LTL-2620HR LED Display Datasheet - Rectangular Light Bar - Red-Orange Color - 2.6V Forward Voltage - 75mW Power Dissipation

1. Product Overview

The LTL-2620HR is a rectangular light bar designed as a bright, uniform light source for applications requiring significant illumination. This solid-state device utilizes red-orange LED chips, which are manufactured using GaAsP on a transparent GaP substrate or AlInGaP on a non-transparent GaAs substrate, and features a white bar housing. It is categorized for luminous intensity and is offered in a lead-free package compliant with RoHS directives.

1.1 Key Features

• Rectangular light bar form factor.
• Large, bright, and uniform light emitting area.
• Low power requirement for energy efficiency.
• High brightness and high contrast output.
• Solid-state reliability for long operational life.
• Luminous intensity is categorized (binned).
• Lead-free package compliant with RoHS.

1.2 Device Identification

The part number LTL-2620HR corresponds to a red-orange universal rectangular bar LED display.

2. Technical Specifications Deep Dive

2.1 Absolute Maximum Ratings

All ratings are specified at an ambient temperature (Ta) of 25°C. Exceeding these values may cause permanent damage to the device.

• Power Dissipation per Segment: 75 mW maximum.
• Peak Forward Current per Segment: 60 mA (at 1/10 duty cycle, 0.1ms pulse width).
• Continuous Forward Current per Segment: 25 mA. This rating derates linearly from 25°C at a rate of 0.33 mA/°C.
• Operating Temperature Range: -35°C to +85°C.
• Storage Temperature Range: -35°C to +85°C.
• Solder Temperature: Maximum 260°C for a maximum of 3 seconds, measured 1.6mm below the seating plane.

2.2 Electrical and Optical Characteristics

These typical and minimum/maximum values are measured at Ta=25°C under the specified test conditions.

• Average Luminous Intensity (Iv): Minimum 1400 µcd, Typical 4200 µcd, measured at a forward current (IF) of 10mA. Intensity is measured using a sensor and filter approximating the CIE eye-response curve.
• Peak Emission Wavelength (λp): 630 nm (typical) at IF=20mA.
• Spectral Line Half-Width (Δλ): 40 nm (typical) at IF=20mA.
• Dominant Wavelength (λd): 621 nm (typical) at IF=20mA.
• Forward Voltage per Segment (VF): Typical 2.6V, Maximum 2.6V at IF=20mA. Minimum is 2.0V.
• Reverse Current per Segment (IR): Maximum 100 µA at a reverse voltage (VR) of 5V. Note: The device is not intended for continuous operation under reverse bias.
• Luminous Intensity Matching Ratio (Iv-m): Maximum 2:1 ratio between segments at IF=10mA.

3. Binning and Categorization System

The LTL-2620HR LEDs are categorized (binned) primarily for luminous intensity. This ensures consistency in brightness output between different units. The typical value is 4200 µcd, with a minimum guaranteed value of 1400 µcd at 10mA. For applications requiring multiple displays assembled together, it is strongly recommended to use LEDs from the same intensity bin to avoid noticeable hue or brightness unevenness across the assembly.

4. Performance Curve Analysis

The datasheet references typical electrical and optical characteristic curves, which are essential for design engineers. These curves, typically plotted against ambient temperature or forward current, would illustrate relationships such as:

• Forward Current (IF) vs. Forward Voltage (VF): Shows the voltage drop across the LED at different drive currents, crucial for driver circuit design.
• Luminous Intensity (Iv) vs. Forward Current (IF): Demonstrates how light output scales with current, helping to optimize the drive current for desired brightness and efficiency.
• Luminous Intensity (Iv) vs. Ambient Temperature (Ta): Illustrates the derating of light output as junction temperature increases, which is vital for thermal management in the final application.

Designers should consult these curves to understand the device's behavior under non-standard conditions (different currents or temperatures) and to ensure reliable operation within safe operating areas.

5. Mechanical and Package Information

5.1 Package Dimensions

The device features a rectangular bar package. All dimensions are provided in millimeters (mm). Unless otherwise specified, dimensional tolerances are ±0.25 mm (equivalent to ±0.01 inches). A detailed mechanical drawing is included in the datasheet for precise integration into PCB layouts and enclosures.

5.2 Pin Connection and Internal Circuit

The LTL-2620HR is a multi-segment display with 16 pins. The pinout is as follows:

1. Cathode A
2. Anode A
3. Anode B
4. Cathode B
5. Cathode C
6. Anode C
7. Anode D
8. Cathode D
9. Cathode E
10. Anode E
11. Anode F
12. Cathode F
13. Cathode G
14. Anode G
15. Anode H
16. Cathode H

An internal circuit diagram is provided, showing the interconnection of the individual LED segments (likely 8 segments, A through H) with their respective anodes and cathodes. This diagram is critical for designing the correct multiplexing or direct drive circuitry.

6. Soldering, Assembly, and Storage Guidelines

6.1 Soldering Process

The absolute maximum rating for soldering is 260°C for a maximum duration of 3 seconds, measured 1.6mm below the seating plane. This guideline is intended for wave or reflow soldering processes. Exceeding these parameters can damage the internal die, wire bonds, or package material.

6.2 Storage Conditions

Proper storage is essential to prevent oxidation of the pins or solder pads.

• For LED Displays (in original packaging): Recommended storage temperature is between 5°C and 30°C with relative humidity below 60% RH.
• For SMD LED Displays (in original sealed bag): Same as above: 5°C to 30°C, below 60% RH.
• For SMD LED Displays (opened bag): Storage conditions are 5°C to 30°C and below 60% RH, but the device must be used within 168 hours (7 days) of opening the moisture-sensitive bag (MSL Level 3). If unpacked for more than 168 hours, a baking process at 60°C for 24 hours is recommended before soldering.

It is advised to consume inventory promptly and avoid long-term storage of large quantities to maintain solderability. The general recommendation is to use the displays within 12 months from the shipping date.

7. Application Design Recommendations

7.1 General Application Notes

This display is intended for ordinary electronic equipment in office, communication, and household applications. For applications requiring exceptional reliability where failure could jeopardize life or health (e.g., aviation, medical systems), specific consultation is required prior to use.

7.2 Circuit Design Considerations

• Drive Method: Constant current driving is strongly recommended to ensure consistent luminous intensity and color output, as LED brightness is primarily a function of current, not voltage.
• Current Limiting: The driver circuit must be designed to supply the intended current across the entire forward voltage (VF) range of the LEDs (2.0V to 2.6V per segment).
• Current Derating: The safe operating current must be selected after considering the maximum ambient temperature of the application environment, as the continuous forward current rating derates with temperature.
• Protection Circuits: The driving circuit should incorporate protection against reverse voltages and transient voltage spikes that may occur during power-up or shutdown to prevent damage.
• Avoid Reverse Bias: Continuous reverse bias operation should be avoided as it can cause metal migration, leading to increased leakage current or short-circuit failure.

7.3 Thermal and Mechanical Considerations

• Thermal Management: Operating the device at currents or ambient temperatures higher than recommended can cause severe light output degradation or premature failure. Adequate heat sinking or airflow should be considered in high-power or high-temperature applications.
• Condensation: Avoid rapid changes in ambient temperature, especially in high-humidity environments, as this can cause condensation to form on the LED surface, potentially leading to performance issues or corrosion.
• Mechanical Stress: Do not apply abnormal force to the display body during assembly. Use appropriate tools and methods.
• Film Application: If a printing or pattern film is applied using pressure-sensitive adhesive, it is not recommended to let this side of the display come into direct, tight contact with a front panel or cover, as external force may cause the film to shift from its original position.

8. Technical Comparison and Positioning

The LTL-2620HR differentiates itself through its specific form factor as a rectangular light bar. Compared to discrete round LEDs or smaller SMD packages, it provides a large, continuous, and uniform emitting area, which is ideal for status indicators, backlighting bars, or illumination strips where a diffuse line of light is desired rather than multiple point sources. Its use of red-orange AlInGaP or GaAsP technology offers high brightness and efficiency in that specific color range. The categorization for luminous intensity provides an added level of quality control for brightness consistency.

9. Frequently Asked Questions (Based on Technical Parameters)

Q: What is the difference between peak wavelength (630nm) and dominant wavelength (621nm)?
A: Peak wavelength is the single wavelength where the spectral power distribution is highest. Dominant wavelength is the perceived color of the light, calculated from the spectrum and the CIE color matching functions. For a monochromatic source like this LED, they are close, but dominant wavelength is more relevant for color specification.

Q: Why is constant current drive recommended over constant voltage?
A: An LED's forward voltage (VF) has a tolerance and varies with temperature. A constant voltage source with a simple series resistor can lead to significant variation in current, and thus brightness, between units or under different thermal conditions. A constant current source ensures the desired current (and brightness) is delivered consistently.

Q: Can I drive this LED with a 5V supply and a resistor?
A: Yes, but careful calculation is needed. For example, targeting IF=20mA with a typical VF of 2.6V from a 5V supply: R = (5V - 2.6V) / 0.02A = 120 Ohms. The resistor power rating should be P = I^2 * R = (0.02^2)*120 = 0.048W, so a 1/8W or 1/4W resistor is sufficient. Remember that VF can be as low as 2.0V, which would increase current to ~25mA, still within the 25mA continuous rating at 25°C.

Q: What does the luminous intensity matching ratio of 2:1 mean?
A: It means that the luminous intensity of any one segment compared to any other segment in the same device will not differ by more than a factor of two. For instance, the dimmest segment will be at least half as bright as the brightest segment when driven under the same conditions (IF=10mA).

10. Design and Use Case Examples

Case 1: Industrial Control Panel Status Bar
Multiple LTL-2620HR units can be aligned to form a long, continuous status bar on a machine control panel. Each bar can be assigned to a different machine state (e.g., idle, running, fault). The uniform rectangular emission provides clear, long-distance visibility. Using constant current drivers for each bar ensures consistent brightness. The high contrast and red-orange color are excellent for alert indicators.

Case 2: Consumer Audio Equipment VU Meter
Several bars can be stacked vertically to create an analog-style VU meter for audio level display. A microcontroller with a multi-channel PWM or DAC can drive the segments via transistor arrays to vary brightness proportional to the audio signal. The large, bright area makes the levels easily readable.

Case 3: Backlighting for Membrane Switch Panels
The rectangular bar shape is ideal for backlighting specific zones or legends on a membrane switch panel. It provides even illumination across a labeled area, improving usability in low-light conditions.

11. Operating Principle

The LTL-2620HR is based on light-emitting diode (LED) technology. When a forward voltage exceeding the diode's junction potential (around 2.0-2.6V) is applied, electrons and holes recombine in the semiconductor's active region (made of GaAsP or AlInGaP). This recombination process releases energy in the form of photons (light). The specific semiconductor material composition determines the wavelength (color) of the emitted light, in this case, red-orange. The white bar housing acts as a diffuser and lens, shaping the light output into a uniform rectangular beam.

12. Technology Trends

The LED industry continues to advance in several key areas relevant to components like the LTL-2620HR. Efficiency (lumens per watt) for all colors, including red and amber, is steadily improving, allowing for higher brightness at lower power or reduced thermal load. Packaging technology is evolving to enable higher power density and better thermal management from smaller footprints. There is also a strong trend towards tighter binning and better color consistency, driven by applications in displays and architectural lighting. Furthermore, the integration of control electronics (e.g., constant current drivers, PWM controllers) directly into LED packages is becoming more common, simplifying system design for the end user.