LTL816GE3T Green LED Lamp Datasheet - T-1 Package - 2.6V - 52mW - English Technical Document

1. Product Overview

The LTL816GE3T is a green light-emitting diode (LED) lamp designed for through-hole mounting on printed circuit boards (PCBs). It belongs to the popular T-1 package family, offering a standard form factor compatible with a wide range of applications requiring status indication or illumination.

1.1 Core Advantages

This LED offers several key advantages for designers. It features low power consumption and high luminous efficiency, making it suitable for energy-sensitive applications. The device is constructed using lead-free materials and is fully compliant with RoHS (Restriction of Hazardous Substances) directives. Its AlInGaP (Aluminum Indium Gallium Phosphide) semiconductor technology combined with a green transparent lens produces a clear, bright green light output.

1.2 Target Market and Applications

The LTL816GE3T is designed for flexibility across multiple industries. Its primary applications include status indicators and backlighting in communication equipment, computers, consumer electronics, home appliances, and various industrial control systems. The standard T-1 package ensures easy integration into existing designs and manufacturing processes.

2. In-Depth Technical Parameter Analysis

Understanding the electrical and optical characteristics is crucial for reliable circuit design and performance prediction.

2.1 Absolute Maximum Ratings

These ratings define the limits beyond which permanent damage to the device may occur. They are specified at an ambient temperature (TA) of 25°C.

• Power Dissipation (Pd): 52 mW maximum. This is the total power the device can safely dissipate as heat.
• DC Forward Current (IF): 20 mA continuous. Exceeding this current can cause overheating and rapid degradation.
• Peak Forward Current: 60 mA maximum, but only under pulsed conditions (duty cycle ≤ 1/10, pulse width ≤ 10 μs). This is useful for brief, high-intensity flashes.
• Derating: The maximum DC forward current must be linearly derated by 0.27 mA for every degree Celsius above 30°C. For example, at 85°C, the maximum allowable continuous current is significantly lower than 20 mA.
• Operating Temperature Range: -40°C to +85°C. The device is rated for operation in harsh environments.
• Lead Soldering Temperature: 260°C for a maximum of 5 seconds, measured at a distance of 1.6mm (0.063") from the LED body. This is critical for wave or hand soldering processes.

2.2 Electrical and Optical Characteristics

These are the typical performance parameters measured at TA=25°C and a forward current (IF) of 10 mA, unless otherwise stated.

• Luminous Intensity (Iv): Ranges from a minimum of 12.6 mcd to a typical value of 29 mcd, with a maximum of 110 mcd. The actual intensity is binned (see Section 4). The measurement uses a sensor/filter approximating the CIE photopic eye-response curve. A ±15% testing tolerance is applied to the guaranteed Iv value.
• Viewing Angle (2θ1/2): 35 degrees (typical). This is the full angle at which the luminous intensity drops to half of its axial (on-center) value. It defines the beam spread of the LED.
• Peak Emission Wavelength (λP): 568 nm (typical). This is the wavelength at the highest point in the emitted light spectrum.
• Dominant Wavelength (λd): Ranges from 563 nm to 573 nm (see Bin Table). This is derived from the CIE chromaticity diagram and represents the perceived color of the light.
• Spectral Line Half-Width (Δλ): 30 nm (typical). This indicates the spectral purity; a smaller value means a more monochromatic light.
• Forward Voltage (VF): 2.1V (minimum) to 2.6V (typical) at 10 mA. This is the voltage drop across the LED when operating.
• Reverse Current (IR): 10 μA maximum at a reverse voltage (VR) of 5V. Important: This device is not designed for reverse operation; this parameter is for test purposes only.

3. Binning System Specification

To ensure color and brightness consistency in production, LEDs are sorted into bins. The LTL816GE3T uses a two-dimensional binning system.

3.1 Luminous Intensity Binning

LEDs are classified based on their measured luminous intensity at 10 mA. The bin codes and their ranges are as follows (tolerance on each bin limit is ±15%):

• O1: 60.0 - 110 mcd
• N1: 40.0 - 60.0 mcd
• N2: 29.0 - 40.0 mcd
• N3: 19.0 - 29.0 mcd
• N4: 12.6 - 19.0 mcd

The Iv classification code is marked on each packing bag for traceability.

3.2 Dominant Wavelength Binning

LEDs are also sorted by their dominant wavelength to control the precise shade of green. The bin codes and ranges are as follows (tolerance on each bin limit is ±1 nm):

• YG: 571.0 - 573.0 nm
• PG: 569.0 - 571.0 nm
• GG: 567.0 - 569.0 nm
• GG1: 565.0 - 567.0 nm
• GG2: 563.0 - 565.0 nm

4. Mechanical and Packaging Information

4.1 Outline Dimensions

The LED conforms to the standard T-1 (3mm) radial leaded package. Key dimensional notes include:

• All dimensions are in millimeters (inches provided in the original drawing).
• A standard tolerance of ±0.25mm (.010") applies unless otherwise specified.
• The resin under the flange may protrude up to 1.0mm (.04") maximum.
• Lead spacing is measured where the leads emerge from the package body.
• The anode (positive) lead is typically the longer lead, which is a common industry practice for polarity identification.

4.2 Packaging Specification

The LEDs are packaged for automated handling and bulk shipping:

• Basic Unit: 500, 200, or 100 pieces per anti-static packing bag.
• Inner Carton: Contains 10 packing bags, totaling 5,000 pieces (when using 500pc bags).
• Outer Carton: Contains 8 inner cartons, totaling 40,000 pieces per outer carton.
• A note specifies that in every shipping lot, only the final pack may not be a full pack.

5. Soldering and Assembly Guidelines

Proper handling is essential to prevent damage and ensure long-term reliability.

5.1 Storage and Cleaning

LEDs should be stored in an environment not exceeding 30°C and 70% relative humidity. If removed from the original packaging, they should be used within three months. For longer storage, use a sealed container with desiccant or a nitrogen ambient. Cleaning, if necessary, should be done with alcohol-based solvents like isopropyl alcohol.

5.2 Lead Forming and PCB Assembly

Leads must be bent at a point at least 3mm from the base of the LED lens. The base of the lead frame should not be used as a fulcrum. All forming must be done at room temperature and before soldering. During PCB insertion, use the minimum clinch force necessary to avoid mechanical stress on the package.

5.3 Soldering Process

A minimum clearance of 1.6mm must be maintained from the base of the lens to the solder point. Dipping the lens into solder must be avoided. Do not apply stress to the leads during soldering while the LED is hot.

Recommended Soldering Conditions:

• Soldering Iron: Temperature 350°C max. Time: 3 seconds max (one time only). Position: No closer than 1.6mm from the lens base.
• Wave Soldering: Pre-heat: 100°C max for 60 seconds max. Solder Wave: 260°C max. Soldering Time: 5 seconds max. Dipping Position: No lower than 1.6mm from the lens base.

Critical Warning: Excessive temperature or time can deform the lens or cause catastrophic failure. Infrared (IR) reflow soldering is not suitable for this through-hole type LED product.

6. Application Design and Drive Method

6.1 Drive Circuit Design

An LED is a current-operated device. To ensure uniform brightness when multiple LEDs are used in parallel, it is strongly recommended to use a current-limiting resistor in series with each individual LED (Circuit A). This compensates for minor variations in the forward voltage (Vf) characteristic between individual LEDs. Using a single resistor for multiple parallel LEDs (Circuit B) is not recommended, as differences in Vf will cause significant brightness variation between the LEDs.

6.2 Electrostatic Discharge (ESD) Protection

Static electricity can damage the semiconductor junction. To prevent ESD damage:

• Operators should use conductive wrist straps or anti-static gloves.
• All equipment, worktables, and storage racks must be properly grounded.
• Use an ion blower to neutralize static charge that may build up on the plastic lens surface due to friction.
• Ensure personnel working in static-safe areas are properly trained and ESD-certified.

7. Performance Curves and Analysis

The datasheet references typical characteristic curves which are essential for detailed design analysis. These curves graphically represent the relationship between key parameters under varying conditions.

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

This curve shows the non-linear relationship between the current flowing through the LED and the voltage across it. It is crucial for selecting the appropriate series resistor value to achieve the desired operating current from a given supply voltage. The curve will show the typical "knee" voltage around 2V, after which current increases rapidly with a small increase in voltage.

7.2 Luminous Intensity vs. Forward Current

This curve demonstrates how light output increases with drive current. It is generally linear over a range but will saturate at higher currents due to thermal effects and efficiency droop. This helps designers balance brightness requirements against power consumption and heat generation.

7.3 Spectral Distribution

The spectral distribution plot shows the relative intensity of light emitted across different wavelengths. For this green AlInGaP LED, it will typically show a narrow peak centered around 568 nm (peak wavelength) with a characteristic half-width of approximately 30 nm, defining the color purity.

8. Technical Comparison and Design Considerations

8.1 Differentiation from Other Technologies

The use of AlInGaP technology for green light offers advantages over older technologies like Gallium Phosphide (GaP). AlInGaP LEDs generally provide higher luminous efficiency and better temperature stability, resulting in brighter and more consistent light output over the operating temperature range.

8.2 Thermal Management Considerations

While the power dissipation is low (52mW max), the derating specification is critical. In high ambient temperature applications or when driving at the maximum continuous current, the effective current limit decreases. Designers must calculate the actual junction temperature based on ambient temperature, forward current, and the thermal resistance path through the leads to the PCB to ensure reliable operation.

8.3 Optical Design in Application

The 35-degree viewing angle provides a reasonably wide beam, suitable for status indicators that need to be visible from various angles. For applications requiring a more focused or diffused beam, secondary optics (lenses or light pipes) can be used in conjunction with the LED. The green transparent lens offers good color saturation.

9. Frequently Asked Questions (Based on Technical Parameters)

9.1 Can I drive this LED without a series resistor?

No. The forward voltage has a range (2.1V to 2.6V) and is temperature-dependent. Connecting it directly to a voltage source even slightly above its Vf can cause an uncontrolled surge in current, exceeding the absolute maximum rating and destroying the device. A series resistor is mandatory for current regulation.

9.2 What is the difference between Peak and Dominant Wavelength?

Peak Wavelength (λP) is the physical wavelength at the highest point of the emission spectrum. Dominant Wavelength (λd) is a calculated value from colorimetry that represents the perceived color. For a monochromatic source like this green LED, they are often close, but λd is the more relevant parameter for color specification in applications.

9.3 Why is there a ±15% tolerance on the luminous intensity?

This tolerance accounts for measurement system variations and minor production variances. The binning system (N1, N2, etc.) is used to provide guaranteed minimum and maximum intensity ranges for production consistency. Designers should use the minimum value from the selected bin for worst-case brightness calculations.

9.4 Can I use this LED for outdoor applications?

The datasheet states it is suitable for indoor and outdoor signs. The operating temperature range of -40°C to +85°C supports outdoor use. However, for long-term outdoor exposure, additional design considerations are needed, such as protection from UV radiation (which can degrade the epoxy lens over time) and moisture ingress, which are not covered in this component-level datasheet.

10. Practical Design Case Study

10.1 Designing a Status Indicator Panel

Consider a control panel requiring ten green status indicators. The system power supply is 5V DC. The goal is to achieve a bright, uniform indication.

1. Current Selection: Choose a drive current of 10 mA, which is within the 20 mA maximum and provides good brightness (typ. 29 mcd).
2. Resistor Calculation: Using the typical Vf of 2.6V at 10 mA. Resistor value R = (Vsupply - Vf) / If = (5V - 2.6V) / 0.01A = 240 Ω. Use the nearest standard value (240 Ω or 220 Ω). Power rating: P = I^2 * R = (0.01)^2 * 240 = 0.024W, so a standard 1/8W or 1/10W resistor is sufficient.
3. Circuit Topology: Implement Circuit A from the datasheet: one independent current-limiting resistor for each of the ten LEDs, all connected in parallel to the 5V rail. This ensures uniform brightness even if the Vf of individual LEDs varies within the bin.
4. PCB Layout: Maintain the 1.6mm solder clearance. Ensure the anode (longer lead) is correctly oriented on the PCB silkscreen. Provide adequate copper pour for heat dissipation if operating in a high ambient temperature.
5. Binning: Specify a tight intensity bin (e.g., N2 or N1) and a specific dominant wavelength bin (e.g., PG) in the purchase order to ensure visual consistency across all ten indicators on the panel.

11. Operating Principle

The LTL816GE3T operates on the principle of electroluminescence in a semiconductor p-n junction. When a forward voltage exceeding the junction's built-in potential is applied, electrons from the n-type AlInGaP semiconductor layer are injected across the junction into the p-type layer, and holes are injected in the opposite direction. These charge carriers recombine in the active region near the junction. A portion of the energy released during this recombination process is emitted as photons (light). The specific composition of the AlInGaP semiconductor alloy determines the bandgap energy, which directly defines the wavelength (color) of the emitted light—in this case, green. The transparent epoxy lens serves to protect the semiconductor chip, shape the light output beam, and enhance light extraction efficiency.

12. Technology Trends

Through-hole LEDs like the T-1 package remain widely used due to their simplicity, robustness, and ease of manual assembly or repair. However, the broader industry trend is towards surface-mount device (SMD) packages for automated assembly, higher density, and better thermal performance. For indicator applications, smaller SMD packages (e.g., 0603, 0402) are increasingly common. In terms of materials, AlInGaP technology for red, orange, and yellow/green LEDs is mature and offers high efficiency. For true green and blue, InGaN (Indium Gallium Nitride) is the dominant technology. Future developments in through-hole indicator LEDs may focus on further increasing efficiency (lumens per watt) and improving color consistency and stability over temperature and lifetime, though major architectural shifts are more likely in high-power and lighting-grade SMD packages.