LTL2V3WFK LED Lamp Datasheet - T-1 3/4 Package - 2.0V Forward Voltage - Yellow Orange Color - English Technical Document

1. Product Overview

This document provides the complete technical specifications for a high-efficiency, through-hole mounted LED lamp. The device is designed for general-purpose indicator and illumination applications where reliable performance and clear visibility are required. It utilizes AlInGaP (Aluminum Indium Gallium Phosphide) semiconductor technology to produce a yellow-orange light output. The product is characterized by its popular T-1 3/4 package diameter, making it compatible with a wide range of standard PCB layouts and panel cutouts.

The core advantages of this component include its high luminous intensity output, which ensures bright visibility even in well-lit environments, and its low power consumption, contributing to energy-efficient system design. It is designed for versatile mounting on printed circuit boards or directly onto panels. The device is also IC-compatible, featuring low current requirements that allow for direct drive from many logic-level outputs with a simple series resistor.

The target market for this LED encompasses a broad spectrum of electronic equipment, including office automation devices, communication equipment, consumer appliances, and various household applications. Its design prioritizes a balance of performance, reliability, and ease of integration.

2. In-Depth Technical Parameter Analysis

2.1 Absolute Maximum Ratings

The absolute maximum ratings define the stress limits beyond which permanent damage to the device may occur. These ratings are specified at an ambient temperature (T_A) of 25°C. The maximum continuous power dissipation is 120 mW. The DC forward current should not exceed 50 mA under normal operating conditions. For pulsed operation, a peak forward current of 90 mA is permissible under specific conditions: a 1/10 duty cycle and a pulse width of 0.1 ms.

The device can withstand a reverse voltage of up to 5 V. The operating temperature range is specified from -40°C to +80°C, while the storage temperature range is wider, from -55°C to +100°C. For soldering, the leads can be subjected to a temperature of 260°C for a maximum of 5 seconds, provided the soldering point is at least 2 mm (0.08 inches) away from the body of the LED.

A derating factor of 0.75 mA/°C applies to the DC forward current from 40°C upwards. This means that as the ambient temperature increases beyond 40°C, the maximum allowable continuous current must be reduced linearly to prevent overheating and ensure long-term reliability.

2.2 Electrical and Optical Characteristics

The electrical and optical characteristics are the key performance parameters under typical operating conditions, also specified at T_A=25°C.

Optical Parameters:

• Luminous Intensity (I_V): This is the measure of the perceived power of light. The value ranges from a minimum of 3200 mcd (millicandela) to a typical 9300 mcd when driven at a forward current (I_F) of 20 mA. The measurement is performed using a sensor and filter combination that approximates the standard CIE photopic eye-response curve. A tolerance of ±15% is applied to the guaranteed luminous intensity value.
• Viewing Angle (2θ_1/2): Defined as the full angle at which the luminous intensity is half of the intensity measured on the central axis. For this LED, the viewing angle is 30 degrees, indicating a relatively focused beam suitable for directional indication.
• Peak Emission Wavelength (λ_P): The wavelength at which the optical output power is maximum. It is specified as 611 nm.
• Dominant Wavelength (λ_d): This parameter defines the perceived color of the LED. It is derived from the CIE chromaticity diagram and represents the single wavelength that best matches the color. The value ranges from 600 nm to 610 nm.
• Spectral Line Half-Width (Δλ): The spectral bandwidth measured at half the maximum intensity (Full Width at Half Maximum - FWHM). It is 17 nm, which is characteristic of the relatively narrow emission spectrum of AlInGaP materials.

Electrical Parameters:

• Forward Voltage (V_F): The voltage drop across the LED when conducting. At I_F = 20 mA, the forward voltage is typically 2.0 V, with a range from 1.8 V (min) to 2.4 V (max). This parameter is crucial for designing the current-limiting circuitry.
• Reverse Current (I_R): The small leakage current that flows when a reverse voltage is applied. It is 100 μA maximum when a reverse voltage (V_R) of 5 V is applied.

3. Binning System Explanation

The LEDs are sorted into bins based on key optical parameters to ensure consistency within a production batch and for specific application requirements.

3.1 Luminous Intensity Binning

The luminous intensity is classified into four bins, identified by the codes U, V, W, and X. The classification is marked on each packing bag.

• Bin U: 3200 mcd (min) to 4200 mcd (max)
• Bin V: 4200 mcd (min) to 5500 mcd (max)
• Bin W: 5500 mcd (min) to 7200 mcd (max)
• Bin X: 7200 mcd (min) to 9300 mcd (max)

All measurements are taken at I_F = 20 mA, with an allowance of ±15% for measurement precision.

3.2 Hue (Dominant Wavelength) Binning

The color, defined by the dominant wavelength, is also binned to control color consistency. The bins are identified as H23, H24, and H25.

• Bin H23: 600.0 nm (min) to 603.0 nm (max)
• Bin H24: 603.0 nm (min) to 606.5 nm (max)
• Bin H25: 606.5 nm (min) to 610.0 nm (max)

The tolerance for measurement precision is ±1 nm. This binning allows designers to select LEDs with very specific color points if required for their application.

4. Performance Curve Analysis

While the PDF references typical performance curves, the specific graphical data for parameters like the current vs. luminous intensity (I-V curve), temperature dependence of forward voltage, and the spectral distribution curve are not provided in the text excerpt. In a full datasheet, these curves are critical for design.

Typically, for an AlInGaP LED like this one, the I-V curve would show an exponential relationship between current and voltage once the turn-on voltage (around 1.8-2.0V) is exceeded. The luminous intensity curve is generally linear with current in the normal operating range (e.g., up to 20-30mA), after which efficiency may drop due to heating. The forward voltage has a negative temperature coefficient, meaning it decreases slightly as the junction temperature increases. The spectral distribution curve would show a single peak centered around 611 nm with the stated 17 nm FWHM, confirming the yellow-orange color output.

5. Mechanical and Packaging Information

5.1 Package Dimensions and Tolerances

The LED is housed in a standard T-1 3/4 diameter package. All dimensions are provided in millimeters, with inches in parentheses. The general tolerance for dimensions is ±0.25 mm (±0.010") unless a specific note states otherwise. Key mechanical notes include:

• The resin under the flange may protrude by a maximum of 1.0 mm (0.04").
• Lead spacing is measured at the point where the leads emerge from the package body.

The specific dimensional drawing, which would detail the body diameter, lens shape, lead length, and lead diameter, is referenced but not described in detail in the provided text.

5.2 Polarity Identification

For through-hole LEDs, polarity is typically indicated by the lead length (the longer lead is usually the anode, or positive terminal) and sometimes by a flat spot on the lens rim or a notch in the flange. The exact method for this specific part should be verified on the physical component or the detailed package drawing.

6. Soldering and Assembly Guidelines

Proper handling is essential to maintain device integrity and performance.

6.1 Lead Forming and PCB Assembly

• Lead forming must be performed before soldering and at normal room temperature.
• The bend should be made at a point at least 3 mm from the base of the LED lens. The base of the lead frame itself must not be used as a fulcrum during bending.
• During PCB assembly, use the minimum clinching force necessary to hold the component in place, avoiding excessive mechanical stress on the leads or package.

6.2 Soldering Process

A minimum clearance of 2 mm must be maintained between the base of the lens and the soldering point. The lens must never be immersed in solder.

Recommended Soldering Conditions:

• Soldering Iron: Maximum temperature of 300°C. Soldering time should not exceed 3 seconds per lead. This should be done only once.
• Wave Soldering:
  • Pre-heat temperature: Maximum 100°C.
  • Pre-heat time: Maximum 60 seconds.
  • Solder wave temperature: Maximum 260°C.
  • Soldering time: Maximum 5 seconds.

Important Note: Infrared (IR) reflow soldering is explicitly stated as not suitable for this through-hole type LED lamp product. Excessive soldering temperature or time can cause lens deformation or catastrophic failure of the LED.

6.3 Cleaning

If cleaning is necessary, only alcohol-based solvents such as isopropyl alcohol should be used.

7. Packaging and Ordering Information

7.1 Packaging Specifications

The LEDs are packaged in the following hierarchy:

• Packing Bag: Contains 1000, 500, or 250 pieces.
• Inner Carton: Contains 8 packing bags, totaling 8000 pieces.
• Outer Carton (Shipping Carton): Contains 8 inner cartons, totaling 64,000 pieces.

A note specifies that in every shipping lot, only the final pack may contain a non-full quantity.

7.2 Part Number and Labeling

The primary part number for this device is LTL2V3WFK. The luminous intensity bin code (U, V, W, X) is marked on each individual packing bag, allowing for traceability and selection of specific brightness grades.

8. Application Recommendations

8.1 Typical Application Circuits

An LED is a current-operated device. To ensure uniform brightness when driving multiple LEDs, especially in parallel, it is strongly recommended to use a dedicated current-limiting resistor in series with each LED (Circuit Model A).

Connecting LEDs directly in parallel without individual resistors (Circuit Model B) is discouraged. Due to natural variations in the forward voltage (V_F) characteristic from one LED to another, the current—and therefore the brightness—will not be evenly distributed. The LED with the lowest V_F will draw more current and appear brighter, potentially leading to premature failure, while others may be dim.

The series resistor value (R_s) can be calculated using Ohm's Law: R_s = (V_supply - V_F) / I_F. Using the typical V_F of 2.0V and a desired I_F of 20mA with a 5V supply, the resistor would be (5V - 2.0V) / 0.02A = 150 Ω. A standard value like 150 Ω or 180 Ω would be appropriate, considering the min/max V_F range to ensure current stays within safe limits.

8.2 Electrostatic Discharge (ESD) Protection

LEDs are sensitive to electrostatic discharge. To prevent ESD damage during handling and assembly:

• Operators should wear a conductive wrist strap or anti-static gloves.
• All equipment, workbenches, and storage racks must be properly grounded.
• An ionizer (ion blower) can be used to neutralize static charge that may accumulate on the plastic lens.

8.3 Storage Conditions

For extended storage outside the original packaging, it is recommended to store the LEDs in a sealed container with desiccant or in a nitrogen ambient. If removed from the original packaging, the LEDs should ideally be used within three months. The recommended storage environment should not exceed 30°C and 70% relative humidity.

9. Technical Comparison and Design Considerations

Compared to older technologies like GaAsP (Gallium Arsenide Phosphide), this AlInGaP LED offers significantly higher luminous efficiency, resulting in much brighter output for the same drive current. The 30-degree viewing angle provides a more focused beam compared to wide-angle or diffused LEDs, making it suitable for applications where the light needs to be directed, such as in panel indicators viewed from a specific angle.

The forward voltage of ~2.0V is lower than that of blue or white InGaN LEDs (typically ~3.0V+), which can be advantageous in low-voltage systems. Designers must carefully consider heat dissipation, especially when operating near the maximum current rating or in elevated ambient temperatures, utilizing the provided derating curve.

10. Frequently Asked Questions (Based on Technical Parameters)

Q: Can I drive this LED directly from a 3.3V microcontroller pin?
A: Possibly, but a series resistor is still mandatory. Calculate the resistor value based on the pin's output voltage (likely 3.3V), the LED's V_F (~2.0V), and the desired current (e.g., 10-20mA). Ensure the microcontroller pin can source the required current.

Q: What is the difference between Peak Wavelength and Dominant Wavelength?
A: Peak Wavelength (λ_P=611 nm) is the physical point of highest power in the emission spectrum. Dominant Wavelength (λ_d=600-610 nm) is a calculated value that defines the perceived color by the human eye, based on the CIE color matching functions. They are often close but not identical.

Q: Why is a 30-degree viewing angle specified as 2θ_1/2?
A> The symbol 2θ_1/2 denotes the full viewing angle. The half-angle (θ_1/2) is 15 degrees off-axis, where intensity drops to 50%. The full angle between the two 50% intensity points is therefore 30 degrees.

Q: Can I use this for a battery-powered device?
A: Yes, its low V_F and ability to operate at currents as low as a few milliamperes (with reduced brightness) make it suitable for battery-powered applications. Always include a series resistor to control current.

11. Practical Application Example

Scenario: Designing a multi-status indicator panel for a piece of test equipment.

The panel requires four distinct yellow-orange indicators for "Power," "Standby," "Test in Progress," and "Fault." Uniform brightness is critical for a professional appearance.

Design Steps:

1. Component Selection: Specify the LTL2V3WFK LED and request components from the same luminous intensity bin (e.g., all from Bin W) to minimize brightness variation.
2. Circuit Design: The system uses a 5V rail. For each LED, place a 150 Ω, 1/4W resistor in series. Calculation: (5V - 2.0V) / 0.02A = 150Ω. Power dissipation in the resistor: (0.02A)^2 * 150Ω = 0.06W, well within rating.
3. PCB Layout: Ensure the holes for the LED leads are spaced according to the datasheet's lead spacing dimension. Include a silkscreen outline showing polarity (e.g., a flat side or "+" for anode).
4. Assembly: During manual assembly, bend the leads carefully >3mm from the body. Use a temperature-controlled soldering iron set to 280°C, applying heat for less than 3 seconds per joint.
5. Drive Circuit: Connect each LED-resistor pair to a separate digital output pin of a microcontroller. Driving the pin HIGH (5V) will illuminate the LED with ~20mA.

This approach ensures reliable, consistent, and long-lasting operation of all indicator lights.

12. Operating Principle Introduction

This LED operates on the principle of electroluminescence in a semiconductor p-n junction. The active region is composed of AlInGaP (Aluminum Indium Gallium Phosphide). When a forward voltage exceeding the junction's built-in potential (approximately 1.8-2.4V) is applied, electrons from the n-type region and holes from the p-type region are injected into the active region. Here, they recombine, releasing energy in the form of photons (light). The specific composition of the AlInGaP alloy determines the bandgap energy of the semiconductor, which directly dictates the wavelength (color) of the emitted light—in this case, in the yellow-orange spectrum around 611 nm. The epoxy lens serves to protect the semiconductor chip, shape the light output beam (30-degree viewing angle), and in this "diffused" version, it also scatters the light to reduce glare and create a more uniform appearance when viewed directly.

13. Technology Trends and Context

Through-hole LEDs like the T-1 3/4 package remain widely used in applications where manual assembly, high reliability in harsh environments, or easy field replacement are priorities. However, the broader industry trend is strongly towards surface-mount device (SMD) packages (e.g., 0603, 0805, 2835) for automated assembly, higher density, and better thermal management.

In terms of materials, AlInGaP technology represents a mature and highly efficient solution for red, orange, amber, and yellow colors. It has largely superseded older, less efficient technologies like GaAsP. For colors like blue, green, and white, InGaN (Indium Gallium Nitride) is the dominant material system. Ongoing development focuses on increasing luminous efficacy (lumens per watt), improving color consistency and stability over temperature and lifetime, and enabling higher power densities in smaller packages. While this datasheet represents a standard, reliable component, newer products may offer higher brightness in similar packages or the same brightness with lower drive currents.