LTL-14FGSAJ4H79G LED Lamp Datasheet - Yellow/Green Bi-Color - 20mA - 52mW - Through Hole Package - English Technical Document

1. Product Overview

The LTL-14FGSAJ4H79G is a bi-color (Yellow/Green) LED lamp designed for through-hole mounting on printed circuit boards (PCBs). It is housed in a black plastic right-angle holder, which is part of a Circuit Board Indicator (CBI) system. This design enhances contrast ratio and facilitates easy assembly and stacking in both horizontal and vertical array configurations. The product is a lead-free, RoHS compliant solid-state light source characterized by low power consumption and high efficiency.

1.1 Core Features

• Designed for ease of circuit board assembly and integration.
• Black housing material improves visual contrast and light definition.
• Utilizes a solid-state light source for reliability and long life.
• Features low power consumption with high luminous efficiency.
• Compliant with lead-free and RoHS environmental standards.
• Incorporates a T-1 sized lamp with a white diffused lens, emitting Yellow/Green bi-color light.

1.2 Target Applications

This LED is suitable for a variety of electronic equipment requiring status indication, including:

• Communication devices
• Computer systems and peripherals
• Consumer electronics
• Home appliances

2. Technical Parameters: In-Depth Objective Interpretation

2.1 Absolute Maximum Ratings

All ratings are specified at an ambient temperature (TA) of 25°C. Exceeding these limits may cause permanent damage.

• Power Dissipation (PD): 52 mW (for both Yellow and Green colors). This defines the maximum power the LED can safely dissipate as heat.
• Peak Forward Current (IFP): 60 mA, permissible only under pulsed conditions (duty cycle ≤ 1/10, pulse width ≤ 0.1ms).
• DC Forward Current (IF): 20 mA. This is the recommended continuous operating current for reliable performance.
• Operating Temperature Range: -40°C to +85°C. The device is rated to function within this wide temperature span.
• Storage Temperature Range: -40°C to +100°C.
• Lead Soldering Temperature: Withstands 260°C for a maximum of 5 seconds, measured 2.0mm (0.079\") from the LED body.

2.2 Electrical and Optical Characteristics

Key performance parameters measured at TA=25°C and a test current (IF) of 10mA, unless otherwise stated.

• Luminous Intensity (Iv): Ranges from 4 mcd (Min) to 29 mcd (Max), with a typical value of 11 mcd for both colors. This is the perceived brightness as measured by a sensor filtered to the CIE photopic eye response.
• Viewing Angle (2θ1/2): Approximately 110 degrees. This is the full angle at which luminous intensity drops to half its axial (on-axis) value, indicating a wide viewing cone.
• Peak Wavelength (λP): Typically 574 nm for Green and 590 nm for Yellow. This is the wavelength at which the spectral power distribution is highest.
• Dominant Wavelength (λd): Defines the perceived color. For Green: 564-576 nm (Typ: 570 nm). For Yellow: 582-594 nm (Typ: 590 nm).
• Spectral Line Half-Width (Δλ): Approximately 20 nm for both colors, indicating the spectral purity.
• Forward Voltage (VF): Ranges from 1.6V (Min) to 2.5V (Max), with a typical value of 2.0V at 10mA.
• Reverse Current (IR): Maximum of 100 μA when a reverse voltage (VR) of 5V is applied. Important: The device is not designed for operation in reverse bias; this test condition is for characterization only.

3. Binning System Specification

The LEDs are sorted (binned) based on key optical parameters to ensure consistency within a batch. The bin codes are marked on the packaging.

3.1 Luminous Intensity Binning

Two intensity bins are defined for each color, with a tolerance of ±30% on each bin limit.

• Bin Code A: 4 mcd to 13 mcd @ 10mA.
• Bin Code B: 13 mcd to 29 mcd @ 10mA.

3.2 Dominant Wavelength Binning

Two wavelength bins are defined for each color, with a tolerance of ±1 nm on each bin limit.

• For Green (Yellow Green):
  • Bin Code 1: 564 nm to 570 nm.
  • Bin Code 2: 570 nm to 576 nm.
• For Yellow:
  • Bin Code 1: 582 nm to 588 nm.
  • Bin Code 2: 588 nm to 594 nm.

4. Performance Curve Analysis

The datasheet references typical characteristic curves which illustrate the relationship between key parameters. While specific graphs are not provided in the text, standard LED curves would typically include:

• Relative Luminous Intensity vs. Forward Current (I-V Curve): Shows how light output increases with current, typically in a non-linear fashion, emphasizing the need for current control.
• Forward Voltage vs. Forward Current: Demonstrates the diode's exponential I-V characteristic.
• Relative Luminous Intensity vs. Ambient Temperature: Illustrates the decrease in light output as junction temperature rises, a critical factor for thermal management.
• Spectral Distribution: A plot showing the relative power emitted across wavelengths, peaking at the specified λP values for yellow and green.

5. Mechanical and Packaging Information

5.1 Outline Dimensions

The LED is housed in a right-angle black plastic holder. Key dimensional notes:

• All dimensions are in millimeters (with inch equivalents).
• General tolerance is ±0.25mm (±0.010\") unless otherwise specified.
• The holder (housing) material is black plastic.
• The product contains four LED dice (LED1~4) which are yellow/green bi-color.

5.2 Polarity Identification

For through-hole LEDs, polarity is typically indicated by lead length (the longer lead is the anode) or a flat spot on the lens or housing. The specific marking for this model should be verified on the physical component or detailed drawing.

6. Soldering and Assembly Guidelines

6.1 Storage Conditions

For optimal shelf life, store LEDs in an environment not exceeding 30°C and 70% relative humidity. If removed from the original moisture-barrier bag, use within three months. For longer storage outside original packaging, use a sealed container with desiccant or a nitrogen ambient.

6.2 Cleaning

If cleaning is necessary, use alcohol-based solvents like isopropyl alcohol. Avoid harsh chemicals.

6.3 Lead Forming

• Bend leads at a point at least 3mm from the base of the LED lens.
• Do not use the base of the lead frame as a fulcrum.
• Perform lead forming at room temperature and before soldering.
• During PCB insertion, use minimal clinch force to avoid mechanical stress.

6.4 Soldering Process

Critical Rule: Maintain a minimum clearance of 2mm from the base of the lens/holder to the solder point. Never immerse the lens/holder in solder.

• Hand Soldering (Iron):
  • Temperature: Maximum 350°C.
  • Time: Maximum 3 seconds per joint (one time only).
• Wave Soldering:
  • Pre-heat Temperature: Maximum 120°C.
  • Pre-heat Time: Maximum 100 seconds.
  • Solder Wave Temperature: Maximum 260°C.
  • Contact Time: Maximum 5 seconds.
  • Dipping Position: No lower than 2mm from the base of the epoxy bulb.
• Important: Excessive temperature or time can deform the lens or cause catastrophic failure. IR reflow is not suitable for this through-hole type product.

7. Application Suggestions and Design Considerations

7.1 Drive Circuit Design

LEDs are current-operated devices. To ensure uniform brightness when using multiple LEDs:

• Recommended Circuit (Circuit A): Use a individual current-limiting resistor in series with each LED. This compensates for variations in the forward voltage (VF) of individual LEDs, ensuring each receives the same current.
• Not Recommended (Circuit B): Connecting multiple LEDs directly in parallel with a single shared resistor is discouraged. Small differences in VF can cause significant current imbalance, leading to uneven brightness and potential over-current in some LEDs.

7.2 Electrostatic Discharge (ESD) Protection

LEDs are sensitive to static electricity. Prevention measures include:

• Use a grounded wrist strap or anti-static gloves when handling.
• Ensure all equipment, workstations, and storage racks are properly grounded.
• Use an ionizer to neutralize static charge that may build up on the plastic lens.

7.3 Thermal Management

While the power dissipation is low (52mW), operating at high ambient temperatures or at currents above the recommended 20mA will increase the junction temperature. This can lead to reduced luminous output, accelerated aging, and color shift. Ensure adequate ventilation if used in high-density arrays or enclosed spaces.

8. Packaging and Ordering Information

The datasheet includes a packing specification section (visually represented). Typical packaging for such components involves tape-and-reel for automated assembly or bulk packaging in anti-static bags. The specific part number for ordering is LTL-14FGSAJ4H79G.

9. Technical Comparison and Differentiation

The LTL-14FGSAJ4H79G offers specific advantages within its category:

• Bi-Color in a Single Package: Integrates Yellow and Green emission, potentially saving board space compared to using two separate single-color LEDs.
• Right-Angle Holder: The integrated black housing provides mechanical stability, improves contrast, and simplifies assembly into right-angle viewing applications without needing a separate socket.
• Stackable Design: The holder design allows for creating vertical or horizontal arrays of indicators, useful for multi-level status displays.
• Wide Viewing Angle (110°): Provides good visibility from a broad range of angles, suitable for panel indicators.

10. Frequently Asked Questions (Based on Technical Parameters)

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

Peak Wavelength (λP) is the literal highest point on the spectral output curve. Dominant Wavelength (λd) is a calculated value from the CIE color chart that best represents the perceived color hue by the human eye. λd is often more relevant for color specification.

10.2 Can I drive this LED at 20mA continuously?

Yes, 20mA is the specified maximum continuous DC forward current at TA=25°C. For reliable long-term operation, especially at higher ambient temperatures, driving at a lower current (e.g., 10-15mA) is often recommended to reduce thermal stress and increase lifetime.

10.3 How do I interpret the bin codes?

The bin codes (A/B for intensity, 1/2 for wavelength) allow you to select LEDs with tightly grouped characteristics. For a uniform appearance in an array, specify the same bin code for all units in your order. The codes are marked on the packaging bag.

10.4 Why is a series resistor necessary?

An LED's forward voltage has a negative temperature coefficient and varies from unit to unit. A voltage source would cause large current variations. A series resistor (with a voltage source higher than VF) provides simple, passive current limiting, making the current through the LED primarily dependent on the resistor value and the supply voltage, stabilizing the light output.

11. Practical Design and Usage Case

Scenario: Designing a multi-status indicator panel for a network router.

The LTL-14FGSAJ4H79G is an ideal choice. Four units could be used to indicate Power (steady green), System Activity (blinking green), Network Link (steady yellow), and Data Transfer (blinking yellow). The right-angle mount allows them to be placed perpendicular to the main PCB, facing the front panel cutout. The black housing ensures high contrast against the panel. Each LED would be driven by a microcontroller GPIO pin through a 150-200Ω series resistor (calculated for a 3.3V or 5V supply and ~10-15mA current). The wide viewing angle ensures status is visible from various positions in a room.

12. Operating Principle Introduction

Light Emitting Diodes (LEDs) are semiconductor devices that emit light through electroluminescence. When a forward voltage is applied across the p-n junction, electrons and holes recombine in the active region, releasing energy in the form of photons. The specific color of the light is determined by the bandgap energy of the semiconductor materials used. In a bi-color LED like this one, two different semiconductor chip materials (or one chip with specific doping/phosphor) are integrated within the same package, allowing emission at two distinct wavelength bands (yellow and green) depending on the polarity of the applied current.

13. Technology Trends

The through-hole LED lamp remains a reliable and cost-effective solution for many indication applications, especially where manual assembly or high-reliability solder joints are required. Industry trends show a gradual shift towards surface-mount device (SMD) LEDs for most new designs due to their smaller size and suitability for automated pick-and-place assembly. However, through-hole LEDs maintain advantages in mechanical robustness, ease of hand prototyping, and superior thermal connection to the PCB via their leads. The integration of features like built-in resistors, IC drivers, and multiple colors in a single package continues to evolve, enhancing functionality while simplifying circuit design.