Brown Corporation - 16-Bit, High-Speed, 2.7V to 5V microPower Sampling ANALOG-TO-DIGITAL CONVERTER # ADS8320EB Technical Documentation
## 1. Application Scenarios
### Typical Use Cases
The ADS8320EB is a 16-bit, 100kSPS successive approximation register (SAR) analog-to-digital converter (ADC) commonly employed in precision measurement applications requiring moderate sampling rates with high resolution.
Primary Use Cases:
- Industrial Process Control : Monitoring temperature, pressure, and flow sensors with 4-20mA current loops
- Medical Instrumentation : Portable patient monitoring devices, blood pressure monitors, and diagnostic equipment
- Battery-Powered Systems : Data acquisition in portable test equipment and field measurement devices
- Motor Control : Position and current sensing in servo drives and industrial automation
### Industry Applications
Industrial Automation
- PLC analog input modules
- Distributed control systems
- Process variable transmitters
- Advantages : Excellent DC accuracy, low power consumption (2mW at 100kSPS), small package (MSOP-8)
- Limitations : Limited to single-ended inputs, requires external reference voltage
Medical Devices
- Portable vital signs monitors
- Infusion pump pressure monitoring
- Laboratory analyzers
- Advantages : High 16-bit resolution suitable for biomedical signals, low noise performance
- Limitations : No integrated PGA, requires external signal conditioning
Test and Measurement
- Portable data loggers
- Multimeter front-ends
- Sensor interface modules
- Advantages : Simple SPI interface, low power enables battery operation
- Limitations : Maximum 100kSPS may be insufficient for high-speed applications
### Practical Advantages and Limitations
Advantages:
- True 16-bit performance with no missing codes
- Low power consumption: 2.7mW at 5V, 100kSPS
- Small MSOP-8 package saves board space
- Simple 4-wire SPI interface
- Wide supply range: 2.7V to 5.25V
Limitations:
- Requires external reference voltage (typically 2.5V or 5V)
- Single-ended input only (no differential capability)
- No integrated multiplexer for multiple channels
- Limited to 100kSPS maximum sampling rate
## 2. Design Considerations
### Common Design Pitfalls and Solutions
Power Supply Decoupling
- Pitfall : Inadequate decoupling causing noise and reduced accuracy
- Solution : Use 10μF tantalum + 0.1μF ceramic capacitor at supply pins, placed within 5mm of device
Reference Voltage Stability
- Pitfall : Using noisy or unstable reference degrading ADC performance
- Solution : Implement low-noise reference IC (e.g., REF5025) with proper decoupling
Digital Interface Timing
- Pitfall : SPI timing violations due to microcontroller compatibility issues
- Solution : Verify timing margins, use appropriate clock speeds (max 20MHz SCLK)
### Compatibility Issues with Other Components
Microcontroller Interfaces
- Issue : Some MCUs have limited SPI clock speeds or timing constraints
- Resolution : Use MCUs with configurable SPI peripherals, ensure SCLK ≤ 20MHz
Analog Front-End Compatibility
- Issue : Driving the ADC input without proper buffering
- Resolution : Use precision op-amp (e.g., OPA350) with adequate bandwidth and settling time
Reference Voltage Circuits
- Issue : Reference loading affecting accuracy
- Resolution : Select references with low output impedance and adequate current capability
### PCB Layout Recommendations
Power Distribution
- Use separate analog and digital ground planes
- Connect grounds at single point near ADC
- Route analog and digital traces on different layers when possible
Signal Routing
- Keep analog input traces short and away from digital signals
- Use guard rings
