IR Emitter and Detector LTE-R38386AS-S Datasheet - 850nm Wavelength - 3.6W Power - 3.1V Forward Voltage - English Technical Documentation

1. Product Overview

This document details the specifications for a discrete infrared (IR) component designed for applications requiring a reliable light source and sensing capability. The device integrates an infrared emitter and detector, operating at a peak wavelength of 850 nanometers. It is engineered for high-performance applications demanding robust output and consistent operation.

The core advantage of this component lies in its combination of a high-power infrared emitter with a compatible detector in a single package. This integration simplifies design for reflective or proximity sensing applications. The emitter is characterized by high radiant intensity and a wide viewing angle, while the detector provides the necessary sensitivity for signal reception. The product is compliant with environmental regulations, being a RoHS and Green Product.

The target market includes applications in remote control systems, short-range wireless data transmission, security and alarm systems, and various forms of industrial or consumer electronic sensing where infrared technology is preferred.

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 under or at these limits is not guaranteed and should be avoided for reliable long-term performance.

• Power Dissipation (Pd): 3.6 Watts. This is the maximum amount of power the device can dissipate as heat at an ambient temperature (Ta) of 25°C. Exceeding this will cause the junction temperature to rise excessively.
• Peak Forward Current (I_FP): 5 Amperes. This is the maximum allowable current under pulsed conditions (300 pulses per second, 10μs pulse width). It is significantly higher than the DC rating, leveraging the device's transient thermal capacity.
• DC Forward Current (I_F): 1 Ampere. The maximum continuous forward current the emitter can handle.
• Reverse Voltage (V_R): 5 Volts. Applying a reverse voltage higher than this can break down the semiconductor junction.
• Thermal Resistance (R_θJ): 9 K/W. This parameter indicates how effectively heat travels from the semiconductor junction to the ambient. A lower value signifies better heat dissipation.
• Operating Temperature Range: -40°C to +85°C. The ambient temperature range over which the device is specified to operate correctly.
• Storage Temperature Range: -55°C to +100°C.
• Infrared Soldering Condition: The package can withstand a peak reflow temperature of 260°C for a maximum of 10 seconds.

2.2 Electrical and Optical Characteristics

These parameters are measured under standard test conditions (Ta=25°C) and represent the typical performance of the device.

• Radiant Intensity (I_E): 630 mW/sr (Typical) at I_F=1A. This measures the optical power emitted per unit solid angle along the central axis, indicating the brightness of the source.
• Total Radiant Flux (Φ_e): 1340 mW (Typical) at I_F=1A. This is the total optical power emitted in all directions.
• Peak Emission Wavelength (λ_P): 850 nm (Typical). The wavelength at which the optical output power is maximum.
• Spectral Line Half-Width (Δλ): 50 nm (Typical). The width of the emission spectrum at half the maximum intensity, indicating the spectral purity.
• Forward Voltage (V_F): 3.1 V (Typical), with a range of 2.5V to 3.6V at I_F=1A. The voltage drop across the device when conducting the specified current.
• Reverse Current (I_R): 10 μA (Maximum) at V_R=5V. The small leakage current when the device is reverse-biased.
• Rise/Fall Time (t_r/t_f): 30 ns (Typical). The time required for the optical output to rise from 10% to 90% of its maximum value (or fall from 90% to 10%). This determines the maximum modulation speed.
• Viewing Angle (2θ_1/2): 90 degrees (Typical). The full angle at which the radiant intensity is half the value at the center (0°). A wide angle is beneficial for broad coverage applications.

3. Performance Curve Analysis

The datasheet provides several characteristic curves that are crucial for understanding device behavior under varying conditions.

3.1 Spectral Distribution

The spectral distribution curve shows the relative radiant intensity as a function of wavelength. For this device, the peak is centered at 850nm with a typical half-width of 50nm. This characteristic is important for matching with the spectral sensitivity of the paired detector or for ensuring compatibility with optical filters in the system.

3.2 Forward Current vs. Ambient Temperature

This derating curve illustrates how the maximum allowable DC forward current decreases as the ambient temperature increases. To prevent exceeding the maximum junction temperature, the drive current must be reduced when operating in high-temperature environments. The curve typically shows a linear decrease from the rated current at 25°C down to zero at the maximum junction temperature.

3.3 Forward Current vs. Forward Voltage

The I-V curve shows the exponential relationship between forward current and forward voltage. The typical V_F of 3.1V at 1A is a key parameter for designing the drive circuitry and calculating power dissipation (P_d = V_F * I_F).

3.4 Relative Radiant Intensity vs. Forward Current and Temperature

These curves show how the optical output power changes with drive current and ambient temperature. The output typically increases linearly with current up to a point, but efficiency may drop at very high currents due to heating. The output also decreases as temperature rises due to reduced internal quantum efficiency.

3.5 Radiation Diagram

The polar radiation pattern visually represents the viewing angle. The diagram confirms the 90-degree half-angle, showing the relative intensity at various off-axis angles. This is critical for designing optics and aligning the emitter and detector in a system.

4. Mechanical and Package Information

4.1 Outline Dimensions

The device is provided in a surface-mount package. The outline drawing specifies all critical physical dimensions including length, width, height, lead spacing, and positioning of the optical window. Tolerances are typically ±0.1mm unless otherwise noted. It is essential to refer to this drawing for PCB footprint design.

4.2 Suggested Soldering Pad Dimensions

A recommended land pattern (footprint) for the PCB is provided. This includes the pad size, shape, and spacing to ensure reliable solder joint formation during reflow soldering and to provide adequate mechanical strength. Following these recommendations helps prevent tombstoning and poor solder connections.

4.3 Polarity Identification

The cathode is clearly marked in the package drawing. Correct polarity must be observed during assembly to prevent device damage. The provided tape and reel packaging also maintains consistent orientation for automated placement.

5. Soldering and Assembly Guidelines

5.1 Storage Conditions

The device is moisture-sensitive. Unopened packages should be stored at ≤30°C and ≤90% RH, with a recommended use-within period of one year. Once the moisture-proof bag is opened, components should be stored at ≤30°C and ≤60% RH. If exposed to ambient air for more than one week, a bake-out at approximately 60°C for at least 20 hours is required before soldering to remove absorbed moisture and prevent "popcorning" during reflow.

5.2 Reflow Soldering Profile

A JEDEC-compliant reflow profile is recommended. Key parameters include:

• Pre-heat: 150–200°C for up to 120 seconds maximum to gradually heat the board and activate the flux.
• Peak Temperature: 260°C maximum. The time above 260°C should be minimized.
• Time at Peak: 10 seconds maximum. The device can withstand this profile a maximum of two times.

The specific profile must be characterized for the actual PCB design, solder paste, and oven used.

5.3 Hand Soldering

If hand soldering is necessary, the soldering iron tip temperature should not exceed 300°C, and the contact time should be limited to 3 seconds per joint. This should be performed only once.

5.4 Cleaning

If post-solder cleaning is required, only alcohol-based solvents like isopropyl alcohol should be used. Harsh or aggressive chemical cleaners should be avoided.

6. Packaging and Ordering Information

6.1 Tape and Reel Specifications

The components are supplied on embossed carrier tape wound onto 7-inch reels. Each reel contains 600 pieces. The packaging conforms to ANSI/EIA 481-1-A-1994 standards. The tape has a cover seal to protect components, and specifications allow for a maximum of two consecutive missing components in a reel.

6.2 Part Number

The base part number is LTE-R38386AS-S. This number should be used for ordering and identification.

7. Application Suggestions and Design Considerations

7.1 Typical Application Circuits

The device is intended for ordinary electronic equipment. For driving the emitter, it is a current-operated device. Circuit Model (A) is strongly recommended: a current-limiting resistor should be placed in series with each LED when multiple devices are connected in parallel. This ensures intensity uniformity by compensating for natural variations in forward voltage (V_F) between individual LEDs. Circuit Model (B), where LEDs are directly paralleled without individual resistors, is discouraged as it can lead to significant brightness mismatch and potential current hogging by the LED with the lowest V_F.

7.2 Design Considerations

• Heat Management: With a power dissipation up to 3.6W, proper thermal design on the PCB is crucial. Use adequate copper area (thermal pads) connected to the device leads to conduct heat away from the junction.
• Drive Current Selection: Choose the operating current based on the required radiant intensity and the thermal derating for the application's maximum ambient temperature. Do not exceed the absolute maximum DC current of 1A.
• Optical Alignment: For reflective sensing applications using both the emitter and detector, careful mechanical design is needed to align the field of view of the detector with the illuminated area of the emitter.
• Electrical Noise: For the detector side, consider the potential for ambient light noise. The datasheet mentions that photodiodes/transistors can be provided with filters for this purpose, though it's not specified if this particular detector includes one.

7.3 Application Limitations

The device is not designed for applications where failure could jeopardize life or health, such as aviation, transportation control, medical, or critical safety systems. For such applications, consultation with the manufacturer is required prior to design-in.

8. Technical Comparison and Differentiation

While a direct comparison with other part numbers is not provided in this datasheet, key differentiating features of this component can be inferred:

• Integrated Solution: Combines emitter and detector, reducing part count and simplifying optical alignment compared to sourcing separate components.
• High Power: The 630 mW/sr radiant intensity and 3.6W power dissipation rating indicate a high-output device suitable for applications requiring longer range or stronger signal.
• High Speed: The 30 ns rise/fall time enables high-frequency modulation for fast data transmission or pulsed operation.
• Wide Viewing Angle: The 90-degree half-angle provides broad coverage, useful in proximity sensing or applications where alignment is less critical.

9. Frequently Asked Questions (Based on Technical Parameters)

Q: Can I drive this LED at 1A continuously?
A: Yes, but only if the ambient temperature is 25°C or lower, and you have implemented sufficient heat sinking to keep the junction temperature within limits. At higher ambient temperatures, the current must be derated according to the provided curve.

Q: What is the difference between Radiant Intensity and Total Radiant Flux?
A: Radiant Intensity (mW/sr) measures power per solid angle in a specific direction (typically on-axis). Total Radiant Flux (mW) measures the sum of optical power emitted in all directions. The former is relevant for focused applications, the latter for total light output.

Q: Why is a series resistor necessary for each LED in parallel?
A: LEDs have a negative temperature coefficient for V_F and manufacturing variances. Without individual resistors, the LED with the slightly lower V_F will draw disproportionately more current, leading to uneven brightness and potential thermal runaway in that device.

Q: How do I interpret the 260°C for 10 seconds soldering condition?
A: This means the device package can survive the high temperatures of lead-free reflow soldering. Your oven profile should be designed so that the component's body temperature does not exceed 260°C, and the time spent within a few degrees of that peak is less than 10 seconds.

10. Practical Application Example

Design Case: Proximity Sensor for an Automatic Faucet
In this application, the emitter and detector are mounted side-by-side behind a water-resistant window. The emitter constantly sends out an 850nm infrared beam. When a hand is placed under the faucet, the infrared light reflects off the hand back to the detector. The microcontroller monitoring the detector's output sees a significant increase in signal, triggering the water valve to open.

Design Steps:
1. Drive Circuit: Use Circuit Model (A). A constant current source or a voltage source with a series resistor sets the emitter current to, for example, 500mA to provide strong signal while staying well within limits.
2. Detector Interface: The photodetector (likely a phototransistor in this package) will be connected in a common-emitter configuration with a pull-up resistor. The voltage at the collector will drop when IR light is detected.
3. PCB Layout: Follow the suggested pad layout. Include a generous copper pour connected to the ground pins of the device for heat dissipation. Keep analog sensing traces away from noisy digital lines.
4. Optics/Mechanics: Design the housing so the emitter's 90-degree cone and the detector's field of view overlap in the desired sensing zone (e.g., 5-15cm from the faucet head).
5. Software: Implement filtering in the microcontroller to distinguish the reflected signal from ambient IR noise (e.g., from sunlight or heaters).

11. Operational Principle

The device contains two primary elements:
Infrared Emitter (IRED): This is typically a Gallium Arsenide (GaAs) or Aluminum Gallium Arsenide (AlGaAs) semiconductor diode. When forward biased, electrons and holes recombine in the active region, releasing energy in the form of photons. The material composition (AlGaAs) is engineered to produce photons with a wavelength around 850nm, which is in the near-infrared spectrum, invisible to the human eye.

Infrared Detector: This is a photodiode or phototransistor made from silicon or other semiconductor materials sensitive to infrared light. When photons with sufficient energy strike the detector's active area, they generate electron-hole pairs. In a photodiode, this creates a photocurrent proportional to the light intensity when reverse-biased. In a phototransistor, the photocurrent acts as a base current, causing a much larger collector current to flow, providing internal gain.

12. Technology Trends

Infrared components continue to evolve in several directions relevant to this product category:
Increased Efficiency: Ongoing material science research aims to improve the wall-plug efficiency (optical power out / electrical power in) of IREDs, reducing heat generation and power consumption for the same optical output.
Higher Speed: Demand for faster data transmission in consumer electronics (e.g., IR data association protocols) drives the development of devices with even shorter rise/fall times, enabling higher bandwidth communication.
Miniaturization: The trend towards smaller electronic devices pushes for components in ever-smaller package footprints while maintaining or improving performance.
Integration: Beyond combining emitter and detector, future trends may include integrating the drive circuitry or signal conditioning amplifiers into the same package, creating smarter, more complete sensor modules.