T-1 3/4 Yellow LED Lamp Datasheet - 5mm Diameter - 2.4V Forward Voltage - 75mW Power Dissipation - English Technical Document

1. Product Overview

This document provides the complete technical specifications for a high-performance, through-hole mounted LED lamp. The device is designed for general-purpose indicator and illumination applications where reliability, efficiency, and ease of integration are paramount. It utilizes an AlInGaP (Aluminum Indium Gallium Phosphide) semiconductor material to produce a distinct yellow light output, offering a balance of visual clarity and energy efficiency.

The LED is housed in a popular T-1 3/4 package, corresponding to a 5mm diameter lens, making it compatible with a vast array of existing PCB layouts and panel cutouts. Its design emphasizes low power consumption and high luminous intensity, making it suitable for battery-powered devices or applications where minimizing energy use is critical. The product is compliant with RoHS directives, indicating it is free from hazardous substances like lead (Pb).

2. Technical Parameters Deep Dive

2.1 Absolute Maximum Ratings

The device's operational limits are defined under specific ambient conditions (TA=25°C). Exceeding these ratings may cause permanent damage.

• Power Dissipation (Pd): 75 mW. This is the maximum amount of power the device can safely dissipate as heat.
• Continuous Forward Current (IF): 30 mA. The maximum DC current that can be applied continuously.
• Peak Forward Current: 60 mA. This higher current is permissible only under pulsed conditions (1/10 duty cycle, 0.1ms pulse width) to handle brief surges.
• Derating Factor: 0.4 mA/°C above 50°C. The maximum continuous current must be reduced linearly as the ambient temperature increases beyond 50°C to prevent overheating.
• Operating Temperature Range: -40°C to +100°C. The ambient temperature range within which the device is specified to operate.
• Storage Temperature Range: -55°C to +100°C.
• Lead Soldering Temperature: 260°C for 5 seconds, measured 1.6mm from the LED body. This defines the thermal profile for hand or wave soldering processes.

2.2 Electrical & Optical Characteristics

These parameters are measured at a standard test condition of IF = 20mA and TA = 25°C, providing the baseline performance.

• Luminous Intensity (Iv): 400 - 2500 mcd (millicandela), with a typical value of 1150 mcd. This wide range is managed through a binning system (detailed later). Intensity is measured using a sensor filtered to match the human eye's photopic response (CIE curve).
• Viewing Angle (2θ1/2): 30 degrees. This is the full angle at which the luminous intensity drops to half of its value measured on the central axis. It indicates a moderately focused beam.
• Peak Emission Wavelength (λP): 591 nm. The wavelength at which the spectral power output is highest.
• Dominant Wavelength (λd): 582 - 596 nm. This is the single wavelength perceived by the human eye that defines the color, derived from the CIE chromaticity diagram. It ensures the yellow color falls within a specified range.
• Spectral Line Half-Width (Δλ): 15 nm. The width of the emitted spectrum at half its maximum power, indicating color purity.
• Forward Voltage (VF): 2.05 - 2.4 V, with a typical of 2.4V at 20mA. This is the voltage drop across the LED when operating.
• Reverse Current (IR): 100 µA maximum at VR = 5V. LEDs are not designed for reverse bias operation; this parameter is for leakage test purposes only.

3. Binning System Explanation

To ensure consistency in applications, LEDs are sorted (binned) based on key optical parameters. This datasheet details a binning system for luminous intensity.

Luminous Intensity Binning (@ 20mA): The LEDs are categorized into six bins (SB1 to SB6), each with a minimum and maximum intensity range. The tolerance for each bin limit is ±15%.

• SB1: 1900 - 2500 mcd
• SB2: 1500 - 1900 mcd
• SB3: 1150 - 1500 mcd
• SB4: 880 - 1150 mcd
• SB5: 680 - 880 mcd
• SB6: 400 - 680 mcd

This system allows designers to select LEDs with the required brightness level for their specific application, ensuring visual uniformity when multiple LEDs are used together.

4. Performance Curve Analysis

While specific graphical data is referenced in the document (Typical Electrical/Optical Characteristics Curves on page 4), the parameters imply standard LED behavior curves that should be considered in design:

• Forward Current vs. Forward Voltage (I-V Curve): The relationship is exponential. A small increase in voltage beyond the typical VF causes a large increase in current, necessitating current-limiting measures.
• Luminous Intensity vs. Forward Current (I-Iv Curve): Intensity generally increases with current but may saturate or degrade at very high currents due to heating effects.
• Luminous Intensity vs. Ambient Temperature: The light output typically decreases as the junction temperature of the LED rises. The derating factor for current indirectly manages this thermal effect.
• Spectral Distribution: The output is a narrow band centered around the peak wavelength of 591 nm, characteristic of AlInGaP technology, which provides good color saturation.

5. Mechanical & Packaging Information

5.1 Package Dimensions

The device uses a standard radial leaded package with a T-1 3/4 (5mm) diameter water-clear lens. Key dimensional notes include:

• All dimensions are in millimeters (inches provided in tolerance).
• Standard tolerance is ±0.25mm unless specified otherwise.
• The maximum protrusion of resin under the flange is 1.0mm.
• Lead spacing is measured at the point where leads exit the package body.

5.2 Polarity Identification

For through-hole LEDs, the cathode is typically identified by a flat spot on the lens rim, a shorter lead, or a notch in the flange. The datasheet's dimensional drawing would clarify the specific marker. Correct polarity is essential for operation.

6. Soldering & Assembly Guidelines

Proper handling is crucial for reliability. The document provides detailed cautions:

• Lead Forming: Must be done at room temperature, before soldering. Bend leads at a point at least 3mm from the base of the LED lens. Do not use the package body as a fulcrum.
• Soldering:
  • Iron Soldering: Max temperature 350°C for max 3 seconds (one time only).
  • Wave Soldering: Pre-heat to max 100°C for max 60 sec, solder wave at max 260°C for max 5 sec.
  • Critical Rule: Maintain a minimum 3mm clearance from the base of the lens to the solder point. Avoid dipping the lens into solder to prevent resin climb-up on leads, which can cause soldering issues.
  • Not Recommended: IR reflow soldering is unsuitable for this through-hole type product.
• Cleaning: Use alcohol-based solvents like isopropyl alcohol if necessary.
• Storage: Store in conditions not exceeding 30°C and 70% relative humidity. LEDs removed from original packaging should be used within three months. For longer storage, use sealed containers with desiccant or nitrogen ambient.

7. Packaging & Ordering Information

The standard packaging flow is as follows:

• Unit Packing: 1000, 500, 200, or 100 pieces per anti-static packing bag.
• Inner Carton: 8 packing bags per carton, totaling 8000 pieces.
• Outer Carton (Shipping Lot): 8 inner cartons per outer carton, totaling 64,000 pieces. The final pack in a shipping lot may not be full.

The specific part number for this device is LTL2R3KSK, which encodes information about the lens type (Water Clear), source technology (AlInGaP), and color (Yellow).

8. Application Suggestions

8.1 Typical Application Scenarios

This LED is intended for ordinary electronic equipment, including:

• Status and power indicators in consumer electronics, appliances, and office equipment.
• Panel illumination and backlighting for switches and displays.
• General-purpose signaling and decorative lighting where a clear yellow indication is required.

Important Note: For applications requiring exceptional reliability where failure could jeopardize life or health (aviation, medical devices, safety systems), specific consultation and qualification are necessary.

8.2 Design Considerations & Drive Method

An LED is a current-operated device. To ensure consistent brightness, especially when driving multiple LEDs in parallel, a series current-limiting resistor for each LED is strongly recommended (Circuit Model A).

Using a common voltage source with a single resistor for multiple parallel LEDs (Circuit Model B) is not recommended. Small variations in the forward voltage (VF) characteristic from one LED to another will cause significant differences in the current flowing through each, leading to uneven brightness. The series resistor for each LED stabilizes the current and compensates for these minor VF differences.

The resistor value (R) can be calculated using Ohm's Law: R = (Vcc - VF) / IF, where Vcc is the supply voltage, VF is the LED's forward voltage (use max value for reliability), and IF is the desired forward current (e.g., 20mA).

9. Electrostatic Discharge (ESD) Protection

LEDs are sensitive to electrostatic discharge. To prevent damage:

• Operators should wear conductive wrist straps or anti-static gloves.
• All equipment, workstations, and storage racks must be properly grounded.
• Use an ionizer to neutralize static charges that may accumulate on the plastic lens.
• Handle devices in ESD-protected areas.

10. Technical Comparison & Differentiation

This AlInGaP yellow LED offers distinct advantages:

• vs. Traditional Phosphor-Based Yellow LEDs: AlInGaP is a direct semiconductor material for yellow light, offering higher efficiency, better color stability over time and temperature, and potentially longer lifetime compared to older technologies like a blue LED with a yellow phosphor.
• vs. Other Colors in Similar Package: The specified viewing angle (30°) provides a more focused beam than wide-angle LEDs, making it suitable for applications requiring directed light or higher axial intensity.
• Key Advantages Summarized: High luminous intensity output, low power consumption, high efficiency, RoHS compliance, and compatibility with standard T-1 3/4 mounting.

11. Frequently Asked Questions (FAQs)

Q1: Can I drive this LED directly from a 5V or 3.3V logic output?
A: No. You must use a series current-limiting resistor. For example, with a 5V supply and a typical VF of 2.4V at 20mA, a resistor of approximately (5V - 2.4V) / 0.02A = 130 Ohms is required. Always check the maximum current rating.

Q2: Why is there such a wide range in luminous intensity (400-2500 mcd)?
A: This reflects the natural variation in semiconductor manufacturing. The binning system (SB1-SB6) allows you to purchase LEDs within a tighter, specified brightness range for your application to ensure consistency.

Q3: What is the difference between Peak Wavelength and Dominant Wavelength?
A: Peak Wavelength (λP) is the physical peak of the light spectrum emitted. Dominant Wavelength (λd) is calculated from color coordinates and represents the single wavelength the human eye perceives the color to be. λd is more relevant for color specification.

Q4: Can I use this for outdoor applications?
A: The operating temperature range (-40°C to +100°C) allows for many outdoor environments. However, consider additional factors like lens durability against UV radiation and moisture ingress, which are not specified in this datasheet. Conformal coating or using an LED rated for outdoor use may be necessary.

12. Practical Design Case Study

Scenario: Designing a control panel with 10 uniform yellow status indicators, powered by a 12V DC rail.

Design Steps:

1. LED Selection: Choose LEDs from the same intensity bin (e.g., SB3: 1150-1500 mcd) to guarantee brightness matching.
2. Current Setting: Select a standard drive current of 20mA for good brightness and longevity.
3. Resistor Calculation: Using the maximum VF (2.4V) for reliability: R = (12V - 2.4V) / 0.02A = 480 Ohms. The nearest standard value is 470 Ohms. Re-calculating current: IF = (12V - 2.4V) / 470Ω ≈ 20.4 mA (safe).
4. Power in Resistor: P_R = IF^2 * R = (0.0204A)^2 * 470Ω ≈ 0.196W. Use a 1/4 Watt resistor.
5. Layout: Place each LED with its dedicated 470Ω resistor in series. Ensure PCB holes match the lead spacing from the datasheet's dimensional drawing. Maintain the 3mm minimum distance from the LED body to the solder pad.
6. Assembly: Follow the soldering guidelines precisely, using a controlled-temperature iron to avoid thermal damage.

This approach ensures all 10 indicators have consistent, reliable performance.

13. Operating Principle

This LED operates on the principle of electroluminescence in a semiconductor p-n junction. The active region is composed of AlInGaP. When a forward voltage exceeding the material's bandgap energy is applied, electrons from the n-type region and holes from the p-type region are injected into the active region. When these charge carriers recombine, they release energy in the form of photons (light). The specific composition of the AlInGaP alloy determines the bandgap energy, which directly corresponds to the wavelength (color) of the emitted light—in this case, yellow (~590 nm). The water-clear epoxy lens encapsulates the semiconductor chip, provides mechanical protection, and shapes the light output beam.

14. Technology Trends

While through-hole LEDs remain vital for prototyping, repair, and certain industrial applications, the broader optoelectronics industry is trending towards surface-mount device (SMD) packages for most new designs. SMD LEDs offer advantages in automated assembly, smaller footprint, and better thermal management. For through-hole components, ongoing developments focus on increasing efficiency (more light output per watt), improving color consistency through advanced binning, and enhancing reliability under harsh environmental conditions. The AlInGaP material system used here represents a mature and efficient technology for amber, yellow, and red colors, with incremental improvements in epitaxial growth and packaging continuing to push performance boundaries.