LTL-R42FTBN4D Blue LED Lamp Datasheet - 5mm Diameter - 3.8V Forward Voltage - 20mA Current - 117mW Power - English Technical Document

1. Product Overview

This document provides the complete technical specifications for the LTL-R42FTBN4D, a through-hole mounted LED indicator lamp. This device is part of a family of LEDs offered in various package sizes, including 3mm, 4mm, 5mm, rectangular, and cylindrical forms, designed to meet the needs of diverse status indication applications across multiple industries. The specific model LTL-R42FTBN4D is characterized by its blue emission, utilizing an InGaN semiconductor chip with a typical peak wavelength of 470nm, housed in a standard T-1 (5mm) package with a white diffused lens.

1.1 Core Features and Advantages

The LTL-R42FTBN4D is engineered for reliability and ease of integration into electronic circuits. Its key features include a design optimized for straightforward circuit board assembly, contributing to efficient manufacturing processes. The device boasts low halogen content, aligning with environmental and regulatory considerations. It is fully compatible with integrated circuit logic levels, requiring only a low drive current, which simplifies power supply design and reduces overall system power consumption. The white diffused lens provides a wide, uniform viewing angle, enhancing visibility. Furthermore, the LED offers high luminous efficiency, delivering bright output while maintaining low power dissipation.

1.2 Target Applications and Markets

This LED is suitable for a broad spectrum of applications requiring clear, reliable visual status indication. Primary target markets include the computer industry, where it can be used for power, disk activity, or network status lights on desktops, servers, and peripherals. In the communications sector, it is applicable for indicators on routers, switches, modems, and other networking equipment. Consumer electronics such as audio/video equipment, home appliances, and various portable devices represent another significant application area. Its robustness also makes it suitable for use in industrial control panels and instrumentation.

2. Technical Parameter Deep-Dive Analysis

A thorough understanding of the device's limits and operating characteristics is crucial for reliable design.

2.1 Absolute Maximum Ratings

These ratings define the stress limits beyond which permanent damage to the device may occur. Operation under or at these limits is not guaranteed. The absolute maximum ratings are specified at an ambient temperature (TA) of 25°C. The maximum continuous power dissipation is 117 milliwatts. The device can handle a DC forward current of 20mA continuously. For pulsed operation, a peak forward current of 100mA is permissible, but only under strict conditions: a duty cycle of 1/10 or less and a pulse width not exceeding 10 microseconds. The operating temperature range is from -40°C to +85°C, while the storage temperature range extends from -55°C to +100°C. During soldering, the leads can withstand a temperature of 260°C for a maximum of 5 seconds, provided the soldering point is at least 2.0mm (0.079 inches) away from the LED body.

2.2 Electrical and Optical Characteristics

These parameters define the device's performance under normal operating conditions, typically at TA=25°C and a forward current (IF) of 20mA. The luminous intensity (Iv) has a typical value of 400 millicandelas (mcd), with a guaranteed minimum of 180 mcd and a maximum of 880 mcd, subject to a ±15% testing tolerance. The viewing angle (2θ1/2), defined as the full angle at which intensity drops to half its axial value, is 60 degrees. The peak emission wavelength (λP) is 468 nm. The dominant wavelength (λd), which perceptually defines the color, ranges from 460 nm to 475 nm. The spectral bandwidth (Δλ) is 25 nm. The forward voltage (VF) typically measures 3.8V, with a maximum of 3.8V. The reverse current (IR) is a maximum of 10 microamperes when a reverse voltage (VR) of 5V is applied; it is critical to note that this device is not designed for operation under reverse bias.

3. Binning System Specification

To ensure color and brightness consistency in production, LEDs are sorted into bins based on key parameters.

3.1 Luminous Intensity Binning

The luminous output is classified into bins identified by a single-letter code. Each bin has a defined minimum and maximum intensity value measured in millicandelas (mcd) at IF=20mA. The binning structure is as follows: Bin H (180-240 mcd), Bin J (240-310 mcd), Bin K (310-400 mcd), Bin L (400-520 mcd), Bin M (520-680 mcd), and Bin N (680-880 mcd). A tolerance of ±15% applies to the limits of each bin. The specific bin code for intensity is marked on each packing bag, allowing designers to select LEDs with the desired brightness range for their application.

3.2 Dominant Wavelength Binning

The color, defined by dominant wavelength, is also binned to guarantee hue consistency. Bins are identified by an alphanumeric code (e.g., B07, B08, B09). The corresponding wavelength ranges are: B07 (460.0 - 465.0 nm), B08 (465.0 - 470.0 nm), and B09 (470.0 - 475.0 nm). A tight tolerance of ±1 nanometer is maintained for each bin limit. This precise binning is essential for applications where color matching between multiple LEDs is critical.

4. Performance Curve Analysis

Graphical representations of key characteristics provide deeper insight into device behavior under varying conditions.

The datasheet includes typical characteristic curves, which are invaluable for design analysis. These curves visually depict the relationship between forward current and luminous intensity, showing how light output increases with current. They also illustrate the forward voltage versus forward current relationship, which is necessary for calculating the appropriate current-limiting resistor. Furthermore, temperature dependency curves would typically show how parameters like luminous intensity and forward voltage shift with changes in the ambient or junction temperature, although specific curve data points are not detailed in the provided text. Designers should refer to the full graphical data to understand derating requirements and performance under non-standard temperatures.

5. Mechanical and Package Information

5.1 Outline Dimensions and Tolerances

The LED conforms to a standard T-1 (5mm) round through-hole package outline. All dimensions are provided in millimeters, with an accompanying inch conversion. The general tolerance for dimensions is ±0.25mm (0.010 inches) unless a specific note states otherwise. Key mechanical notes include: the maximum protrusion of resin under the flange is 1.0mm (0.04 inches); lead spacing is measured at the point where the leads emerge from the package body. Designers must incorporate these tolerances into their PCB layout and mechanical designs.

6. Soldering and Assembly Guidelines

Proper handling is essential to maintain device integrity and performance.

6.1 Storage and Cleaning

For long-term storage, the ambient should not exceed 30°C or 70% relative humidity. LEDs removed from their original, moisture-protective packaging should ideally be used within three months. For extended storage outside the original pack, they should be kept in a sealed container with desiccant or in a nitrogen ambient. If cleaning is necessary, only alcohol-based solvents like isopropyl alcohol should be used.

6.2 Lead Forming

If leads need to be bent, this must be done before the soldering process and at normal room temperature. The bend must be made at a point no closer than 3mm from the base of the LED lens. Crucially, the base of the lead frame itself must not be used as a fulcrum during bending, as this can stress the internal die attach and cause failure.

6.3 Soldering Process Parameters

A minimum clearance of 2mm must be maintained between the base of the lens and the soldering point. Dipping the lens into solder must be avoided. No external stress should be applied to the leads while the LED is at high temperature. Recommended conditions are:
Hand Soldering (Iron): Maximum temperature 350°C, maximum time 3 seconds per lead (one time only).
Wave Soldering: Pre-heat to a maximum of 100°C for up to 60 seconds. Solder wave at a maximum of 260°C for up to 5 seconds. The dipping position must ensure the solder does not come within 2mm of the lens base.
Exceeding these temperature or time limits can cause lens deformation or catastrophic failure of the LED.

7. Packaging and Ordering Information

The LTL-R42FTBN4D is available in standard packaging quantities to suit different production scales. The base unit is a packing bag, available in quantities of 1000, 500, 200, or 100 pieces per bag. For larger volumes, ten of these packing bags are combined into an inner carton, totaling 10,000 pieces. Finally, eight inner cartons are packed into one master outer carton, providing a bulk quantity of 80,000 pieces per outer carton. It is noted that within a shipping lot, only the final pack may contain a non-full quantity.

8. Application Design Recommendations

8.1 Drive Circuit Design

LEDs are current-operated devices. To ensure uniform brightness when multiple LEDs are connected in parallel, it is strongly recommended to use a individual current-limiting resistor in series with each LED. The schematic labeled \"Circuit Model (A)\" in the datasheet illustrates this correct approach. Simply connecting LEDs in parallel without individual resistors (as in \"Circuit Model (B)\") is discouraged because small variances in the forward voltage (Vf) characteristic of each LED will cause current to divide unevenly, leading to noticeable differences in brightness.

8.2 Electrostatic Discharge (ESD) Protection

This LED is susceptible to damage from electrostatic discharge or power surges. A comprehensive ESD control program is advised for handling and assembly. Key measures include: operators wearing conductive wrist straps or anti-static gloves; ensuring all equipment, workstations, and storage racks are properly grounded; and using ionizers to neutralize static charge that may build up on the plastic lens due to friction. A training and certification program for personnel working in the static-safe area is also recommended.

9. Technical Comparison and Design Considerations

Compared to non-diffused or water-clear lens LEDs, the white diffused lens of the LTL-R42FTBN4D offers a wider and more uniform viewing angle, making it superior for applications where the indicator needs to be visible from various angles. Its low current requirement makes it compatible with direct drive from microcontroller GPIO pins, often without the need for a transistor driver stage, simplifying circuit design. Designers must carefully calculate the series resistor value based on the supply voltage, the LED's forward voltage (using the maximum value of 3.8V for a conservative design), and the desired forward current (typically 20mA or lower for longer life). Power dissipation in the resistor must also be checked.

10. Frequently Asked Questions (Based on Technical Parameters)

Q: Can I drive this LED with a 5V supply?
A: Yes, but you must use a series current-limiting resistor. The value can be calculated using Ohm's Law: R = (Vsupply - Vf_LED) / If. Using typical values (5V - 3.8V) / 0.020A = 60 ohms. A standard 62 or 68 ohm resistor would be suitable, ensuring the current stays near or below 20mA.

Q: What is the difference between peak wavelength and dominant wavelength?
A: Peak wavelength (λP) is the wavelength at which the spectral power output is highest (468 nm). Dominant wavelength (λd) is derived from the color coordinates on the CIE chromaticity diagram and represents the single wavelength that best matches the perceived color of the light (460-475 nm). For design, the dominant wavelength is more relevant for color specification.

Q: How do I interpret the luminous intensity bin code?
A: The bin code (e.g., H, J, K) printed on the bag indicates the guaranteed minimum and maximum light output range for the LEDs inside. For consistent brightness in an array, specify and use LEDs from the same intensity bin.

11. Practical Application Example

Scenario: Designing a 4-LED status bar for a network switch. The bar should indicate link speed (e.g., 10/100/1000 Mbps) and activity. Using the LTL-R42FTBN4D, the designer would: 1) Select LEDs from the same luminous intensity bin (e.g., Bin K) and dominant wavelength bin (e.g., B08) for uniformity. 2) For a 3.3V microcontroller supply, calculate the series resistor: R = (3.3V - 3.8V) / 0.02A = -25 ohms. This negative result indicates 3.3V is insufficient to forward bias the LED at 20mA. The designer must either use a higher supply voltage (like 5V) or drive the LED at a lower current, accepting reduced brightness. With a 5V supply, a 68-ohm resistor would yield approximately 17.6mA, which is safe and provides good brightness. 3) Ensure PCB holes are sized for the 0.6mm lead diameter and maintain the 2mm solder-to-body clearance. 4) Program the microcontroller to light the appropriate LEDs based on the network status.

12. Operational Principle

Light Emitting Diodes (LEDs) are semiconductor devices that emit light through electroluminescence. When a forward voltage is applied across the p-n junction, electrons from the n-type material recombine with holes from the p-type material in the active region. This recombination process releases energy in the form of photons (light). The specific wavelength (color) of the emitted light is determined by the energy bandgap of the semiconductor material used. The LTL-R42FTBN4D utilizes an Indium Gallium Nitride (InGaN) compound semiconductor, which is engineered to have a bandgap corresponding to blue light emission with a peak around 470 nanometers. The white diffused epoxy lens encapsulates the semiconductor chip, provides mechanical protection, and scatters the emitted light to create a wide viewing angle.

13. Technology Trends

The through-hole LED market, while mature, continues to see incremental improvements in efficiency and reliability. Trends in the broader LED industry, such as the development of materials with higher internal quantum efficiency and improved packaging techniques for better thermal management and light extraction, indirectly benefit all LED form factors. There is a constant drive for lower forward voltages and higher luminous efficacy (more light output per watt of electrical input). For indicator applications, the demand for consistent color and brightness (tight binning) remains high, driven by automation and quality expectations in end products. While surface-mount device (SMD) LEDs dominate new designs for their smaller size and suitability for automated pick-and-place assembly, through-hole LEDs retain significant markets in prototyping, educational kits, repair sectors, and applications where mechanical robustness or manual assembly is preferred.