Precision, Micropower 2.5 V XFET(TM) Reference# ADR291 Ultra-Precision Voltage Reference Technical Documentation
## 1. Application Scenarios
### Typical Use Cases
The ADR291 is primarily employed in precision measurement and control systems requiring stable voltage references:
High-Precision Data Acquisition Systems
- 16-bit to 24-bit analog-to-digital converters (ADCs)
- Precision analog-to-digital conversion front-ends
- Industrial measurement instrumentation
- Medical diagnostic equipment reference circuits
Test and Measurement Equipment
- Digital multimeters (DMMs)
- Oscilloscope calibration circuits
- Spectrum analyzer reference circuits
- Laboratory-grade power supplies
Communication Systems
- Base station power management
- RF power amplifier bias circuits
- Wireless infrastructure equipment
- Satellite communication systems
### Industry Applications
Industrial Automation
- Process control systems requiring ±0.04% initial accuracy
- Temperature measurement systems (-40°C to +125°C operation)
- Pressure transducer excitation circuits
- 4-20mA current loop transmitters
Medical Electronics
- Patient monitoring equipment
- Diagnostic imaging systems
- Portable medical devices
- Laboratory analyzers
Automotive Systems
- Engine control units (ECUs)
- Advanced driver-assistance systems (ADAS)
- Battery management systems (BMS)
- Sensor interface circuits
### Practical Advantages and Limitations
Advantages:
- Exceptional Temperature Stability : 3 ppm/°C maximum temperature coefficient
- Low Noise Performance : 3.8 μV p-p typical noise (0.1 Hz to 10 Hz)
- High Initial Accuracy : ±0.04% maximum initial error
- Low Power Consumption : 120 μA maximum supply current
- Long-Term Stability : 50 ppm/1000 hours typical
Limitations:
- Limited Output Current : 10 mA maximum output current
- Temperature Range : -40°C to +125°C operational range
- Cost Considerations : Premium pricing compared to basic references
- Board Space : May require additional decoupling components
## 2. Design Considerations
### Common Design Pitfalls and Solutions
Thermal Management Issues
- Pitfall : Ignoring thermal gradients across PCB
- Solution : Place ADR291 away from heat-generating components
- Implementation : Use thermal relief patterns and adequate copper pours
Noise Coupling Problems
- Pitfall : Poor decoupling capacitor placement
- Solution : Place 0.1 μF ceramic capacitor within 5 mm of VIN pin
- Implementation : Add 1 μF tantalum capacitor for bulk decoupling
Load Regulation Challenges
- Pitfall : Exceeding 10 mA output current limit
- Solution : Implement buffer amplifier for higher current requirements
- Implementation : Use precision op-amp as voltage follower
### Compatibility Issues with Other Components
ADC Interface Considerations
- Issue : Reference voltage noise affecting ADC performance
- Resolution : Ensure reference noise is below ADC LSB/2 requirement
- Compatible ADCs : ADI AD768x, AD769x series
Digital Circuit Isolation
- Issue : Digital switching noise coupling into reference
- Resolution : Implement proper ground separation techniques
- Implementation : Use star ground point and separate analog/digital grounds
Power Supply Requirements
- Compatible Regulators : LDO regulators with <100 μV RMS noise
- Minimum Headroom : VIN must exceed VOUT by 0.2V minimum
- Maximum Voltage : Absolute maximum 18V supply voltage
### PCB Layout Recommendations
Component Placement
- Position ADR291 close to load circuit
- Keep decoupling capacitors adjacent to device pins
- Maintain minimum 5 mm clearance from digital components
Routing Guidelines
- Use dedicated ground plane for reference circuit
- Route reference output as a
