SMD Infrared Emitter 930nm Datasheet - Package 5.0x5.0x1.6mm - Forward Voltage 2.9V - Radiant Intensity 480mW/sr - English Technical Document

1. Product Overview

This document details the specifications for a discrete, high-power infrared emitter component designed for surface-mount technology (SMT) assembly. The device is part of a broad range of infrared components intended for applications requiring reliable, efficient infrared light sources. Its core function is to emit infrared radiation at a specific peak wavelength when electrically driven.

1.1 Core Advantages and Target Market

The primary advantages of this emitter include its high radiant output, suitability for automated PCB assembly due to its SMD package, and a defined spectral output centered in the near-infrared region. It is engineered to meet industry standards for environmental compliance. The target applications are primarily in consumer electronics and industrial sensing, where infrared signals are used for wireless communication, proximity detection, or encoding data.

2. In-Depth Technical Parameter Analysis

The following sections provide a detailed, objective interpretation of the key parameters defined in the datasheet, explaining their significance for design engineers.

2.1 Absolute Maximum Ratings

These ratings define the stress limits beyond which permanent damage to the device may occur. They are not intended for normal operation.

• Power Dissipation (3.8W): 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.
• Peak Forward Current (2A, 300pps, 10μs pulse): The maximum allowable current in pulsed operation. The 10μs pulse width and 300 pulses per second (pps) define a specific duty cycle. This rating is typically higher than the DC rating due to reduced thermal buildup during short pulses.
• DC Forward Current (1A): The maximum continuous current that can be passed through the device under DC conditions. Operating at or near this limit requires careful thermal management.
• Reverse Voltage (5V): The maximum voltage that can be applied in the reverse-biased direction. Infrared emitters are not designed for reverse operation; exceeding this voltage can cause breakdown.
• Thermal Resistance (9 K/W, junction to soldering pad): A critical parameter for thermal design. It indicates how much the junction temperature will rise for every watt of power dissipated. A lower value means heat is more easily transferred from the semiconductor die to the PCB.
• Operating & Storage Temperature Ranges: Define the environmental limits for reliable function and non-operational storage, respectively.

2.2 Electrical & Optical Characteristics

These are the typical performance parameters measured under specified test conditions (Ta=25°C, IF=500mA unless noted).

• Radiant Intensity (I_E): 480 mW/sr (Typical). This measures the optical power emitted per unit solid angle (steradian) along the central axis of the device. It is a key metric for the "brightness" of the IR source in a directed beam.
• Total Radiant Flux (Φ_e): 700 mW (Typical). This is the total optical power emitted in all directions. The ratio between Flux and Intensity is influenced by the viewing angle.
• Peak Emission Wavelength (λ_Peak): 930 nm (Typical). The wavelength at which the emitted optical power is maximum. This must be matched with the spectral sensitivity of the receiving sensor (e.g., a silicon photodiode is most sensitive around 900-1000nm).
• Spectral Line Half-Width (Δλ): 35 nm (Typical). The bandwidth of the emitted spectrum measured at half the peak intensity. A narrower width indicates a more monochromatic source.
• Forward Voltage (V_F): 2.9 V (Typical) at 500mA. The voltage drop across the device when operating. This is crucial for designing the drive circuitry and calculating power consumption (Power = V_F * I_F).
• Reverse Current (I_R): < 10 μA at V_R=5V. A 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 switch from 10% to 90% of its final value (rise) or 90% to 10% (fall). This determines the maximum modulation speed for data transmission.
• Viewing Angle (2θ_1/2): 70° (Typical). The full angle at which the radiant intensity drops to half of its on-axis value. A wider angle provides broader coverage but lower intensity in any single direction.

3. Performance Curve Analysis

The provided graphs offer visual insights into device behavior under varying conditions.

3.1 Spectral Distribution (Fig. 1)

The curve shows the relative radiant intensity as a function of wavelength. It confirms the peak at ~930nm and the approximately 35nm half-width. This shape is characteristic of the semiconductor material (likely GaAs or AlGaAs).

3.2 Forward Current vs. Ambient Temperature (Fig. 2)

This derating curve is essential for thermal management. It shows the maximum allowable forward current decreasing as ambient temperature increases. At 85°C, the maximum current is significantly lower than at 25°C. Designers must use this graph to ensure the operating current-temperature combination falls within the safe area.

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

This is the current-voltage (I-V) characteristic curve. It is non-linear, typical of a diode. The curve allows designers to determine the expected V_F for a chosen operating current, which is necessary for selecting a series current-limiting resistor.

3.4 Relative Radiant Intensity vs. Temperature & Current (Fig. 4 & 5)

Figure 4 shows how optical output power decreases as junction temperature rises (at a fixed current). Figure 5 shows how output power increases with current (at a fixed temperature). Both demonstrate the temperature-dependent efficiency of the device. Output drops with higher temperature, a phenomenon common to LEDs.

3.5 Radiation Diagram (Fig. 6)

This polar plot visually represents the spatial distribution of emitted light. The concentric circles represent relative intensity. The plot confirms the 70° viewing angle (2θ_1/2), where the intensity falls to 0.5 relative to the center (1.0). The pattern appears roughly Lambertian (cosine distribution), common for LEDs with a simple dome lens.

4. Mechanical & Packaging Information

4.1 Outline Dimensions

The device is housed in a surface-mount package with dimensions of approximately 5.0mm in length and width, and 1.6mm in height. The drawing specifies the location of the optical lens and the solder pads. Tolerances are typically ±0.1mm unless otherwise noted.

4.2 Polarity Identification

The cathode (negative terminal) is clearly marked in the package drawing. Correct polarity must be observed during PCB layout and assembly to prevent damage.

4.3 Suggested Soldering Pad Dimensions

A land pattern recommendation is provided to ensure reliable solder joints and proper mechanical alignment during reflow soldering. Following these dimensions helps prevent tombstoning and ensures good thermal connection to the PCB for heat dissipation.

5. Soldering & Assembly Guidelines

5.1 Storage Conditions

The device is moisture-sensitive. Unopened packages should be stored below 30°C and 90% RH. Once the moisture-proof bag is opened, components should be used within one week or stored in a dry environment (<30°C, <60% RH). Components exposed to ambient humidity for over a week require a baking process (approx. 60°C for 20 hours) before reflow to prevent "popcorning" damage during soldering.

5.2 Reflow Soldering Profile

A JEDEC-compliant reflow profile is recommended. Key parameters include: a pre-heat stage (150-200°C, max 120s), a peak temperature not exceeding 260°C, and a time above liquidus (TAL) where the peak temperature is maintained for a maximum of 10 seconds. The profile emphasizes controlling the maximum temperature and the time the component is exposed to high heat to prevent damage to the plastic package and the semiconductor die.

5.3 Hand Soldering

If hand soldering is necessary, a soldering iron temperature should not exceed 300°C, and contact time should be limited to 3 seconds per pad. This minimizes thermal stress.

5.4 Cleaning

Isopropyl alcohol or similar alcohol-based solvents are recommended for post-solder cleaning. Harsh or unknown chemicals should be avoided as they may damage the package or lens.

6. Packaging and Handling

6.1 Tape and Reel Specifications

The components are supplied on standard 13-inch reels, with 2400 pieces per reel. The tape and reel dimensions conform to ANSI/EIA-481-1-A-1994 specifications, ensuring compatibility with automated pick-and-place machines. The orientation of the cathode is standardized within the tape pockets.

7. Application Notes and Design Considerations

7.1 Drive Circuit Design

The device is a current-operated component. For consistent performance and longevity, it must be driven by a current source or via a voltage source with a series current-limiting resistor. The datasheet strongly recommends using an individual series resistor for each LED when multiple units are connected in parallel (Circuit Model A). Using a single resistor for a parallel array (Circuit Model B) is discouraged due to variations in the forward voltage (V_F) between individual LEDs, which can lead to significant current imbalance and uneven brightness or premature failure of the device with the lowest V_F.

7.2 Thermal Management

Given the power dissipation (up to 3.8W max) and thermal resistance (9 K/W), effective heat sinking is critical for operation at high currents or elevated ambient temperatures. The primary heat path is through the solder pads to the PCB. Using the recommended pad layout with adequate copper area (thermal relief pads) on the PCB is essential. For high-power applications, additional thermal vias connecting to internal ground planes or dedicated heat sinks may be necessary to keep the junction temperature within safe limits, as defined by the derating curve.

7.3 Optical Design Considerations

The 70-degree viewing angle defines the beam spread. For applications requiring a narrower beam, secondary optics (lenses) may be added. The peak wavelength of 930nm should be paired with a receiver (photodiode, phototransistor) that has high sensitivity in that spectral region. Many silicon-based sensors have peak sensitivity around 850-950nm, making them a good match. For remote control applications, this wavelength is commonly used as it is less visible to the human eye than 850nm but still efficiently detected by silicon.

8. Technical Comparison and Differentiation

Compared to standard low-power infrared LEDs, this device offers significantly higher radiant intensity (480 mW/sr typical), enabling longer range or operation in noisier optical environments. Its surface-mount package differentiates it from through-hole variants, allowing for smaller, more automated PCB assemblies. The fast rise/fall time (30ns) makes it suitable for medium-speed data transmission, not just simple on/off signaling. The defined spectral characteristics and viewing angle provide consistent, predictable performance for optical system design.

9. Frequently Asked Questions (Based on Technical Parameters)

Q: Can I drive this LED directly from a 5V microcontroller pin?

A: No. You must use a series current-limiting resistor. The resistor value is calculated as R = (V_supply - V_F) / I_F. For example, with a 5V supply, V_F=2.9V, and a desired I_F of 100mA, R = (5 - 2.9) / 0.1 = 21 Ohms. The resistor power rating must also be considered (P = I²R).

Q: What is the difference between Radiant Intensity and Total Radiant Flux?

A: Radiant Intensity (mW/sr) measures power in a specific direction (like the brightness of a flashlight beam). Total Radiant Flux (mW) measures the sum of power emitted in all directions (like the total light output of a light bulb). For a directional source, Intensity is often the more relevant metric.

Q: How do I determine the maximum safe operating current for my application?

A: You must consider both the Absolute Maximum DC Current (1A) and the thermal derating. Use Figure 2. Find your maximum expected ambient temperature on the x-axis. Draw a line up to the curve, then left to the y-axis to find the maximum allowable current. Your chosen operating current must be lower than this value and the 1A absolute max.

Q: Why is the peak wavelength specified as 930nm, but the part description mentions 940nm?

A: The part description refers to the general product line which includes 940nm devices. This specific part number (LTE-R38385S-OE8) has a typical peak wavelength of 930nm as per its detailed specifications. Always refer to the specific datasheet for the exact parameters of the ordered component.

10. Practical Design and Usage Examples

10.1 Example 1: Long-Range Infrared Transmitter

Scenario: Designing a weatherproof outdoor IR transmitter for data communication over 15 meters in daylight conditions.

Design Approach: Use the high radiant intensity (480mW/sr) to overcome ambient light noise. Drive the LED at or near its maximum DC current (1A) for maximum output, but implement a robust thermal management strategy. Use a large copper pour on the PCB connected to the LED's thermal pads, with multiple thermal vias to inner layers. Consider adding a simple plastic collimating lens to narrow the beam from 70° to ~15°, further increasing intensity on-axis for the required range. The drive circuit would use a transistor (e.g., MOSFET) switched by a microcontroller, with the calculated series resistor to set the 1A current.

10.2 Example 2: Multi-Element Proximity Sensor Array

Scenario: Creating a proximity sensor ring with 8 IR emitters placed around a central receiver.

Design Approach: Uniform illumination is key. Use the recommended Circuit Model A: each of the 8 LEDs gets its own identical current-limiting resistor connected to a common voltage rail. This compensates for small V_F variations between LEDs. Operate the LEDs at a moderate current (e.g., 200mA) to balance output and thermal load. Pulse the array synchronously with the receiver's sampling to improve signal-to-noise ratio, taking advantage of the fast 30ns rise/fall time for clean pulses. The 70° viewing angle of each LED will create a wide, overlapping detection field.

11. Operating Principle Introduction

This infrared emitter is a semiconductor diode. Its core is a chip made from materials like Gallium Arsenide (GaAs) or Aluminum Gallium Arsenide (AlGaAs). When a forward voltage is applied, electrons are injected across the p-n junction. As these electrons recombine with holes in the active region, energy is released in the form of photons (light particles). The specific bandgap energy of the semiconductor material determines the wavelength (color) of the emitted light. For GaAs/AlGaAs, this bandgap corresponds to photons in the infrared spectrum (typically 850-940nm). The plastic package encapsulates the chip, provides a mechanical structure, and includes a molded lens that shapes the emitted light's radiation pattern.

12. Technology Trends and Context

Infrared emitters of this type are mature, highly reliable components. Current trends in the field focus on increasing power density and efficiency (more light output per electrical watt), enabling smaller packages or longer battery life in portable devices. Integration is another trend, with combined emitter-sensor pairs or arrays becoming common for gesture recognition and 3D sensing. There is also ongoing development in expanding the wavelength range for specialized applications like gas sensing or optical communications. The move towards surface-mount packages, as seen with this component, continues to dominate for automated, high-volume manufacturing, replacing older through-hole designs. The emphasis on detailed thermal specifications and soldering profiles reflects the industry's focus on reliability and process control in modern electronics assembly.