LTW-327DSKF-5A Dual Color SMD LED Datasheet - Side View - White & Orange - 5mA - English Technical Document

1. Product Overview

The LTW-327DSKF-5A is a dual-color, side-viewing Surface Mount Device (SMD) LED designed primarily for applications requiring compact backlighting solutions, such as in Liquid Crystal Display (LCD) panels. This component integrates two distinct semiconductor chips within a single package: an InGaN (Indium Gallium Nitride) chip for white light emission and an AlInGaP (Aluminum Indium Gallium Phosphide) chip for orange light emission. Its right-angle form factor allows light to be emitted parallel to the mounting surface, making it ideal for edge-lighting thin displays or providing indicator functions in space-constrained environments.

The device is constructed to be compatible with standard automated pick-and-place assembly equipment and is supplied on 8mm tape reels for efficient high-volume manufacturing. It complies with RoHS (Restriction of Hazardous Substances) directives, classifying it as a green product. The package conforms to EIA (Electronic Industries Alliance) standard outlines, ensuring broad compatibility with industry-standard footprints and processes.

2. Technical Specifications Deep Dive

2.1 Absolute Maximum Ratings

Operating the device beyond these limits may cause permanent damage. Key ratings at an ambient temperature (Ta) of 25°C are defined separately for the white and orange chips.

• Power Dissipation: White: 72 mW, Orange: 75 mW. This parameter indicates the maximum power the LED can dissipate as heat under continuous operation.
• Peak Forward Current: White: 100 mA, Orange: 80 mA. This is the maximum allowable pulsed current, typically specified at a 1/10 duty cycle and 0.1ms pulse width, used for brief, high-intensity flashes.
• DC Forward Current: 20 mA for both colors. This is the recommended maximum continuous forward current for reliable long-term operation.
• Reverse Voltage: 5 V for both colors. Exceeding this voltage in reverse bias can damage the LED's PN junction.
• Operating Temperature Range: -20°C to +80°C. The device is guaranteed to function within this ambient temperature range.
• Storage Temperature Range: -40°C to +85°C.
• Infrared Reflow Soldering Condition: 260°C peak temperature for 10 seconds. This defines the thermal profile the component can withstand during assembly.

2.2 Electrical & Optical Characteristics

These are typical performance parameters measured at Ta=25°C with a forward current (IF) of 5mA, unless otherwise stated.

• Luminous Intensity (Iv): A measure of perceived light output. For the white LED, it ranges from a minimum of 28.0 mcd to a maximum of 112.0 mcd. For the orange LED, it ranges from 11.2 mcd to 71.0 mcd. The actual value for a specific unit is determined by its bin code.
• Viewing Angle (2θ1/2): Approximately 130 degrees for both colors. This is the full angle at which the luminous intensity drops to half of its peak value, defining the beam spread.
• Forward Voltage (VF): The voltage drop across the LED when operating. Typical values are 2.85V for white and 2.00V for orange at 5mA, with maximums of 3.15V and 2.40V respectively.
• Peak Emission Wavelength (λP): For the orange LED, the typical peak wavelength is 611 nm.
• Dominant Wavelength (λd): For the orange LED, the typical dominant wavelength is 605 nm. This is the single wavelength perceived by the human eye to represent the color.
• Chromaticity Coordinates (x, y): For the white LED, typical coordinates are x=0.3, y=0.3 on the CIE 1931 chromaticity diagram, representing a cool white point. A tolerance of ±0.01 applies.
• Reverse Current (IR): Maximum leakage current is 10 µA for white and 100 µA for orange when a 5V reverse bias is applied.

3. Binning System Explanation

To ensure consistency in mass production, LEDs are sorted into performance bins. The LTW-327DSKF-5A uses a multi-parameter binning system.

3.1 White LED Binning

• Forward Voltage (VF) Bin: Groups LEDs by their voltage drop at 5mA.
  • Bin A: 2.55V - 2.75V
  • Bin B: 2.75V - 2.95V
  • Bin C: 2.95V - 3.15V
  Tolerance on each bin is ±0.1V.
• Luminous Intensity (Iv) Bin: Groups LEDs by their light output at 5mA.
  • Bin N: 28.0 - 45.0 mcd
  • Bin P: 45.0 - 71.0 mcd
  • Bin Q: 71.0 - 112.0 mcd
  Tolerance is ±15%.
• Hue (Chromaticity) Bin: Groups white LEDs by their color coordinates on the CIE diagram. Bins S1 through S6 define specific quadrilaterals on the x,y coordinate plane. Tolerance on each (x,y) coordinate is ±0.01. This ensures color consistency, which is critical for backlighting applications.

3.2 Orange LED Binning

• Luminous Intensity (Iv) Bin:
  • Bin L: 11.2 - 18.0 mcd
  • Bin M: 18.0 - 28.0 mcd
  • Bin N: 28.0 - 45.0 mcd
  • Bin P: 45.0 - 71.0 mcd
  Tolerance is ±15%.

The specific combination of VF, Iv, and Hue bins for a given production lot defines its complete bin code, allowing designers to select LEDs with tightly matched performance for their application.

4. Performance Curve Analysis

While specific graphical data is referenced in the datasheet (e.g., Fig.1, Fig.2, Fig.6), the typical relationships can be described.

• IV Curve (Current vs. Voltage): Like all diodes, LEDs exhibit a non-linear relationship. Forward voltage increases with current, and the curve's shape is temperature-dependent. The specified VF at 5mA provides a key operating point for circuit design.
• Luminous Intensity vs. Current: Light output generally increases with forward current but not linearly, especially at higher currents where efficiency drops due to heating.
• Temperature Characteristics: Luminous intensity typically decreases as junction temperature rises. The operating temperature range of -20°C to +80°C defines the environment where specified performance is maintained.
• Spectral Distribution: The white LED's spectrum is broad, generated typically by a blue InGaN chip exciting a yellow phosphor. The orange AlInGaP LED has a narrower spectrum centered around 605-611 nm.

5. Mechanical & Package Information

The device features a right-angle, side-viewing package. Key mechanical notes include:

• All dimensions are provided in millimeters, with a standard tolerance of ±0.10 mm unless otherwise specified.
• The lens color is yellow.
• Pin Assignment: Pin A2 is assigned to the InGaN White LED anode. Pin A1 is assigned to the AlInGaP Orange LED anode. The cathodes are likely common or internally configured; the schematic should be consulted for the exact circuit.
• The datasheet includes detailed dimensioned drawings of the LED package itself, suggested soldering pad layouts on the PCB, and the orientation for soldering.
• Package dimensions for the carrier tape and the 7-inch diameter reel are also specified, important for feeder setup in automated assembly.

6. Soldering & Assembly Guidelines

6.1 Reflow Soldering

The component is compatible with infrared (IR) reflow soldering processes. The maximum recommended condition is a peak temperature of 260°C for 10 seconds. It is crucial to follow a controlled thermal profile with preheat, soak, reflow, and cooling stages to prevent thermal shock and ensure reliable solder joints.

6.2 Cleaning

If cleaning is necessary after soldering, only specified chemicals should be used. The datasheet recommends immersion in ethyl alcohol or isopropyl alcohol at normal temperature for less than one minute. Unspecified chemicals may damage the LED package or lens.

6.3 Storage & Handling

• ESD (Electrostatic Discharge) Precautions: LEDs are sensitive to static electricity. Use wrist straps, anti-static mats, and properly grounded equipment when handling.
• Moisture Sensitivity: As a surface-mount component, it may absorb moisture. If the original sealed moisture-proof bag with desiccant is opened, it is recommended to complete IR reflow within one week. For longer storage out of the original bag, store in a sealed container with desiccant or in a nitrogen atmosphere. Components stored out of packaging for more than a week should be baked at approximately 60°C for at least 20 hours before soldering to prevent \"popcorning\" during reflow.
• Storage Conditions (Sealed): ≤30°C and ≤90% Relative Humidity. Shelf life is one year in the sealed bag.
• Storage Conditions (Opened): ≤30°C and ≤60% Relative Humidity.

7. Packaging & Ordering Information

• The standard packaging is 8mm wide embossed carrier tape on 7-inch (178mm) diameter reels.
• Standard reel quantity is 3000 pieces.
• A minimum packing quantity of 500 pieces is available for remainder orders.
• The tape and reel specifications comply with ANSI/EIA 481-1-A-1994.
• Empty pockets in the tape are sealed with a cover tape.
• The maximum allowable number of consecutive missing components (empty pockets) on a reel is two.

8. Application Suggestions

8.1 Typical Application Scenarios

• LCD Backlighting: The primary design target. The side-view form factor is perfect for edge-lighting small to medium LCDs in consumer electronics, industrial displays, and automotive clusters.
• Dual-Status Indicators: The two colors in one package allow for compact status indication (e.g., power on/standby, network activity, charge status).
• Front Panel Illumination: Illuminating symbols, buttons, or light guides in control panels.

8.2 Design Considerations

• Current Limiting: Always use a series resistor or constant current driver to limit the forward current to 20mA DC or less per chip. Calculate the resistor value using R = (Vsupply - VF) / IF.
• Thermal Management: While power dissipation is low, ensuring adequate PCB copper area or thermal vias can help manage junction temperature, especially in high ambient temperatures or when driving near maximum current.
• Optical Design: Consider the 130-degree viewing angle when designing light guides or diffusers to achieve uniform illumination.
• Reverse Voltage Protection: Avoid applying reverse bias. In circuits where reverse voltage is possible (e.g., AC coupling, inductive loads), consider adding a protection diode in parallel with the LED.

9. Technical Comparison & Differentiation

The key differentiating features of this component are its dual-color capability in a single side-view package and its use of specific chip technologies optimized for their respective colors.

• InGaN for White: This material system is the industry standard for high-efficiency blue and white LEDs. It offers good luminous efficacy and stability.
• AlInGaP for Orange: This material system is highly efficient for producing red, orange, and amber light, offering superior brightness and color purity compared to older technologies like GaAsP.
• The combination allows for a compact, two-in-one solution compared to using two separate single-color LEDs, saving PCB space and simplifying assembly.
• The right-angle form factor is a specific advantage over top-view LEDs for edge-lighting applications.

10. Frequently Asked Questions (Based on Technical Parameters)

Q: Can I drive both LED chips simultaneously at their maximum DC current of 20mA each?

A: Yes, but you must consider the total power dissipation and thermal implications. The combined power would be significant for the small package. For continuous operation, it is often advisable to drive them at lower currents (e.g., 5-10mA) to ensure reliability and longevity, especially in high ambient temperatures.

Q: What is the difference between Peak Wavelength and Dominant Wavelength?

A: Peak Wavelength (λP) is the wavelength at which the spectral power distribution is highest. Dominant Wavelength (λd) is the single wavelength of monochromatic light that matches the perceived color of the LED when compared to a reference white light. For LEDs with a broad spectrum (like phosphor-converted white), λd is more meaningful for color specification. For monochromatic LEDs (like the orange one here), λP and λd are often close.

Q: Why is the reverse current specification for the orange LED (100 µA) ten times higher than for the white LED (10 µA)?

A> This is a characteristic of the different semiconductor materials (AlInGaP vs. InGaN) and their respective bandgaps and junction properties. It highlights the importance of avoiding reverse bias, as even a small reverse voltage can cause significant leakage in the orange LED.

Q: How do I interpret the Hue binning coordinates (S1-S6)?

A> Each bin (S1, S2, etc.) defines a small quadrilateral area on the CIE 1931 chromaticity diagram. LEDs are tested, and their measured (x,y) coordinates are sorted into these predefined areas. Selecting LEDs from the same Hue bin guarantees they will have nearly identical white color points, which is critical for applications requiring uniform white backlighting without visible color variation.

11. Design-in Case Study

Scenario: Designing a status indicator for a portable medical device.

The device requires a single, compact indicator to show two states: \"Ready/On\" (White) and \"Battery Low/Alert\" (Orange). Space on the PCB is extremely limited.

Solution: The LTW-327DSKF-5A is an ideal choice. Its dual-color capability replaces two separate LEDs. The side-view package allows it to be mounted at the edge of the PCB, with its light channeled through a small light pipe to a front panel icon. The designer selects LEDs from a specific Iv bin (e.g., P for orange, Q for white) to ensure consistent brightness. They drive each chip at 10mA via microcontroller GPIO pins with series resistors, providing ample brightness while keeping power consumption and heat low. The tight Hue binning for white ensures the \"Ready\" light has a consistent, professional appearance across all units.

12. Operating Principle Introduction

An LED is a semiconductor diode. When a forward voltage exceeding its bandgap voltage is applied, electrons and holes recombine at the PN junction, releasing energy in the form of photons (light). The color of the light is determined by the energy bandgap of the semiconductor material.

• InGaN White LED: Typically, a blue-emitting InGaN chip is coated with a yellow phosphor. Some blue light escapes, and the rest excites the phosphor to emit yellow light. The combination of blue and yellow light is perceived as white by the human eye.
• AlInGaP Orange LED: The Aluminum, Indium, Gallium, and Phosphide elements are combined in specific ratios to create a semiconductor with a bandgap corresponding to orange/red light. When current flows, it emits photons directly in the orange wavelength range (~605-611 nm).

13. Technology Trends

The field of optoelectronics is driven by demands for higher efficiency, smaller size, better color rendering, and lower cost.

• Efficiency (Luminous Efficacy): Ongoing research focuses on improving internal quantum efficiency (more photons generated per electron) and light extraction efficiency (getting more photons out of the chip).
• Color Quality: For white LEDs, there is a trend towards higher Color Rendering Index (CRI) values, especially in applications where accurate color perception is important (e.g., retail lighting, photography). This involves developing more sophisticated phosphor blends.
• Miniaturization: Packages continue to shrink (e.g., from 0603 to 0402 to 0201 metric sizes) while maintaining or improving light output, enabling ever-thinner devices.
• Integrated Solutions: The trend of combining multiple functions (like this dual-color LED) or integrating drivers and control circuitry directly with the LED chip (\"smart LEDs\") continues to grow, simplifying end-product design.