SMD LED LTW-482DS5 Datasheet - White InGaN, Yellow Lens - Electrical & Optical Specifications

1. Product Overview

The LTW-482DS5 is a surface-mount device (SMD) LED lamp designed for automated printed circuit board (PCB) assembly. It is part of a family of components engineered for applications where space is a critical constraint. The device combines an ultra-bright white InGaN (Indium Gallium Nitride) semiconductor chip with a yellow-tinted lens, resulting in a specific color output. This LED is constructed to be compatible with standard infrared (IR) reflow soldering processes commonly used in high-volume electronics manufacturing.

The core advantage of this component lies in its miniaturized form factor and its suitability for automated pick-and-place equipment, which streamlines production. It is classified as an EIA (Electronic Industries Alliance) standard package, ensuring broad compatibility with industry assembly lines. The device is also specified as I.C. (Integrated Circuit) compatible, indicating it can be driven directly by typical logic-level voltages from microcontrollers or other digital circuits without requiring complex intermediary driver stages in many cases.

The target market for this LED encompasses a wide range of consumer and industrial electronics. Primary applications include status indication, backlighting for keypads and keyboards, and integration into microdisplays. It is also found in telecommunications equipment, office automation devices, various home appliances, and indoor signage or symbol illumination where a compact, reliable light source is required.

2. Technical Specifications Deep Dive

2.1 Absolute Maximum Ratings

The absolute maximum ratings define the limits beyond which permanent damage to the LED may occur. These values are specified at an ambient temperature (Ta) of 25°C. The maximum continuous DC forward current (IF) is 20 mA. A higher peak forward current of 100 mA is permissible, but only under pulsed conditions with a strict 1/10 duty cycle and a pulse width not exceeding 0.1 milliseconds. The maximum power dissipation is 72 milliwatts (mW). The device is rated for operation within a temperature range of -20°C to +80°C and can be stored in environments from -40°C to +85°C. A critical rating for assembly is the infrared soldering condition, which must not exceed 260°C for a duration of 10 seconds during reflow.

2.2 Electrical and Optical Characteristics

The typical operating characteristics are measured at Ta=25°C and a forward current (IF) of 5 mA, which is a common test condition. The forward voltage (VF) ranges from a minimum of 2.55 volts to a maximum of 3.15 volts, with a typical value implied within this band. The luminous intensity (Iv), a measure of perceived brightness, has a wide range from 71.0 millicandelas (mcd) to 280.0 mcd. This variation is managed through a binning system. The viewing angle (2θ1/2), defined as the angle where luminous intensity drops to half of its on-axis value, is 130 degrees, indicating a very wide beam pattern. The chromaticity coordinates, which define the color point in the CIE 1931 color space, are specified as x=0.304 and y=0.301 under test conditions. The reverse current (IR) is guaranteed to be less than 10 microamperes at a reverse voltage (VR) of 5V, though the device is not designed for reverse operation.

3. Binning System Explanation

To ensure consistency in mass production, LEDs are sorted into performance bins. The LTW-482DS5 uses a three-dimensional binning system for Forward Voltage (VF), Luminous Intensity (Iv), and Hue (color point).

3.1 Forward Voltage (VF) Binning

The VF is binned in 0.1V steps from V1 (2.55V - 2.65V) to V6 (3.05V - 3.15V). A tolerance of ±0.1V is applied to each bin. This allows designers to select LEDs with tighter voltage ranges for applications requiring uniform brightness when driven by a constant voltage source or to better match current-limiting resistor calculations.

3.2 Luminous Intensity (Iv) Binning

The luminous intensity is binned into three primary codes: Q (71.0 - 112.0 mcd), R (112.0 - 180.0 mcd), and S (180.0 - 280.0 mcd). A tolerance of ±15% is applied to each bin range. This binning is crucial for applications where consistent perceived brightness is important across multiple LEDs, such as in backlighting arrays or status indicator clusters.

3.3 Hue (Color) Binning

The chromaticity coordinates (x, y) are binned into six regions labeled S1 through S6. Each bin defines a quadrilateral area on the CIE 1931 chromaticity diagram. The bins are arranged to group LEDs with similar white color temperatures and tints. A tolerance of ±0.01 is applied to each coordinate within its bin. This ensures color uniformity when multiple LEDs are used side-by-side. The provided diagram visually maps these S1-S6 regions on the chromaticity chart.

4. Performance Curve Analysis

The datasheet references typical performance curves which graphically represent the relationship between key parameters. While the specific graphs are not detailed in the provided text, standard curves for such an LED would typically include:

• Forward Current vs. Forward Voltage (I-V Curve): This non-linear curve shows how voltage increases with current. It is essential for designing the driving circuit, especially when using a constant-voltage supply with a series resistor.
• Luminous Intensity vs. Forward Current: This curve shows how light output increases with drive current. It is typically linear over a range but will saturate at higher currents.
• Luminous Intensity vs. Ambient Temperature: This curve demonstrates the thermal derating of light output. As the junction temperature of the LED increases, its luminous efficacy decreases. Understanding this is critical for thermal management in the application.
• Relative Spectral Power Distribution: For a white LED, this graph shows the intensity of light emitted at each wavelength. A white LED like the InGaN type typically has a blue emission peak from the chip itself, combined with a broader yellow emission from the phosphor coating, resulting in the perceived white light.

5. Mechanical and Packaging Information

5.1 Package Dimensions

The LED conforms to a standard SMD package outline. All critical dimensions such as length, width, height, and lead spacing are provided in millimeters with a standard tolerance of ±0.1 mm unless otherwise noted. The lens color is yellow, and the source (chip) color is white. Detailed dimensioned drawings are included in the datasheet for PCB footprint design.

5.2 Polarity Identification and Pad Design

The component includes markings or structural features (like a chamfered corner or a dot) to indicate the cathode (negative) lead. A recommended PCB land pattern (attachment pad) layout is provided to ensure proper solder joint formation, reliable electrical connection, and optimal mechanical stability during and after the reflow process. The soldering direction relative to the package orientation may also be specified to prevent tombstoning (where one end lifts off the pad).

6. Soldering and Assembly Guidelines

6.1 IR Reflow Soldering Profile

A suggested reflow profile is provided for lead-free (Pb-free) solder processes. Key parameters include a pre-heat stage, a defined time above liquidus, a peak temperature not exceeding 260°C, and a time at that peak temperature limited to a maximum of 10 seconds. The profile is designed to minimize thermal stress on the LED package while ensuring a reliable solder joint. It is emphasized that the optimal profile may vary based on the specific PCB design, solder paste, and oven characteristics.

6.2 Storage and Handling

The LEDs are moisture-sensitive devices (MSL 3). When sealed in their original moisture-proof bag with desiccant, they have a shelf life of one year when stored at ≤30°C and ≤90% relative humidity (RH). Once the bag is opened, the components should be stored at ≤30°C and ≤60% RH. It is recommended to complete the IR reflow process within one week of opening. For storage beyond one week outside the original packaging, baking at approximately 60°C for at least 20 hours is required before soldering to remove absorbed moisture and prevent \"popcorning\" damage during reflow.

6.3 Cleaning

If cleaning after soldering is necessary, only specified solvents should be used. Immersing the LED in ethyl alcohol or isopropyl alcohol at room temperature for less than one minute is recommended. Unspecified chemical cleaners may damage the plastic lens or package material.

6.4 ESD (Electrostatic Discharge) Precautions

The LED is susceptible to damage from static electricity and voltage surges. Proper ESD controls must be implemented during handling and assembly. This includes the use of grounded wrist straps, anti-static gloves, and ensuring all equipment and work surfaces are properly grounded.

7. Packaging and Ordering Information

The LTW-482DS5 is supplied packaged for automated assembly. The components are placed in embossed carrier tape that is 8 mm wide. This tape is wound onto standard 7-inch (approximately 178 mm) diameter reels. Each full reel contains 3000 pieces. For quantities less than a full reel, a minimum packing quantity of 500 pieces is available for remainder stock. The tape and reel packaging conforms to ANSI/EIA-481 specifications. The tape has a cover seal to protect components, and there is a limit on the maximum number of consecutive missing components in the tape.

8. Application Notes and Design Considerations

8.1 Driving the LED

An LED is a current-driven device. The most common and stable method of operation is to use a constant current source. If using a constant voltage source (like a microcontroller GPIO pin or a regulated power rail), a current-limiting resistor must be placed in series with the LED. The resistor value (R) can be calculated using Ohm's Law: R = (V_supply - VF_LED) / I_desired. For example, to drive the LED at its typical test current of 5mA from a 5V supply, assuming a VF of 2.8V: R = (5V - 2.8V) / 0.005A = 440 Ohms. A standard 470 Ohm resistor would be a suitable choice. The power rating of the resistor should also be checked: P = I²R = (0.005)² * 470 = 0.01175W, so a standard 1/8W (0.125W) resistor is more than adequate.

8.2 Thermal Management

While the power dissipation is low (72 mW max), effective thermal management is still important for longevity and maintaining light output. The LED's performance degrades with increasing junction temperature. The PCB itself acts as a heat sink. Ensuring adequate copper area connected to the thermal pad or leads of the LED, and providing ventilation if enclosed, helps dissipate heat. Avoid operating the LED at its absolute maximum current and temperature simultaneously for extended periods.

8.3 Optical Design

The 130-degree viewing angle produces a very wide, diffuse beam. This is ideal for area illumination or status indicators that need to be visible from a wide range of angles. For applications requiring a more focused beam, secondary optics (like lenses or light pipes) would need to be added externally. The yellow lens will filter the emitted white light, shifting the final output color towards warmer tones.

9. Technical Comparison and Differentiation

The LTW-482DS5 differentiates itself through its specific combination of a white InGaN chip and a yellow lens. Compared to a standard white LED with a clear lens, this product offers a distinct, warmer color output which may be desirable for specific aesthetic or functional requirements (e.g., mimicking incandescent indicator lights). Its wide viewing angle is a key feature versus narrower-angle LEDs used for spotlighting. The comprehensive binning system for voltage, intensity, and color provides a level of consistency important for multi-LED applications, which may not be as rigorously defined in lower-cost or generic LED offerings. Its compliance with automatic placement and IR reflow standards makes it a reliable choice for modern, automated electronics manufacturing.

10. Frequently Asked Questions (FAQ)

Q: Can I drive this LED directly from a 3.3V microcontroller pin?
A: Possibly, but it depends on the LED's forward voltage (VF). If the LED's VF is at the lower end of its range (e.g., 2.6V), there is 0.7V difference. At a desired 5mA, this requires a resistor of R = 0.7V / 0.005A = 140 Ohms. This is feasible. However, if the LED's VF is 3.1V, the difference is only 0.2V, requiring a 40 Ohm resistor. At 5mA, the voltage drop across the MCU's internal driver may become significant, potentially preventing the LED from lighting properly or causing inconsistent brightness. A driver circuit (like a transistor) is more reliable for consistent performance across all VF bins.

Q: What is the difference between \"Lens Color\" and \"Source Color\"?
A: The \"Source Color\" refers to the light emitted by the semiconductor chip itself before it passes through the package lens. Here, it is a white InGaN chip. The \"Lens Color\" is the color of the plastic encapsulant that forms the LED's dome. A yellow lens acts as a filter, absorbing some wavelengths (like blue) and transmitting others (yellow, red), resulting in a final emitted light that appears warmer (more yellow/amber) than the original white chip output.

Q: Why is the reverse current (IR) specification important if the device isn't for reverse operation?
A: The IR test is primarily a quality and reliability test. A high reverse leakage current can indicate a defect in the semiconductor junction. Furthermore, in circuit designs where the LED might be exposed to reverse voltage transients (even briefly), knowing the maximum leakage helps in designing protection circuits to prevent damage or unexpected circuit behavior.

Q: How do I interpret the bin code on the packaging?
A>The packaging label should include codes for VF, Iv, and Hue bins (e.g., V3R-S4). This allows you to know the specific performance range of the LEDs in that batch. For critical applications requiring tight consistency, you can specify the exact bin codes when ordering.

11. Practical Application Examples

Example 1: Keyboard Backlighting
In a notebook computer keyboard, multiple LTW-482DS5 LEDs could be placed under a translucent keycap layer. Their wide 130-degree viewing angle ensures even illumination across the keypad. The yellow lens provides a warm white backlight that is often considered less harsh than cool white, especially in low-light environments. Designers would select LEDs from the same intensity (Iv) and hue (Sx) bins to ensure uniform color and brightness across the entire keyboard.

Example 2: Industrial Status Indicator Panel
On a control panel for industrial equipment, these LEDs can be used as status indicators for \"Power On\\