ITR20002 Photointerrupter Datasheet - Side-Looking Package - 940nm Wavelength - English Technical Document

1. Product Overview

The ITR20002 is a compact, side-looking infrared photointerrupter module. It integrates an infrared emitting diode and an NPN silicon phototransistor mounted side-by-side on a converging optical axis within a black thermoplastic housing. This configuration is designed for object detection, position sensing, and non-contact switching applications by interrupting the infrared beam path between the emitter and detector.

1.1 Core Features and Advantages

• Fast Response Time: Enables quick detection and switching, suitable for high-speed applications.
• High Sensitivity: The silicon phototransistor provides reliable signal detection from the IR emitter.
• Specific Cut-off Wavelength: Peak emission wavelength (λp) of 940nm, optimized for infrared sensing while minimizing interference from visible light.
• Environmental Compliance: The product is Pb-free, compliant with RoHS, EU REACH, and Halogen-Free standards (Br <900ppm, Cl <900ppm, Br+Cl <1500ppm).
• Converging Optical Axis: The side-by-side, converging design simplifies alignment for object detection in the gap between the components.

1.2 Target Applications

The module is designed for a variety of optoelectronic sensing tasks, including:

• Mouse and copier mechanisms for detecting movement or paper presence.
• Floppy disk drives for sensing disk insertion or track position.
• General-purpose non-contact switching.
• Direct mounting on printed circuit boards (PCBs).

2. Technical Parameter Deep-Dive

This section provides a detailed, objective interpretation of the key electrical and optical parameters specified in the datasheet.

2.1 Absolute Maximum Ratings

These ratings define the limits beyond which permanent damage to the device may occur. Operation under these conditions is not guaranteed.

• Input (IR LED):
  • Power Dissipation (Pd): 100 mW at 25°C. Derating is necessary at higher ambient temperatures.
  • Reverse Voltage (VR): 5 V. Exceeding this can break down the LED junction.
  • Forward Current (IF): 60 mA continuous.
  • Peak Forward Current (IFP): 1 A for pulses ≤100μs at a 1% duty cycle. This allows for brief, high-intensity pulses.
• Output (Phototransistor):
  • Collector Power Dissipation (Pc): 80 mW. This limits the combination of collector current and voltage.
  • Collector Current (IC): 20 mA maximum continuous current.
  • Collector-Emitter Voltage (BV_CEO): 35 V. The maximum voltage that can be applied across the transistor when the base is open.
  • Emitter-Collector Voltage (BV_ECO): 6 V. The maximum reverse voltage across the emitter and collector.
• Thermal Ratings:
  • 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 at 1/16 inch (1.6mm) from the package body.

2.2 Electro-Optical Characteristics (Ta=25°C)

These are the typical operating parameters under specified test conditions.

• Input Characteristics (IR LED):
  • Forward Voltage (V_F): Typically 1.2V to 1.5V at I_F=20mA. This is important for designing the current-limiting driver circuit.
  • Peak Wavelength (λ_P): 940nm. This is the wavelength at which the IR LED emits the most optical power.
• Output Characteristics (Phototransistor):
  • Dark Current (I_CEO): Maximum 100 nA at V_CE=20V with no illumination (E_e=0). 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=0.04mA and I_F=40mA. A low V_CE(sat) is desirable when the transistor is used as a switch.
  • Collector Current (I_C(ON)): Ranges from 0.04mA to 0.9mA at V_CE=5V and I_F=20mA. This parameter, the transfer characteristic, defines the sensitivity of the coupler. The wide range indicates it is a critical parameter that may be binned.
  • Rise/Fall Time (t_r/t_f): Typical 20μs and 25μs respectively, under specific test conditions (V_CE=2V, I_C=100μA, R_L=100Ω). These values determine the maximum switching frequency of the device.

3. Performance Curve Analysis

The datasheet references typical characteristic curves for both the IR emitter and the phototransistor. While the exact graphs are not reproduced here, their significance is explained.

3.1 IR Emitter Curves

These curves typically illustrate the relationship between forward current (I_F) and forward voltage (V_F) at different temperatures, showing the negative temperature coefficient of V_F. They may also show relative radiant intensity vs. forward current and the angular radiation pattern, which is crucial for understanding the beam spread in the side-looking package.

3.2 Phototransistor Curves

These curves are essential for circuit design. They typically include:

• Collector Current vs. Collector-Emitter Voltage (I_C-V_CE): Family of curves for different levels of irradiance (or different IR LED currents). This shows the transistor's output characteristics and helps determine the load line.
• Collector Current vs. Irradiance (or I_F): This transfer curve quantifies the sensitivity, showing how much output current is generated for a given input light level.
• Dark Current vs. Temperature: Shows how the leakage current increases with temperature, which can affect the signal-to-noise ratio in high-temperature environments.

4. Mechanical and Package Information

4.1 Package Dimensions

The ITR20002 comes in a standard side-looking, through-hole package. The dimensional drawing in the datasheet provides critical measurements for PCB layout and mechanical integration. Key features include the lead spacing, package body dimensions, and the location of the optical aperture. The note specifies that tolerances are ±0.25mm unless otherwise stated on the dimensioned drawing.

4.2 Polarity Identification

For through-hole packages, polarity is typically indicated by the physical shape of the package (a flat or notch) or by the length of the leads. The datasheet drawing should clearly mark the anode and cathode of the IR LED and the collector and emitter of the phototransistor. Correct polarity is essential for device operation and to prevent damage.

5. Application and Design Guidelines

5.1 Typical Application Circuit

A basic application involves driving the IR LED with a current-limiting resistor connected to a voltage source. The phototransistor is typically connected in a common-emitter configuration: the collector is pulled up to a supply voltage through a load resistor (R_L), and the emitter is grounded. The output signal is taken from the collector. The value of R_L affects the output voltage swing, speed, and current consumption. A smaller R_L provides faster switching but a smaller voltage swing; a larger R_L gives a larger swing but slower response.

5.2 Design Considerations

• Alignment: The side-by-side, converging axis design means the sensitive detection area is in the gap between the emitter and detector. Precise mechanical alignment of the object path is necessary for reliable operation.
• Ambient Light Immunity: While the 940nm filter in the housing helps, strong ambient IR sources (sunlight, incandescent bulbs) can saturate the phototransistor. Using a modulated IR signal and synchronous detection can greatly improve immunity.
• Current Drive: Operate the IR LED at or below the recommended I_F (e.g., 20mA) for long-term reliability. Pulsing the LED at a higher current (within I_FP limits) can increase the sensing range or signal strength.
• Output Interface: The phototransistor output can be fed directly into a digital input of a microcontroller (with appropriate pull-up) or into a comparator for precise threshold detection in analog applications.

6. Packaging and Ordering Information

6.1 Label Specification

The product label contains several codes:

• CPN: Customer's Part Number.
• P/N: Manufacturer's Product Number (ITR20002).
• QTY: Quantity in the package.
• CAT / HUE / REF: These likely refer to internal binning codes for parameters like luminous intensity (CAT), dominant wavelength (HUE), and forward voltage (REF).
• LOT No: Traceability lot number.

6.2 Packing Specification

The standard packing is 150 pieces per bag, 5 bags per box, and 10 boxes per carton. This information is vital for inventory planning and production line feeding.

7. Technical Comparison and Positioning

The ITR20002 represents a classic, cost-effective solution for object detection. Its key differentiators are its specific side-looking mechanical form factor and converging optical axis, which are designed for detecting objects passing through a specific slot or gap. Compared to reflective sensors, it offers higher reliability and consistency as it is less dependent on the reflectivity of the target object. Compared to transmissive sensors with opposed emitters and detectors, it allows for a more compact mechanical design where the object breaks the beam within a single module. The 940nm wavelength is a common standard, offering a good balance between component availability, cost, and ambient light rejection.

8. Frequently Asked Questions (FAQ)

8.1 What is the typical sensing distance or gap?

The datasheet specifies the I_C(ON) test condition as "with reflector in 5mm away." This suggests the device is optimized for very short-range detection, likely in the range of a few millimeters. The actual usable gap depends on the drive current to the IR LED, the sensitivity of the receiver circuit, and the required signal margin.

8.2 How do I protect the device from electrical transients?

For the IR LED, a simple series resistor is usually sufficient. For the phototransistor operating in noisy environments, consider adding a small capacitor (e.g., 1-10nF) across the collector and emitter to filter high-frequency noise, keeping in mind this will slow the response time. For harsh industrial environments, additional external clamping diodes or TVS diodes may be required on the input/output lines.

8.3 Can I use this for speed sensing on a rotating slotted disk?

Yes, this is a common application. The maximum switching frequency will be limited by the rise/fall times (typically ~20-25μs), which theoretically allows frequencies up to roughly 20 kHz. In practice, the frequency will be lower due to circuit and duty cycle constraints. Ensure the slots and gaps on the disk are wide enough to allow the phototransistor to fully switch on and off.

9. Operational Principle

The ITR20002 operates on the principle of transmitted light interruption. The internal infrared emitting diode (IRED) is forward-biased, causing it to emit light at a peak wavelength of 940nm. The NPN silicon phototransistor, positioned on a converging axis, normally receives this radiation when nothing obstructs the path. Photons with sufficient energy strike the base region of the phototransistor, generating electron-hole pairs. This photocurrent acts as a base current, which is then amplified by the transistor's current gain (beta), resulting in a much larger collector current. When an opaque object is placed in the gap between the emitter and detector, the light path is interrupted. The photocurrent ceases, and the transistor turns off, causing the collector current to drop to a very low value (the dark current). This on/off change in collector current provides a digital signal indicating the presence or absence of an object.

10. Disclaimer and Reliability Notes

The information provided in this technical document is based on the original datasheet. Key disclaimers and notes from the manufacturer include:

• Specifications and materials are subject to change.
• The product meets published specifications for 12 months from the date of shipment.
• Graphs and typical values are for reference only and are not guaranteed.
• Operation outside the Absolute Maximum Ratings can cause permanent damage.
• The product is not intended for safety-critical, military, aviation, automotive, medical, or life-support applications without explicit authorization.

It is the responsibility of the designer to validate the device's suitability and performance in their specific application.