?
A: The precalibrated output spans include 4-20 mA, 0-20 mA, and 12 ± 8 mA.
- Q: How much excitation current is available in loop-powered mode?
A: Up to 3.5 mA of excitation current is available in loop-powered mode.
- Q: What is the operating temperature range for the AD693AQ?
A: The operating temperature range is from -40°C to +85°C.
- Q: What types of packages are available for the AD693AQ?
A: The AD693AQ is available in CERDIP-20, CDIP-20, and LCCC-20 packages.
- Q: What is the total unadjusted error for the AD693AQ at +25°C?
A: The total unadjusted error is less than ±0.5% of full scale at +25°C.
- Q: Can the AD693AQ be used with RTDs?
A: Yes, the AD693AQ has a precalibrated 100 Ω RTD interface with six precalibrated temperature ranges.
- Q: What is the purpose of the auxiliary amplifier in the AD693AQ?
A: The auxiliary amplifier can be used for transducer excitation and provides additional flexibility in the circuit.
- Q: How does the AD693AQ reduce self-heating errors?
A: The AD693AQ allows for the use of an external pass transistor to further reduce errors caused by self-heating.
- Q: In which applications is the AD693AQ commonly used?
A: The AD693AQ is commonly used in process control, factory automation, and system monitoring.
