LTE-5228A IR Emitter Datasheet - High Current, Low Forward Voltage, 940nm Wavelength - English Technical Document

1. Product Overview

The LTE-5228A is a high-power infrared (IR) light-emitting diode (LED) designed for applications requiring robust optical output. Its core advantages stem from its engineering for high current drive capability while maintaining a relatively low forward voltage, making it efficient for pulsed and continuous operation. The device is packaged in a clear, transparent housing, which is typical for IR emitters to minimize absorption of the emitted non-visible light. The primary target markets include industrial automation, security systems (e.g., surveillance camera illumination), optical sensors, and remote control units where reliable, invisible light sources are critical.

2. In-Depth Technical Parameter Analysis

2.1 Absolute Maximum Ratings

These ratings define the limits beyond which permanent damage to the device may occur. The LTE-5228A can dissipate up to 150 mW of power. Its peak forward current rating is exceptionally high at 2 Amperes, but this is only permissible under specific pulsed conditions (300 pulses per second with a 10 microsecond pulse width). The continuous forward current is rated at a more conventional 100 mA. The device can withstand a reverse voltage of up to 5V. The operating and storage temperature ranges are from -40°C to +85°C and -55°C to +100°C, respectively, indicating suitability for harsh environments. The lead soldering temperature is specified as 260°C for 5 seconds at a distance of 1.6mm from the package body, which is a critical parameter for assembly processes.

2.2 Electrical & Optical Characteristics

These parameters are measured at a standard test condition of 25°C ambient temperature and a forward current (I_F) of 20mA. The key optical outputs are defined in two ways: Aperture Radiant Incidence (E_e in mW/cm²) and Radiant Intensity (I_E in mW/sr). Both parameters are binned, meaning devices are sorted into performance groups (BIN A, B, C, D) after manufacturing, with BIN D representing the highest output. The peak emission wavelength (λ_Peak) is typically 940 nm, placing it firmly in the near-infrared spectrum. The spectral line half-width (Δλ) is 50 nm, indicating the spectral bandwidth of the emitted light. Electrically, the forward voltage (V_F) is between 1.2V and 1.6V at 20mA, confirming its low-voltage operation claim. The reverse current (I_R) is a maximum of 100 µA at 5V reverse bias. The viewing angle (2θ_1/2) is 40 degrees, defining the angular spread where the radiant intensity is at least half of its peak value.

3. Binning System Explanation

The datasheet clearly employs a performance binning system for the radiant output. Devices are tested and categorized into four bins (A, B, C, D) based on their measured Aperture Radiant Incidence and Radiant Intensity at I_F = 20mA. BIN A represents the lower output range, while BIN D represents the highest guaranteed output. This system allows manufacturers to offer consistent performance levels and enables designers to select a bin that precisely meets their application's sensitivity or range requirements. There is no indication of voltage or wavelength binning for this specific part number; the forward voltage and peak wavelength are given as typical/maximum ranges without bin codes.

4. Performance Curve Analysis

The datasheet provides several graphs illustrating device behavior under varying conditions.

4.1 Spectral Distribution (Fig.1)

This curve shows the relative radiant intensity as a function of wavelength. It confirms the peak at 940 nm and the approximately 50 nm spectral half-width. The shape is typical for an AlGaAs-based IR LED.

4.2 Forward Current vs. Ambient Temperature (Fig.2)

This derating curve shows how the maximum allowable continuous forward current decreases as the ambient temperature increases. This is crucial for thermal management design to ensure the junction temperature does not exceed safe limits.

4.3 Forward Current vs. Forward Voltage (Fig.3)

This is the standard I-V (current-voltage) characteristic curve. It shows the exponential relationship, with the voltage rising as current increases. The curve allows designers to determine the necessary drive voltage for a desired operating current.

4.4 Relative Radiant Intensity vs. Ambient Temperature (Fig.4) & vs. Forward Current (Fig.5)

Figure 4 illustrates the temperature dependence of light output, typically showing a decrease in efficiency as temperature rises. Figure 5 shows how the optical output increases with forward current, highlighting the non-linear relationship, especially at higher currents where efficiency may drop due to heating.

4.5 Radiation Diagram (Fig.6)

This polar plot visually represents the spatial distribution of the emitted light, confirming the 40-degree viewing angle. The diagram shows the relative intensity at different angles from the central axis (0°).

5. Mechanical & Package Information

The package is a standard LED style with a flange. Key dimensions include the lead spacing, which is measured where the leads emerge from the package body. A note specifies that the maximum protrusion of resin under the flange is 1.5mm. The package is described as "clear transparent," which is optimal for IR emission. The polarity is typically indicated by the longer lead being the anode (+) and/or a flat spot on the package rim near the cathode (-) lead, though this specific marking is not detailed in the provided text. The dimensional drawing (referenced but not provided in text) would show the exact length, width, and height.

6. Soldering & Assembly Guidelines

The primary guideline provided is the absolute maximum rating for lead soldering: 260°C for 5 seconds, measured 1.6mm (0.063") from the package body. This is a critical parameter for wave soldering or hand-soldering processes. Exceeding this can damage the internal die attach or the epoxy package. For reflow soldering, a profile with a peak temperature below 260°C and a time above liquidus tailored to the solder paste should be used. It is generally advised to avoid excessive mechanical stress on the leads during handling. Storage conditions should adhere to the specified range of -55°C to +100°C in a dry environment to prevent moisture absorption.

7. Application Suggestions

7.1 Typical Application Scenarios

• Infrared Illumination: For CCTV cameras in low-light or no-light conditions.
• Optical Sensors: As a light source in proximity sensors, object detection, and line-following robots.
• Remote Controls: For transmitting coded signals to televisions, air conditioners, etc.
• Industrial Data Links: Short-range, free-space optical communication in electrically noisy environments.
• Biometric Sensors: As part of systems for heart rate monitoring or fingerprint recognition.

7.2 Design Considerations

• Current Limiting: Always use a series resistor or constant current driver to prevent exceeding the maximum continuous current, especially given the low V_F which makes it easy to draw excessive current from a voltage source.
• Heat Sinking: For continuous operation near the maximum current, consider the thermal path. The flange may be used for mounting to a PCB with thermal vias or a heatsink.
• Pulsed Operation: To achieve very high peak output (for longer range), use the pulsed mode specification (2A peak). Ensure the driver circuit can deliver the required short, high-current pulses.
• Optical Design: Pair with an appropriate lens or reflector to collimate or shape the 40-degree beam according to the application need. The clear package is compatible with secondary optics.
• ESD Protection: Although not explicitly stated, IR LEDs can be sensitive to electrostatic discharge. Implementing standard ESD precautions during handling and circuit design is recommended.

8. Technical Comparison & Differentiation

Compared to standard low-power IR LEDs, the LTE-5228A's key differentiators are its high current capability (100mA continuous, 2A pulsed) and relatively low forward voltage. This combination allows for higher radiant output without proportionally higher power dissipation from excessive voltage drop. The wide 40-degree viewing angle is broader than some focused IR emitters, providing more uniform illumination for area coverage rather than long-distance spotting. The clear package offers higher transmission efficiency for 940nm light compared to tinted packages used for visible LEDs.

9. Frequently Asked Questions (Based on Technical Parameters)

Q: Can I drive this LED directly from a 3.3V or 5V microcontroller pin?
A: No. The low forward voltage (max 1.6V at 20mA) means a direct connection would likely destroy the LED and potentially damage the microcontroller pin due to excessive current. A current-limiting resistor or driver circuit is mandatory.

Q: What is the difference between Aperture Radiant Incidence and Radiant Intensity?
A: Aperture Radiant Incidence (E_e) is the power density (mW/cm²) arriving at a surface placed close to and perpendicular to the LED. Radiant Intensity (I_E) is the power emitted per solid angle (mW/sr), describing the inherent directionality of the source. I_E is more useful for calculating illumination at a distance.

Q: How do I select the correct BIN?
A> Choose based on your system's sensitivity. If your receiver needs a minimum signal level, select a bin that guarantees that level at your operating current and distance. Higher bins (C, D) provide more output margin.

Q: Is a heatsink required?
A: It depends on the operating current and ambient temperature. At the maximum continuous current (100mA) and elevated ambient temperature, the power dissipation (P = V_F * I_F) approaches 160mW, which exceeds the absolute maximum power dissipation of 150mW. Therefore, for full-power continuous operation, thermal management via PCB copper area or a heatsink is necessary. For pulsed operation or lower currents, it may not be needed.

10. Practical Use Case Example

Designing a Long-Range Passive Infrared Motion Sensor Activator: A PIR motion sensor often has limited range. To extend its range at night, an IR illuminator can be used. For this application, the LTE-5228A would be driven in pulsed mode. A circuit would be designed to deliver 1A pulses (within the 2A max) at a low duty cycle (e.g., 1%) to keep average power low. This high peak current would generate very high instantaneous optical output, illuminating a scene at a distance of 20-30 meters effectively. The wide 40-degree angle would cover a broad area in front of the sensor. The clear package ensures maximum energy is projected outward. The designer would select BIN D LEDs for maximum range and use the derating curves to ensure the device temperature remains stable in an outdoor enclosure.

11. Operating Principle

The LTE-5228A is a semiconductor p-n junction diode. When a forward voltage exceeding its bandgap energy is applied, electrons and holes recombine in the active region, releasing energy in the form of photons. The specific material composition (typically Aluminum Gallium Arsenide - AlGaAs) determines the bandgap energy, which corresponds to the infrared wavelength of 940 nm. The clear epoxy package encapsulates the semiconductor chip, provides mechanical protection, and acts as a lens to shape the output beam. The radiant output is directly proportional to the rate of carrier recombination, which is controlled by the forward current.

12. Technology Trends

Infrared emitter technology continues to evolve alongside visible LED technology. Trends include:
Increased Efficiency: Development of new semiconductor materials and structures (e.g., multi-quantum wells) to extract more photons per unit of electrical input power, reducing heat generation.
Higher Power Density: Packaging improvements to handle higher drive currents and dissipate heat more effectively, enabling smaller devices with equal or greater output.
Integrated Solutions: Combining the IR emitter with a driver IC, photodiode, or even a microcontroller in a single module for simplified design in sensor applications.
Wavelength Diversification: While 940nm is common (invisible, good for silicon detectors), other wavelengths like 850nm (slightly visible red glow) or 1050nm are used for specific applications like eye-tracking or longer atmospheric transmission.
The LTE-5228A represents a mature, high-reliability component in this landscape, optimized for robust performance in demanding conditions rather than the absolute cutting edge of efficiency.