LTL2R3KRK LED Lamp Datasheet - T-1 3/4 Package - 2.4V Forward Voltage - Super Red Color - 75mW Power - English Technical Document

1. Product Overview

This document provides the complete technical specifications for a high-efficiency, through-hole mounted LED lamp. The device utilizes AlInGaP (Aluminum Indium Gallium Phosphide) technology to produce a super red light output. It is designed in the popular T-1 3/4 package diameter, making it suitable for a wide range of applications requiring indicator lights, backlighting, or status displays on printed circuit boards (PCBs) or panels.

The core advantages of this component include high luminous intensity output, low power consumption, and high efficiency. It is compatible with integrated circuits due to its low current requirements, facilitating easy integration into various electronic designs.

2. In-Depth Technical Parameter Analysis

2.1 Absolute Maximum Ratings

The device must not be operated beyond these limits to prevent permanent damage. Key ratings are specified at an ambient temperature (T_A) of 25°C.

• Power Dissipation (P_D): 75 mW maximum.
• DC Forward Current (I_F): 30 mA continuous.
• Peak Forward Current: 90 mA under pulsed conditions (1/10 duty cycle, 0.1ms pulse width).
• Reverse Voltage (V_R): 5 V maximum.
• Operating Temperature Range: -40°C to +100°C.
• Storage Temperature Range: -55°C to +100°C.
• Lead Soldering Temperature: 260°C for a maximum of 5 seconds, measured 1.6mm from the LED body.

A derating factor of 0.4 mA/°C applies to the DC forward current for ambient temperatures above 50°C.

2.2 Electrical and Optical Characteristics

These parameters define the typical performance of the LED under standard test conditions (T_A=25°C).

• Luminous Intensity (I_V): 310 mcd (minimum), 680 mcd (typical) at a forward current (I_F) of 20 mA. The guarantee includes a ±15% tolerance.
• Viewing Angle (2θ_1/2): 30 degrees. This is the full angle at which the luminous intensity drops to half of its axial (on-axis) value.
• Peak Emission Wavelength (λ_P): 639 nm.
• Dominant Wavelength (λ_d): 631 nm. This is the single wavelength perceived by the human eye that defines the color (super red).
• Spectral Line Half-Width (Δλ): 20 nm, indicating the spectral purity of the emitted light.
• Forward Voltage (V_F): 2.0 V (minimum), 2.4 V (typical) at I_F = 20 mA.
• Reverse Current (I_R): 100 µA maximum at V_R = 5 V.
• Capacitance (C): 40 pF typical at zero bias and 1 MHz frequency.

3. Binning System Explanation

To ensure consistency in applications, LEDs are sorted (binned) based on key optical parameters. The bin code for a specific parameter is typically marked on the packaging.

3.1 Luminous Intensity Binning

Units are in millicandelas (mcd) measured at 20mA. Each bin has a ±15% tolerance on its limits.

• Bin K: 310 mcd (Min) to 400 mcd (Max)
• Bin L: 400 mcd to 520 mcd
• Bin M: 520 mcd to 680 mcd
• Bin N: 680 mcd to 880 mcd
• Bin P: 880 mcd to 1150 mcd
• Bin Q: 1150 mcd to 1500 mcd

3.2 Dominant Wavelength Binning

Units are in nanometers (nm) measured at 20mA. Each bin has a ±1nm tolerance on its limits.

• Bin H29: 621.0 nm to 625.0 nm
• Bin H30: 625.0 nm to 629.0 nm
• Bin H31: 629.0 nm to 633.0 nm
• Bin H32: 633.0 nm to 637.0 nm
• Bin H33: 637.0 nm to 642.0 nm

4. Performance Curve Analysis

While specific graphs are referenced in the datasheet (e.g., Figure 1 for spectral distribution, Figure 5 for viewing angle), the provided data allows for analysis of key relationships.

The forward voltage (V_F) shows a typical value of 2.4V at 20mA. Designers must consider this when calculating series resistor values for current limiting. The relationship between luminous intensity (I_V) and forward current (I_F) is generally linear within the operating range, but exceeding the maximum DC current will reduce lifetime and can cause failure. The spectral characteristics, defined by the peak (639 nm) and dominant (631 nm) wavelengths with a 20 nm half-width, confirm a saturated red color output suitable for applications requiring high color purity.

5. Mechanical and Packaging Information

5.1 Package Dimensions

The LED uses a standard T-1 3/4 (approximately 5mm) diameter package with a water-clear lens. Key dimensional notes include:

• All dimensions are in millimeters (inches provided in parentheses).
• A general tolerance of ±0.25mm (±0.010") applies unless specified otherwise.
• The maximum protrusion of resin under the flange is 1.0mm (0.04").
• Lead spacing is measured at the point where the leads emerge from the package body.

5.2 Polarity Identification

For through-hole LEDs, the longer lead typically denotes the anode (positive terminal), while the shorter lead denotes the cathode (negative terminal). The cathode may also be indicated by a flat spot on the lens rim or the LED body. Correct polarity must be observed during circuit assembly.

6. Soldering and Assembly Guidelines

Proper handling is critical to ensure reliability and prevent damage.

6.1 Storage Conditions

LEDs should be stored in an environment not exceeding 30°C and 70% relative humidity. If removed from their original moisture-barrier packaging, they should be used within three months. For longer storage outside the original bag, use a sealed container with desiccant or a nitrogen-filled desiccator.

6.2 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.
• Use minimum clinch force during PCB assembly to avoid mechanical stress.

6.3 Soldering Parameters

Maintain a minimum clearance of 2mm from the base of the lens to the solder point. Never immerse the lens in solder.

• Soldering Iron: Maximum temperature 300°C, maximum time 3 seconds (one-time soldering only).
• Wave Soldering: Maximum pre-heat temperature 100°C for 60 seconds; solder wave temperature 260°C maximum for 10 seconds maximum.

Excessive temperature or time can deform the lens or cause catastrophic failure.

6.4 Cleaning

If cleaning is necessary, use alcohol-based solvents such as isopropyl alcohol.

7. Packaging and Ordering Information

The standard packaging configuration is as follows:

• Packing Bag: Contains 1000, 500, or 250 pieces.
• Inner Carton: Contains 8 packing bags, totaling 8000 pieces.
• Outer Carton (Shipping Lot): Contains 8 inner cartons, totaling 64,000 pieces. The final pack in a shipping lot may not be full.

The part number LTL2R3KRK identifies this specific product variant (Water Clear Lens, AlInGaP Super Red source).

8. Application Recommendations and Design Considerations

8.1 Intended Use and Limitations

This LED is designed for ordinary electronic equipment including office equipment, communication devices, and household applications. It is not recommended for safety-critical systems (e.g., aviation, medical life-support, transportation control) without prior consultation and qualification, as failure could jeopardize life or health.

8.2 Drive Circuit Design

LEDs are current-operated devices. To ensure uniform brightness when driving multiple LEDs in parallel, it is strongly recommended to use a individual current-limiting resistor in series with each LED (Circuit Model A). Driving LEDs in parallel without individual resistors (Circuit Model B) is not recommended, as slight variations in the forward voltage (V_F) characteristic of each LED can cause significant differences in current sharing and, consequently, brightness.

The series resistor value (R_s) can be calculated using Ohm's Law: R_s = (V_supply - V_F) / I_F, where V_F is the LED forward voltage (use 2.4V typical or 2.0V min for conservative design) and I_F is the desired forward current (e.g., 20mA).

8.3 Electrostatic Discharge (ESD) Protection

These LEDs are susceptible to damage from electrostatic discharge. Precautions must be taken:

• Operators should wear grounded wrist straps or anti-static gloves.
• All equipment, workbenches, and storage racks must be properly grounded.
• Use an ionizer to neutralize static charge that may accumulate on the plastic lens due to handling friction.

9. Technical Comparison and Differentiation

The use of AlInGaP technology for red LEDs offers distinct advantages over older technologies like GaAsP (Gallium Arsenide Phosphide). AlInGaP LEDs provide significantly higher luminous efficiency, meaning more light output (mcd) for the same input current (mA). They also offer better temperature stability and longer operational lifetime. The T-1 3/4 package remains an industry standard, ensuring wide compatibility with existing PCB layouts and panel cutouts, while the through-hole design provides robust mechanical attachment suitable for applications subject to vibration or physical stress.

10. Frequently Asked Questions (FAQs)

10.1 What is the difference between peak wavelength and dominant wavelength?

Peak Wavelength (λ_P): The wavelength at which the spectral power distribution of the LED is at its maximum (639 nm for this device). Dominant Wavelength (λ_d): The single wavelength that, when combined with a reference white light, matches the perceived color of the LED (631 nm). It is derived from the CIE chromaticity diagram and is more relevant for color perception.

10.2 Can I drive this LED without a series resistor?

No. An LED must be driven with a controlled current. Connecting it directly to a voltage source will cause excessive current to flow, rapidly destroying the device. A series resistor (or a constant current driver) is essential.

10.3 How do I interpret the luminous intensity bin code?

The bin code (e.g., K, L, M) printed on the packing bag indicates the guaranteed range of luminous intensity for the LEDs in that bag. For example, Bin M guarantees I_V between 520 and 680 mcd at 20mA. Designers can select a specific bin to ensure brightness consistency in their application.

11. Practical Design and Usage Examples

Example 1: Status Indicator on a 5V System. To operate the LED at 20mA from a 5V supply: V_supply = 5V, V_F (typical) = 2.4V, I_F = 0.020A. The required series resistor is R = (5V - 2.4V) / 0.020A = 130 Ohms. The nearest standard value of 130Ω or 120Ω can be used. The resistor power rating should be at least P = I²R = (0.02)² * 130 = 0.052W, so a standard 1/8W (0.125W) resistor is sufficient.

Example 2: Panel Mounting. The through-hole design allows the LED to be mounted directly through a panel. A matching panel-mount bezel or a simple drilled hole (slightly larger than 5mm) can be used. The leads are bent after insertion to secure the LED, and then soldered to a PCB behind the panel.

12. Operating Principle Introduction

An LED is a semiconductor diode. When a forward voltage exceeding its characteristic forward voltage (V_F) is applied, electrons and holes recombine in the active region (the AlInGaP layer in this case). This recombination releases energy in the form of photons (light). The specific material composition of the semiconductor (the bandgap energy) determines the wavelength, and thus the color, of the emitted light. AlInGaP is engineered to produce light in the red to amber part of the visible spectrum with high efficiency.

13. Technology Trends and Context

While surface-mount device (SMD) LEDs dominate modern high-volume electronics for their smaller size and suitability for automated assembly, through-hole LEDs like the T-1 3/4 remain relevant. Their key advantages include superior mechanical strength (the leads are anchored through the PCB), easier manual prototyping and repair, and better heat dissipation via the leads for some higher-power variants. They are commonly found in industrial controls, automotive aftermarket products, hobbyist projects, and applications where robustness is prioritized over miniaturization. The ongoing development in semiconductor materials continues to improve the efficiency and lifetime of all LED types, including through-hole packages.