ITR9707 Opto Interrupter Datasheet - Dimensions 7.0x4.0x3.0mm - Forward Voltage 1.2V - Peak Wavelength 940nm - English Technical Documentation

1. Product Overview

The ITR9707 is a compact opto interrupter module, also known as a photo interrupter or slot sensor. It integrates an infrared emitting diode (IRED) and a silicon phototransistor within a single black thermoplastic housing. The components are positioned side-by-side on converging optical axes. The fundamental operating principle is based on the interruption of an infrared light beam. In its normal state, the phototransistor receives radiation emitted by the co-located IR LED. When an opaque object passes through the slot between the emitter and detector, the light path is blocked, causing the phototransistor's output to change state. This provides a reliable, non-contact method for detecting the presence, absence, or position of an object.

1.1 Core Features and Advantages

• Fast Response Time: Enables detection of high-speed events with typical rise and fall times of 15 microseconds.
• High Sensitivity: The silicon phototransistor provides a strong electrical response to the infrared illumination.
• Specific Wavelength: Utilizes an IR LED with a peak emission wavelength (λp) of 940nm, which is outside the visible spectrum, reducing interference from ambient light.
• Environmental Compliance: The product is Pb-free, compliant with the RoHS directive, and adheres to EU REACH regulations.

1.2 Target Applications

This device is designed for a variety of non-contact sensing and switching applications, including but not limited to: position sensing in computer mice and copiers, edge detection in scanners and floppy disk drives, general-purpose non-contact switching, and direct board mounting in various electronic assemblies.

2. Technical Specifications and In-Depth Interpretation

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): Maximum continuous forward current (IF) is 50 mA. Maximum reverse voltage (VR) is 5 V. Power dissipation (Pd) is 75 mW at or below 25°C free air temperature.
• Output (Phototransistor): Maximum collector current (IC) is 20 mA. Collector-emitter breakdown voltage (BVCEO) is 30 V. Power dissipation (Pd) is 75 mW.
• Thermal: Operating temperature range (Topr) is -25°C to +85°C. Storage temperature range (Tstg) is -40°C to +85°C.
• Soldering: Lead soldering temperature (Tsol) must not exceed 260°C for a duration of 5 seconds or less, measured 3mm from the package body.

2.2 Electro-Optical Characteristics

These are the typical performance parameters measured at Ta=25°C, defining the device's operational behavior.

• Input Characteristics: The forward voltage (VF) of the IR LED is typically 1.2V at a drive current (IF) of 20mA, with a maximum of 1.5V. Reverse current (IR) is a maximum of 10 µA at VR=5V.
• Output Characteristics: The collector dark current (ICEO), which is the leakage current with no illumination, is a maximum of 100 nA at VCE=20V. The collector-emitter saturation voltage (VCE(sat)) is a maximum of 0.4V when the phototransistor is driven into saturation (IC=2mA, Ee=1mW/cm²).
• Transfer Characteristics: This defines the relationship between input and output. The on-state collector current (IC(on)) is guaranteed to be at least 0.5mA when the IR LED is driven with IF=20mA and the phototransistor is biased with VCE=5V. This parameter, known as the current transfer ratio (CTR), is crucial for designing the interface circuit.
• Dynamic Response: Both the rise time (tr) and fall time (tf) are typically 15 µs under specified test conditions (VCE=5V, IC=1mA, RL=1kΩ). This determines the maximum switching frequency.

3. Performance Curve Analysis

3.1 IR LED Characteristics

The datasheet provides typical curves for the infrared emitter component. The Forward Current vs. Ambient Temperature graph shows how the maximum allowable forward current derates as ambient temperature increases above 25°C, which is critical for thermal management. The Forward Current vs. Forward Voltage curve illustrates the diode's IV characteristic, essential for selecting the current-limiting resistor. The Spectral Sensitivity plot confirms the peak emission at 940nm and the width of the emission band.

3.2 Phototransistor Characteristics

The Spectral Sensitivity curve for the phototransistor shows its responsivity across different wavelengths. It peaks in the near-infrared region, closely matching the 940nm output of the paired IR LED. This spectral matching maximizes sensitivity and minimizes response to unwanted ambient light sources.

4. Mechanical and Package Information

4.1 Package Dimensions

The ITR9707 is housed in a standard, compact package. Key dimensions include an overall body width of approximately 7.0mm, a height of 4.0mm, and a depth of 3.0mm. The slot gap width, which determines the size of object that can be detected, is a critical dimension. Lead spacing is standardized for through-hole PCB mounting. All dimensional tolerances are typically ±0.3mm unless otherwise specified.

4.2 Polarity Identification and Mounting

The component has a standard pinout where the anode and cathode of the IR LED are on one side, and the emitter and collector of the phototransistor are on the other. The black housing and specific lead lengths or package markings typically indicate orientation. Correct polarity must be observed during PCB layout and assembly.

5. Soldering and Assembly Guidelines

5.1 Lead Forming Precautions

If leads need to be bent for mounting, it must be done before soldering. Bending should occur no closer than 3mm from the base of the epoxy package body to avoid transmitting stress that could crack the housing or damage the internal die. The leads must be secured during bending, and the operation should be performed at room temperature.

5.2 Recommended Soldering Parameters

• Hand Soldering: Iron tip temperature should not exceed 300°C (for a 30W iron max). Soldering time per lead should be 3 seconds or less. The solder joint must be at least 3mm away from the epoxy bulb.
• Wave/Dip Soldering: Preheat temperature should be 100°C max for up to 60 seconds. The solder bath temperature should not exceed 260°C, with a dwell time in the wave of 5 seconds or less. Again, maintain a 3mm minimum distance from the package.

A soldering temperature profile is recommended, emphasizing a controlled ramp-up, a peak temperature plateau, and a controlled cooldown to prevent thermal shock.

5.3 Post-Soldering Handling

Avoid applying mechanical stress or vibration to the device while it is still hot from soldering. Allow it to cool naturally to room temperature. Dip or hand soldering should not be repeated more than once. Ultrasonic cleaning is not recommended for this device.

6. Storage and Handling

For long-term storage exceeding the standard 3-month shelf life from shipment, devices should be kept in a sealed container with a nitrogen atmosphere at 10°C~25°C and 20%~60% relative humidity. After opening the moisture-sensitive packaging, components should be used within 24 hours or as soon as possible. Rapid temperature changes in high-humidity environments must be avoided to prevent condensation, which can lead to corrosion or other damage during subsequent soldering.

7. Packaging and Ordering Information

The standard packaging configuration is 78 pieces per tube. Forty-two tubes are packed into one box, and four boxes are packed into one master carton. The label on the packaging includes fields for Customer Part Number (CPN), Manufacturer Part Number (P/N), quantity (QTY), reference designators (REF), and Lot Number (LOT No) for traceability.

8. Application Design Considerations

8.1 Typical Circuit Configuration

A typical application circuit involves a current-limiting resistor in series with the IR LED anode. The value is calculated based on the supply voltage (Vcc), the LED's forward voltage (VF ~1.2V), and the desired forward current (IF, e.g., 20mA). The phototransistor is commonly used in a switch mode, connected as a pull-down device with its collector to Vcc (through a pull-up resistor if needed) and its emitter to ground. The voltage at the collector node will be low when the beam is uninterrupted (transistor ON) and high when the beam is blocked (transistor OFF).

8.2 Design Factors

• Object Detection: The device detects opaque objects that fully interrupt the infrared beam within the slot. Reflective or translucent materials may not trigger a reliable state change.
• Ambient Light Immunity: The 940nm wavelength and matched spectral response offer good rejection of common visible ambient light. However, strong sources of infrared light (e.g., sunlight, incandescent bulbs) can potentially cause interference and may require optical shielding or modulation/demodulation techniques for critical applications.
• Response Speed: The 15 µs response time allows for detection of objects moving at relatively high speeds, suitable for encoders and speed sensors.
• Alignment: The built-in converging optics simplify alignment, but the PCB must be designed so that the leads insert without stress, and the slot must remain unobstructed.

9. Technical Comparison and Positioning

The ITR9707 represents a standard, cost-effective solution for through-hole mounting. Its key differentiators are its specific 940nm wavelength, which is a common industry standard, and its robust construction. Compared to reflective sensors, interrupters provide more reliable and consistent detection as they are less susceptible to variations in target surface reflectivity. Compared to modern surface-mount devices, the through-hole package offers mechanical robustness in applications subject to vibration or where manual assembly is used.

10. Frequently Asked Questions (FAQ)

Q: What is the typical operating distance or gap?
A: The operating "gap" is the physical slot within the package itself. The device detects any opaque object that enters and blocks this internal slot. It is not used for sensing objects at a distance outside the package.

Q: Can I drive the IR LED with a voltage source directly?
A: No. An LED is a current-driven device. A series current-limiting resistor is mandatory to prevent excessive current that would destroy the LED, even if the supply voltage seems low.

Q: How do I interpret the minimum IC(on) value of 0.5mA?
A> This is the guaranteed minimum output current when the input is driven under standard test conditions (IF=20mA, VCE=5V). Your circuit design should function correctly even if the actual device is at this minimum specification, ensuring robustness over production variations.

Q: Is this sensor immune to sunlight?
A> While the 940nm filter helps, direct sunlight contains a significant amount of infrared radiation and can saturate the sensor. For outdoor use or in very bright indoor environments, additional optical shielding or electronic filtering (e.g., modulated light) is recommended.

11. Practical Application Examples

Example 1: Paper Jam Detection in a Printer. The interrupter is mounted so that a paper flag or the paper itself passes through its slot. When paper is present, the beam is blocked, and the phototransistor is off. A paper jam or out-of-paper condition (no blockage) causes the transistor to turn on, signaling the microcontroller.

Example 2: Rotary Encoder for Motor Speed. A slotted disk attached to a motor shaft rotates between the arms of the interrupter. As each slot passes through, the beam is alternately interrupted and allowed to pass, generating a square wave pulse train. The frequency of this signal is directly proportional to the motor's rotational speed.

12. Operating Principle

The ITR9707 operates on the principle of transmitted light interruption. An infrared light beam is generated by the GaAlAs LED. This beam travels across a small air gap within the device's housing and is focused onto the sensitive area of the silicon NPN phototransistor. The phototransistor acts as a current source; incident photons generate electron-hole pairs in its base region, inducing a base current which is then amplified by the transistor's gain, resulting in a much larger collector current. When an object blocks the beam, the photon flux drops to zero, the base current ceases, and the collector current falls to its very low dark current level. This sharp change in output current is used as a digital signal indicating the object's presence.

13. Technology Trends

Opto interrupters remain fundamental components in position and motion sensing. Current trends include the development of surface-mount device (SMD) versions for automated assembly, which offer smaller footprints and lower profiles. There is also a move towards integrating additional circuitry on-chip, such as Schmitt triggers for digital output with hysteresis, amplifiers for analog output, or even full encoder logic. Furthermore, advancements in packaging materials aim to improve thermal performance and resistance to board-washing processes. The core principle of optical interruption, however, continues to be valued for its simplicity, reliability, and non-contact nature.