LTL2W3TGPCK LED Lamp Datasheet - T-1 3/4 Package - 3.2V - 20mA - 519nm Green - English Technical Document

1. Product Overview

The LTL2W3TGPCK is a through-hole mounted LED lamp designed for status indication and general illumination in a wide range of electronic applications. It features a T-1 3/4 (approximately 5mm) diameter package with a water-clear lens, producing a green light output. Its primary advantages include low power consumption, high efficiency, and compatibility with standard PCB mounting processes, making it a versatile component for designers.

1.1 Core Features

• Lead (Pb)-free and RoHS compliant construction.
• High luminous efficiency for low current operation.
• Designed for versatile mounting on printed circuit boards or panels.
• Low current requirement, making it compatible with integrated circuit (IC) drive.
• Utilizes InGaN (Indium Gallium Nitride) technology for the green emitter.

1.2 Target Applications

This LED is suitable for various sectors requiring reliable and efficient indicator lights, including computer systems, communication equipment, consumer electronics, home appliances, and industrial control panels.

2. Technical Parameters: In-Depth Objective Interpretation

2.1 Absolute Maximum Ratings

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

• Power Dissipation: 72 mW maximum. This is the total power the LED package can dissipate as heat.
• DC Forward Current (I_F): 20 mA continuous. This is the standard operating current.
• Peak Forward Current: 60 mA, but only under pulsed conditions (duty cycle ≤ 1/10, pulse width ≤ 10ms).
• Derating: The maximum forward current must be linearly reduced by 0.3 mA for every degree Celsius above 30°C ambient temperature to prevent overheating.
• Operating Temperature: -30°C to +85°C. The device is functional within this range.
• Storage Temperature: -40°C to +100°C.
• Lead Soldering Temperature: 260°C for a maximum of 5 seconds, measured 2.0mm from the LED body.

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 20 mA.

• Luminous Intensity (I_V): 700 mcd (min), 1150 mcd (typ), 1900 mcd (max). Measured with a sensor/filter approximating the CIE photopic eye response. A ±15% testing tolerance is applied to guaranteed values.
• Viewing Angle (2θ_1/2): 120 degrees (typical). This is the full angle at which luminous intensity drops to half its axial (on-axis) value.
• Peak Emission Wavelength (λ_P): 519 nm (typical). The wavelength at which the spectral output is strongest.
• Dominant Wavelength (λ_d): Ranges from 512 nm to 535 nm. This is the single wavelength perceived by the human eye, derived from the CIE chromaticity diagram.
• Spectral Line Half-Width (Δλ): 35 nm (typical). The width of the emission spectrum at half its maximum intensity.
• Forward Voltage (V_F): 2.6V (min), 3.2V (typ), 3.8V (max) at 20mA. This is the voltage drop across the LED when operating.
• Reverse Current (I_R): 10 μA maximum at a reverse voltage (V_R) of 5V. Important: This device is not designed for reverse-bias operation; this parameter is for test purposes only.

3. Bin Table Specification

The product is sorted into bins based on key optical parameters to ensure consistency within a production batch. This allows designers to select LEDs with closely matched performance.

3.1 Luminous Intensity Binning

Binning is performed at I_F = 20 mA. Tolerance for each bin limit is ±15%.

• Bin N: 700 mcd (Min) to 880 mcd (Max)
• Bin P: 880 mcd to 1150 mcd
• Bin Q: 1150 mcd to 1500 mcd
• Bin R: 1500 mcd to 1900 mcd

3.2 Dominant Wavelength Binning

Binning is performed at I_F = 20 mA. Tolerance for each bin limit is ±1 nm.

• Bin G08: 512.0 nm to 516.0 nm
• Bin G09: 516.0 nm to 520.0 nm
• Bin G10: 520.0 nm to 527.0 nm
• Bin G11: 527.0 nm to 535.0 nm

4. Performance Curve Analysis

While specific graphical curves are referenced in the datasheet, the following typical behaviors can be inferred from the provided specifications:

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

The LED exhibits a non-linear I-V characteristic typical of a diode. The forward voltage (V_F) increases with current but has a specified range (2.6V to 3.8V) at the standard 20mA operating point. Driving the LED with a constant current source, as recommended, ensures stable luminous output regardless of minor V_F variations between individual units.

4.2 Luminous Intensity vs. Forward Current

The light output (luminous intensity) is approximately proportional to the forward current over its normal operating range. Exceeding the absolute maximum ratings, especially the DC forward current, can lead to accelerated degradation of the LED chip and epoxy lens due to excessive heat and current density.

4.3 Temperature Dependence

The luminous intensity of LEDs generally decreases as the junction temperature increases. The derating specification (0.3 mA/°C above 30°C) is a critical design rule to manage this thermal effect and maintain long-term reliability. Proper PCB layout for heat dissipation is essential for high-current or high-ambient-temperature applications.

5. Mechanical & Packaging Information

5.1 Outline Dimensions

The device conforms to the standard T-1 3/4 through-hole LED package profile. Key dimensional notes include:

• All dimensions are in millimeters (inches provided as reference).
• General tolerance is ±0.25mm unless otherwise specified.
• The maximum protrusion of resin under the flange is 1.0mm.
• Lead spacing is measured where the leads exit the package body.

5.2 Polarity Identification

For through-hole LEDs, the cathode is typically identified by a flat spot on the lens rim or by the shorter lead. Always refer to the device marking or package documentation to confirm polarity before installation to prevent reverse connection.

6. Soldering & Assembly Guidelines

6.1 Storage Conditions

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

6.2 Cleaning

If cleaning is necessary, use alcohol-based solvents like isopropyl alcohol. Avoid harsh chemicals that may damage the epoxy lens.

6.3 Lead Forming

Bend leads at a point at least 3mm from the base of the LED lens. Do not use the package body as a fulcrum. Perform all bending at room temperature and before the soldering process. Apply minimal force during PCB insertion to avoid mechanical stress on the leads or epoxy seal.

6.4 Soldering Process

Critical Rule: Maintain a minimum distance of 2mm from the base of the lens to the solder point. Never immerse the lens in solder.

• Soldering Iron: Maximum temperature 350°C. Maximum soldering 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.
• Important: Infrared (IR) reflow soldering is NOT suitable for this through-hole type LED product. Excessive heat or time will damage the device.

7. Packaging & Ordering Information

7.1 Packaging Specification

The LEDs are packed in anti-static bags.

• Basic Unit: 500, 200, or 100 pieces per packing bag.
• Inner Carton: Contains 10 packing bags, totaling 5,000 pieces.
• Outer Carton (Shipping Lot): Contains 8 inner cartons, totaling 40,000 pieces. The final pack in a lot may contain a non-full quantity.

8. Application Suggestions

8.1 Typical Application Circuits

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

Circuit A (Recommended): [Vcc] — [Resistor] — [LED] — [GND]. Each LED has its own dedicated resistor. This compensates for the natural variation in forward voltage (V_F) between individual LEDs, ensuring each receives the correct current and emits light uniformly.

Circuit B (Not Recommended for Parallel): Connecting multiple LEDs directly in parallel to a single current-limiting resistor is discouraged. Small differences in the I-V characteristics of each LED can cause significant current imbalance, leading to uneven brightness and potential over-current failure of the LED with the lowest V_F.

8.2 Electrostatic Discharge (ESD) Protection

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

• 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.
• Implement an ESD control program with training and regular certification for personnel.

8.3 Design Considerations

• Heat Management: Adhere to the power dissipation and derating specifications. Provide adequate copper area on the PCB for the LED leads to act as a heat sink.
• Current Drive: Always use a constant current driver or a voltage source with a series resistor. Never connect the LED directly to a voltage source without current limiting.
• Optical Design: The 120-degree viewing angle provides a wide beam, suitable for status indicators that need to be visible from various angles.

9. Technical Comparison & Differentiation

Compared to older technologies like incandescent bulbs or wider-angle diffused LEDs, the LTL2W3TGPCK offers distinct advantages:

• Efficiency & Longevity: Solid-state InGaN technology provides significantly higher luminous efficacy and operational lifetime (typically tens of thousands of hours) compared to filament-based indicators.
• Robustness: More resistant to shock and vibration than glass-based bulbs.
• Color Purity: The narrow spectral half-width (35nm) and specific dominant wavelength bins allow for consistent, saturated green color output, which is critical for color-coded indicators.
• Standardization: The T-1 3/4 package is an industry-standard form factor, allowing for easy replacement and compatibility with existing PCB footprints and panel cutouts.

10. Frequently Asked Questions (Based on Technical Parameters)

10.1 Can I drive this LED at 30mA for more brightness?

No. The Absolute Maximum Rating for DC forward current is 20mA. Operating continuously at 30mA exceeds this rating, which will generate excessive heat, accelerate lumen depreciation, and likely cause premature failure. For higher brightness, select an LED bin with higher luminous intensity (e.g., Bin Q or R) or consider a different LED model rated for higher current.

10.2 Why is a series resistor necessary even if my power supply is 3.2V (the typical V_F)?

The forward voltage has a range (2.6V to 3.8V). If you apply exactly 3.2V to an LED with a V_F of 2.6V, the current will be much higher than 20mA, potentially damaging it. The resistor acts as a simple, reliable current regulator, setting the current based on the supply voltage and the actual V_F of the specific LED. It also protects against supply voltage variations.

10.3 What does the "Water Clear" lens mean for the light output?

A water-clear (non-diffused) lens produces a more focused beam pattern compared to a milky or diffused lens. The light appears to come from a distinct point source. This, combined with the 120-degree viewing angle, results in a bright central hotspot that is visible over a wide area, making it excellent for direct-view status indicators.

11. Practical Use Case Example

Scenario: Designing a control panel with 10 green "System Active" status indicators.

1. Component Selection: Choose LTL2W3TGPCK LEDs from Bin P for consistent medium-high brightness (880-1150 mcd).
2. Circuit Design: Use a 5V rail. Calculate the series resistor: R = (V_supply - V_F) / I_F. Using typical V_F=3.2V and I_F=20mA, R = (5V - 3.2V) / 0.02A = 90 Ohms. Use a standard 91 Ohm, 1/4W resistor for each of the 10 LEDs.
3. PCB Layout: Place the LEDs on 0.1" (2.54mm) grid spacing. Include a small copper pour connected to the cathode lead for minor heat dissipation.
4. Assembly: Follow the lead forming and soldering guidelines precisely, ensuring the 2mm clearance from the lens base is maintained.
5. Result: Ten uniformly bright, reliable green indicators with a long operational life.

12. Operating Principle Introduction

The LTL2W3TGPCK is a semiconductor light source. Its core is a chip made of InGaN (Indium Gallium Nitride) materials. When a forward voltage is applied, electrons and holes recombine within the semiconductor's active region, releasing energy in the form of photons (light). The specific composition of the InGaN layers determines the wavelength of the emitted light, in this case, green (~519 nm peak). The epoxy lens serves to protect the semiconductor chip, shape the light output beam, and enhance light extraction from the chip.

13. Technology Trends

While through-hole LEDs remain vital for many applications, the broader optoelectronics industry shows clear trends. Surface-mount device (SMD) LEDs are increasingly dominant due to their smaller size, suitability for automated pick-and-place assembly, and often better thermal performance. Furthermore, advancements in phosphor-converted and direct-emission technologies continue to push the boundaries of efficiency (lumens per watt), color rendering, and maximum allowable drive currents for both through-hole and SMD packages. The fundamental reliability and cost-effectiveness of through-hole packages like the T-1 3/4 ensure their continued use in applications where manual assembly, high-reliability solder joints, or easy field replacement are priorities.