LTE-3226 IR Emitter Data Sheet - 5.0mm Package - 850nm Wavelength - 1.6V Forward Voltage - 120mW Power Dissipation - English Technical Documentation

1. Product Overview

The LTE-3226 is a high-performance infrared (IR) emitter designed for applications requiring fast response times and significant optical output. Its core advantages include high-speed operation, high radiant power output, suitability for pulsed driving schemes, and a clear transparent package that facilitates precise optical alignment. This device is typically targeted at markets involving remote control systems, optical switches, industrial sensors, and short-range data communication links where reliable infrared signaling is essential.

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): 120 mW. This is the maximum total power the device can dissipate as heat under any operating condition at an ambient temperature (T_A) of 25°C.
• Peak Forward Current (I_FP): 1 A. This high current is permissible only under specific pulsed conditions: a pulse width of 10 µs and a pulse repetition rate not exceeding 300 pulses per second (pps). This rating is crucial for applications like high-brightness, short-duration signaling.
• Continuous Forward Current (I_F): 60 mA. This is the maximum DC current that can be applied continuously to the device.
• Reverse Voltage (V_R): 5 V. Exceeding this voltage in the reverse direction can cause junction breakdown.
• Operating & Storage Temperature Range: -40°C to +85°C. This wide range ensures reliability in harsh environmental conditions.
• Lead Soldering Temperature: 260°C for 6 seconds, measured 1.6mm from the package body. This defines the thermal profile tolerance for assembly processes.

2.2 Electrical & Optical Characteristics

These parameters are measured at T_A=25°C and define the typical performance of the device under specified test conditions.

• Radiant Intensity (I_e): A key optical output parameter. Typical values are 26 mW/sr at I_F=20mA and 65 mW/sr at I_F=50mA. The significant increase with current highlights the device's capability for high-power output.
• Peak Emission Wavelength (λ_P): 850 nm (typical). This places the device in the near-infrared spectrum, which is ideal for silicon photodetectors and is less visible to the human eye than shorter wavelengths.
• Spectral Line Half-Width (Δλ): 40 nm (typical). This indicates the spectral bandwidth of the emitted light.
• Forward Voltage (V_F): 1.6 V (typical), with a maximum of 2.0 V at I_F=50mA. This low voltage is beneficial for low-power circuit design.
• Reverse Current (I_R): 100 µA (maximum) at V_R=5V.
• Viewing Angle (2θ_1/2): 25 degrees (typical). This is the full angle at which the radiant intensity drops to half of its peak value, defining the beam's angular spread.

3. Performance Curve Analysis

The datasheet provides several graphical representations of device behavior, which are critical for design optimization.

3.1 Spectral Distribution (Fig. 1)

This curve shows the relative radiant intensity as a function of wavelength, centered around the 850nm peak with the characteristic 40nm half-width. It confirms the device emits in the intended infrared band.

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

This IV curve illustrates the nonlinear relationship between current and voltage. The typical V_F of 1.6V at 50mA is visible. Designers use this to calculate series resistor values and power dissipation in the LED.

3.3 Relative Radiant Intensity vs. Forward Current (Fig. 5)

This graph demonstrates the super-linear increase in optical output with drive current, justifying the use of pulsed high-current operation (up to the 1A peak rating) to achieve very high instantaneous brightness.

3.4 Relative Radiant Intensity vs. Ambient Temperature (Fig. 4)

This curve shows the negative temperature coefficient of the optical output. As ambient temperature rises, the radiant intensity decreases. This must be factored into designs operating over the full temperature range to ensure consistent signal strength.

3.5 Radiation Diagram (Fig. 6)

This polar plot visually represents the 25-degree viewing angle, showing the spatial distribution of the emitted infrared light. It is essential for designing lenses, reflectors, and aligning the emitter with a detector.

4. Mechanical & Packaging Information

4.1 Package Dimensions

The LTE-3226 comes in a standard 5.0mm radial leaded package with a clear transparent lens. Key dimensional notes include: all dimensions are in millimeters, with a general tolerance of ±0.25mm; the maximum resin protrusion under the flange is 1.5mm; and lead spacing is measured at the point where leads exit the package body.

4.2 Polarity Identification

The device has a flat side on the package body, which typically indicates the cathode (negative) lead. The longer lead is usually the anode (positive). Always verify polarity before connection to prevent reverse bias damage.

5. Soldering & Assembly Guidelines

Adherence to soldering specifications is vital for reliability. The absolute maximum rating specifies that leads can be subjected to 260°C for 6 seconds when measured 1.6mm from the package body. This implies that during wave or hand soldering, the heat exposure time should be minimized. For reflow soldering, a profile with a peak temperature below 260°C is recommended to stay within this limit. Prolonged exposure to high temperatures can degrade the internal epoxy and semiconductor materials.

6. Application Suggestions

6.1 Typical Application Scenarios

• Infrared Remote Controls: The high speed and power make it suitable for transmitting coded data pulses.
• Optical Switches & Sensors: Used in object detection, counting, and position sensing when paired with a photodetector.
• Industrial Data Links: For short-range, noise-immune serial communication in electrically noisy environments.
• Security Systems: As an invisible illumination source for IR-sensitive cameras.

6.2 Design Considerations

• Current Limiting: Always use a series resistor or constant current driver to limit the forward current to the desired level (e.g., 20mA, 50mA, or pulsed 1A), never connect directly to a voltage source.
• Heat Management: While the package can dissipate 120mW, operating at high continuous currents or in high ambient temperatures may require consideration of the thermal environment to maintain performance and longevity.
• Optical Design: The 25-degree viewing angle and clear package allow for easy coupling with lenses or light pipes to shape the beam for specific applications.
• Circuit Protection: Consider adding a reverse-biased protection diode in parallel if the circuit exposes the LED to potential voltage reversals beyond 5V.

7. Technical Comparison & Differentiation

Compared to standard low-power IR LEDs, the LTE-3226's key differentiators are its high-speed capability and high-power output, especially under pulsed conditions. The 1A peak current rating is significantly higher than that of typical indicator IR LEDs. The clear package, as opposed to a diffused or tinted one, provides a more directed and efficient beam, which is advantageous for focused applications. Its 850nm wavelength is a common standard, ensuring broad compatibility with silicon photodetectors and receivers.

8. Frequently Asked Questions (Based on Technical Parameters)

Q: Can I drive this LED with a 5V microcontroller pin directly?
A: No. A typical microcontroller pin cannot source 50-60mA continuously, and the LED requires current limiting. You must use a transistor switch (e.g., BJT or MOSFET) driven by the MCU pin, with a series resistor to set the LED current based on the supply voltage and the LED's V_F.

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 beam is. Aperture Radiant Incidence measures the power density arriving at a specific surface area (cm²) at a given distance. The latter is more directly useful for calculating the signal level on a detector of known area.

Q: How does the 25-degree viewing angle affect my design?
A: It defines the beam spread. For long-range or narrow-beam applications, you may need a collimating lens. For wider coverage, the native angle may be sufficient, or a diffuser might be used.

9. Practical Design Case

Scenario: Designing a Long-Range Infrared Beacon.
Goal: Maximize detection range for a pulsed beacon.
Design Approach:
1. Drive Circuit: Use a MOSFET switch controlled by a timer IC to pulse the LED at its maximum rating: 1A pulses with a 10µs width and a low duty cycle (e.g., <0.3% at 300pps). This delivers peak optical power far exceeding DC operation.
2. Current Setting: Calculate the series resistor: R = (V_supply - V_F) / I_FP. For a 5V supply and V_F ~1.8V at high current, R = (5 - 1.8) / 1 = 3.2Ω. Use a 3.3Ω, high-wattage resistor.
3. Optics: Pair the LED with a small collimating lens to reduce the effective beam angle from 25 degrees to perhaps 5-10 degrees, concentrating the emitted power into a narrower beam for increased intensity at a distance.
4. Thermal Check: Calculate average power: P_avg = V_F * I_FP * duty cycle. With a 0.3% duty cycle, P_avg ≈ 1.8V * 1A * 0.003 = 5.4mW, well within the 120mW dissipation limit, ensuring no overheating.

10. Operating Principle Introduction

The LTE-3226 is a light-emitting diode (LED). Its operation is based on electroluminescence in a semiconductor p-n junction. When a forward voltage exceeding the junction's built-in potential (approximately 1.6V for this material) 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 semiconductor materials used (typically aluminum gallium arsenide - AlGaAs) determine the wavelength of the emitted photons, which in this case is in the 850nm infrared range. The clear epoxy package acts as a lens, shaping the output beam.

11. Technology Trends

In the field of infrared emitters, general trends include:
Increased Efficiency: Development of materials and structures to produce more optical power (lumens or radiant flux) per unit of electrical input power (watts), reducing heat generation and energy consumption.
Higher Speed: Optimization for faster modulation rates to support higher data transmission speeds in optical communication applications.
Miniaturization: Moving towards surface-mount device (SMD) packages for automated assembly and smaller form factors, though radial leaded packages like the 5mm remain popular for prototyping and certain high-power/legacy applications.
Wavelength Diversification: While 850nm and 940nm are standards, other wavelengths are being developed for specific sensing applications (e.g., gas sensing, biomedical monitoring). The LTE-3226, as an 850nm device, remains a mainstream component due to its compatibility with silicon detectors.