LTL42FGRBBH281 LED Lamp Datasheet - Multi-Color (Green/Red/Blue) - 20mA - Through-Hole Package - English Technical Document

1. Product Overview

The LTL42FGRBBH281 is a multi-color through-hole LED lamp designed for circuit board indication. It features a black plastic right-angle holder (housing) that mates with the LED components, enhancing contrast ratio. The product is designed for ease of assembly on printed circuit boards (PCBs) and is available in configurations that allow for stacking and simple installation.

1.1 Core Advantages

• Designed for ease of circuit board assembly.
• Black housing enhances contrast ratio for improved visibility.
• Low power consumption and high efficiency.
• Lead-free product compliant with RoHS directives.
• Utilizes specific semiconductor materials for color emission: InGaN for blue (470nm), AlInGaP for red (631nm), and AlInGaP for green (569nm) chips.

1.2 Target Applications

• Computer systems and peripherals
• Communication equipment
• Consumer electronics
• Industrial controls and instrumentation

2. Technical Parameters: In-Depth Objective Interpretation

2.1 Absolute Maximum Ratings (TA=25°C)

The following table details the limits beyond which permanent damage to the device may occur. Operation outside these ranges is not recommended.

2.2 Electrical and Optical Characteristics (TA=25°C)

These parameters define the typical performance of the device under specified test conditions.

Notes: 1. Luminous intensity measurement approximates CIE eye-response. 2. Viewing angle is the off-axis angle where intensity is half the axial value. 3. Dominant wavelength defines color per CIE diagram. 4. Iv includes ±15% test tolerance. 5. Reverse current is source-controlled. 6. Reverse voltage is for test only; device is not for reverse operation.

3. Binning System Explanation

The datasheet indicates typical values for key parameters. For production, devices are typically binned (grouped) based on specific characteristics to ensure consistency within an application. While exact bin codes are not provided in this document, the parameters subject to binning likely include:

• Wavelength/Dominant Wavelength (λd): As shown in the characteristics table, each color has a min/typ/max range. Products are sorted into bins based on measured dominant wavelength to provide consistent color points.
• Luminous Intensity (Iv): The wide range (Min to Max) for each color suggests that devices are binned according to their light output to match brightness requirements in different applications.
• Forward Voltage (VF): The specified range indicates that LEDs may be grouped by forward voltage drop, which is important for designing current-limiting circuits and ensuring uniform brightness in parallel configurations.

Designers should consult specific binning information from the manufacturer for critical color-matching or current-matching applications.

4. Performance Curve Analysis

The datasheet references typical characteristic curves for each LED color (Green/Yellow Green, Red, Blue). These curves graphically represent the relationship between key parameters and are essential for circuit design.

4.1 Typical IV (Current-Voltage) Curves

These curves plot forward current (IF) against forward voltage (VF) for each LED color at 25°C. They show the non-linear relationship typical of diodes. The knee voltage is approximately 2.0V for Green/Red and 3.2V for Blue LEDs. Designers use these curves to determine the necessary supply voltage and series resistor value to achieve the desired operating current (typically 10mA or 20mA as per specs).

4.2 Luminous Intensity vs. Forward Current

These curves illustrate how light output (Iv) increases with forward current (IF). The relationship is generally linear within the recommended operating range (up to 20mA DC). Operating above the absolute maximum current can lead to super-linear increase in junction temperature and rapid degradation of light output and lifespan.

4.3 Spectral Distribution

While not explicitly graphed, the parameters for Peak Emission Wavelength (λP), Dominant Wavelength (λd), and Spectral Line Half-Width (Δλ) define the spectral characteristics. Δλ indicates the color purity; a smaller value denotes a more monochromatic light. Blue LEDs have the widest Δλ (35nm), while Green is the narrowest (15nm).

5. Mechanical and Packaging Information

5.1 Outline Dimensions

The device uses a through-hole package with a black plastic right-angle holder. Key mechanical notes from the datasheet:

• All dimensions are in millimeters (inches).
• Tolerance is ±0.25mm (.010\") unless otherwise noted.
• The holder (housing) material is black plastic.
• LED1 is green (yellow green) color with a green diffused lens.
• LED2 is red color with a white diffused lens.
• LED3 and LED4 are blue color with white diffused lenses.

The exact dimensional drawing is referenced in the datasheet, providing critical measurements for PCB footprint design, including lead spacing, body size, and mounting hole placement.

5.2 Polarity Identification

For through-hole LEDs, polarity is typically indicated by lead length (longer lead is anode) or a flat spot on the lens or housing. The datasheet's outline drawing should clearly mark the cathode (usually the shorter lead or the lead nearest a flat edge). Correct polarity is essential for device operation.

6. Soldering and Assembly Guidelines

6.1 Storage Conditions

The storage ambient should not exceed 30°C or 70% relative humidity. LEDs removed from their original packaging should be used within three months. For extended storage outside original packaging, store in a sealed container with desiccant or in a nitrogen ambient desiccator.

6.2 Cleaning

Use alcohol-based cleaning solvents like isopropyl alcohol if cleaning is necessary. Avoid harsh chemicals that may damage the plastic lens or housing.

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 before soldering at normal temperature. During PCB assembly, use the minimum clinch force possible to avoid excessive mechanical stress on the component.

6.4 Soldering Parameters

Maintain a minimum 2mm clearance from the base of the lens/holder to the soldering point. Avoid dipping the lens/holder into solder.

Important: Excessive temperature or time can deform the lens or cause failure. IR reflow is NOT suitable for this through-hole product. The maximum wave soldering temperature does not define the holder's Heat Deflection Temperature (HDT) or melting point.

7. Packaging and Ordering Information

7.1 Packing Specification

The datasheet includes a dedicated packing specification section (referenced as page 7/10). This details how the components are supplied, typically in anti-static tubes, reels, or trays. It includes information on quantity per package, reel dimensions, and orientation for automated handling.

7.2 Model Numbering Rule

The part number LTL42FGRBBH281 likely encodes key attributes. A common convention includes: Series (LTL), Size/package code (42), Color (FGRB for a combination of colors), and specific variant/optics code (BH281). The exact decoding should be confirmed with the manufacturer's product guide.

8. Application Recommendations

8.1 Typical Application Circuits

LEDs are current-operated devices. To ensure uniform brightness when connecting multiple LEDs in parallel, a current-limiting resistor must be used in series with EACH LED (Circuit Model A). Avoid connecting LEDs directly in parallel without individual resistors (Circuit Model B), as slight variations in forward voltage (VF) will cause significant differences in current share and, therefore, brightness.

Circuit A (Recommended): [Vcc] -- [Resistor] -- [LED] -- [GND]. A separate resistor-LED branch for each LED in parallel.

Circuit B (Not Recommended for uniformity): [Vcc] -- [Resistor] -- [LED1 // LED2 // LED3] -- [GND].

8.2 Electrostatic Discharge (ESD) Protection

LEDs are sensitive to static electricity. Prevention measures include:

• Use a conductive 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 during handling.

8.3 Thermal Considerations

While power dissipation is low (52-76 mW), maintaining the junction temperature within the operating range (-30°C to +85°C) is crucial for longevity and stable light output. Ensure adequate spacing on the PCB and consider ambient temperature in the enclosure. Operating at or near the maximum DC current will generate more heat.

9. Technical Comparison and Differentiation

The LTL42FGRBBH281 offers specific advantages in its category:

• Multi-Color in Single Package: Integrates multiple LED chips (Green/Yellow Green, Red, Blue) with distinct diffused lenses, suitable for multi-status indication.
• Right-Angle Holder: The black right-angle housing is designed for easy PCB mounting and provides a defined viewing direction, enhancing contrast.
• Stackable Design: The housing design allows for stacking, enabling the creation of vertical or horizontal arrays for bar-graph or multi-segment displays.
• Through-Hole Reliability: Offers robust mechanical connection to the PCB, suitable for applications subject to vibration or requiring manual assembly/rework.

10. Frequently Asked Questions (Based on Technical Parameters)

Q1: Can I drive the blue LED at 20mA like the red one?
A: The Absolute Maximum Ratings table specifies a DC Forward Current of 20mA for all colors. However, the Electrical Characteristics table lists test conditions of IF=10mA for Blue and Green, and IF=20mA for Red. For reliable long-term operation, it is advisable to operate the Blue and Green LEDs at or near 10mA, as this is the condition under which their optical specs are guaranteed. Exceeding this may reduce lifespan or shift color.

Q2: Why is the reverse current for Blue LED (10μA) much lower than for Green/Red (100μA)?
A: This difference is inherent to the semiconductor materials used (InGaN for Blue vs. AlInGaP for Red/Green). The diode junction characteristics, including reverse leakage current, vary with material bandgap and fabrication process.

Q3: What is the difference between Peak Wavelength (λP) and Dominant Wavelength (λd)?
A: Peak Wavelength is the single wavelength at which the spectral power distribution is maximum. Dominant Wavelength is derived from the CIE chromaticity diagram and represents the perceived color of the light; it is the single wavelength that would match the color sensation. λd is more relevant for color specification in human-centric applications.

Q4: Is a heat sink required?
A: Given the low power dissipation (max 76mW for Blue), a dedicated heat sink is generally not required for standard operation within the specified current limits. Proper PCB layout with some copper area around the leads will suffice for heat dissipation in most environments.

11. Practical Application Case Study

Scenario: Designing a Multi-Function Status Indicator for an Industrial Controller.
An industrial programmable logic controller (PLC) requires a single indicator to show multiple states: Standby (Green), Running (Flashing Green), Fault (Red), and Communication Active (Blue).

Design Implementation:
1. The LTL42FGRBBH281 is selected for its integrated multi-color capability in one through-hole package, saving board space compared to using three separate LEDs.
2. A microcontroller GPIO pin is connected to each LED cathode (via a current-limiting resistor), with the anodes connected to the supply rail. This allows independent control of each color.
3. Resistor values are calculated using R = (Vcc - VF) / IF. For a 5V supply: R_Green/Red ≈ (5V - 2.5V) / 0.01A = 250Ω; R_Blue ≈ (5V - 3.8V) / 0.01A = 120Ω. Standard resistor values (270Ω and 120Ω) are chosen.
4. The right-angle housing allows the indicator to be mounted on the edge of the PCB, facing outward through a panel cutout. The black housing ensures high contrast against the panel.
5. Software controls the flashing pattern for the \"Running\" state by toggling the Green LED pin.

This design leverages the product's key features: multi-color integration, ease of assembly, and high-contrast housing.

12. Principle of Operation

Light Emitting Diodes (LEDs) are semiconductor p-n junction devices that emit light through electroluminescence. When a forward voltage exceeding the junction's built-in potential is applied, electrons from the n-region recombine with holes from the p-region in the active region. This recombination releases energy in the form of photons (light). The wavelength (color) of the emitted light is determined by the bandgap energy of the semiconductor material used in the active region. The LTL42FGRBBH281 utilizes AlInGaP for red and green emission and InGaN for blue emission. The plastic lens serves to focus the light, protect the semiconductor die, and, when diffused, to widen the viewing angle and soften the light appearance.

13. Technology Trends

The through-hole LED lamp represents a mature and reliable packaging technology. Current industry trends show a strong shift towards surface-mount device (SMD) packages (e.g., 0603, 0805, 1206, and larger power packages) for most new designs due to their smaller footprint, suitability for automated pick-and-place assembly, and lower profile. However, through-hole components like the LTL42FGRBBH281 remain relevant in specific niches: applications requiring extreme mechanical robustness, high-voltage isolation, manual assembly/repair, educational kits, or where the right-angle viewing and stacking features are specifically advantageous. The technology continues to benefit from improvements in semiconductor materials (e.g., higher efficiency, better color rendering) and plastic molding techniques, even within the through-hole form factor.