LTLR42FTBGAJ LED Lamp Datasheet - T-1 Package - 470nm Blue/White - 3.2V 20mA - English Technical Document

1. Product Overview

The LTLR42FTBGAJ is a through-hole LED lamp designed for status indication and general illumination in a wide range of electronic applications. It features a popular T-1 (3mm) diameter package with a white diffused lens, emitting light with a dominant wavelength in the blue spectrum (470nm). This component is characterized by its low power consumption, high reliability, and compatibility with standard PCB mounting processes.

1.1 Core Advantages

• RoHS Compliance: The product is lead (Pb) free, meeting environmental regulations.
• High Efficiency: Offers high luminous intensity relative to its power consumption.
• Design Flexibility: Available in standard T-1 package, suitable for versatile mounting on PCBs or panels.
• Low Current Drive: IC-compatible with low current requirements, simplifying circuit design.
• Reliability: Built for stable operation across a defined temperature range.

1.2 Target Applications

This LED is suitable for various sectors requiring clear, reliable visual indicators. Primary application areas include:

• Communication Equipment: Status lights on routers, modems, switches.
• Computer Peripherals: Power, HDD activity, and function indicators.
• Consumer Electronics: Indicators on audio/video equipment, home appliances.
• Home Appliances: Display and control panel indicators.
• Industrial Controls: Machine status, fault, and operational indicators.

2. Technical Parameter Analysis

This section provides a detailed, objective interpretation of the key electrical, optical, and thermal parameters defined in the datasheet. Understanding these specifications is crucial for proper circuit design and reliable operation.

2.1 Absolute Maximum Ratings

These ratings define the limits beyond which permanent damage to the device may occur. Operation under these conditions is not guaranteed.

• Power Dissipation (P_D): 72 mW maximum. This is the total power the LED package can dissipate as heat. Exceeding this limit risks thermal damage.
• DC Forward Current (I_F): 20 mA continuous. The LED should not be driven with a continuous DC current exceeding this value.
• Peak Forward Current: 60 mA, permissible only under pulsed conditions (duty cycle ≤ 1/10, pulse width ≤ 10µs). Useful for brief, high-brightness flashes.
• Operating Temperature (T_A): -30°C to +85°C. The ambient temperature range for normal operation.
• Storage Temperature: -40°C to +100°C. The temperature range for non-operational storage.
• Lead Soldering Temperature: 260°C for a maximum of 5 seconds, measured 2.0mm from the LED body. Critical for hand or wave soldering processes.

2.2 Electrical & Optical Characteristics

These are the typical performance parameters measured at an ambient temperature (T_A) of 25°C and a forward current (I_F) of 10mA, unless otherwise specified.

• Luminous Intensity (I_V): 65 to 310 mcd (millicandela). The actual intensity is binned (see Section 4). The test includes a ±15% measurement tolerance.
• Viewing Angle (2θ_1/2): 100 degrees (typical). This is the full angle at which the luminous intensity drops to half of its axial (on-center) value. The white diffused lens creates a wide, even viewing pattern.
• Peak Emission Wavelength (λ_P): 468 nm. The wavelength at which the spectral output is strongest.
• Dominant Wavelength (λ_d): 460 to 475 nm (binned). This is the single wavelength perceived by the human eye that defines the color of the LED, derived from the CIE chromaticity diagram.
• Spectral Line Half-Width (Δλ): 25 nm (typical). This indicates the spectral purity; a smaller value means a more monochromatic light.
• Forward Voltage (V_F): 2.6V to 3.6V, with a typical value of 3.2V at 10mA. This is the voltage drop across the LED when conducting current.
• Reverse Current (I_R): 10 µA maximum at a reverse voltage (V_R) of 5V. Important: This device is not designed for reverse operation; this parameter is for test purposes only.

2.3 Thermal Considerations

While not explicitly detailed in curves, thermal management is implied by the power dissipation rating and operating temperature range. Driving the LED at its maximum continuous current (20mA) with a typical V_F of 3.2V results in a power dissipation of 64mW, close to the absolute maximum of 72mW. Therefore, in high ambient temperatures or enclosed spaces, derating the operating current is advisable to ensure long-term reliability and prevent luminous intensity degradation.

3. Binning System Specification

To ensure consistency in production, LEDs are sorted into performance bins. The LTLR42FTBGAJ uses a two-dimensional binning system for luminous intensity and dominant wavelength.

3.1 Luminous Intensity Binning

Units are in millicandela (mcd) measured at I_F = 10mA. Each bin has a ±15% tolerance on its limits.

• Bin DE: Minimum 65 mcd, Maximum 110 mcd.
• Bin FG: Minimum 110 mcd, Maximum 180 mcd.
• Bin HJ: Minimum 180 mcd, Maximum 310 mcd.

The bin code is marked on each packing bag, allowing designers to select the appropriate brightness grade for their application.

3.2 Dominant Wavelength Binning

Units are in nanometers (nm) measured at I_F = 10mA. Each bin has a ±1nm tolerance on its limits.

• Bin B07: 460.0 nm to 465.0 nm.
• Bin B08: 465.0 nm to 470.0 nm.
• Bin B09: 470.0 nm to 475.0 nm.

This binning ensures color consistency within a defined blue hue range for applications where color matching is important.

4. Mechanical & Package Information

4.1 Outline Dimensions

The LED conforms to the standard T-1 (3mm) radial leaded package profile. Key dimensional notes from the datasheet include:

• All dimensions are in millimeters (inches provided in parenthesis).
• Standard tolerance is ±0.25mm (±0.010\") unless otherwise specified.
• The maximum protrusion of resin under the flange is 1.0mm (0.04\").
• Lead spacing is measured where the leads emerge from the package body.
• The minimum pin length is 27.5mm.

4.2 Polarity Identification

For through-hole LEDs, the longer lead is typically the anode (positive), and the shorter lead is the cathode (negative). Additionally, the LED body often has a flat side near the cathode lead. Correct polarity must be observed during PCB layout and assembly.

5. Assembly & Handling Guidelines

Proper handling is essential to maintain LED performance and reliability.

5.1 Storage Conditions

For optimal shelf life, LEDs should be stored in an environment not exceeding 30°C and 70% relative humidity. If removed from the original moisture-barrier packaging, it is recommended to use the components within three months. For longer-term storage outside the original bag, use a sealed container with desiccant or a nitrogen-filled desiccator.

5.2 Lead Forming

• Bending must be performed before soldering, at room temperature.
• The bend should be made at a point at least 3mm from the base of the LED lens.
• Do not use the base of the LED (the lead frame) as a fulcrum during bending.
• During PCB insertion, apply the minimum clinch force necessary to avoid mechanical stress on the package.

5.3 Soldering Process

Critical Rule: Maintain a minimum distance of 2mm from the base of the epoxy lens to the solder point. Do not immerse the lens in solder.

• Soldering Iron: Maximum temperature 350°C. Maximum soldering time 3 seconds per lead. Soldering should be performed only once.
• Wave Soldering: Maximum pre-heat temperature 100°C for up to 60 seconds. Solder wave temperature maximum 260°C. Maximum soldering time 5 seconds.
• Important: Infrared (IR) reflow soldering is not suitable for this through-hole LED product. Excessive heat or time can deform the lens or cause catastrophic failure.

5.4 Cleaning

If cleaning is necessary after soldering, use only alcohol-based solvents such as isopropyl alcohol. Avoid harsh or aggressive chemicals.

5.5 Electrostatic Discharge (ESD) Protection

LEDs are sensitive to electrostatic discharge. Preventive measures 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 build up on the plastic lens due to handling friction.

6. Circuit Design & Drive Method

6.1 Fundamental Drive Principle

An LED is a current-operated device. Its brightness is primarily controlled by the forward current (I_F), not the voltage. Therefore, a current-limiting mechanism is mandatory.

6.2 Recommended Circuit

The datasheet strongly recommends using a series resistor for each LED, even when multiple LEDs are connected in parallel to a voltage source (Circuit A).

Circuit A (Recommended): Each LED has its own dedicated current-limiting resistor (R_limit). The resistor value is calculated using Ohm's Law: R_limit = (V_supply - V_F) / I_F. This ensures uniform brightness across all LEDs by compensating for minor variations in the forward voltage (V_F) of individual devices.

6.3 Non-Recommended Circuit

Circuit B (Not Recommended): Multiple LEDs connected in parallel with a single shared current-limiting resistor. This configuration is problematic because the LED with the lowest V_F will draw more current, becoming brighter and potentially overstressed, while the others remain dimmer. This leads to uneven illumination and reduced reliability.

7. Packaging & Ordering Information

7.1 Packaging Specification

The product is packed in a tiered system:

1. Packing Bag: Contains 1000, 500, 200, or 100 pieces. The luminous intensity bin code is marked on each bag.
2. Inner Carton: Contains 10 packing bags, totaling 10,000 pieces.
3. Outer Carton (Shipping Carton): Contains 8 inner cartons, totaling 80,000 pieces. In a shipping lot, only the final pack may contain a non-full quantity.

8. Application Notes & Design Considerations

8.1 Suitable Applications

This LED is well-suited for both indoor and outdoor signage, as well as standard electronic equipment where a blue or white diffused indicator is required. The wide viewing angle makes it ideal for panels where the indicator needs to be visible from various angles.

8.2 Design Checklist

• Current Limit: Always use a series resistor. Calculate for the desired I_F (≤20mA DC) using the maximum V_F from the datasheet for a safe design.
• Thermal Management: Consider ambient temperature and airflow. Derate operating current in high-temperature environments.
• PCB Layout: Ensure correct polarity footprint. Maintain the 2mm minimum solder-to-lens distance in pad design.
• Binning: Specify the required luminous intensity (I_V) and dominant wavelength (λ_d) bins for color and brightness consistency in production.
• ESD Precautions: Implement ESD controls in the assembly area.

9. Technical Comparison & Positioning

The LTLR42FTBGAJ occupies a standard position in the optoelectronics market. Its primary differentiators are:

• Package: The ubiquitous T-1 through-hole package offers ease of use for prototyping, manual assembly, and applications where surface-mount technology (SMT) is not required or desired.
• Lens: The white diffused lens provides a wide, uniform viewing angle and softens the light point compared to a clear lens, making it excellent for front-panel indicators.
• Color: The 470nm blue/white output is a common choice for power, status, and functional indicators, offering good visibility.
• Reliability Focus: The detailed handling, soldering, and ESD guidelines emphasize design for reliability, making it suitable for industrial and consumer products requiring long service life.

10. Frequently Asked Questions (FAQs)

10.1 Can I drive this LED without a series resistor?

No. Connecting an LED directly to a voltage source will cause excessive current to flow, instantly destroying the device. A series resistor (or other current-regulating circuit) is always required.

10.2 What is the difference between Peak and Dominant Wavelength?

Peak Wavelength (λ_P): The physical wavelength where the LED emits the most optical power. Dominant Wavelength (λ_d): The perceived color as defined by human eye response (CIE standard). For blue LEDs, these values are often close. λ_d is more relevant for color specification.

10.3 Can I use this for reverse voltage indication?

No. The datasheet explicitly states the device is not designed for reverse operation. The reverse current (I_R) parameter is for test purposes only. Applying reverse voltage can damage the LED.

10.4 How do I choose the right bin?

Select the luminous intensity bin (DE, FG, HJ) based on the required brightness for your application. Select the dominant wavelength bin (B07, B08, B09) based on the specific shade of blue/white needed, especially if matching multiple LEDs on a panel.

11. Practical Design Example

Scenario: Design a 12V DC power indicator using the LTLR42FTBGAJ LED. Target a forward current (I_F) of 15mA for a balance of brightness and longevity.

1. Determine Forward Voltage (V_F): Use the maximum value from the datasheet for a conservative design: V_F(max) = 3.6V.
2. Calculate Series Resistor: R = (V_supply - V_F) / I_F = (12V - 3.6V) / 0.015A = 560 Ohms. The nearest standard E24 resistor value is 560Ω.
3. Calculate Resistor Power: P = I_F² * R = (0.015)² * 560 = 0.126W. A standard 1/4W (0.25W) resistor is sufficient.
4. PCB Layout: Place the resistor in series with the LED anode. Ensure the LED cathode pad is at least 2mm from the edge of the LED body footprint to maintain the solder distance requirement.

12. Operating Principle & Technology

The LTLR42FTBGAJ is based on a semiconductor diode structure using Indium Gallium Nitride (InGaN) material for the light-emitting active region. When a forward voltage exceeding the diode's threshold is applied, electrons and holes recombine in the active region, releasing energy in the form of photons (light). The specific composition of the InGaN layers determines the peak emission wavelength, in this case, around 468nm (blue light). The white diffused appearance is achieved by combining the blue LED chip with a phosphor-coated or diffused epoxy lens, which scatters the light to create a wider beam and a softer visual effect.

13. Industry Trends & Context

Through-hole LEDs like the T-1 package remain relevant in specific niches despite the industry's dominant shift to surface-mount device (SMD) technology. Their key advantages are mechanical robustness, ease of hand-soldering for prototyping and repair, and suitability for applications requiring mounting perpendicular to a PCB or into a panel. The trend within the through-hole segment is towards higher efficiency (more light output per mA), improved reliability under harsh conditions, and continued RoHS/REACH compliance. For new designs, engineers typically evaluate SMD alternatives for space savings and automated assembly benefits, but through-hole options are often preferred for educational kits, hobbyist projects, industrial controls with high vibration, or when the design specifically calls for a traditional \"lamp\" style indicator.