Pch+SBD# Technical Documentation: CPH5802 Phototransistor
*Manufacturer: SANYO*
## 1. Application Scenarios
### Typical Use Cases
The CPH5802 is a high-sensitivity silicon NPN phototransistor designed for optical detection applications. Typical use cases include:
- Optical Switching Systems : Position detection in industrial automation equipment
- Object Detection : Presence/absence sensing in conveyor systems and assembly lines
- Rotary Encoders : Speed and position measurement in motor control systems
- Light Barrier Systems : Safety interlocks and counting mechanisms
- Ambient Light Sensing : Automatic brightness control in display systems
### Industry Applications
- Industrial Automation : Machine vision systems, robotic positioning sensors
- Consumer Electronics : Automatic backlight control for displays, proximity sensors
- Automotive : Rain sensors, twilight sensors, position detection
- Medical Equipment : Fluid level detection, equipment positioning
- Security Systems : Intrusion detection, beam interruption sensors
### Practical Advantages and Limitations
Advantages:
- High photosensitivity with typical collector current of 2mA (at 20mW/cm², VCE=5V)
- Fast response time (typical rise/fall time: 15μs)
- Wide operating temperature range (-25°C to +85°C)
- Compact package (3mm diameter) for space-constrained applications
- Low dark current (maximum 100nA at VCE=20V)
Limitations:
- Susceptible to ambient light interference in uncontrolled environments
- Limited linearity range for analog light measurement applications
- Temperature-dependent sensitivity requires compensation in precision applications
- Direct sunlight exposure may cause saturation and potential damage
## 2. Design Considerations
### Common Design Pitfalls and Solutions
Pitfall 1: Ambient Light Interference
- Problem : Unwanted ambient light triggers false detection
- Solution : Implement optical filtering, use modulated light sources with synchronous detection
Pitfall 2: Temperature Drift
- Problem : Sensitivity varies with temperature changes
- Solution : Incorporate temperature compensation circuits or use temperature-stable biasing
Pitfall 3: Saturation in High-Light Conditions
- Problem : Phototransistor enters saturation, losing detection capability
- Solution : Implement automatic gain control or use neutral density filters
### Compatibility Issues with Other Components
LED Driver Compatibility:
- Requires current-limited drivers (typically 20-50mA)
- Incompatible with voltage-driven LED circuits without current regulation
Microcontroller Interface:
- Output compatible with 3.3V and 5V logic systems
- May require pull-up resistors for proper logic level definition
- Analog interfaces need ADC with appropriate input impedance
Power Supply Considerations:
- Sensitive to power supply noise
- Requires clean, regulated power supplies with proper decoupling
### PCB Layout Recommendations
Placement Guidelines:
- Position away from heat-generating components to minimize temperature effects
- Maintain minimum 5mm clearance from high-frequency digital circuits
- Orient for optimal light path alignment with external optical elements
Routing Considerations:
- Keep collector and emitter traces short to minimize noise pickup
- Use ground planes for shielding from electromagnetic interference
- Route sensitive analog traces away from digital noise sources
Thermal Management:
- Provide adequate copper area for heat dissipation in high-temperature environments
- Avoid placing near components with significant thermal output
## 3. Technical Specifications
### Key Parameter Explanations
Absolute Maximum Ratings:
- Collector-Emitter Voltage (VCEO): 30V
- Emitter-Collector Voltage (VECO): 5V
- Collector Current (IC): 20mA
- Power Dissipation (PC): 75mW
- Operating Temperature Range: -25°C to +85°C
- Storage
