LTE-3271T IR Emitter Datasheet - 940nm Wavelength - High Current & Low Forward Voltage - English Technical Document

1. Product Overview

The LTE-3271T is a high-power infrared (IR) light-emitting diode (LED) designed for applications requiring robust optical output. Its core advantages lie in its specialized construction for handling high drive currents while maintaining a relatively low forward voltage drop, which contributes to higher efficiency in power-sensitive designs. This emitter operates at a peak wavelength of 940 nanometers, placing it in the near-infrared spectrum, which is ideal for applications like proximity sensors, optical switches, and remote control systems where visible light emission is undesirable. The device is characterized by a wide viewing angle, ensuring a broad and uniform radiation pattern suitable for area illumination or sensing.

2. In-Depth Technical Parameter Analysis

2.1 Absolute Maximum Ratings

The device is rated for a maximum continuous forward current (I_F) of 100 mA. However, it is capable of handling significantly higher peak currents under pulsed operation, with a rating of 2 Amperes for pulses of 10 microseconds duration at a 300 pulses-per-second rate. This highlights its suitability for pulsed applications like data transmission or burst-mode sensing. The maximum power dissipation is 150 mW. The operating and storage temperature ranges are specified from -40°C to +85°C and -55°C to +100°C, respectively, indicating robust performance across a wide range of environmental conditions. The device can withstand a reverse voltage (V_R) of up to 5 Volts.

2.2 Electrical & Optical Characteristics

Key performance parameters are measured at an ambient temperature (T_A) of 25°C. The device features a binning system for its radiant output:

• BIN B: Aperture Radiant Incidence (E_e) 0.64 - 1.20 mW/cm²; Radiant Intensity (I_E) 4.81 - 9.02 mW/sr (at I_F=20mA).
• BIN C: E_e 0.80 - 1.68 mW/cm²; I_E 6.02 - 12.63 mW/sr.
• BIN D: E_e 1.12 mW/cm² (Min); I_E 8.42 mW/sr (Min).

The forward voltage (V_F) is typically 1.6V at 50mA and 2.1V at 250mA, confirming its low-voltage operation characteristic. The peak emission wavelength is centered at 940 nm with a typical spectral half-width (Δλ) of 50 nm. The viewing angle (2θ_1/2) is 50 degrees, defining the cone within which the radiant intensity is at least half of its maximum value.

3. Binning System Explanation

The product utilizes a performance binning system based on radiant output. This system groups devices according to their measured optical power (Radiant Intensity and Aperture Radiant Incidence) at a standard test current of 20mA. Bins B, C, and D represent different tiers of optical output, with Bin D offering the highest minimum guaranteed output. This allows designers to select components that precisely match the sensitivity requirements of their paired detectors or the illumination needs of their application, ensuring consistent system performance.

4. Performance Curve Analysis

The datasheet provides several characteristic graphs. Figure 1 shows the Spectral Distribution, illustrating the narrow band of emission around 940nm. Figure 2 depicts the Forward Current vs. Ambient Temperature derating curve, showing how the maximum allowable continuous current decreases as ambient temperature increases to prevent overheating. Figure 3 is the standard Current-Voltage (I-V) Curve, showing the relationship between forward current and forward voltage. Figure 4 shows how Relative Radiant Intensity decreases with increasing ambient temperature. Figure 5 shows how Relative Radiant Intensity increases with forward current, demonstrating the device's output scalability. Figure 6 is the Radiation Diagram, a polar plot visually representing the 50-degree viewing angle. Figure 7 details the Peak Forward Current vs. Pulse Duration, providing crucial data for designing safe pulsed driving circuits by showing the maximum allowable current for a given pulse width and duty cycle.

5. Mechanical & Package Information

The device comes in a standard LED package with a flange. Key dimensional notes include: all dimensions are in millimeters, with a general tolerance of ±0.25mm unless specified otherwise. The maximum protrusion of resin under the flange is 1.5mm. Lead spacing is measured at the point where the leads exit the package body. The specific dimensional drawing from the datasheet defines the exact length, width, height, lead diameter, and positioning.

6. Soldering & Assembly Guidelines

The absolute maximum ratings specify that the leads can be soldered at a temperature of 260°C for a duration of 5 seconds, measured at a distance of 1.6mm (0.063 inches) from the package body. This is a critical parameter for wave or reflow soldering processes. Exceeding this temperature or time can damage the internal semiconductor die or the package integrity. Standard ESD (Electrostatic Discharge) precautions should be observed during handling and assembly.

7. Application Recommendations

7.1 Typical Application Scenarios

The LTE-3271T is well-suited for a variety of infrared applications, including: Infrared Remote Control Units for consumer electronics, Proximity and Presence Sensors in appliances or security systems, Optical Switches and Encoders in industrial equipment, Object Detection in automation, and Night Vision Illumination when paired with an IR-sensitive camera.

7.2 Design Considerations

• Current Driving: A constant current source is recommended for stable optical output, as LED intensity is primarily current-dependent. The driver circuit must respect both the continuous and pulsed current limits.
• Thermal Management: Although the device has a wide operating range, maintaining a lower junction temperature will ensure longer lifespan and stable output. Consider heat sinking for high-duty-cycle or high-current applications.
• Optical Design: The 50-degree viewing angle should be factored into lens or housing design. For longer-range applications, a secondary lens may be required to collimate the beam.
• Pairing with Detector: Ensure the selected photodetector or sensor is sensitive in the 940nm region for optimal system performance.

8. Technical Comparison & Differentiation

Compared to standard low-current IR LEDs, the LTE-3271T's key differentiators are its high current capability (up to 2A pulsed) and low forward voltage. This combination allows it to deliver higher optical power from a given supply voltage, improving efficiency. The explicit binning for radiant intensity provides guaranteed performance levels, offering an advantage over unbinned parts where output can vary significantly. The wide viewing angle is beneficial for applications requiring broad coverage rather than a narrow beam.

9. Frequently Asked Questions (Based on Technical Parameters)

Q: Can I drive this LED directly from a 5V microcontroller pin?
A: No. A microcontroller pin typically cannot source 100mA continuously. You must use a transistor or dedicated driver circuit. Furthermore, you must include a current-limiting resistor, as the LED's low forward voltage would cause excessive current if connected directly to 5V.

Q: What is the difference between Radiant Intensity (mW/sr) and Aperture Radiant Incidence (mW/cm²)?
A: Radiant Intensity measures optical power per solid angle (steradian), describing how concentrated the light is. Aperture Radiant Incidence measures power per unit area at a specific distance/position, often relevant for sensors. Both are related through geometry and the radiation pattern.

Q: How do I choose between Bin B, C, or D?
A: Select based on the sensitivity of your receiver circuit and the required operating distance. Bin D offers the highest guaranteed output for maximum range or signal strength. For less demanding applications, Bin B or C may be sufficient and cost-effective.

10. Practical Design Case

Case: Designing a Long-Range Proximity Sensor.
For a sensor needing a 2-meter range, the designer would select the LTE-3271T in Bin D for maximum output. They would design a pulsed driver circuit operating at the maximum rated 2A for very short pulses (e.g., 10μs) at a low duty cycle (e.g., 1%), as shown in Figure 7. This delivers high instantaneous optical power for better signal-to-noise ratio at the detector without exceeding the average power dissipation limit. A lens would be placed over the emitter to narrow the beam from the native 50 degrees to perhaps 10-15 degrees, concentrating the energy on the target area at 2 meters. The paired photodetector would have a narrow-band filter centered at 940nm to reject ambient light.

11. Operating Principle Introduction

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 into the active region. When these charge carriers recombine, they release energy in the form of photons (light). The specific wavelength of 940nm is determined by the bandgap energy of the semiconductor materials used in the construction of the diode (typically aluminum gallium arsenide, AlGaAs). The wide viewing angle is a result of the package design and the placement of the semiconductor chip relative to the epoxy lens.

12. Technology Trends

The trend in IR emitter technology continues towards higher efficiency (more optical output power per electrical input watt), which reduces heat generation and power consumption. There is also development towards higher-speed modulation capabilities for data communication applications like IrDA or optical wireless networks. Integration is another trend, with emitters being combined with drivers, sensors, or logic into single modules or ICs to simplify system design. The fundamental operating principle remains based on semiconductor physics, but advancements in materials (like new III-V compounds) and packaging techniques drive performance improvements.