Infrared LED Emitter LTE-3271BL Datasheet - High Power - Blue Package - 940nm Wavelength - English Technical Document

1. Product Overview

The LTE-3271BL is a high-power infrared (IR) light-emitting diode (LED) designed for applications requiring robust optical output. Its core design philosophy centers on delivering high radiant intensity while maintaining operational efficiency, particularly under high-current and pulse-driving conditions. The device is housed in a distinctive blue transparent package, which can aid in visual identification during assembly and inspection processes.

The primary target markets for this component include industrial automation, security systems (e.g., surveillance camera illumination), optical sensors, and communication systems utilizing infrared signals. Its ability to handle high peak forward currents makes it suitable for pulsed operation scenarios common in distance measurement, object detection, and data transmission.

2. In-Depth Technical Parameter Analysis

2.1 Absolute Maximum Ratings

These ratings define the stress limits beyond which permanent damage to the device may occur. Operation at or near these limits is not recommended for extended periods.

• Power Dissipation (P_D): 150 mW. This is the maximum amount of power the device can dissipate as heat at an ambient temperature (T_A) of 25°C. Exceeding this limit risks thermal runaway and failure.
• Peak Forward Current (I_FP): 2 A. This is the maximum allowable instantaneous forward current, specified under pulse conditions of 300 pulses per second (pps) with a 10 µs pulse width. This rating is crucial for pulsed IR applications like remote controls or proximity sensors.
• Continuous Forward Current (I_F): 100 mA. The maximum DC current that can be applied continuously without exceeding the power dissipation rating.
• Reverse Voltage (V_R): 5 V. Applying a reverse voltage higher than this can cause junction breakdown.
• Operating & Storage Temperature: -40°C to +85°C and -55°C to +100°C, respectively. These ranges ensure reliable performance in harsh environments.
• Lead Soldering Temperature: 260°C for 5 seconds at a distance of 1.6mm from the package body. This defines the thermal profile tolerance during assembly.

2.2 Electro-Optical Characteristics

These parameters, measured at T_A=25°C, define the device's performance under typical operating conditions.

• Radiant Intensity (I_E): This is the core optical output parameter, measured in milliwatts per steradian (mW/sr). The device is sorted into Binning Grades (B, C, D, E) based on this value at I_F = 100mA, with minimum values ranging from 30 mW/sr (BIN B) to 62 mW/sr (BIN E). This binning allows for selection based on required output power.
• Peak Emission Wavelength (λ_P): 940 nm. This places the LED in the near-infrared spectrum, invisible to the human eye but detectable by silicon photodiodes and many imaging sensors.
• Spectral Line Half-Width (Δλ): 50 nm (typical). This indicates the spectral bandwidth; a narrower width would indicate a more monochromatic source.
• Forward Voltage (V_F): Has two specified conditions: 1.6V typical at 50mA and 2.3V typical at 500mA. The increase with current is due to the diode's internal series resistance. The low V_F contributes to higher electrical efficiency.
• Reverse Current (I_R): 100 µA maximum at V_R=5V. This is the leakage current when the device is reverse-biased.
• Viewing Angle (2θ_1/2): 50 degrees (typical). This is the full angle at which the radiant intensity drops to half of its maximum value (on-axis). A wide viewing angle is beneficial for applications requiring broad area illumination.

3. Binning System Explanation

The LTE-3271BL employs a performance-based binning system primarily for Radiant Intensity. This is a critical quality control and selection feature.

• BIN B: Minimum Radiant Intensity of 30 mW/sr at I_F=100mA.
• BIN C: Minimum Radiant Intensity of 44 mW/sr at I_F=100mA.
• BIN D: Minimum Radiant Intensity of 52 mW/sr at I_F=100mA.
• BIN E: Minimum Radiant Intensity of 62 mW/sr at I_F=100mA.

This system allows designers to select components that guarantee a minimum optical output for their application, ensuring consistency in system performance, especially in volume production. There is no indicated binning for forward voltage or peak wavelength in this datasheet; these parameters are given as typical/maximum values.

4. Performance Curve Analysis

The datasheet provides several characteristic curves that illustrate device behavior beyond the tabulated single-point specifications.

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 approximate 50 nm spectral half-width. The curve shape is typical for an AlGaAs-based IR LED.

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

This is the fundamental I-V curve. It shows the exponential relationship at low currents transitioning to a more linear relationship at higher currents due to series resistance. Designers use this to determine the necessary drive voltage for a target operating current.

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

This derating curve is essential for thermal management. It shows the maximum allowable continuous forward current decreasing as ambient temperature increases. At 85°C, the maximum I_F is significantly lower than the 100mA rating at 25°C. Failure to adhere to this curve can lead to overheating.

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

Figure 4 shows that optical output decreases as temperature increases (a negative temperature coefficient), a common trait in LEDs. Figure 5 shows that output increases super-linearly with current at lower currents, then tends to saturate at higher currents due to thermal and efficiency droop effects.

4.5 Radiation Diagram (Fig. 6)

This polar plot visually represents the spatial distribution of light (viewing angle). The concentric circles represent relative intensity (from 0 to 1.0). The plot confirms the approximately 50-degree half-angle, showing a smooth, wide beam pattern suitable for area illumination.

5. Mechanical and Package Information

The device uses a standard LED package format with a flange for mechanical stability and heat dissipation.

• Package Type: Blue transparent epoxy resin.
• Lead Finish: Tin-dipped, providing good solderability.
• Packaging: Supplied in ammo pack (embossed carrier tape) for automated assembly.
• Key Dimensional Tolerances: Overall dimensions have a tolerance of ±0.25mm unless otherwise specified. Lead spacing is measured at the point where leads exit the package. A maximum resin protrusion of 1.5mm under the flange is allowed.
• Polarity Identification: Typically, the longer lead denotes the anode (+). The datasheet diagram should be consulted for definitive identification, often indicated by a flat or notch on the package.

6. Soldering and Assembly Guidelines

Proper handling is critical to reliability.

• Reflow Soldering: While specific profile details are not provided, the absolute rating for lead soldering (260°C for 5s at 1.6mm from body) must be respected. A standard lead-free reflow profile with a peak temperature below 260°C is generally applicable, but the time above liquidus should be minimized.
• Manual Soldering: Use a temperature-controlled iron. Apply heat to the lead, not the package body, and complete the joint within 3 seconds.
• ESD Precautions: Although not explicitly stated, LEDs are semiconductor devices and should be handled with standard ESD (Electrostatic Discharge) precautions.
• Storage Conditions: Store in the specified temperature range (-55°C to +100°C) in a dry, non-corrosive environment. Moisture-sensitive devices should be kept in sealed bags with desiccant if intended for reflow soldering.

7. Application Suggestions

7.1 Typical Application Scenarios

• Infrared Illumination: For CCTV cameras in low-light or no-light conditions. The wide viewing angle provides broad coverage.
• Optical Sensors: Used as the light source in proximity sensors, object counters, and liquid level detectors.
• Data Transmission: Suitable for short-range, line-of-sight IR data links (e.g., remote controls, IrDA), especially when driven in pulsed mode at its high peak current rating.
• Industrial Automation: Machine vision lighting, position sensing, and safety curtain emitters.

7.2 Design Considerations

• Current Limiting: Always use a series current-limiting resistor or a constant-current driver circuit. The low forward voltage means it can be easily damaged by direct connection to a voltage source.
• Thermal Management: For continuous operation at high currents (e.g., >70mA), consider the derating curve (Fig. 2). Adequate PCB copper area (thermal pad) connected to the leads can help dissipate heat.
• Pulse Driving: For pulse operation up to 2A, ensure the driver circuit can deliver the required peak current with a fast rise/fall time. The duty cycle must be low enough to keep the average power dissipation within limits.
• Optical Design: The wide viewing angle may require lenses or reflectors to collimate the beam for long-range applications. The blue package does not filter the IR light; it is transparent to 940nm.

8. Technical Comparison and Differentiation

The LTE-3271BL's key differentiators in its class are its combination of high radiant intensity (up to BIN E: 62 mW/sr min) and high peak current capability (2A). Many standard IR LEDs offer lower peak current ratings (e.g., 1A or less). This makes it particularly strong in applications requiring bright, pulsed IR flashes. The wide 50-degree viewing angle is also broader than some competitors aimed at more focused beams, giving it an advantage in area illumination tasks. The low forward voltage contributes to better power efficiency compared to devices with higher V_F at similar currents.

9. Frequently Asked Questions (Based on Technical Parameters)

Q1: Can I drive this LED directly from a 5V microcontroller pin?
A: No. A microcontroller pin typically sources 20-40mA. Even if it could source 100mA, the LED's forward voltage is only ~1.6-2.3V. Connecting it directly would attempt to pull excessive current, damaging both the LED and the microcontroller. Always use a driver circuit (transistor/MOSFET) with a current-limiting resistor.

Q2: What is the difference between BIN B and BIN E?
A: BIN E guarantees at least twice the minimum radiant intensity of BIN B (62 vs. 30 mW/sr at 100mA). This means a BIN E device will produce a significantly brighter infrared beam under the same electrical conditions. BIN E parts are typically selected for applications requiring maximum range or signal strength.

Q3: How do I use the 2A peak current rating?
A: This rating is for pulsed operation only (300pps, 10µs pulse width). The average current must still comply with the continuous current and power dissipation limits. For example, a 2A pulse at 10µs and 300Hz has a duty cycle of 0.3% and an average current of only 6mA, well within limits. This allows for very bright, short pulses for long-distance sensing.

Q4: Why is the package blue if it emits infrared light?
A: The blue dye in the epoxy is transparent to the 940nm infrared light generated by the semiconductor chip inside. The color is for human visual identification and branding; it does not affect the optical output wavelength.

10. Practical Use Case Example

Designing a Long-Range Passive Infrared (PIR) Sensor Trigger Illuminator:
A security system uses a PIR motion sensor that has a range of 15 meters in daylight but only 5 meters in total darkness. To extend its nighttime range, an IR illuminator is added.
1. Component Selection: The LTE-3271BL (BIN E) is chosen for its high radiant intensity, ensuring enough IR light reaches distant objects.
2. Circuit Design: The LED is driven by a MOSFET switch controlled by the system's microcontroller. A series resistor sets the continuous current to 80mA for general area illumination. For a 'boost' mode upon detecting potential motion, the microcontroller pulses the LED at 1.5A (within the 2A rating) with a 20µs pulse width and 100Hz frequency, dramatically increasing instantaneous illumination for sensor confirmation.
3. Thermal Design: The PCB includes a generous copper pour connected to the LED's cathode lead to act as a heat sink, ensuring the 80mA continuous operation stays within the derated current limit at the expected maximum ambient temperature of 60°C.
4. Optical Result: The wide 50-degree viewing angle of the LED adequately covers the sensor's field of view, successfully restoring the system's detection range to 15 meters at night.

11. Operational Principle

The LTE-3271BL is a semiconductor photonic device. When a forward voltage exceeding its junction potential (V_F) is applied, electrons are injected across the p-n junction. These electrons recombine with holes in the active region of the semiconductor material (typically aluminum gallium arsenide - AlGaAs). This recombination process releases energy in the form of photons. The specific composition of the AlGaAs alloy is engineered so that the energy bandgap corresponds to a photon wavelength of approximately 940 nanometers, which is in the near-infrared region of the electromagnetic spectrum. The generated light is emitted through the transparent epoxy package. The radiant intensity is directly related to the rate of carrier recombination, which is proportional to the forward current (I_F).

12. Technology Trends

Infrared emitter technology continues to evolve alongside broader LED and optoelectronic trends. Key directions include:
Increased Efficiency: Research focuses on improving the wall-plug efficiency (optical power out / electrical power in) of IR LEDs, reducing heat generation and power consumption for battery-operated devices.
Higher Power Density: Development of chip-scale packages and advanced thermal management materials allows for higher continuous and pulsed power from smaller form factors.
Integrated Solutions: There is a trend toward combining the IR emitter with a driver IC, photodiode, or even a microcontroller in a single module, simplifying system design for smart sensors and IoT devices.
Wavelength Precision & Variety: While 940nm is common (avoiding solar spectral peaks for reduced ambient light interference), emitters at 850nm (often with slight visible red glow) and longer wavelengths like 1050nm or 1550nm are gaining traction for specific applications like eye-safe LiDAR or gas sensing. The fundamental operating principle remains the same, but material science advances enable these new wavelengths and improved performance characteristics.