Infrared LED Emitter LTE-209 Datasheet - Package Dimensions 5.0mm - Forward Voltage 1.6V - Peak Wavelength 940nm - English Technical Document

1. Product Overview

The LTE-209 series represents a family of infrared (IR) light-emitting diodes (LEDs) designed for reliable optoelectronic applications. These components are engineered to emit light at a peak wavelength of 940 nanometers, which is within the near-infrared spectrum. This specific wavelength is commonly used in applications requiring non-visible light sources, such as proximity sensors, object detection, and optical encoders. The core advantage of this series lies in its precise manufacturing, which ensures consistent radiant intensity and spectral characteristics. The device is housed in a low-cost, miniature plastic package with an end-looking configuration, making it suitable for space-constrained designs. A key feature is its mechanical and spectral matching to specific series of phototransistors, facilitating the design of optimized emitter-detector pairs for improved system performance and signal integrity.

2. In-Depth Technical Parameter Analysis

2.1 Absolute Maximum Ratings

The absolute maximum ratings define the stress limits beyond which permanent damage to the device may occur. These ratings are specified at an ambient temperature (T_A) of 25°C. The maximum continuous forward current is 60 mA, with a peak forward current capability of 1 A under pulsed conditions (300 pulses per second, 10 μs pulse width). The maximum power dissipation is 90 mW. The device can withstand a reverse voltage of up to 5 V. The operating temperature range is from -40°C to +85°C, while the storage temperature range extends from -55°C to +100°C. For assembly, the leads can be soldered at a temperature of 260°C for a maximum duration of 5 seconds, measured 1.6mm from the package body.

2.2 Electro-Optical Characteristics

The electro-optical characteristics are the key performance parameters measured under standard test conditions (T_A=25°C, I_F=20mA). The radiant intensity (I_E), a measure of optical power emitted per unit solid angle, has a typical value of 1.383 mW/sr. The aperture radiant incidence (E_e), representing power density, is typically 0.184 mW/cm². The peak emission wavelength (λ_Peak) is centered at 940 nm, with a spectral half-width (Δλ) of 50 nm, defining the spectral purity of the emitted light. The forward voltage (V_F) typically ranges from 1.2V to a maximum of 1.6V at the test current. The reverse current (I_R) is a maximum of 100 μA when a 5V reverse bias is applied. The viewing angle (2θ_1/2), where the radiant intensity drops to half of its peak value, is 16 degrees, indicating a relatively narrow beam pattern.

3. Binning System Explanation

While the provided datasheet does not explicitly detail a multi-parameter binning system, it indicates that devices are \"SELECTED TO SPECIFIC ON-LINE INTENSITY AND RADIANT INTENSITY RANGES.\" This implies a selection or sorting process based on measured radiant intensity and possibly radiant incidence values. This pre-selection ensures that components delivered for a specific order fall within a tighter tolerance band for these key optical parameters than the absolute minimum and maximum limits stated in the general specifications. This practice enhances consistency in application performance, particularly in systems where optical output matching is critical.

4. Performance Curve Analysis

The datasheet includes several typical characteristic curves that illustrate device behavior under varying conditions.

4.1 Spectral Distribution

Figure 1 shows the spectral distribution curve, plotting relative radiant intensity against wavelength. It confirms the peak emission at 940 nm and the approximately 50 nm spectral half-width, showing the spread of emitted wavelengths around the peak.

4.2 Forward Current vs. Forward Voltage (I-V Curve)

Figure 3 depicts the forward current versus forward voltage characteristic. This curve is non-linear, typical for a diode. It shows the relationship where a small increase in voltage beyond the turn-on threshold leads to a rapid increase in current. The specified V_F of 1.2V to 1.6V at 20mA can be contextualized within this curve.

4.3 Relative Radiant Intensity vs. Forward Current

Figure 5 illustrates how the optical output (relative radiant intensity) changes with the forward drive current. Generally, the output increases with current, but the relationship may not be perfectly linear across the entire operating range. This curve is essential for determining the required drive current to achieve a desired optical output level.

4.4 Temperature Dependence

Figures 2 and 4 show the effects of ambient temperature. Figure 2 (Forward Current vs. Ambient Temperature, likely at a constant voltage) and Figure 4 (Relative Radiant Intensity vs. Ambient Temperature, at a constant current) demonstrate that both the electrical and optical properties of the LED are temperature-dependent. Typically, for infrared LEDs, the forward voltage decreases and the optical output decreases as temperature increases. These curves are critical for designing circuits with temperature compensation or for estimating performance in non-ambient environments.

4.5 Radiation Pattern

Figure 6 is the radiation diagram or viewing angle pattern. It is a polar plot showing the angular distribution of the emitted radiant intensity. The 16-degree half-angle is visually represented here, showing the intensity dropping to 50% of the on-axis value at ±8 degrees from the center.

5. Mechanical and Package Information

The device uses a miniature plastic end-looking package. Key dimensions from the package drawing include a body diameter, lead spacing, and overall length. The leads emerge from the package with a specific spacing that is critical for PCB layout. The package includes a flange, and notes specify a maximum protrusion of resin under this flange. The notes also clarify that lead spacing is measured at the point where the leads exit the package body, and general tolerances are ±0.25mm unless otherwise stated. The physical configuration is designed to be mechanically matched to corresponding phototransistors, ensuring proper alignment in assembled modules.

6. Soldering and Assembly Guidelines

The primary assembly guideline provided is related to soldering temperature. The absolute maximum rating specifies that the leads can be subjected to a temperature of 260°C for a maximum of 5 seconds. This rating is measured at a distance of 1.6mm (0.063\") from the package body. This information is crucial for defining reflow soldering profiles or hand-soldering procedures. Exceeding this temperature or time can damage the internal die attach, wire bonds, or the plastic package material itself. Standard ESD (Electrostatic Discharge) precautions should be observed during handling. The device should be stored within the specified temperature range of -55°C to +100°C in a dry environment to prevent moisture absorption, which could cause \"popcorning\" during reflow.

7. Packaging and Ordering Information

The datasheet identifies the part number as LTE-209. The \"Spec No.\" is DS-50-92-0001, and the revision is C. Specific details on tape-and-reel packaging, reel quantities, or moisture sensitivity level (MSL) are not provided in the excerpt. Ordering would typically be based on the base part number LTE-209, with potential suffixes indicating specific intensity bins as implied by the selection process mentioned in the features.

8. Application Recommendations

8.1 Typical Application Scenarios

The LTE-209 is ideal for applications requiring a compact, efficient infrared source. Its 940nm wavelength is invisible to the human eye and is well-suited for:

• Optical Switches and Object Detection: Paired with a phototransistor (like the mentioned LTR-4206 series) to detect the presence, absence, or position of an object by interrupting the IR beam.
• Proximity Sensing: Used in devices to detect the proximity of a user or object, often employing reflective sensing.
• Encoders: Providing the light source for incremental or absolute optical encoders in motor control and position sensing systems.
• Data Transmission: Can be used for short-range, low-data-rate infrared communication links (e.g., remote control systems), though its narrow viewing angle may require alignment.

8.2 Design Considerations

• Current Limiting: Always use a series resistor or constant current driver to limit the forward current to the desired operating point, never exceeding the absolute maximum ratings.
• Thermal Management: Consider the power dissipation (V_F * I_F) and the effect of ambient temperature on output. For high-reliability applications, derate the maximum current at elevated temperatures.
• Optical Alignment: The narrow 16-degree viewing angle requires precise mechanical alignment with the paired detector or the target area for optimal signal strength.
• Circuit Protection: Although it has a 5V reverse voltage rating, incorporating protection against reverse voltage or voltage spikes in the circuit is good practice.
• Matched Pair: For best performance in sensing applications, use the device with its spectrally and mechanically matched phototransistor as suggested.

9. Technical Comparison and Differentiation

The key differentiators of the LTE-209 series, as presented, are its specific selection for intensity parameters and its matched pairing with a phototransistor series. Compared to generic IR LEDs, this pre-selection offers greater consistency in optical output, which can simplify circuit calibration and improve yield in mass production. The mechanical matching ensures that when used with the designated phototransistor, the physical alignment and optical coupling are optimized, leading to stronger and more reliable signals. The use of Gallium Aluminum Arsenide (GaAlAs) on a Gallium Arsenide (GaAs) substrate is a standard technology for producing efficient near-infrared emitters with a wavelength around 940nm.

10. Frequently Asked Questions (FAQs)

Q: What is the purpose of the 940nm wavelength?
A: 940nm is in the near-infrared spectrum, invisible to the human eye. It is commonly used in sensing and communication to avoid visible light interference and is efficiently detected by silicon photodetectors.

Q: Can I drive this LED directly from a 5V microcontroller pin?
A: No. You must use a current-limiting resistor. With a typical V_F of 1.6V at 20mA, the resistor value for a 5V supply would be R = (5V - 1.6V) / 0.02A = 170Ω. A standard 180Ω resistor would result in a current close to 19mA.

Q: How does temperature affect performance?
A: As shown in the characteristic curves, increasing temperature generally decreases the optical output for a given current and decreases the forward voltage. Designs for wide temperature ranges must account for this.

Q: What does \"spectrally matched\" mean?
A: It means the emission spectrum of the LED (centered at 940nm) aligns well with the peak responsivity region of the specified phototransistor. This maximizes the amount of emitted light that the detector can convert into an electrical signal.

11. Practical Design and Usage Examples

Example 1: Object Detection Gate: Two LTE-209 IR LEDs can be placed on one side of a conveyor belt, each paired with a matched phototransistor on the opposite side, creating two independent detection beams. A microcontroller monitors the phototransistor outputs. When an object passes through, it breaks one or both beams, allowing the system to count objects, measure size (by timing the beam break), or trigger an action.

Example 2: Reflective Proximity Sensor: An LTE-209 and its matched phototransistor are placed side-by-side on a PCB, facing the same direction. The LED emits a beam. When an object comes near, it reflects some of this light back to the phototransistor. The strength of the detected signal correlates with the object's proximity. This setup is common in touchless faucets or automatic soap dispensers.

12. 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-type region and holes from the p-type region are injected into the junction region. When these charge carriers recombine, energy is released. In the specific material system used here (GaAlAs/GaAs), this energy corresponds to photons in the infrared spectrum, approximately 940nm in wavelength. The structure of the diode, including the window layer mentioned, is designed to allow this generated light to escape the semiconductor material efficiently. The plastic package serves to protect the semiconductor die, provide mechanical structure, and can also act as a lens to shape the emitted light beam, contributing to the specified 16-degree viewing angle.

13. Technology Trends and Developments

Infrared emitter technology continues to evolve. General trends in the field include:

• Increased Efficiency: Development of new semiconductor materials and structures (e.g., multi-quantum wells) to achieve higher optical output power for a given electrical input, reducing power consumption and heat generation.
• Miniaturization: Ongoing reduction in package size (e.g., chip-scale packages) to enable integration into ever-smaller consumer electronics and IoT devices.
• Enhanced Functionality: Integration of the emitter with driver circuitry, photodetectors, or even microcontrollers into single modules or system-in-package (SiP) solutions.
• Wavelength Diversification: While 940nm remains standard, other IR wavelengths (e.g., 850nm, 1050nm) are being optimized for specific applications like eye-safe systems or different atmospheric transmission windows.
• Improved Reliability: Advancements in packaging materials and die attach technologies to withstand higher temperatures and more demanding environmental conditions, such as those required in automotive applications.