LTW2P3D12J LED Lamp Datasheet - T-1 3/4 Package - 3.0V - 165mW - White - English Technical Document

1. Product Overview

This document details the specifications for a high-brightness white LED lamp designed for through-hole mounting. The device is engineered for robust outdoor applications, featuring a clear lens and a package size conforming to the popular T-1 3/4 standard. Its primary design goals are high luminous efficiency, reliability in harsh environments, and low power consumption, making it suitable for electronic signage and indicator applications.

1.1 Key Features and Target Market

The LED offers several advantages for designers. It is a lead-free product compliant with RoHS directives. It provides high luminous output with relatively low current requirements, ensuring compatibility with integrated circuits. The package is versatile for mounting on printed circuit boards or panels. The primary target markets include message display signs (such as those on buses or public information boards), outdoor advertising applications, and traffic signal systems where clear, bright white light is required.

2. Technical Parameters: In-Depth Objective Interpretation

2.1 Absolute Maximum Ratings

The device's operational limits are defined at an ambient temperature (TA) of 25°C. The maximum continuous power dissipation is 165 mW. The absolute maximum DC forward current is 50 mA, with a higher peak forward current of 100 mA permissible under pulsed conditions (duty cycle ≤ 1/10, pulse width ≤ 10ms). The operating temperature range is specified from -40°C to +85°C, and the storage range extends from -40°C to +100°C. For soldering, the leads can withstand 260°C for a maximum of 5 seconds when measured 2.0mm from the LED body. A derating factor of 0.77 mA/°C applies linearly from 30°C upwards, meaning the permissible continuous current decreases as temperature increases to stay within the power dissipation limit.

2.2 Electrical and Optical Characteristics

The core performance is measured at TA=25°C and a forward current (IF) of 20 mA. The luminous intensity (Iv) has a typical value of 16000 millicandelas (mcd), with a minimum of 12000 mcd and a maximum of 27000 mcd. It is crucial to note that the Iv guarantee includes a ±15% testing tolerance. The viewing angle (2θ1/2), defined as the full angle at which intensity drops to half its axial value, is typically 25 degrees. The forward voltage (VF) typically measures 3.0V, ranging from 2.6V to 3.3V. The reverse current (IR) is a maximum of 10 μA at a reverse voltage (VR) of 5V, though the device is explicitly not designed for reverse operation. The chromaticity coordinates (x, y) on the CIE 1931 diagram are approximately (0.32, 0.33).

3. Binning System Explanation

The product is classified according to performance bins to ensure consistency in applications.

3.1 Luminous Flux Binning

LEDs are sorted into bins based on their luminous intensity measured at 20mA. The bin codes and their ranges are: Bin Z (12,000 - 16,000 mcd), Bin 1 (16,000 - 21,000 mcd), and Bin 2 (21,000 - 27,000 mcd). A tolerance of ±15% applies to each bin limit.

3.2 Hue (Chromaticity) Binning

The white color point is also binned. The datasheet provides a table of hue ranks (e.g., 5U, 5L, 6U, 6L, 7U, 7L), each defined by a set of four chromaticity coordinate pairs (x, y) that form a quadrilateral on the CIE diagram. LEDs are sorted into these predefined color regions. The measurement allowance for color coordinates is ±0.01.

4. Performance Curve Analysis

While specific graphical data is referenced in the PDF, typical curves for such a device would illustrate key relationships. The Forward Current vs. Forward Voltage (I-V) curve shows the exponential relationship, critical for designing current-limiting circuits. The Relative Luminous Intensity vs. Forward Current curve demonstrates how light output increases with current, typically in a near-linear fashion before efficiency drops at higher currents. The Relative Luminous Intensity vs. Ambient Temperature curve would show the expected decrease in light output as the junction temperature rises, which is a crucial consideration for thermal management in high-power or high-temperature applications.

5. Mechanical and Packaging Information

5.1 Outline Dimensions

The LED conforms to a standard T-1 3/4 (approximately 5mm) diameter package. Key dimensional notes include: all dimensions are in millimeters, with a general tolerance of ±0.25mm unless specified otherwise; the maximum protrusion of resin under the flange is 1.0mm; and lead spacing is measured where the leads emerge from the package body. A detailed dimensional drawing would specify the exact body diameter, lens shape, lead length, and lead diameter.

5.2 Polarity Identification

For through-hole LEDs, polarity is typically indicated by lead length (the longer lead is the anode) and/or by a flat spot or notch on the lens flange near the cathode lead. The datasheet's outline drawing should clearly indicate the anode and cathode.

6. Soldering and Assembly Guidelines

Proper handling is essential for reliability.

6.1 Lead Forming

If leads need to be bent, this must be done before soldering and at normal room temperature. The bend should be at least 3mm away from the base of the LED lens. The base of the lead frame must not be used as a fulcrum during bending to avoid stress on the internal die attach.

6.2 Soldering Process

A minimum clearance of 2mm must be maintained between the base of the lens and the solder point. Dipping the lens into solder must be avoided. Two soldering methods are specified:

• 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 be no lower than 2mm from the base of the epoxy lens.

Important Note: Infrared (IR) reflow soldering is explicitly stated as unsuitable for this through-hole LED product. Excessive temperature or time can deform the lens or cause catastrophic failure.

6.3 Storage and Cleaning

For storage, the ambient should not exceed 30°C or 70% relative humidity. LEDs removed from their original packaging should be used within three months. For longer 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.

7. Packaging and Ordering Information

The standard packing specification is as follows: 500, 200, or 100 pieces per anti-static packing bag. Ten of these bags are placed into an inner carton, totaling 5,000 pieces. Eight inner cartons are then packed into an outer shipping carton, resulting in a total of 40,000 pieces per outer carton. The datasheet notes that in every shipping lot, only the final pack may contain a non-full quantity. The luminous intensity bin code is marked on each individual packing bag for identification.

8. Application Recommendations

8.1 Typical Application Circuits

An LED is a current-operated device. To ensure uniform brightness when multiple LEDs are connected in parallel, it is strongly recommended to use a current-limiting resistor in series with each LED (Circuit A). Connecting LEDs directly in parallel without individual resistors (Circuit B) is discouraged because slight variations in the forward voltage (Vf) characteristic of each LED will cause significant differences in the current flowing through each one, leading to uneven brightness.

8.2 Electrostatic Discharge (ESD) Protection

The LED can be damaged by electrostatic discharge or power surges. Standard ESD prevention practices must be observed during handling and assembly. This includes the use of grounded workstations, wrist straps, and conductive containers.

8.3 Design Considerations

When designing the PCB layout, use the minimum possible clinch force during insertion to avoid mechanical stress. Consider the thermal environment, as the light output will decrease with rising ambient/junction temperature (refer to derating curve). For outdoor applications, ensure the drive circuit is protected from voltage transients. The device's epoxy formulation offers moisture resistance and UV protection, but the overall system design should also consider environmental sealing if necessary.

9. Technical Comparison and Differentiation

Compared to generic through-hole LEDs, this product emphasizes features for demanding environments. The use of advanced epoxy technology for enhanced moisture resistance and UV protection is a key differentiator for long-term outdoor reliability. The specified wide operating temperature range (-40°C to +85°C) exceeds that of many standard indoor LEDs. The clear lens and specific radiation pattern are tailored for signage applications requiring a smooth, wide beam suitable for message readability.

10. Frequently Asked Questions (Based on Technical Parameters)

Q: What resistor value should I use for a 12V supply?

A: Using Ohm's Law: R = (Vsupply - Vf_LED) / If. For a typical Vf of 3.0V at 20mA: R = (12V - 3.0V) / 0.020A = 450 Ohms. A standard 470 Ohm resistor would be suitable, resulting in a slightly lower current (~19mA). Always calculate power rating for the resistor as well: P = I^2 * R.

Q: Can I drive this LED with a constant voltage source?

A: It is not recommended. The LED's forward voltage has a range (2.6V-3.3V). A constant voltage set within this range could cause excessive current in some LEDs (those with low Vf) and insufficient current in others (those with high Vf). Always use a current-limiting mechanism, simplest being a series resistor with a voltage source, or a dedicated constant-current driver.

Q: Why is the viewing angle important for my sign?

A: The viewing angle (25° typical) defines the cone of light within which the LED appears bright. A narrower angle produces a more focused beam, which might be good for long-distance viewing but could create hotspots on a sign. A wider, smoother pattern is generally better for evenly illuminating a message board viewed from various angles.

11. Practical Application Case Study

Scenario: Designing a Bus Destination Sign. A designer needs bright, reliable white LEDs to backlight an LCD or segmented display that shows route numbers and destinations. The LTW2P3D12J is a candidate. The designer would:

1. Determine the required luminous intensity per LED based on display size, diffuser properties, and daytime visibility needs, selecting the appropriate flux bin (e.g., Bin 2 for highest brightness).

2. Design a series-parallel array, ensuring each LED has its own current-limiting resistor connected to a stable DC power supply (e.g., the vehicle's 12V/24V system with appropriate regulation and transient protection).

3. Design the PCB with correct hole spacing and ensure the LED lens height fits within the sign's mechanical enclosure.

4. Specify wave soldering during PCB assembly, adhering strictly to the 2mm clearance and temperature/time limits to prevent damage.

5. Plan for potential dimming at night by using a PWM (Pulse Width Modulation) signal to control the LED driver, reducing power consumption and glare.

12. Operating Principle Introduction

A light-emitting diode (LED) is a semiconductor p-n junction device. When a forward voltage is applied, electrons from the n-type region and holes from the p-type region are injected into the junction region. When these charge carriers recombine, energy is released in the form of photons (light). The color of the light is determined by the energy bandgap of the semiconductor material. This white LED likely uses a blue-emitting indium gallium nitride (InGaN) chip combined with a phosphor coating. The blue light from the chip excites the phosphor, which then emits yellow light. The combination of blue and yellow light is perceived by the human eye as white light. The clear epoxy lens serves to protect the semiconductor die and wire bonds, and also shapes the radiation pattern of the emitted light.

13. Technology Trends

The through-hole LED market, while mature, continues to see incremental improvements. Trends include:

Increased Efficiency: Ongoing development in semiconductor epitaxy and phosphor technology yields higher lumens per watt (lm/W), allowing for either brighter displays or lower power consumption.

Enhanced Reliability: Improvements in epoxy and silicone encapsulant materials provide better resistance to thermal cycling, humidity, and UV radiation, extending operational lifetime in outdoor settings.

Color Consistency: Tighter binning specifications and advanced manufacturing controls lead to better color uniformity across large arrays of LEDs, which is critical for high-quality signage.

Integration: While this is a discrete component, there is a parallel trend towards integrated LED modules or light engines that combine multiple LEDs, drivers, and optics into a single unit for easier assembly. However, discrete through-hole LEDs remain popular for their design flexibility, low cost, and ease of repair.