LTL-2500G Green LED Light Bar Datasheet - Rectangular Source - High Brightness - English Technical Document

1. Product Overview

The LTL-2500G is a light bar rectangular light source designed for a variety of applications where a large, bright source of illumination is required. This device utilizes green LED chips, which are fabricated from GaP epi on GaP substrate or AlInGaP on a non-transparent GaAs substrate, and features a white bar housing. It is categorized as a universal rectangular bar LED display component.

1.1 Core Advantages and Target Market

The primary advantages of this device include its rectangular light bar form factor, which provides a large, bright, and uniform light-emitting area. It is designed for low power requirement while delivering high brightness and high contrast. The solid-state construction ensures high reliability. The device is categorized for luminous intensity, allowing for consistent performance selection. Furthermore, it is offered in a lead-free package compliant with RoHS directives. Its target applications are in ordinary electronic equipment such as office equipment, communication devices, and household applications where a prominent visual indicator or backlighting element is needed.

2. Technical Parameters: In-Depth Objective Interpretation

2.1 Electrical and Optical Characteristics

The performance of the LTL-2500G is defined under standard test conditions at an ambient temperature (Ta) of 25°C. Key parameters include:

• Average Luminous Intensity (Iv): Ranges from a minimum of 1400 µcd to a typical value of 4200 µcd when driven at a forward current (IF) of 10mA. Luminous intensity is measured using a light sensor and filter combination that approximates the CIE (Commission Internationale de L'Éclairage) photopic eye-response curve.
• Peak Emission Wavelength (λp): Typically 565 nm at IF=20mA.
• Spectral Line Half-Width (Δλ): Typically 30 nm at IF=20mA.
• Dominant Wavelength (λd): Typically 569 nm at IF=20mA.
• Forward Voltage per Segment (VF): Ranges from 2.1V (min) to 2.6V (max) at IF=20mA.
• Reverse Current per Segment (IR): Maximum of 100 µA at a reverse voltage (VR) of 5V. It is critical to note that this reverse voltage condition is specified only for leakage current testing and the device must not be continuously operated under reverse bias.
• Luminous Intensity Matching Ratio (Iv-m): The ratio between segments is typically 2:1 or better at IF=10mA.

2.2 Absolute Maximum Ratings and Thermal Characteristics

Operating the device beyond these limits may cause permanent damage.

• Power Dissipation per Segment: 70 mW maximum.
• Peak Forward Current per Segment: 60 mA maximum under pulsed conditions (1/10 duty cycle, 0.1ms pulse width).
• Continuous Forward Current per Segment: 25 mA maximum at 25°C. This rating derates linearly at a rate of 0.33 mA/°C as ambient temperature increases above 25°C.
• Operating Temperature Range: -35°C to +85°C.
• Storage Temperature Range: -35°C to +85°C.
• Solder Temperature: Withstands a maximum of 260°C for up to 3 seconds, measured 1.6mm below the seating plane.

3. Binning System Explanation

The datasheet indicates that the LTL-2500G is "Categorized for Luminous Intensity." This implies a binning system is applied to the devices based on their measured light output at a standard test current (IF=10mA). The typical luminous intensity is 4200 µcd, with a minimum specified value of 1400 µcd. For applications requiring multiple units, it is strongly recommended to select devices from the same luminous intensity bin to ensure uniform brightness and avoid hue unevenness across the assembly. The datasheet does not specify detailed bin codes for wavelength or forward voltage, so designers should account for the full specified ranges in their circuit design.

4. Performance Curve Analysis

The datasheet references "Typical Electrical/Optical Characteristics Curves." While the specific graphs are not detailed in the provided text, such curves typically included in full datasheets would illustrate the relationship between forward current (IF) and luminous intensity (Iv), forward voltage (VF) versus forward current, and the effect of ambient temperature on luminous intensity. These curves are essential for designers to understand the non-linear behavior of LEDs, optimize drive current for desired brightness, and implement proper thermal management to maintain performance and longevity.

5. Mechanical and Package Information

5.1 Dimensions and Polarity Identification

The device features a rectangular bar package. All dimensions are provided in millimeters, with standard tolerances of ±0.25 mm (0.01") unless otherwise noted. A detailed dimensioned drawing would be present in the full datasheet. The internal circuit consists of segments, each with its own anode and cathode. The pin connection is clearly defined:

• Pin 1: Cathode A
• Pin 2: Anode A
• Pin 3: Cathode B
• Pin 4: Anode B

This configuration allows for independent control of different segments within the light bar. The polarity must be strictly observed during assembly to prevent reverse bias damage.

6. Soldering, Assembly, and Storage Guidelines

6.1 Soldering and Application Cautions

Several critical cautions are provided for reliable application:

• Drive Circuit Design: Constant current driving is recommended for consistent performance. The circuit must be designed to accommodate the full range of forward voltage (VF: 2.1V to 2.6V) to ensure the intended drive current is always delivered. The circuit should also protect the LEDs from reverse voltages and transient voltage spikes during power-up or shutdown.
• Thermal Management: The safe operating current must be derated based on the maximum ambient temperature of the application environment. Exceeding recommended current or temperature leads to severe light degradation or premature failure.
• Avoid Reverse Bias: Continuous reverse bias should be avoided as it can cause metal migration, increasing leakage current or causing short circuits.
• Environmental Considerations: Avoid rapid ambient temperature changes, especially in high humidity, to prevent condensation on the LED. Do not apply abnormal mechanical force to the display body.
• Assembly with Films: If a printing/pattern film is applied with pressure-sensitive adhesive, avoid letting this side come into direct contact with a front panel/cover, as external force may shift the film.

6.2 Storage Conditions

Proper storage is crucial to prevent pin oxidation.

• LED Display (Standard): Store in original packaging at 5°C to 30°C and below 60% RH. Long-term storage outside these conditions may oxidize pins, requiring re-plating before use. Consumption as soon as possible is advised.
• LED SMD Display: In original sealed bag: 5°C to 30°C, below 60% RH. Once opened and not in the original sealed bag: store at 5°C to 30°C, below 60% RH, and use within 168 hours (MSL Level 3). If unpacked for more than 168 hours, baking at 60°C for 24 hours before soldering is recommended.
• General: Displays should be used within 12 months from the shipping date and must not be exposed to high moisture or corrosive gas environments.

7. Application Recommendations

7.1 Typical Application Scenarios and Design Considerations

The LTL-2500G is suited for applications requiring a prominent, rectangular light source. This includes status indicators, backlighting for legends or panels, and general illumination in consumer electronics, industrial controls, and communication equipment. Key design considerations include:

• Current Setting: Choose a drive current (e.g., 10mA or 20mA as per test conditions) that provides sufficient brightness while staying within the absolute maximum ratings and considering thermal derating.
• Voltage Compliance: The driver power supply must provide enough voltage to overcome the maximum VF of the LED segment at the chosen current, plus any voltage drops across series resistors or current-regulating components.
• Thermal Design: Ensure the PCB and overall enclosure design allow for adequate heat dissipation, especially if multiple LEDs are used or if the ambient temperature is high.
• Optical Integration: The white bar housing and rectangular shape facilitate integration into slots or behind diffusers to create uniform illuminated areas.

8. Technical Comparison and Differentiation

While a direct comparison with other part numbers is not provided in this single datasheet, the LTL-2500G's key differentiators within its category are its specific rectangular bar form factor, the use of green GaP/AlInGaP chip technology for its particular wavelength output, its categorization for luminous intensity ensuring brightness consistency, and its compliance with lead-free/RoHS standards. Its relatively high typical luminous intensity (4200 µcd at 10mA) for a bar-type device is a notable performance characteristic.

9. Frequently Asked Questions (Based on Technical Parameters)

Q: Can I drive this LED with a constant voltage source?
A: It is not recommended. LEDs are current-driven devices. A constant voltage source with only a series resistor is common but less stable. A dedicated constant current driver or regulator is preferred for consistent brightness and longevity, especially as VF varies with temperature and between units.

Q: What happens if I briefly apply a reverse voltage?
A: The device can withstand a reverse voltage of 5V for the purpose of testing leakage current (IR). However, continuous operation or application of higher reverse voltages is prohibited as it can cause irreversible damage.

Q: How do I select the current-limiting resistor?
A: If using a simple voltage source (Vcc) and series resistor (R), use Ohm's law: R = (Vcc - VF) / IF. Use the maximum VF (2.6V) from the datasheet to ensure enough current flows at worst-case conditions. Also, calculate the resistor power rating: P = (IF)^2 * R.

Q: Why is matching LEDs from the same bin important?
A: LEDs have natural variations in luminous intensity and forward voltage. Using devices from the same bin minimizes brightness and color differences between adjacent units in a multi-LED assembly, ensuring a uniform appearance.

10. Practical Use Case Example

Consider designing a multi-level status indicator for a network router. Two LTL-2500G bars could be used: one to indicate "Power On" and another to indicate "Network Activity." Each bar would be driven by a separate GPIO pin from a microcontroller via a simple transistor switch circuit. A constant current of 15mA could be chosen as a balance between brightness and power consumption. The rectangular shape would fit neatly into a labeled slot on the router's front panel. The design would include current-limiting resistors calculated using the max VF, and the PCB layout would provide some copper pour for heat dissipation. To ensure visual consistency, the two LED bars would be specified to be from the same luminous intensity bin.

11. Operating Principle Introduction

The LTL-2500G is a solid-state light source based on semiconductor electroluminescence. The active region contains a p-n junction fabricated from Gallium Phosphide (GaP) or Aluminum Indium Gallium Phosphide (AlInGaP) materials. When a forward voltage is applied, electrons and holes are injected into the junction region where they recombine. In these direct bandgap materials, this recombination releases energy in the form of photons (light). The specific composition of the semiconductor alloy determines the bandgap energy, which directly correlates to the wavelength (color) of the emitted light—in this case, green (~565-569 nm). The white plastic package acts as a diffuser and protector for the semiconductor chip.

12. Technology Trends and Context

Discrete LED indicators like the LTL-2500G represent a mature and reliable technology. Current trends in the broader LED industry include a continued push for higher efficiency (more lumens per watt), improved color rendering, and the development of micro-LEDs and mini-LEDs for advanced display applications. For indicator and simple lighting functions, the trend is towards greater integration (e.g., LED drivers with built-in diagnostics), lower operating voltages, and enhanced reliability under harsh environmental conditions. The move to lead-free and RoHS-compliant packaging, as seen with this device, is now a standard requirement driven by global environmental regulations. The underlying material technology, such as AlInGaP used here for green/red/orange LEDs, continues to be optimized for performance and cost.