ITR9909 Opto Interrupter Datasheet - Package 4.0mm - Wavelength 940nm - English Technical Document

1. Product Overview

The ITR9909 is a compact opto interrupter module designed for non-contact sensing applications. It integrates an infrared emitting diode (IRED) and a silicon NPN phototransistor within a single black thermoplastic housing. The components are positioned side-by-side on converging optical axes. The fundamental operating principle involves the phototransistor normally receiving radiation from the co-located IR emitter. When an opaque object passes through the gap between them, it interrupts this infrared beam, causing a detectable change in the phototransistor's output state, enabling object detection, position sensing, or switching functions.

1.1 Core Features and Advantages

• Fast Response Time: Enables detection of rapidly moving objects.
• High Sensitivity: The silicon phototransistor provides a strong electrical response to infrared light.
• Specific Wavelength: The IRED emits at a peak wavelength (λp) of 940nm, which is invisible to the human eye and helps mitigate interference from ambient visible light.
• Environmental Compliance: The device is manufactured to be Pb-free, compliant with RoHS, EU REACH, and halogen-free standards (Br <900ppm, Cl <900ppm, Br+Cl <1500ppm).
• Compact Integration: The combined package simplifies PCB design and assembly for slot-type sensing applications.

1.2 Target Applications

The ITR9909 is suited for a variety of applications requiring reliable, non-contact detection:

• Rotary encoders and position sensors in computer mice and copiers.
• Paper detection and edge sensing in scanners and printers.
• Disk presence detection in floppy disk drives and other media drives.
• General-purpose non-contact switching.
• Board-level sensing where direct mounting is required.

2. Technical Specifications and In-Depth Analysis

2.1 Absolute Maximum Ratings

Operating the device beyond these limits may cause permanent damage. All specifications are at Ta=25°C unless otherwise noted.

• Input (IRED):
  • Power Dissipation (Pd): 75 mW
  • Reverse Voltage (VR): 5 V
  • Continuous Forward Current (IF): 50 mA
  • Peak Forward Current (IFP): 1 A (Pulse width ≤100μs, Duty cycle 1%)
• Output (Phototransistor):
  • Collector Power Dissipation (Pd): 75 mW
  • Collector Current (IC): 50 mA
  • Collector-Emitter Voltage (BV_CEO): 30 V
  • Emitter-Collector Voltage (BV_ECO): 5 V
• Environmental:
  • Operating Temperature (T_opr): -25°C to +85°C
  • Storage Temperature (T_stg): -40°C to +85°C
  • Lead Soldering Temperature (T_sol): 260°C for 5 seconds (1/16 inch from body)

2.2 Electro-Optical Characteristics

Typical performance parameters at Ta=25°C define the device's operational behavior.

• Input (IRED) Characteristics:
  • Forward Voltage (V_F): Typically 1.2V at IF=20mA (Max 1.5V). Increases with higher pulsed currents.
  • Peak Wavelength (λ_P): 940 nm (typical) when driven at 20mA.
• Output (Phototransistor) Characteristics:
  • Dark Current (I_CEO): Maximum 100 nA at V_CE=20V in complete darkness. This is the leakage current that defines the \"off\" state noise floor.
  • Collector-Emitter Saturation Voltage (V_CE(sat)): Maximum 0.4V at I_C=2mA under sufficient illumination (1mW/cm²). A low V_CE(sat) is desirable for clean digital switching.
  • Collector Current (I_C(ON)): Minimum 200 µA at V_CE=5V and I_F=20mA. This is the guaranteed minimum photocurrent under standard test conditions.
• Dynamic Characteristics:
  • Rise Time (t_r) & Fall Time (t_f): Typically 15 µs each. These parameters, measured under specific load conditions (V_CE=5V, I_C=1mA, R_L=1kΩ), determine the maximum switching frequency the device can reliably handle.

3. Performance Curve Analysis

The datasheet provides several graphs illustrating key relationships between operating parameters. These curves are essential for understanding device behavior under non-standard conditions.

3.1 Infrared Emitter (IRED) Curves

• Forward Current vs. Ambient Temperature: Shows the derating of the maximum allowable forward current as ambient temperature increases above 25°C.
• Spectral Sensitivity: A plot of relative radiant intensity versus wavelength, peaking at 940nm and showing the narrow bandwidth of the emitter.
• Relative Radiant Intensity vs. Forward Current: Demonstrates the non-linear relationship between drive current and light output, which tends to saturate at higher currents.
• Relative Radiant Intensity vs. Angular Displacement: Illustrates the emission pattern or viewing angle of the IRED, crucial for optical alignment.

3.2 Phototransistor (PT) Curves

• Collector Power Dissipation vs. Ambient Temperature: Provides the power derating curve for the phototransistor output.
• Spectral Sensitivity: Shows the phototransistor's responsivity across wavelengths, with peak sensitivity typically in the near-infrared region, matching the 940nm emitter.
• Relative Collector Current vs. Ambient Temperature: Indicates how the phototransistor's gain or responsivity changes with temperature.
• Collector Current vs. Irradiance: A fundamental curve showing the linear (or near-linear) relationship between incident light power (irradiance) on the phototransistor and the resulting collector current.
• Collector Dark Current vs. Ambient Temperature: Shows how leakage current (I_CEO) increases exponentially with rising temperature, which can affect the signal-to-noise ratio in high-temperature applications.
• Collector Current vs. Collector-Emitter Voltage: Similar to a transistor output characteristic, showing the operating regions for different levels of illumination.

3.3 Complete Module (ITR) Curve

• Relative Collector Current vs. Distance Between Sensor: This is a critical system-level curve. It shows how the received signal (collector current) varies as the distance between the interrupting object and the sensor gap changes. It defines the effective sensing range and the relationship between object position and output signal strength.

4. Mechanical and Package Information

4.1 Package Dimensions

The ITR9909 comes in a standard through-hole package. Key dimensions from the drawing include:

• Overall body width and height defining the slot size.
• Lead spacing and diameter for PCB mounting.
• The gap width between the internal IRED and phototransistor, which determines the size of object that can be detected.
• The dimensional drawing specifies a standard tolerance of ±0.25mm unless otherwise noted.

4.2 Polarity Identification

The device uses a standard pinout configuration common to many opto interrupters: Anode and Cathode for the IRED input, and Collector and Emitter for the phototransistor output. The housing typically has a marking or notch to indicate pin 1.

5. Assembly and Handling Guidelines

5.1 Soldering Recommendations

The absolute maximum rating specifies that leads can be soldered at 260°C for a maximum of 5 seconds, with the stipulation that the soldering point is at least 1/16 inch (approximately 1.6mm) away from the plastic body. This is to prevent thermal damage to the epoxy housing and the internal wire bonds. For wave or reflow soldering, standard profiles for through-hole components with similar thermal limits should be followed.

5.2 Storage and Handling

The device should be stored within the specified temperature range of -40°C to +85°C in a dry environment. Standard ESD (Electrostatic Discharge) precautions should be observed during handling, as the semiconductor components inside are susceptible to damage from static electricity.

6. Packaging and Ordering Information

6.1 Packing Specification

The standard packing quantity is as follows:

• 150 pieces per bag.
• 5 bags per box.
• 10 boxes per carton.

6.2 Label Information

The product label includes several codes for traceability and specification:

• CPN: Customer's Product Number.
• P/N: Manufacturer's Product Number (e.g., ITR9909).
• QTY: Quantity in the package.
• CAT, HUE, REF: These likely refer to internal binning codes for parameters like luminous intensity rank, dominant wavelength rank, and forward voltage rank, though specific binning details are not provided in this datasheet excerpt.
• LOT No: Manufacturing lot number for traceability.

7. Application Design Considerations

7.1 Circuit Design

Designing with the ITR9909 involves two main circuits:

1. IRED Drive Circuit: A simple current-limiting resistor in series with the IRED is standard. The resistor value is calculated as R = (V_CC - V_F) / I_F. For reliable operation and long life, driving the IRED at or below the typical 20mA is recommended unless a pulsed, high-current drive is needed for specific signal-to-noise requirements.
2. Phototransistor Output Circuit: The phototransistor can be used in two common configurations:
   • Switch Mode (Digital Output): Connect a pull-up resistor from the collector to V_CC. The emitter is grounded. When light falls on the transistor, it turns on, pulling the collector voltage low (near V_CE(sat)). When the beam is interrupted, the transistor turns off, and the pull-up resistor brings the collector voltage high. The value of the pull-up resistor determines the switching speed and current consumption.
   • Linear Mode (Analog Output): Using the phototransistor in a common-emitter configuration with a collector resistor, the voltage at the collector will vary approximately linearly with the amount of received light, useful for analog position sensing.

7.2 Optical Considerations

• Alignment: Precise mechanical alignment of the object path with the sensor gap is crucial for consistent operation.
• Ambient Light: While the 940nm filter and matched sensor provide good rejection of visible light, strong sources of infrared light (e.g., sunlight, incandescent bulbs) can cause interference. Using a modulated IR signal and synchronous detection can greatly improve immunity to ambient light.
• Object Characteristics: The sensor detects interruption of the beam. The object must be opaque to 940nm infrared light. Translucent materials may not be reliably detected.

8. Technical Comparison and Differentiation

The ITR9909 represents a standard, reliable solution in the opto interrupter market. Its key differentiators are its specific combination of a 940nm IRED with a silicon phototransistor in a compact, side-looking package. Compared to reflective sensors, interrupters provide a more definitive \"on/off\" signal as they are less susceptible to variations in object reflectivity or color. The specified fast response time (15µs typical) makes it suitable for speed sensing or encoding applications, while the high sensitivity ensures a good signal even with lower drive currents or in dusty environments. The environmental compliance (RoHS, Halogen-Free) is a critical factor for modern electronics manufacturing.

9. Frequently Asked Questions (Based on Technical Parameters)

9.1 What is the maximum sensing speed or frequency?

The maximum switching frequency is limited by the rise and fall times (t_r, t_f), typically 15µs each. A conservative estimate for a complete on-off cycle is about 4 to 5 times the sum of these times, suggesting a maximum practical frequency in the range of 10-15 kHz. This is suitable for most mechanical encoding applications.

9.2 How do I choose the value for the IRED current-limiting resistor?

Use the formula R = (Supply Voltage - V_F) / I_F. For a 5V supply and driving at the typical test condition of 20mA, with V_F ~1.2V, R = (5 - 1.2) / 0.02 = 190 Ohms. A standard 180 or 200 Ohm resistor would be appropriate. Always ensure the calculated power dissipation in the resistor is within its rating.

9.3 Why is the output signal unstable or noisy?

Potential causes include: 1) Insufficient drive current to the IRED, resulting in a weak signal. 2) High levels of ambient infrared light. 3) The phototransistor's dark current (which increases with temperature) becoming significant relative to the photocurrent. 4) Electrical noise on the supply lines. Solutions include increasing I_F (within limits), adding optical shielding, implementing signal modulation, using a lower-value pull-up resistor for faster response, and ensuring good power supply decoupling.

9.4 Can I use this sensor outdoors?

Direct sunlight contains a significant amount of infrared radiation at 940nm, which can saturate the phototransistor and prevent proper operation. For outdoor use, careful optical filtering, housing design to block direct sunlight, and the use of modulated IR signals are strongly recommended.

10. Operational Principle and Technology Trends

10.1 Working Principle

The ITR9909 operates on the principle of transmitted light interruption. An electric current driven through the infrared light-emitting diode (IRED) causes it to emit photons at a peak wavelength of 940 nanometers. These photons travel across a small air gap and are incident upon the base region of the NPN silicon phototransistor. The photons generate electron-hole pairs in the base-collector junction, which effectively acts as a photodiode. This photocurrent is then amplified by the transistor action of the device, resulting in a much larger collector current that can be easily measured by external circuitry. When an object physically blocks the path between the emitter and detector, the photon flux ceases, the photocurrent drops to nearly zero, and the transistor turns off, signaling the presence of the object.

10.2 Technology Context and Trends

Opto interrupters like the ITR9909 are mature, well-understood components. Current trends in the field focus on several areas:

• Miniaturization: Development of smaller surface-mount (SMD) packages to save board space in modern consumer electronics.
• Integration: Incorporating additional circuitry on-chip, such as Schmitt triggers for digital output, amplifiers for analog output, or even full logic-level interfaces (e.g., open-drain output).
• Enhanced Performance: Improving speed for higher-resolution encoders, reducing power consumption for battery-operated devices, and increasing sensitivity to allow for smaller drive currents or larger sensing gaps.
• Specialization: Creating variants with different slot widths, aperture shapes, or spectral responses for specific market segments like automotive, industrial automation, or medical devices.

The fundamental principle of optical interruption remains a robust and cost-effective method for non-contact sensing, ensuring continued relevance in a wide array of electromechanical systems.