IR3494-30C/H80/L419 Infrared LED Datasheet - 4mm T-1 3/4 Package - Wavelength 940nm - Forward Voltage 1.2V - Radiant Intensity 3.5mW/sr - English Technical Document

1. Product Overview

The IR3494-30C/H80/L419 is a high-intensity infrared emitting diode designed for applications requiring reliable and efficient infrared light emission. Molded in a water-clear plastic package, this device is engineered to deliver consistent performance in a compact T-1 3/4 (4mm) form factor. Its primary function is to emit infrared radiation at a peak wavelength of 940nm, making it spectrally compatible with common phototransistors, photodiodes, and infrared receiver modules. The device features a standard 2.54mm lead spacing for easy integration into standard PCB layouts.

2. Key Features and Advantages

The core advantages of this component stem from its design and material selection. It offers high reliability, which is critical for long-term applications. The high radiant intensity ensures strong signal transmission, improving the operational range and signal-to-noise ratio in sensing systems. A low forward voltage characteristic contributes to overall system energy efficiency. Furthermore, the component is compliant with environmental regulations, being lead-free (Pb-free) and designed to remain within RoHS compliance standards.

3. Absolute Maximum Ratings

Operating the device beyond these limits may cause permanent damage. The ratings are specified at an ambient temperature (Ta) of 25°C.

• Continuous Forward Current (I_F): 100 mA
• Peak Forward Current (I_FP): 1.0 A (Pulse Width ≤100μs, Duty Cycle ≤1%)
• Reverse Voltage (V_R): 5 V
• Operating Temperature (T_opr): -40°C to +85°C
• Storage Temperature (T_stg): -40°C to +100°C
• Soldering Temperature (T_sol): 260°C (for ≤5 seconds)
• Power Dissipation (P_d): 180 mW (at or below 25°C free air temperature)

4. Electro-Optical Characteristics

The following parameters define the device's performance under standard test conditions (Ta=25°C). Typical values represent the most common performance, while minimum and maximum values define the acceptable range.

4.1 Radiant and Spectral Properties

• Radiant Intensity (I_e): 2.5 mW/sr (Min), 3.5 mW/sr (Typ), 5.5 mW/sr (Max) at I_F=20mA. Under pulsed operation (I_F=250mA, f=60Hz, 50% duty cycle), the typical radiant intensity is 40 mW/sr.
• Peak Wavelength (λ_p): 940 nm (Typical) at I_F=20mA.
• Spectral Bandwidth (Δλ): 50 nm (Typical) at I_F=20mA, defining the spectral width at half the maximum intensity.

4.2 Electrical Properties

• Forward Voltage (V_F):
  • At I_F=20mA: 1.10V (Min), 1.20V (Typ), 1.50V (Max)
  • At I_F=100mA: 1.20V (Min), 1.30V (Typ), 1.70V (Max)
• Reverse Current (I_R): 10 μA (Maximum) at V_R=5V.

4.3 Viewing Angle

The spatial distribution of emitted light is not uniform. The viewing angle, defined as the full angle at half the maximum radiant intensity (2θ_1/2), is:

• X position: 95 degrees (Typical)
• Y position: 45 degrees (Typical)

This indicates an asymmetric radiation pattern, which is a critical factor in optical system design for aligning the emitter with a receiver.

5. Performance Curve Analysis

The datasheet provides several characteristic curves that are essential for detailed design work.

5.1 Forward Current vs. Ambient Temperature

This curve shows the derating of the maximum allowable forward current as the ambient temperature increases. To prevent overheating and ensure reliability, the forward current must be reduced when operating above 25°C.

5.2 Spectral Distribution

The graph plots relative radiant intensity against wavelength, centered around the 940nm peak. It visually confirms the 50nm typical bandwidth, showing that most of the optical power is concentrated between approximately 915nm and 965nm. This narrow bandwidth is beneficial for filtering out ambient light noise.

5.3 Radiant Intensity vs. Forward Current

This is a crucial relationship showing that radiant intensity increases with forward current, but not necessarily in a perfectly linear fashion, especially at higher currents due to thermal and efficiency effects. The curve allows designers to select an operating current that delivers the required optical output power.

5.4 Forward Current vs. Forward Voltage

This IV characteristic curve is fundamental for designing the drive circuit. It shows the exponential relationship, helping to determine the necessary voltage compliance for a constant current driver or to calculate series resistor values for a voltage-driven design.

5.5 Relative Radiant Intensity vs. Angular Displacement

Separate curves for the X and Y positions illustrate the asymmetric viewing angle. The intensity drops to half its maximum value at ±47.5 degrees in the X-plane and ±22.5 degrees in the Y-plane. This pattern must be considered when aligning the LED with a sensor to ensure optimal signal strength.

6. Mechanical and Package Information

6.1 Package Dimensions

The device uses a standard T-1 3/4 (4mm diameter) round package. The technical drawing provides all critical dimensions including body diameter, lens shape, lead diameter, and lead spacing. Key notes specify that all dimensions are in millimeters and standard tolerances are ±0.25mm unless otherwise stated. The exact mechanical drawing is essential for creating accurate PCB footprints and ensuring proper placement in assemblies.

6.2 Polarity Identification

Infrared LEDs are polarized components. The datasheet drawing indicates the cathode, typically identified by a flat spot on the package rim or a shorter lead. Correct polarity must be observed during assembly to prevent device failure.

7. Soldering and Assembly Guidelines

The absolute maximum rating for soldering temperature is 260°C for a duration not exceeding 5 seconds. This is typical for wave or reflow soldering processes. It is critical to adhere to these limits to prevent thermal damage to the plastic package and the internal semiconductor die. Standard industry practices for handling moisture-sensitive devices should be followed if applicable.

8. Packaging and Ordering Information

The standard packing specification is as follows: 500 pieces per bag, 5 bags per box, and 10 boxes per carton. The label on the packaging contains several codes for traceability and specification:

• CPN: Customer's Part Number
• P/N: Production Number (the manufacturer's part number)
• QTY: Quantity contained in the package
• CAT: Ranks or performance bins (e.g., for radiant intensity)
• HUE: Indicates the peak wavelength bin.
• REF: Reference code.
• LOT No: Lot number for manufacturing traceability.

9. Application Suggestions

9.1 Typical Application Scenarios

• Infrared Remote Control Units: Its high radiant intensity makes it suitable for remote controls requiring longer range or stronger signal penetration.
• Free-Air Transmission Systems: Used in short-range data links, proximity sensors, and object detection where an infrared beam is modulated.
• Smoke Detectors: Employed in obscuration-type smoke detectors, where smoke particles interrupt a beam of infrared light between an emitter and a receiver.
• General Infrared Systems: Any application requiring a dependable source of 940nm infrared light.

9.2 Design Considerations

• Drive Circuit: Always use a series current-limiting resistor or a constant current driver to prevent exceeding the maximum forward current, especially given the low forward voltage. The IV curve should be used to calculate the appropriate resistor value for a given supply voltage.
• Thermal Management: Observe power dissipation limits. If operating near maximum current or in high ambient temperatures, consider the derating curve and ensure adequate ventilation or heat sinking if the LED is mounted on a board with other heat-generating components.
• Optical Alignment: The asymmetric viewing angle (95° x 45°) is critical. The LED and the corresponding receiver (phototransistor, etc.) must be aligned according to the intended axis of sensitivity to maximize collected signal.
• Reverse Voltage Protection: The maximum reverse voltage is only 5V. In circuits where reverse bias is possible (e.g., AC coupling or inductive loads), external protection such as a diode in parallel (cathode to anode) is strongly recommended.

10. Technical Comparison and Differentiation

Compared to standard low-power infrared LEDs, the IR3494 series offers significantly higher radiant intensity (3.5 mW/sr typical vs. often less than 1 mW/sr for basic devices). This directly translates to longer operational range or the ability to use lower drive currents for the same range, improving efficiency. The 940nm wavelength is ideal as it is less visible to the human eye than 850nm LEDs (which have a faint red glow) while still being highly detectable by silicon-based photodetectors. The asymmetric beam pattern can be an advantage in applications requiring a focused beam in one plane and wider coverage in another.

11. Frequently Asked Questions (Based on Technical Parameters)

Q: Can I drive this LED directly from a 5V microcontroller pin?
A: No. The forward voltage is only about 1.2-1.3V. Connecting it directly to 5V without a current-limiting resistor would cause a very high current to flow, destroying the LED instantly. A series resistor must always be used.

Q: What is the difference between the 'Typical' and 'Maximum' radiant intensity?
A: The typical value (3.5 mW/sr) is what most devices from a production batch will deliver. The maximum (5.5 mW/sr) is the upper limit of the specification; some devices may perform better, but designs should be based on the minimum (2.5 mW/sr) to ensure system functionality under all conditions.

Q: Why is the viewing angle different in X and Y directions?
A> This is a result of the internal chip structure and the shape of the plastic lens. It is an intentional design characteristic that shapes the emitted light pattern, which can be useful for targeting the infrared beam.

Q: Is a heat sink required?
A: For continuous operation at the maximum rated current of 100mA, the power dissipation is approximately 130mW (1.3V * 0.1A), which is below the 180mW rating at 25°C. However, if the ambient temperature is high or the LED is in a sealed enclosure, thermal derating per the performance curves must be applied, and a heat sink or reduced operating current may be necessary.

12. Practical Design and Usage Case

Case: Designing a Long-Range IR Remote Control Transmitter
Objective: To achieve a reliable range of 15 meters in a typical living room environment.
Design Steps:
1. Drive Current Selection: Consult the 'Radiant Intensity vs. Forward Current' curve. To maximize range, operate near the upper limit. Selecting I_F = 80mA provides a radiant intensity of approximately 15 mW/sr (from the curve), a significant increase over the 20mA value.
2. Circuit Design: For a 3.3V supply, calculate the series resistor. Using the typical V_F at 80mA (estimated from the IV curve as ~1.28V): R = (V_supply - V_F) / I_F = (3.3V - 1.28V) / 0.08A = 25.25Ω. Use a standard 24Ω or 27Ω resistor. Verify power in the resistor: P = I²R = (0.08)²*27 = 0.173W, so a 1/4W resistor is sufficient.
3. Thermal Check: LED power dissipation: P_d = V_F * I_F = 1.28V * 0.08A = 102mW. This is well within the 180mW limit at 25°C.
4. Optical Alignment: Mount the LED on the PCB edge of the remote. Orient the LED so its wider 95-degree plane (X) aligns horizontally to cover a broad area, while the narrower 45-degree plane (Y) is vertical to concentrate energy forward. This optimizes the chance of hitting the receiver even if the remote is slightly off-axis horizontally.

13. Operating Principle

An Infrared Light Emitting Diode (IR LED) is a semiconductor p-n junction diode. When a forward voltage is applied, electrons from the n-region and holes from the p-region are injected across the junction. When these charge carriers recombine in the active region of the semiconductor material (typically based on gallium arsenide, GaAs), energy is released in the form of photons. The specific composition of the semiconductor layers determines the wavelength of the emitted light. For this device, the material is engineered to produce photons primarily at a wavelength of 940 nanometers, which is in the near-infrared spectrum, invisible to the human eye but easily detectable by silicon photodiodes and phototransistors.

14. Technology Trends

The development of infrared LEDs continues to focus on several key areas: increasing wall-plug efficiency (optical power out / electrical power in) to enable lower power consumption or higher output from battery-operated devices; improving modulation speed for high-speed data communication applications like IrDA; and developing devices with even narrower spectral bandwidths for applications requiring precise wavelength matching, such as gas sensing. There is also a trend towards surface-mount device (SMD) packages for automated assembly, although through-hole packages like the T-1 3/4 remain popular for their robustness and ease of hand-soldering in prototyping and certain high-reliability applications. The 940nm wavelength remains a industry standard due to its optimal balance between silicon detector sensitivity and low visibility.

Important Notes: The specifications provided in this document are subject to change without notice. When using this product, the absolute maximum ratings and operating conditions outlined herein must be strictly observed. The manufacturer assumes no responsibility for damage resulting from use outside these specified conditions. The information contained in this datasheet is protected by copyright and should not be reproduced without authorization.