LTE-S9511T-E IR Emitter and Detector Datasheet - 940nm Peak Wavelength - 25deg Viewing Angle - 100mW Power Dissipation - English Technical Documentation

1. Product Overview

The LTE-S9511T-E is a discrete infrared component designed for a broad range of optoelectronic applications. It belongs to a family of devices engineered to provide solutions requiring high power, high speed, and specific optical characteristics. The component is built using GaAs technology, which is standard for infrared emitters, to achieve its target performance metrics.

1.1 Core Features and Advantages

The device incorporates several key features that make it suitable for modern electronic assembly and environmental standards. It is compliant with RoHS directives, classifying it as a Green Product. The packaging is designed for compatibility with high-volume manufacturing, supplied in 8mm tape on 7-inch diameter reels, which is compatible with automatic placement equipment. Furthermore, the component can withstand infrared reflow soldering processes, a critical requirement for surface-mount technology (SMT) assembly lines. The package itself conforms to EIA standards, ensuring mechanical compatibility.

1.2 Target Applications and Market

The primary application for this component is as an infrared emitter. Its characteristics make it well-suited for integration into systems such as remote controls for consumer electronics, IR-based wireless data transmission links, security alarms, and other sensing applications. It is intended for PCB-mounted configurations, providing a compact and reliable source of infrared light.

2. Technical Specifications and Objective Interpretation

This section provides a detailed, objective analysis of the device's electrical, optical, and thermal parameters as defined in the datasheet.

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 (Pd): 100 mW. This is the maximum amount of power the device can dissipate as heat without exceeding its thermal limits.
• Peak Forward Current (I_FP): 1 A. This is the maximum allowable current under pulsed conditions (300 pulses per second, 10 μs pulse width). It is significantly higher than the DC rating, highlighting the device's capability for pulsed operation common in data transmission and remote control.
• DC Forward Current (I_F): 50 mA. The maximum continuous forward current the device can handle.
• Reverse Voltage (V_R): 5 V. Applying a reverse voltage higher than this can break down the semiconductor junction.
• Operating Temperature Range (T_op): -40°C to +85°C. The ambient temperature range within which the device is specified to operate correctly.
• Storage Temperature Range (T_stg): -55°C to +100°C. The temperature range for non-operational storage.
• Infrared Soldering Condition: Withstands 260°C for a maximum of 10 seconds. This defines the reflow soldering profile tolerance.

2.2 Electrical and Optical Characteristics

These are the typical performance parameters measured at an ambient temperature (T_A) of 25°C under specified test conditions.

• Radiant Intensity (I_E): 6.0 mW/sr (Typical) at I_F = 20mA. This measures the optical power emitted per unit solid angle (steradian). It is a key parameter for determining the effective range and signal strength in an application.
• Peak Emission Wavelength (λ_p): 940 nm (Typical). The wavelength at which the emitted optical power is maximum. This is in the near-infrared spectrum, invisible to the human eye but detectable by silicon photodiodes and phototransistors.
• Spectral Line Half-Width (Δλ): 50 nm (Typical). This indicates the spectral bandwidth, or the range of wavelengths emitted. A value of 50 nm is common for standard GaAs IREDs.
• Forward Voltage (V_F): 1.2 V (Typical), 1.5 V (Max) at I_F = 20mA. The voltage drop across the device when conducting current. This is crucial for designing the driving circuitry and calculating power consumption.
• Reverse Current (I_R): 10 μA (Max) at V_R = 5V. The small leakage current that flows when the device is reverse-biased.
• Viewing Angle (2θ_1/2): 25 degrees (Typical). Defined as the full angle at which the radiant intensity drops to half of its value on the central axis. A 25-degree angle indicates a relatively focused beam, which can be beneficial for directed communication or sensing.

3. Performance Curve Analysis

The datasheet includes several graphs that illustrate the relationship between key parameters. These curves are essential for understanding device behavior under non-standard conditions.

3.1 Spectral Distribution

The spectral distribution curve (Fig.1) shows the relative radiant intensity as a function of wavelength. It confirms the peak at approximately 940nm and the approximately 50nm half-width, providing a visual representation of the emitted light's spectral purity.

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

This curve (Fig.3) is fundamental for any semiconductor device. It shows the non-linear relationship between the current through the IRED and the voltage across it. The curve will shift with temperature, which is critical for thermal management in the design.

3.3 Temperature Dependence

Figures 2 and 4 depict how the device's performance changes with ambient temperature. Typically, the forward voltage of a diode has a negative temperature coefficient (it decreases as temperature increases), while the optical output power also generally decreases with rising temperature. These graphs allow designers to derate performance for high-temperature environments.

3.4 Relative Radiant Intensity vs. Forward Current

Figure 5 shows how the light output scales with drive current. It is typically sub-linear; doubling the current does not double the optical output. This relationship is important for setting the operating point to achieve desired brightness or signal strength efficiently.

3.5 Radiation Pattern

The polar diagram (Fig.6) provides a detailed map of the emitted intensity as a function of angle from the central axis. This 25-degree viewing angle device shows a beam pattern that is strongest in the center and falls off towards the edges, which is crucial for optical system design, such as aligning with a receiver's field of view.

4. Mechanical and Packaging Information

4.1 Outline Dimensions

The datasheet provides detailed mechanical drawings of the component. Key dimensions include the body size, lead spacing, and overall height. The component features a water-clear plastic package with a side-view lens, which shapes the emitted light's radiation pattern. All critical dimensions are provided with a standard tolerance of ±0.15mm unless otherwise specified.

4.2 Suggested Soldering Pad Layout

A recommended land pattern (footprint) for PCB design is included. Adhering to these dimensions is vital for ensuring proper solder joint formation during reflow, achieving good mechanical strength, and facilitating thermal dissipation from the device.

4.3 Polarity Identification

Standard LED polarity conventions apply. The cathode is typically indicated by a flat edge on the package body, a notch, or a shorter lead. Correct polarity must be observed during assembly to prevent damage.

5. Assembly, Handling, and Reliability Guidelines

5.1 Soldering and Assembly Guide

The device is rated for infrared reflow soldering. The datasheet specifies critical profile parameters:

• Pre-heat: 150–200°C.
• Pre-heat Time: 120 seconds maximum.
• Peak Temperature: 260°C maximum.
• Time Above Liquidus: 10 seconds maximum (for a maximum of two reflow cycles).

For hand soldering with an iron, the recommendation is a maximum temperature of 300°C for no more than 3 seconds per joint. The datasheet emphasizes that the optimal profile depends on the specific PCB design, solder paste, and oven, and recommends using JEDEC-standard profiles as a starting point.

5.2 Storage Conditions

The component has a Moisture Sensitivity Level (MSL) of 3. This means:

• Sealed Bag: Can be stored for up to one year at ≤30°C and ≤90% RH.
• After Bag Opening: Should be stored at ≤30°C and ≤60% RH. Components should be subjected to reflow within one week (168 hours). If stored longer outside the original bag, they must be stored in a dry cabinet or sealed container with desiccant. If exposed for more than one week, a bake-out at 60°C for at least 20 hours is required before soldering to prevent popcorn cracking during reflow.

5.3 Cleaning

If cleaning is necessary after soldering, only alcohol-based solvents like isopropyl alcohol (IPA) should be used. Harsh or aggressive chemicals may damage the plastic package or lens.

6. Packaging and Ordering Information

6.1 Tape and Reel Specifications

The component is supplied in embossed carrier tape with a cover tape, wound onto 7-inch (178mm) diameter reels. Each reel contains 3000 pieces. The packaging conforms to ANSI/EIA-481-1-A-1994 standards. Specifications include pocket dimensions, tape width, and reel hub size to ensure compatibility with automated pick-and-place machines.

7. Application Design Considerations

7.1 Drive Circuit Design

A critical design note is that an LED is a current-operated device. The datasheet strongly recommends against connecting multiple LEDs directly in parallel from a single voltage source with a single current-limiting resistor (Circuit Model B). Due to natural variations in the forward voltage (V_F) of individual devices, current will not be shared equally, leading to significant differences in brightness and potential over-stressing of one device. The recommended method (Circuit Model A) is to use a separate current-limiting resistor in series with each LED. This ensures uniform current and, therefore, uniform radiant intensity across all devices in the array.

7.2 Thermal Management

While the absolute maximum power dissipation is 100mW, practical operation should stay well below this limit, especially at higher ambient temperatures. The derating curves (Fig. 2, Fig. 4) must be consulted. Adequate PCB copper area (using the suggested pad layout helps) is necessary to conduct heat away from the device junction to maintain performance and longevity.

7.3 Optical Design

The 25-degree viewing angle and side-view lens package influence how the IR energy is directed. For optimal performance in a sensing or communication link, the emitter's radiation pattern should be aligned with the receiver's angular sensitivity profile. The radiation diagram (Fig.6) is essential for this alignment. For applications requiring a different beam pattern, external lenses or reflectors may be necessary.

8. Technical Comparison and Differentiation

The LTE-S9511T-E, with its 940nm peak wavelength, is positioned for general-purpose infrared applications. Key differentiators include its side-view package, which is useful for edge-lighting or specific optical path requirements, and its compatibility with automatic assembly processes. Compared to devices with wider viewing angles (e.g., 60-120 degrees), this component offers higher axial intensity for a given drive current, which can translate to longer range or lower power consumption for directed links. Its 940nm wavelength is a common standard, ensuring broad compatibility with silicon-based infrared receivers and filters designed for that spectrum.

9. Frequently Asked Questions (Based on Technical Parameters)

Q1: Can I drive this IRED directly from a microcontroller GPIO pin?
A: It depends on the GPIO's current sourcing capability. At a typical drive current of 20mA, the GPIO must be able to supply at least this much. A series resistor is always required to limit the current, calculated as R = (V_supply - V_F) / I_F. For a 3.3V supply and V_F of 1.2V at 20mA, R = (3.3 - 1.2) / 0.02 = 105 Ohms. A 100 Ohm resistor would be a standard choice.

Q2: What is the difference between peak wavelength (λ_p) and dominant wavelength (λ_d)?
A: Peak wavelength is the wavelength at the maximum point of the spectral power distribution curve. Dominant wavelength is derived from colorimetry and represents the perceived color. For monochromatic IR emitters, they are typically very close, but λ_p is the standard technical specification for optoelectronic performance.

Q3: Why is the pulsed current rating (1A) so much higher than the DC rating (50mA)?
A: This is due to thermal limitations. During a very short pulse (10μs), the semiconductor junction does not have time to heat up significantly, allowing a much higher instantaneous current without exceeding the maximum junction temperature. In DC operation, heat builds up continuously, so the current must be limited to keep the temperature within safe limits.

10. Practical Application Examples

Example 1: Simple IR Remote Control Transmitter. The LTE-S9511T-E can be used as the emitter in a basic remote. A microcontroller generates a modulated digital signal (e.g., 38kHz carrier) corresponding to a command protocol (e.g., NEC, RC5). This signal switches a transistor that drives the IRED with pulsed current up to the 1A peak rating, creating bursts of infrared light. The focused 25-degree beam helps ensure the signal is directed at the receiver.

Example 2: Proximity or Object Detection Sensor. Paired with a separate phototransistor or photodiode receiver, the emitter can be used to detect the presence or absence of an object. The emitter shines IR light across a gap. When an object interrupts the beam, the receiver's signal drops, triggering a detection event. The side-view package can be advantageous in designing compact sensor assemblies where the optical path is parallel to the PCB.

11. Operational Principle

The LTE-S9511T-E is a light-emitting diode (LED) based on Gallium Arsenide (GaAs) semiconductor material. When a forward voltage is applied across the P-N junction, electrons and holes are injected into the active region where they recombine. In a direct bandgap semiconductor like GaAs, this recombination releases energy in the form of photons (light). The specific energy bandgap of the material determines the wavelength of the emitted light; for GaAs, this results in infrared emission around 940nm. The side-view lens is made of water-clear epoxy that encapsulates the semiconductor chip and shapes the emitted light into the specified radiation pattern.

12. Industry Context and Trends

Discrete infrared components like the LTE-S9511T-E remain fundamental building blocks in electronics. While integrated sensor modules (combining emitter, detector, and logic in one package) are growing for specific applications like gesture sensing, discrete components offer design flexibility, cost-effectiveness for high-volume applications, and the ability to optimize the optical path independently. Trends in the industry include the continued demand for miniaturization, higher efficiency (more optical output per electrical input), and increased compatibility with lead-free, high-temperature soldering processes. The RoHS and Green Product compliance of this device aligns with global environmental regulations driving the electronics industry.