LTE-3273L IR Emitter and Detector Datasheet - 940nm Wavelength - High Power - Wide Viewing Angle - English Technical Document

1. Product Overview

The LTE-3273L is a discrete infrared (IR) component designed for applications requiring reliable infrared light emission and detection. It belongs to a family of optoelectronic devices engineered for performance in environments where infrared signaling is critical. The core function of this device is to emit infrared light at a specific wavelength when electrically driven and/or to detect incoming infrared radiation, converting it into an electrical signal.

The product is positioned as a solution for systems demanding a balance of high optical output, efficient electrical characteristics, and a broad emission/detection pattern. Its design caters to the need for components that can operate effectively under pulsed conditions, which is common in digital communication protocols to conserve power and increase signal clarity.

Core Advantages: The LTE-3273L distinguishes itself through several key features. It is engineered for high current operation while maintaining a relatively low forward voltage, which contributes to higher overall electrical efficiency and reduced thermal stress. The device offers high radiant intensity, enabling strong signal transmission over distance or through obstacles. Its wide viewing angle ensures a broad coverage area, making alignment between emitter and detector less critical in system design. Finally, the clear transparent package allows for maximum light transmission with minimal internal absorption or scattering.

Target Markets & Applications: This component is primarily targeted at the consumer electronics, industrial automation, and security sectors. Its typical applications include, but are not limited to, infrared remote controls for televisions and audio equipment, short-range wireless data transmission links, proximity sensors, object counters, and security alarm systems where beam interruption is detected. The high-speed capability also makes it suitable for basic IR data communication protocols.

2. In-Depth Technical Parameter Analysis

This section provides a detailed, objective interpretation of the key parameters listed in the datasheet, explaining their significance for design and application.

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 reliable, long-term performance.

• Power Dissipation (Pd): 150 mW - This is the maximum amount of power the device can dissipate as heat at an ambient temperature (TA) of 25°C. Exceeding this limit risks overheating the semiconductor junction, leading to accelerated degradation or catastrophic failure. Designers must ensure the operating conditions (forward current and voltage) result in a power dissipation (IF * VF) below this value, with a safety margin.
• Peak Forward Current (I_FP): 2 A - This is the maximum allowable current for pulsed operation, specified under conditions of 300 pulses per second (pps) with a 10 µs pulse width. This high rating enables the device to deliver very high instantaneous optical output for short bursts, which is ideal for long-range remote controls or strong signal pulses in noisy environments.
• Continuous Forward Current (I_F): 100 mA - This is the maximum DC current that can be applied continuously. For most constant-on applications, the operating current must be kept at or below this level. The typical operating current is often much lower (e.g., 20-50 mA) to ensure longevity and manage heat.
• Reverse Voltage (V_R): 5 V - The maximum voltage that can be applied in the reverse direction across the LED. Exceeding this can cause breakdown and destroy the device. Circuit protection, such as a series resistor or a parallel protection diode, is often used to prevent reverse voltage spikes.
• Operating & Storage Temperature Ranges: The device is rated for operation from -40°C to +85°C and storage from -55°C to +100°C. These wide ranges make it suitable for automotive, industrial, and outdoor applications where temperature extremes are encountered.
• Lead Soldering Temperature: 260°C for 5 seconds - This defines the reflow soldering profile tolerance. The 1.6mm distance specification from the body is critical; applying heat closer to the plastic package can cause deformation or internal damage.

2.2 Electrical & Optical Characteristics

These are the typical performance parameters measured under specified test conditions (TA=25°C). They define how the device will behave in a circuit.

• Radiant Intensity (I_E):
  • 5.6 - 8.0 mW/sr @ I_F = 20mA - This is the optical power emitted per unit solid angle (steradian). It is a direct measure of the "brightness" of the IR source from the front. The range indicates typical unit-to-unit variation.
  • 28.0 - 40.0 mW/sr @ I_F = 100mA - Shows the non-linear relationship between current and output. Increasing current by 5x increases radiant intensity by approximately 5x, indicating good efficiency even at higher currents.
• Peak Emission Wavelength (λ_Peak): 940 nm - The wavelength at which the device emits the most optical power. 940nm is in the near-infrared spectrum, invisible to the human eye. This is a common wavelength for remote controls as it avoids visible red glow and aligns well with the sensitivity of silicon photodetectors.
• Spectral Line Half-Width (Δλ): 50 nm - This parameter, also called Full Width at Half Maximum (FWHM), indicates the spectral purity of the emitted light. A value of 50 nm means the emitted light spans a band of wavelengths approximately 50nm wide centered on the 940nm peak. This is typical for standard GaAs IREDs.
• Forward Voltage (V_F):
  • 1.25 - 1.6 V @ I_F = 50mA - The voltage drop across the device when conducting 50mA. This low V_F is a key feature, reducing power loss and heat generation.
  • 1.85 - 2.3 V @ I_F = 500mA - V_F increases with current due to the diode's internal resistance. This value is crucial for designing high-current pulse drivers.
• Reverse Current (I_R): 100 µA max @ V_R = 5V - The small leakage current that flows when the maximum reverse voltage is applied. A low value is desirable.
• Viewing Angle (2θ_1/2): 40° - This is the full angle at which the radiant intensity drops to half of its maximum value (on-axis). A 40° angle provides a fairly broad beam, useful for applications where precise alignment is difficult.

2.3 Thermal Characteristics

While not explicitly listed in a separate table, thermal behavior is inferred from several parameters. The Power Dissipation rating (150mW) is intrinsically a thermal limit. The performance curves (discussed later) show how output and forward voltage change with ambient temperature. Effective thermal management, through PCB copper area or heatsinking, is essential to maintain performance and reliability, especially when operating near maximum continuous current.

3. Performance Curve Analysis

The typical curves provide visual and quantitative insight into the device's behavior under varying conditions, which is vital for robust circuit design.

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

This IV curve shows the exponential relationship typical of a diode. At low currents, the voltage is low. As current increases, the voltage rises. The curve allows designers to select the appropriate current-limiting resistor for a given supply voltage. For example, to drive the LED at 100mA from a 5V supply, the resistor value R = (V_supply - V_F) / I_F. Using the typical V_F of ~1.6V at 100mA (extrapolated), R would be (5 - 1.6) / 0.1 = 34 Ohms. The power in the resistor would be I²R = 0.34W.

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

This graph demonstrates the optical output's dependence on drive current. It is generally linear at lower currents but may show signs of saturation or reduced efficiency at very high currents due to thermal and internal quantum efficiency effects. The curve confirms that pulsed operation at 2A (from Absolute Max Ratings) will yield a significantly higher instantaneous output than continuous 100mA operation, justifying its use for long-range signaling.

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

This is a critical curve for understanding environmental impact. It shows that as the ambient temperature increases, the radiant intensity decreases. This is a characteristic of LEDs; higher junction temperature reduces internal quantum efficiency. For example, the output at +85°C might be only 60-70% of the output at +25°C. Designers must account for this derating in systems that must operate reliably over the full temperature range. It may necessitate driving the LED with a slightly higher current at high temperatures to compensate for lost output, provided power dissipation limits are not exceeded.

3.4 Spectral Distribution (Fig. 1)

This plot visualizes the emission spectrum, centered at 940nm with a FWHM of 50nm. It confirms the device emits in the near-IR and helps in selecting compatible optical filters or in assessing potential interference from ambient light sources (like sunlight or incandescent bulbs, which have broad spectra).

3.5 Radiation Diagram (Fig. 6)

This polar plot provides a detailed view of the angular distribution of emitted light. It graphically represents the 40° viewing angle (2θ_1/2). The shape of the curve is important for designing lenses or reflectors to collimate or further spread the beam for specific applications.

4. Mechanical & Packaging Information

4.1 Outline Dimensions & Tolerances

The device features a standard through-hole package with a flange for mechanical stability and potential heatsinking. Key dimensions include the body diameter, lead spacing, and overall length. All dimensions are specified in millimeters. The standard tolerance is ±0.25mm unless a specific feature has a different callout. The lead spacing is measured at the point where the leads exit the package body, which is the standard reference for PCB hole placement. A maximum protrusion of resin under the flange of 1.5mm is noted, which is important for PCB standoff and cleaning.

4.2 Polarity Identification

For an IR emitter (LED), the longer lead is typically the anode (positive), and the shorter lead is the cathode (negative). The datasheet outline should clearly indicate this, often with a flat side on the package or a notch near the cathode lead. Correct polarity is essential; reverse biasing beyond 5V can damage the device.

5. Soldering & Assembly Guidelines

Reflow Soldering: The specified parameter is 260°C for a maximum of 5 seconds, measured at a point 1.6mm from the package body. This aligns with common lead-free reflow profiles (peak temperature 240-260°C). The 1.6mm distance is critical to prevent the plastic package from exceeding its glass transition temperature and deforming.

Hand Soldering: If hand soldering is necessary, a temperature-controlled iron should be used. Contact time per lead should be minimized, ideally less than 3 seconds, using a heat sink clip on the lead between the iron and the package body.

Cleaning: After soldering, standard PCB cleaning processes can be used, but compatibility with the clear resin package should be verified with the cleaning agent manufacturer.

Storage Conditions: To prevent moisture absorption (which can cause "popcorning" during reflow), devices should be stored in a dry environment, typically below 40% relative humidity at room temperature, or in sealed moisture-barrier bags with desiccant if the shelf life is extended.

6. Application Suggestions & Design Considerations

6.1 Typical Application Circuits

Emitter Drive Circuit: The simplest circuit is a series current-limiting resistor. For pulsed operation, a transistor (BJT or MOSFET) is used to switch the high current on and off. The driver must be capable of sourcing the peak current (up to 2A) with low saturation voltage to maximize voltage across the LED. A fast rise/fall time is desirable for data transmission.

Detector Circuit: When used as a photodiode (if applicable per variant), it is typically operated in reverse bias or photovoltaic (zero bias) mode, connected to a transimpedance amplifier to convert the small photocurrent into a usable voltage.

6.2 Key Design Considerations

• Current Limiting: Always use a series resistor or active constant-current driver. Never connect directly to a voltage source.
• Pulse Operation: For pulsed drive, ensure the pulse width and duty cycle keep the average power dissipation within limits. Average current = Peak Current * Duty Cycle. For 2A pulses at 300pps and 10µs width, duty cycle = (10e-6 * 300) = 0.003 (0.3%). Average current = 2A * 0.003 = 6mA, which is well within the continuous rating.
• Optical Path: Consider the 40° viewing angle. For a focused beam, a lens may be required. For wide-area detection, the angle may be sufficient. Keep the optical path free of obstructions and clean.
• Ambient Light Immunity: In detector applications, ambient IR light (from sun, lamps) is a major source of noise. Using a modulated IR signal (e.g., 38kHz) and a corresponding tuned receiver circuit is the standard method to reject this DC and low-frequency noise.
• PCB Layout: For the emitter, ensure sufficient trace width to handle peak pulse currents without excessive voltage drop. For thermal management, connect the flange (if electrically isolated or connected to a lead) to a copper pour on the PCB to act as a heatsink.

7. Technical Comparison & Differentiation

While specific competitor parts are not named, the LTE-3273L's combination of parameters defines its niche:

• vs. Standard 940nm IREDs: Its high peak current rating (2A) and high radiant intensity at 100mA set it apart from lower-power variants used in simple remote controls. This makes it suitable for longer-range or higher-noise-immunity applications.
• vs. High-Speed 850nm IREDs: The LTE-3273L uses GaAs at 940nm, whereas high-speed variants often use AlGaAs at 850nm. The 850nm devices typically have faster rise/fall times for high-speed data but may have a faint red glow. The 940nm device is completely invisible, which is preferable for discreet applications, and its 50nm FWHM is standard.
• vs. Phototransistors/Photodiodes in the same package: The datasheet title suggests a family covering both emitters and detectors. A dedicated photodetector version would have different characteristics (responsivity, dark current, speed). The key advantage of a matched pair from the same family can be optimized spectral matching.

8. Frequently Asked Questions (Based on Technical Parameters)

Q1: Can I drive this LED continuously at 500mA?
A: No. The Absolute Maximum Rating for continuous forward current is 100mA. The 500mA condition listed in the Electrical Characteristics table is a test condition for measuring V_F under high current, likely relevant for its pulsed operation rating. Continuous operation must not exceed 100mA.

Q2: Why is my IR remote's range shorter in a hot car?
A: Refer to Fig. 4 (Relative Radiant Intensity vs. Ambient Temperature). The LED's output decreases as temperature rises. At +85°C, the output could be 30-40% lower than at room temperature, directly reducing the effective range.

Q3: What resistor should I use with a 3.3V supply to get typical output?
A: For a target I_F of 20mA (giving 5.6-8.0 mW/sr), and a typical V_F of 1.6V at 50mA (use ~1.5V as estimate for 20mA), R = (3.3V - 1.5V) / 0.02A = 90 Ohms. The nearest standard value is 91 Ohms. Power in resistor: (0.02^2)*91 = 0.0364W, so a 1/8W or 1/10W resistor is sufficient.

Q4: Is the viewing angle the same for emission and detection?
A: For an IR Emitter (LED), the 40° angle specifies the emission pattern. For a Photodiode or Phototransistor detector, a similar but separate parameter called "Field of View" or "Sensitivity Angle" would define its angular acceptance. They are often similar but not necessarily identical. Check the specific detector datasheet.

9. Practical Design & Usage Case

Case: Designing a Long-Range Garage Door Opener Transmitter.
The design goal is to achieve a reliable 50-meter range in daylight conditions. The LTE-3273L is selected for its high pulsed output capability.
Design Steps:
1. Driver Circuit: Use a MOSFET switched by a microcontroller to pulse the LED. A series resistor is calculated based on the battery voltage (e.g., 12V) and desired peak current. To maximize range, drive near the peak rating: choose I_FP = 1.5A (within the 2A max). V_F at 1.5A (from curve extrapolation) ~2.5V. Resistor R = (12V - 2.5V) / 1.5A = 6.33 Ohms. Use a 6.2 Ohm, 5W resistor to handle the pulse power (P = I²R = 1.5^2 * 6.2 ≈ 14W peak, but average power is low).
2. Pulsing: Encode the command using a 38kHz carrier modulated by the data bits. Pulse width for each 38kHz burst is kept to 10µs or less to stay within the rating. Duty cycle is very low.
3. Optics: Add a simple plastic lens in front of the LED to collimate the naturally 40° beam into a narrower, more focused beam for longer range.
4. Thermal: Due to the low duty cycle, average power and heating are minimal. No special heatsink is required beyond the PCB copper connected to the flange.
This design leverages the key features of the LTE-3273L: high peak current, high radiant intensity, and suitability for pulse operation.

10. Operating Principle Introduction

Infrared Emitter (IRED): The LTE-3273L, when functioning as an emitter, is a Light Emitting Diode (LED) based on Gallium Arsenide (GaAs) semiconductor material. When a forward voltage is applied, electrons and holes are injected into the active region of the semiconductor junction. When these charge carriers recombine, they release energy in the form of photons (light). The specific bandgap energy of the GaAs material determines the wavelength of these photons, which is in the infrared region at 940 nanometers. The clear package allows this light to escape with minimal loss.

Infrared Detector (Photodiode): If configured as a detector, the device contains a semiconductor PIN junction. When photons with energy greater than the semiconductor's bandgap (i.e., infrared light) strike the depletion region, they create electron-hole pairs. These charge carriers are then swept apart by the built-in electric field (or an applied reverse bias), generating a photocurrent that is proportional to the intensity of the incident light. This small current can be amplified and processed by external circuitry.

11. Technology Trends & Context

Discrete infrared components like the LTE-3273L represent a mature and stable technology. The core materials (GaAs, AlGaAs) and package types have been optimized over decades for reliability and cost-effectiveness. The ongoing trends in this field are not about revolutionary changes in the discrete devices themselves, but in their integration and application context:

• Integration: There is a move towards integrated modules that combine the emitter, detector, driver, amplifier, and digital logic (like a decoder for a specific protocol) into a single surface-mount package. These simplify design but may not offer the same level of customization or performance optimization as discrete parts for specialized applications.
• Miniaturization: While through-hole packages remain popular for robustness, there is increasing demand for smaller surface-mount device (SMD) versions to save space on modern PCBs.
• Enhanced Performance: For new applications like LiDAR for consumer electronics or advanced gesture recognition, there is research into faster, more efficient IR emitters (e.g., using VCSEL technology) and detectors with higher sensitivity and lower noise. However, for classic applications like remote controls, proximity sensing, and basic data links, traditional components like the LTE-3273L offer an optimal balance of performance, reliability, and cost.
• Application Expansion: The fundamental principles remain relevant for emerging Internet of Things (IoT) devices, where simple, low-power, wireless communication or sensing is needed without the complexity of radio frequency (RF) systems.

In summary, the LTE-3273L is a well-specified, robust component based on proven technology. Its value lies in its clear, detailed datasheet which allows engineers to accurately predict its behavior and design it effectively into systems requiring dependable infrared functionality for control, sensing, or basic communication.