T-1 3/4 White LED Lamp Datasheet - 5mm Diameter - 3.3V Typical - 120mW Power - English Technical Document

1. Product Overview

This document provides the complete technical specifications for a high-efficiency, through-hole mounted white LED lamp. The device is designed for general-purpose indicator and illumination applications where reliable performance and ease of assembly are required. It features a popular T-1 3/4 package diameter, making it compatible with standard PCB layouts and panel mounts.

The core technology is based on InGaN (Indium Gallium Nitride) semiconductor material deposited on a sapphire substrate, which enables the production of white light. The product is compliant with RoHS directives, meaning it is manufactured without the use of lead (Pb) and other restricted hazardous substances. Key advantages highlighted include low power consumption, high luminous efficiency, and compatibility with integrated circuits due to its low current requirement.

1.1 Target Applications

This LED is intended for use in ordinary electronic equipment. Typical application areas include, but are not limited to, status indicators in office automation equipment, backlighting for switches and panels, general illumination in consumer electronics, and signal indicators in communication devices. It is suitable for applications where standard reliability is sufficient.

2. Technical Parameter Deep-Dive

The performance of the LED is characterized under specific ambient conditions (Ta=25°C). Understanding these parameters is crucial for proper circuit design and achieving expected performance in the final application.

2.1 Absolute Maximum Ratings

These ratings define the limits beyond which permanent damage to the device may occur. Operation under or at these limits is not guaranteed and should be avoided for reliable operation.

• Power Dissipation (Pd): 120 mW maximum. This is the total power the package can safely dissipate as heat.
• Peak Forward Current (I_FP): 100 mA maximum. This is allowed only under pulsed conditions with a 1/10 duty cycle and a 0.1ms pulse width to prevent overheating.
• Continuous Forward Current (I_F): 30 mA DC maximum. This is the recommended maximum current for continuous operation.
• Operating Temperature Range (T_opr): -30°C to +80°C. The device is functional within this ambient temperature range.
• Storage Temperature Range (T_stg): -40°C to +100°C.
• Lead Soldering Temperature: 260°C for 5 seconds maximum, measured 1.6mm (0.063\") from the LED body.

2.2 Electrical & Optical Characteristics

These are the typical and guaranteed performance parameters measured at the standard test condition of I_F = 20mA and T_a=25°C.

• Luminous Intensity (I_v): 2500 mcd (Min), 5200 mcd (Typ), 9300 mcd (Max). Intensity is measured on the mechanical axis per CIE 127 standards. A ±15% tolerance applies to the guaranteed intensity.
• Viewing Angle (2θ_1/2): 50 degrees (Typical). This is the full angle at which the luminous intensity drops to half of its axial value.
• Chromaticity Coordinates (x, y): x=0.29 (Typ), y=0.28 (Typ). These coordinates define the white point on the CIE 1931 chromaticity diagram.
• Forward Voltage (V_F): 2.7V (Min), 3.3V (Typ), 3.7V (Max) at I_F=20mA. This parameter is critical for selecting the appropriate current-limiting resistor.
• Reverse Current (I_R): 50 µA maximum at a Reverse Voltage (V_R) of 5V. The device is not designed for operation in reverse bias.

3. Binning System Explanation

The LEDs are sorted (binned) based on key optical parameters to ensure consistency within a production lot. The bin code is marked on each packing bag.

3.1 Luminous Intensity (I_v) Binning

LEDs are classified into different ranks based on their measured luminous intensity at 20mA. The ranks are: T (2500-3200 mcd), U (3200-4200 mcd), V (4200-5500 mcd), W (5500-7200 mcd), and X (7200-9300 mcd).

3.2 Hue (Chromaticity) Binning

LEDs are also binned according to their chromaticity coordinates to control the color variation of the white light. The datasheet provides a hue specification table with coordinates for bins B1, B2, C1, C2, D1, and D2. The measurement allowance for color coordinates is ±0.01.

4. Performance Curve Analysis

The datasheet includes several typical characteristic curves that illustrate how the LED behaves under varying conditions. These are essential for advanced design considerations.

4.1 Forward Voltage vs. Forward Current (I-V Curve)

This curve shows the non-linear relationship between the voltage across the LED and the current flowing through it. It demonstrates the turn-on voltage and how V_F increases with I_F.

4.2 Forward Current vs. Relative Luminous Intensity

This graph illustrates the dependency of light output on drive current. Generally, luminous intensity increases with current but may saturate or degrade at very high currents due to efficiency droop and heating.

4.3 Ambient Temperature vs. Relative Luminous Intensity

This curve is critical for understanding thermal performance. It shows how the light output decreases as the ambient temperature rises, a characteristic of semiconductor-based light sources.

4.4 Directivity Pattern

The directivity diagram (or radiation pattern) visually represents the spatial distribution of light intensity around the LED, correlating with the 50-degree viewing angle specification.

4.5 Spectrum and Chromaticity vs. Current

The spectral distribution curve shows the relative power emitted at different wavelengths, defining the color quality of the white light. The relationship between forward current and chromaticity coordinates indicates any color shift that may occur when driving the LED at currents other than the test condition.

5. Mechanical & Package Information

The device uses a standard radial leaded package with a T-1 3/4 (approximately 5mm) lens diameter.

• Dimensions: All primary dimensions are provided in millimeters with a general tolerance of ±0.25mm unless otherwise specified.
• Lead Spacing: Measured where the leads emerge from the package body, which is a critical parameter for PCB footprint design.
• Polarity Identification: Typically, the longer lead denotes the anode (positive), and a flat spot on the lens flange may also indicate the cathode side. The specific marking should be verified from the package drawing.
• Resin Protrusion: A maximum of 1.0mm of resin may protrude under the flange.

6. Soldering & Assembly Guidelines

Proper handling is essential to prevent damage and ensure long-term reliability.

6.1 Lead Forming

Bending of leads must be performed at a point at least 3mm from the base of the LED lens. The base of the leadframe should not be used as a fulcrum. Forming must be done at room temperature, before the soldering process.

6.2 Soldering Process

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. External stress should not be applied to the leads while the LED is hot.

• Hand Soldering (Iron): Maximum temperature 350°C for a maximum of 3 seconds (one time only).
• Wave Soldering: Pre-heat to a maximum of 100°C for up to 60 seconds. Solder wave temperature should not exceed 260°C for a maximum of 5 seconds.
• IR Reflow: This process is explicitly stated as not suitable for this through-hole type LED lamp.

6.3 Storage & Cleaning

For storage, the ambient should not exceed 30°C and 70% relative humidity. LEDs removed from their original packaging should be used within three months. For longer storage, a sealed container with desiccant or a nitrogen ambient is recommended. Isopropyl alcohol or similar alcohol-based solvents are suitable for cleaning if necessary.

7. Packaging & Ordering Information

The standard packaging configuration is as follows:

• 500 pieces per anti-static packing bag.
• 10 packing bags per inner carton (total 5,000 pieces).
• 8 inner cartons per master outer carton (total 40,000 pieces).

The part number LTW-2L3DV5S follows a specific coding convention where elements likely indicate Lens Type (Water Clear), Color (White), package (T-1 3/4), and performance bin (V5 related to intensity/hue).

8. Application Design Recommendations

8.1 Drive Circuit Design

An LED is a current-operated device. To ensure uniform brightness and prevent current hogging, especially when multiple LEDs are connected in parallel, it is strongly recommended to use a dedicated current-limiting resistor in series with each LED. Driving LEDs in parallel without individual resistors (as shown in a non-recommended circuit) can lead to significant brightness differences due to natural variations in the forward voltage (V_F) of individual devices.

8.2 Thermal Management

While the through-hole design aids in heat dissipation via the leads, the maximum power dissipation of 120mW and the negative temperature coefficient of light output should be considered. Operating at high ambient temperatures or at high drive currents will reduce light output and may affect long-term reliability. Adequate spacing and possibly ventilation should be considered in the application design.

8.3 Optical Design

The 50-degree viewing angle provides a reasonably wide beam. For applications requiring focusing or diffusion, secondary optics (lenses, light guides) can be used. The water-clear lens is suitable for such applications.

9. Technical Comparison & Considerations

Compared to older technology like incandescent bulbs, this LED offers vastly superior efficiency, longer lifetime, and lower heat generation. Within the LED domain, this through-hole device offers simplicity and robustness for manual or wave-soldered assemblies, contrasting with surface-mount device (SMD) LEDs which require reflow soldering and offer a lower profile. The T-1 3/4 size is a de-facto standard, ensuring wide availability of compatible sockets, holders, and panel cutouts.

10. Frequently Asked Questions (FAQ)

10.1 What resistor value should I use?

The resistor value (R) is calculated using Ohm's Law: R = (V_supply - V_F) / I_F. Use the typical V_F (3.3V) for estimation, but consider the max V_F (3.7V) to ensure the current does not drop below the minimum required intensity at the end of the supply voltage tolerance. For a 5V supply and a target I_F of 20mA: R = (5V - 3.3V) / 0.020A = 85 Ohms. A standard 82 or 100 Ohm resistor would be appropriate, with power rating P = I²R.

10.2 Can I drive it directly from a microcontroller pin?

It is not recommended to drive the LED directly from a microcontroller GPIO pin. Most GPIO pins have limited current sourcing/sinking capability (often 20-25mA absolute max, with less recommended for continuous operation). Using a pin at its limit can stress the microcontroller. It is better practice to use the GPIO to control a transistor (BJT or MOSFET) which then drives the LED with its own current-limiting resistor.

10.3 Why does the light output decrease with temperature?

This is a fundamental characteristic of semiconductor LEDs. As temperature increases, non-radiative recombination processes within the semiconductor become more dominant, reducing the internal quantum efficiency (the number of photons generated per electron). This results in lower luminous output for the same drive current.

11. Practical Design Case Study

Scenario: Designing a mains-powered (120V AC) indicator light for an appliance using a bridge rectifier and capacitor for basic DC conversion, yielding approximately 150V DC.

Design Challenge: The high voltage and the need for electrical isolation and current limiting.

Solution: A series resistor is mandatory. The value would be very high: R ≈ (150V - 3.3V) / 0.020A ≈ 7335 Ohms (7.3 kΩ). The power dissipation in the resistor would be P = I²R = (0.02)² * 7335 ≈ 2.93W, requiring a large, high-power resistor which is inefficient. A better solution is to use a capacitive dropper circuit or a dedicated, efficient LED driver IC designed for high-voltage input, which improves efficiency and safety. This case highlights that while the LED itself is simple, the drive circuit must be carefully designed for the application environment.

12. Technology Principle Introduction

This white LED is based on an InGaN semiconductor chip that emits light in the blue region of the spectrum. To produce white light, the blue light is partially converted to longer wavelengths (yellow, red) using a phosphor coating (typically YAG:Ce - Yttrium Aluminum Garnet doped with Cerium) applied over the chip. The mixture of the remaining blue light and the down-converted yellow/red light is perceived by the human eye as white. This method is known as phosphor-converted white light. The specific blend of phosphors determines the Correlated Color Temperature (CCT) and Color Rendering Index (CRI) of the white light, which are related to the chromaticity coordinates specified in the datasheet.

13. Industry Trends & Context

The optoelectronics industry has seen a continuous trend towards higher efficiency (more lumens per watt), improved color rendering, and lower cost. While surface-mount technology (SMT) dominates volume production for space-constrained applications like displays and lighting modules, through-hole LEDs like this one remain relevant for applications requiring robustness, easier manual assembly, servicing, or for use in sockets. There is also a trend towards tighter binning for color and flux to ensure consistency in applications using multiple LEDs. The RoHS compliance stated is now a global standard, driven by environmental regulations. Future developments may include higher efficacy chips and more advanced phosphor systems for better light quality, even in standard package formats.