LTL-1DEDJ Through Hole LED Lamp Datasheet - T-1 Diameter - Voltage 2.6V - Power 75mW - Yellow/Green - English Technical Document

1. Product Overview

The LTL-1DEDJ is a through-hole LED lamp designed for status indication and visual signaling applications. It is offered in a popular T-1 diameter package, making it compatible with standard PCB layouts and mounting hardware. The device is characterized by its low power consumption, high efficiency, and compliance with lead-free and RoHS environmental standards. It features a white diffused lens which helps in achieving a uniform light distribution.

1.1 Core Advantages

• Low Power Consumption & High Efficiency: Enables energy-saving operation suitable for battery-powered or low-power devices.
• Lead-free & RoHS Compliant: Meets international environmental regulations, making it suitable for global markets.
• Standard T-1 Package: Ensures easy integration and replacement in existing designs and broad component availability.
• Color Options: Available in distinct yellow and green colors with a diffused lens for wide-angle visibility.

1.2 Target Applications

This LED is versatile and finds use across multiple industries requiring reliable status indication. Primary application areas include:

• Communication Equipment: Status lights on routers, modems, and network switches.
• Computer Peripherals: Power and activity indicators on desktops, laptops, and external drives.
• Consumer Electronics: Indicator lights on home audio/video equipment, appliances, and toys.
• Home Appliances: Operational status indicators on microwaves, washing machines, and other household devices.

2. Technical Parameter Deep-Dive

2.1 Absolute Maximum Ratings

These ratings define the limits beyond which permanent damage to the device may occur. Operation outside these conditions is not recommended.

• Power Dissipation (P_D): 75 mW maximum for both yellow and green variants. This parameter is crucial for thermal management.
• Peak Forward Current (I_FP): 60 mA, permissible only under pulsed conditions (duty cycle ≤ 1/10, pulse width ≤ 10 µs).
• DC Forward Current (I_F): 30 mA continuous. This is the standard operating current for achieving rated luminous intensity.
• Temperature Ranges: Operating from -40°C to +85°C; Storage from -40°C to +100°C. The wide range ensures reliability in harsh environments.
• Lead Soldering Temperature: 260°C for a maximum of 5 seconds at a distance of 2.0mm from the LED body. This is critical for assembly process control.

2.2 Electrical & Optical Characteristics

These parameters are specified at an ambient temperature (T_A) of 25°C and a forward current (I_F) of 20mA, unless otherwise noted.

• Luminous Intensity (I_v): Typical value is 110 mcd for both colors, with a minimum of 13.5 mcd. Intensity is measured per the CIE eye-response curve.
• Viewing Angle (2θ_1/2): 75 degrees. This is the full angle at which luminous intensity drops to half its axial value, defining the beam spread.
• Peak Wavelength (λ_P): Yellow: ~591 nm, Green: ~570 nm. This is the wavelength at the highest point in the emission spectrum.
• Dominant Wavelength (λ_d): Yellow: 584-596 nm, Green: 564-574 nm. This single wavelength best represents the perceived color of the LED.
• Spectral Line Half-Width (Δλ): Yellow: 25 nm, Green: 30 nm. This indicates the spectral purity or color bandwidth.
• Forward Voltage (V_F): 2.0V to 2.6V. A current-limiting resistor is mandatory in series to control the current, as V_F has a tolerance.
• Reverse Current (I_R): 100 µA maximum at V_R = 5V. Important: This LED is not designed for reverse bias operation; this parameter is for test purposes only.

3. Binning System Specification

The luminous intensity of the LTL-1DEDJ is classified into bins to ensure consistency in brightness for production applications. The binning is identical for both yellow and green colors.

Note: A tolerance of ±30% applies to each bin limit. The specific bin code is marked on the product packaging, allowing designers to select LEDs with the required brightness range for their application.

4. Performance Curve Analysis

While specific graphical data is referenced in the datasheet, the typical curves provide essential insights into device behavior under varying conditions.

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

The I-V characteristic is non-linear. A small increase in voltage beyond the typical V_F can cause a large, potentially damaging increase in current. This underscores the necessity of using a series resistor or constant current driver.

4.2 Luminous Intensity vs. Forward Current

Intensity generally increases with forward current but will saturate at higher currents. Operating at the recommended 20mA provides optimal efficiency and longevity.

4.3 Temperature Dependence

Luminous intensity typically decreases as the junction temperature increases. For consistent brightness in applications with varying ambient temperatures, thermal design and current derating should be considered.

5. Mechanical & Package Information

5.1 Outline Dimensions

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

• All dimensions are in millimeters (inches).
• General tolerance is ±0.25mm (±0.010\").
• Maximum resin protrusion under the flange is 1.0mm (0.04\").
• Lead spacing is measured at the point where leads exit the package body.

5.2 Polarity Identification

The longer lead denotes the anode (positive terminal), while the shorter lead is the cathode (negative terminal). Additionally, the cathode side often has a flat edge on the LED lens or a notch in the flange for visual identification.

6. Soldering & Assembly Guidelines

6.1 Lead Forming

• Bending must occur at a point at least 3mm away from the base of the LED lens.
• Do not use the package body as a fulcrum. Forming must be done at room temperature and before soldering.
• Apply minimal clinch force during PCB insertion to avoid mechanical stress on the leads or epoxy body.

6.2 Soldering Process

A minimum clearance of 2mm must be maintained between the solder point and the base of the lens. Dipping the lens into solder must be avoided.

• Hand Soldering (Iron): Maximum temperature 350°C for no more than 3 seconds per lead.
• Wave Soldering: Pre-heat to a maximum of 100°C for up to 60 seconds. Solder wave temperature should not exceed 260°C, with a contact time of 5 seconds maximum.
• Critical Warning: Infrared (IR) reflow soldering is not suitable for this through-hole LED product. Excessive heat will damage the epoxy lens and internal structure.

6.3 Storage & Handling

• Store in an environment not exceeding 30°C and 70% relative humidity.
• LEDs removed from their original moisture-barrier bag should be used within three months.
• For longer-term storage outside original packaging, use a sealed container with desiccant or a nitrogen-filled desiccator.
• Clean only with alcohol-based solvents like isopropyl alcohol if necessary.

7. Packaging & Ordering Information

7.1 Packaging Specification

The product is supplied in a tiered packaging system:

1. Packing Bag: Contains 500, 200, or 100 pieces.
2. Inner Carton: Contains 10 packing bags, totaling 5,000 pieces.
3. Master (Outer) Carton: Contains 8 inner cartons, totaling 40,000 pieces.

In every shipping lot, only the final pack may contain a non-full quantity.

8. Application Design Considerations

8.1 Drive Circuit Design

LEDs are current-driven devices. To ensure uniform brightness, especially when connecting multiple LEDs in parallel, a series current-limiting resistor is mandatory for each LED.

• Recommended Circuit (A): Each LED has its own series resistor connected to the voltage supply. This compensates for variances in individual LED forward voltage (V_F).
• Non-Recommended Circuit (B): Multiple LEDs connected in parallel with a single shared resistor. This can lead to significant brightness mismatch due to natural V_F variation between LEDs, causing current hogging.

The resistor value (R) can be calculated using Ohm's Law: R = (V_Supply - V_F) / I_F, where I_F is the desired forward current (e.g., 20mA).

8.2 Electrostatic Discharge (ESD) Protection

These LEDs are sensitive to electrostatic discharge. Preventive measures must be implemented in the handling and assembly environment:

• Operators must wear grounded wrist straps or anti-static gloves.
• All workstations, equipment, and storage racks must be properly grounded.
• Use ionizers to neutralize static charge that may accumulate on the plastic lens.
• Maintain training and certification programs for personnel working in ESD-protected areas.

9. Technical Comparison & Differentiation

Within the through-hole indicator LED segment, the LTL-1DEDJ offers a balanced combination of attributes:

• Standardization: Its T-1 package ensures second-source availability and design compatibility.
• Performance: With a typical intensity of 110 mcd and a 75-degree viewing angle, it provides bright, wide-angle illumination suitable for most indicator roles.
• Reliability: The specified wide operating temperature range (-40°C to +85°C) and robust soldering ratings make it suitable for industrial and consumer applications.
• Environmental Compliance: Being lead-free and RoHS compliant is a baseline requirement, which this product meets.

10. Frequently Asked Questions (FAQ)

10.1 Can I drive this LED without a series resistor?

No. The forward voltage has a range (2.0V-2.6V). Connecting it directly to a voltage source even slightly above its V_F can cause excessive, uncontrolled current flow, leading to immediate failure. A series resistor or constant current driver is essential.

10.2 What is the difference between Peak Wavelength and Dominant Wavelength?

Peak Wavelength (λ_P): The specific wavelength where the optical output power is greatest. Dominant Wavelength (λ_d): The single wavelength of monochromatic light that would produce the same color perception as the LED's actual broad-spectrum output. λ_d is more relevant for color specification.

10.3 Can I use this LED for outdoor applications?

The datasheet states it is suitable for indoor and outdoor signs. However, for prolonged outdoor use, consider additional environmental protection (e.g., conformal coating on the PCB, UV-stable enclosures) as the epoxy lens may degrade under extreme, direct sunlight over many years.

10.4 Why is IR reflow soldering not allowed?

Through-hole components like this LED have epoxy bodies and internal wire bonds that are not designed to withstand the high, uniform temperatures of a reflow oven profile. The thermal stress can crack the epoxy, delaminate internal interfaces, or break the bond wires.

11. Practical Design Case Study

Scenario: Designing a power status indicator for a 5V USB-powered device.

1. Component Selection: Choose the LTL-1DEDJ (Green) for a \"power on\" indication.
2. Current Setting: Target I_F = 20mA for optimal brightness and longevity.
3. Resistor Calculation: Using typical V_F = 2.6V. R = (5V - 2.6V) / 0.020A = 120 Ω. The nearest standard value is 120 Ω. Power dissipation in the resistor: P = I²R = (0.02)² * 120 = 0.048W. A standard 1/8W (0.125W) resistor is sufficient.
4. PCB Layout: Place the LED on the front panel. Ensure the solder pad is >2mm from the LED body. Include silkscreen polarity marking (\"+\" for anode/longer lead).
5. Assembly: Form leads >3mm from body, insert into PCB, and wave solder following the specified profile (260°C max, 5s).

12. Operating Principle

Light Emitting Diodes (LEDs) are semiconductor devices that emit light through electroluminescence. When a forward voltage is applied across the p-n junction, electrons recombine with holes within the semiconductor material, releasing energy in the form of photons. The specific wavelength (color) of the emitted light is determined by the energy bandgap of the semiconductor materials used (e.g., Gallium Phosphide variants for green and yellow). The white diffused lens contains particles that scatter the light, broadening the viewing angle and creating a softer, more uniform appearance.

13. Technology Trends

While through-hole LEDs like the LTL-1DEDJ remain vital for prototyping, repair, and certain industrial applications, the broader industry trend is towards surface-mount device (SMD) LEDs. SMD packages offer significant advantages in automated assembly, board space savings, and thermal management. However, through-hole components continue to be preferred for their mechanical robustness in high-vibration environments, ease of manual soldering, and superior lead strength for applications where the LED may be subject to physical interaction or wired connections. The development focus for such legacy packages often centers on improving efficiency, color consistency, and reliability within the existing form factor.