ITR8307/L24/TR8 Reflective Optical Sensor Datasheet - Pb-Free, RoHS, REACH Compliant - English Technical Document

1. Product Overview

The ITR8307/L24/TR8 is a compact, surface-mount reflective optical switch designed for short-distance sensing applications. It integrates a GaAs infrared (IR) light-emitting diode (LED) transmitter and a high-sensitivity NPN silicon photo-transistor receiver within a single, side-by-side plastic package. This configuration allows it to detect the presence or absence of a reflective surface by measuring the intensity of the IR light reflected back to the receiver.

The device is characterized by its fast response time, high sensitivity to infrared light, and a spectral response that cuts off visible wavelengths, making it immune to ambient visible light interference. It is manufactured to be lead-free (Pb-free), compliant with the EU RoHS and REACH directives, and meets halogen-free requirements (Br <900 ppm, Cl <900 ppm, Br+Cl < 1500 ppm).

1.1 Core Advantages and Target Market

The primary advantages of this sensor include its thin profile, compact footprint, and fast optical response, which are critical for space-constrained and high-speed applications. Its design makes it suitable for various consumer electronics and microcomputer-controlled equipment where reliable, non-contact object detection is required.

Typical target applications include position sensing in devices such as digital cameras (for lens or cover detection), video cassette recorders (VCRs), floppy disk drives, cassette tape recorders, and other automated control systems.

2. In-Depth Technical Parameter Analysis

2.1 Absolute Maximum Ratings

The device must not be operated beyond these limits to prevent permanent damage. Key ratings include an input (LED) power dissipation of 75 mW at 25°C free air temperature, a maximum forward current (IF) of 50 mA, and a peak forward current (IFP) of 1 A for pulses ≤100μs at a 1% duty cycle. For the output (photo-transistor), the maximum collector power dissipation is 75 mW, the collector current (IC) is 50 mA, and the collector-emitter voltage (BV_CEO) is 30 V. The operating temperature range is from -40°C to +85°C.

2.2 Electro-Optical Characteristics

These parameters are specified at an ambient temperature (T_a) of 25°C and define the device's performance under normal operating conditions.

2.2.1 Input (IR LED) Characteristics

• Forward Voltage (V_F): Typically 1.2 V at a forward current (I_F) of 20 mA, with a maximum of 1.6 V. This is crucial for designing the LED driver circuit.
• Peak Wavelength (λ_P): 940 nm, placing its emission firmly in the near-infrared spectrum.

2.2.2 Output (Photo-Transistor) Characteristics

• Dark Current (I_CEO): The leakage current when no light is incident, with a maximum of 100 nA at V_CE=10V. A lower value indicates better off-state performance.
• Light Current (I_C(ON)): The collector current when the LED is active and light is reflected onto the receiver. It has a wide range from 0.5 mA to 15.0 mA under test conditions of V_CE=2V and I_F=4mA. This parameter is highly dependent on the reflectivity and distance of the target object.
• Rise/Fall Time (t_r, t_f): Typically 20 μsec each, defining the sensor's switching speed.

3. Performance Curve Analysis

The datasheet provides several graphs illustrating the relationship between key parameters under varying conditions. These are essential for understanding real-world behavior beyond the typical 25°C point.

3.1 IR LED Characteristics

Curves show how forward current varies with ambient temperature and forward voltage. The forward voltage has a negative temperature coefficient, meaning it decreases as temperature increases. The spectral distribution curve confirms the peak emission at 940 nm, with the peak wavelength itself shifting slightly with temperature.

3.2 Photo-Transistor Characteristics

Important curves include Collector Dark Current vs. Ambient Temperature (increasing exponentially with temperature), Collector Current vs. Irradiance (showing the phototransistor's response to light intensity), and Collector Current vs. Collector-Emitter Voltage. The spectral sensitivity curve shows the receiver is most sensitive to infrared light around 800-900 nm, well-matched to the LED's 940 nm output.

3.3 Complete Sensor (ITR) Characteristics

These graphs model the sensor's behavior in a practical reflective setup. The Relative Collector Current vs. Distance curve is critical for system design, showing how the output signal decays as the gap between the sensor and a reflective surface (like aluminum-evaporated glass) increases. Another curve shows the output variation as a card moves across the sensor's field of view, useful for edge or slot detection. The Response Time vs. Load Resistance graph helps in selecting an appropriate pull-up resistor for optimizing speed.

4. Mechanical and Package Information

4.1 Package Dimensions

The device comes in a compact surface-mount package. The datasheet provides detailed dimensional drawings with critical measurements such as overall length, width, height, lead spacing, and pad dimensions. All tolerances are typically ±0.1 mm unless otherwise specified. Engineers must refer to these exact drawings for PCB footprint design to ensure proper soldering and mechanical alignment.

4.2 Polarity Identification

The package includes markings or a specific shape to indicate pin 1. Correct orientation during assembly is vital, as reverse connection can damage the device. The pinout identifies the anode and cathode of the IR LED and the collector and emitter of the photo-transistor.

5. Soldering, Assembly, and Storage Guidelines

5.1 Moisture Sensitivity and Storage

The device is rated Moisture Sensitivity Level (MSL) 4. Key handling instructions include:

• Shelf life in the original sealed moisture barrier bag: 12 months at <40°C and <90% RH.
• After opening the bag, devices must be mounted within 72 hours if stored at factory conditions (<30°C/60%RH), or stored in a dry environment (<20% RH).
• If the Humidity Indicator Card (HIC) exceeds 20% RH, baking is required before reflow soldering (e.g., 24 hours at 125°C).

5.2 Reflow Soldering Conditions

A recommended Pb-free solder reflow temperature profile is provided. Key precautions include:

• Limiting reflow soldering to a maximum of two cycles.
• Avoiding mechanical stress on the package during heating.
• Preventing warping of the PCB after soldering.

5.3 Repair

Repair after soldering is discouraged. If unavoidable, a double-head soldering iron should be used to simultaneously heat both sides of the component, minimizing thermal stress. The potential impact on device characteristics must be evaluated beforehand.

6. Packaging and Ordering Information

6.1 Packing Specifications

The standard packing flow is: 1000 pieces per reel, 15 reels per box, and 2 boxes per carton.

6.2 Taping and Reel Dimensions

Detailed drawings for the carrier tape (pocket dimensions, pitch) and the reel (diameter, hub size) are provided for use in automated pick-and-place machine programming.

6.3 Label Specification

The packaging labels include fields for Customer Part Number (CPN), Product Number (P/N), Quantity (QTY), and Lot Number (LOT No.), among others, for traceability.

7. Application Suggestions and Design Considerations

7.1 Typical Application Circuits

A basic application circuit involves connecting a current-limiting resistor in series with the IR LED anode. The photo-transistor is typically connected with the collector to a pull-up resistor (V_CC) and the emitter to ground. The voltage at the collector node serves as the digital or analog output signal. The value of the pull-up resistor (R_L) affects both the output voltage swing and the response time, as shown in the datasheet curves.

7.2 Design Considerations

• Object Reflectivity: The sensor's output (I_C(ON)) is directly proportional to the reflectivity of the target surface. Highly reflective materials (e.g., white plastic, metal) provide a strong signal, while dark or absorptive materials may not.
• Distance and Alignment: The sensing distance is short (typically a few millimeters). Precise mechanical alignment between the sensor and the target path is critical for consistent operation.
• Ambient Light Immunity: While the receiver's spectral sensitivity cuts off visible light, strong ambient infrared sources (e.g., sunlight, incandescent bulbs) can cause interference. Optical shielding or modulation/demodulation techniques may be necessary in such environments.
• Electrical Noise: In noisy environments, bypass capacitors near the device and careful PCB layout are recommended.

8. Technical Comparison and Differentiation

Compared to simpler phototransistors or photodiodes, the ITR8307 integrates both emitter and receiver, simplifying optical design and alignment. Versus transmissive sensors (which require an object to break a beam between separate components), reflective sensors allow for simpler mechanical design with sensing on one side of the object. Its key differentiators are its compact SMD package, compliance with modern environmental regulations (Pb-free, Halogen-free), and well-documented performance across temperature.

9. Frequently Asked Questions (FAQs) Based on Technical Parameters

Q: What is the typical sensing distance?
A: The distance is not a fixed specification but depends on target reflectivity and the required output current. The "Relative Collector Current vs. Distance" graph shows the signal decays significantly beyond 1-2 mm for a standard reflective surface. Design for the shortest reliable distance.

Q: Can I drive the LED with a voltage source directly?
A: No. An LED is a current-driven device. You must use a series current-limiting resistor to set the forward current (I_F) to the desired value (e.g., 20 mA) based on your supply voltage (V_CC) and the LED's forward voltage (V_F ≈ 1.2V). R_limit = (V_CC - V_F) / I_F.

Q: Why is there such a wide range for Light Current (0.5 to 15.0 mA)?
A> This range accounts for normal manufacturing variations in both the LED's output power and the photo-transistor's sensitivity. It also underscores the parameter's strong dependence on the specific reflective target and distance in the application. Circuit designs must accommodate this range, often using a comparator with an adjustable threshold rather than relying on an absolute current value.

Q: How do I interpret the MSL 4 rating?
A> MSL 4 means the package can absorb damaging levels of moisture from the air after 72 hours of exposure to standard factory floor conditions. To avoid "popcorning" or delamination during the high-temperature reflow process, you must follow the strict storage, handling, and baking guidelines outlined in Section 5.1.

10. Practical Application Example

Scenario: Paper Detection in a Printer.
The sensor can be mounted near the paper feed path. A reflective strip is placed on a roller or fixed surface opposite the sensor's location. When paper is not present, the IR light reflects off the strip back to the receiver, generating a high output (logic HIGH). When a sheet of paper passes between the sensor and the strip, it blocks or significantly reduces the reflected light, causing the output to drop (logic LOW). This transition can be detected by a microcontroller to confirm paper presence, detect jams, or count pages. The fast response time (20 μs) allows detection even at high paper feed speeds.

11. Operating Principle

The device operates on the principle of modulated light reflection. The internal IR LED emits a beam of 940 nm infrared light. This light travels outward from the package. If a reflective object is within a short range and in the field of view of both the LED and the photo-transistor, a portion of the emitted light will be reflected back. The NPN photo-transistor acts as a light-controlled current source. When the reflected infrared photons strike its base region, they generate electron-hole pairs, effectively creating a base current. This base current is amplified by the transistor's gain, resulting in a much larger collector current (I_C). The magnitude of this collector current is proportional to the intensity of the reflected light, which in turn depends on the distance to and reflectivity of the target object. By monitoring I_C (or the voltage across a load resistor), the system can determine the presence or proximity of the object.

12. Technology Trends

Reflective optical sensors like the ITR8307 represent a mature and reliable technology for short-range, low-cost object detection. Current trends in the field include further miniaturization of packages to fit into ever-smaller consumer devices, integration of signal conditioning circuitry (amplifiers, Schmitt triggers, digital interfaces) within the same package to simplify system design and improve noise immunity, and the development of sensors with even lower power consumption for battery-operated IoT devices. There is also a continuous drive for higher sensitivity and better ambient light rejection through improved optical design and filtering techniques.