LTST-008GEBW SMD LED Datasheet - White Diffused Lens - RGB Chip - EIA Package - English Technical Document

1. Product Overview

The LTST-008GEBW is a surface-mount device (SMD) LED designed for automated printed circuit board (PCB) assembly. It features a white diffused lens and integrates three distinct semiconductor chips within a single package: Green (InGaN), Red (AlInGaP), and Blue (InGaN). This configuration allows for versatile color indication and backlighting applications. The device is housed in an industry-standard EIA package, ensuring compatibility with a wide range of automated pick-and-place and reflow soldering equipment.

1.1 Features

• Compliant with RoHS environmental directives.
• Packaged in 12mm tape on 7-inch diameter reels for high-volume assembly.
• Standard EIA package footprint for design compatibility.
• Input/output compatible with integrated circuits (I.C. compatible).
• Designed for compatibility with automated placement equipment.
• Suitable for infrared (IR) reflow soldering processes.
• Preconditioned to JEDEC Moisture Sensitivity Level 3.

1.2 Applications

This LED is suitable for a broad spectrum of electronic equipment where space-saving, reliable indication, or subtle backlighting is required. Primary application areas include:

• Telecommunication equipment (e.g., routers, switches, phones).
• Office automation devices (e.g., printers, scanners, multifunction devices).
• Home appliances and consumer electronics.
• Industrial control panels and equipment.
• Status and power indicators.
• Signal and symbol illumination.
• Front panel and keyboard backlighting.

2. Package Dimensions and Pin Assignment

The mechanical outline of the LTST-008GEBW conforms to the standard EIA package dimensions. All specified dimensions are in millimeters, with a general tolerance of ±0.1 mm unless otherwise noted. The pin assignment for the integrated RGB chips is as follows:

• Green Chip: Anode on pin (0,1), Cathode on pin 2.
• Red Chip: Anode on pin 3, Cathode on pin 4.
• Blue Chip: Anode on pin 5, Cathode on pin (6,7).

This pinout is critical for correct circuit design and must be adhered to for proper individual color control.

3. Ratings and Characteristics

3.1 Absolute Maximum Ratings

Absolute maximum ratings define the limits beyond which permanent damage to the device may occur. These ratings are specified at an ambient temperature (Ta) of 25°C.

• Power Dissipation: 102 mW (Green, Blue), 72 mW (Red).
• Peak Forward Current: 100 mA for all colors (at 1/10 duty cycle, 0.1ms pulse width).
• DC Forward Current: 30 mA for all colors.
• Operating Temperature Range: -40°C to +85°C.
• Storage Temperature Range: -40°C to +100°C.

Operation outside these ranges is not recommended and may affect reliability and lifetime.

3.2 Suggested IR Reflow Profile

For lead-free soldering processes, the recommended infrared reflow profile should comply with the J-STD-020B standard. The profile typically includes a preheat zone, a soak zone, a reflow zone with a peak temperature, and a cooling zone. Adhering to this profile is essential to prevent thermal shock and ensure reliable solder joints without damaging the LED package or internal die.

3.3 Electrical and Optical Characteristics

These characteristics are measured at Ta=25°C under specified test conditions and represent typical device performance.

• Luminous Flux (Φv): Measured with a sensor/filter approximating the CIE photopic eye response.
  • Green (IF=25mA): Min 2.81 lm, Max 7.12 lm.
  • Red (IF=20mA): Min 1.07 lm, Max 2.71 lm.
  • Blue (IF=15mA): Min 0.32 lm, Max 0.82 lm.
• Viewing Angle (θ1/2): Typically 130 degrees. This is the off-axis angle where luminous intensity is half the value at 0 degrees (on-axis).
• Dominant Wavelength (λd): The single wavelength perceived as the color.
  • Green: 518 nm to 533 nm.
  • Red: 618 nm to 628 nm.
  • Blue: 455 nm to 464 nm.
• Spectral Line Half-Width (Δλ): Typical values are 33 nm (Green), 20 nm (Red), and 22 nm (Blue).
• Forward Voltage (VF): Tolerance is +/-0.1V.
  • Green: 2.9V to 3.4V at 25mA.
  • Red: 1.8V to 2.4V at 20mA.
  • Blue: 2.6V to 3.4V at 15mA.
• Reverse Current (IR): Maximum 10 μA at VR=5V. Note: The device is not designed for reverse bias operation; this parameter is for IR test qualification only.

4. Bin Code System

The LTST-008GEBW is classified using a bin code system to ensure consistency in luminous output and color coordinates for applications requiring uniformity.

4.1 Luminous Flux (IV) Rank

LEDs are sorted into bins based on their measured luminous flux at specified drive currents. The bin codes (H2, J1, J2, K1) define ranges from minimum to maximum luminous flux values. The tolerance on each luminous intensity bin is +/- 11%.

4.2 Color Coordinate (CIE) Rank

Color consistency is managed through a detailed CIE 1931 chromaticity coordinate binning system. The datasheet provides a comprehensive table and a chromaticity diagram plotting various bin codes (e.g., H2-H7, J2-J7, K2-K7, etc.). Each bin is defined by a quadrilateral area on the CIE chart specified by four (x, y) coordinate points. The tolerance for each hue bin (x, y) is +/- 0.01. This precise binning allows designers to select LEDs with nearly identical color points for multi-LED arrays or status indicators where color matching is critical.

5. Typical Performance Curves

The datasheet includes a section for typical performance curves, which graphically represent the relationship between various parameters under different conditions. These curves are essential for in-depth design analysis. While the specific curves are not detailed in the provided text, they typically include:

• Relative Luminous Intensity vs. Forward Current: Shows how light output changes with drive current for each color.
• Forward Voltage vs. Forward Current: Illustrates the IV characteristic of each diode.
• Relative Luminous Intensity vs. Ambient Temperature: Demonstrates the thermal derating of light output.
• Spectral Power Distribution: Plots the relative intensity of emitted light across wavelengths for each color chip.

Consulting these curves helps optimize drive circuitry, manage thermal performance, and predict behavior under non-standard operating conditions.

6. User Guide and Assembly Information

6.1 Cleaning Instructions

Post-assembly cleaning must be performed with care. Only use ethyl alcohol or isopropyl alcohol at normal room temperature. The LED should be immersed for less than one minute. The use of unspecified chemical cleaners can damage the LED package material, epoxy lens, or internal connections.

6.2 Recommended PCB Land Pattern

A recommended footprint (land pattern) for the PCB is provided to ensure proper solder joint formation, mechanical stability, and thermal management during reflow. Following this pattern is crucial for achieving reliable surface mount attachment.

6.3 Tape and Reel Packaging Dimensions

The device is supplied in a standard 12mm wide embossed carrier tape wound onto 7-inch (178mm) diameter reels. The datasheet includes detailed dimensions of the tape pockets, cover tape, and reel hub to facilitate compatibility with automated assembly equipment feeders.

7. Design Considerations and Application Notes

7.1 Current Limiting

As with all LEDs, the forward current must be limited using a series resistor or a constant-current driver. The value should be calculated based on the supply voltage, the forward voltage (VF) of the specific color chip at the desired current, and the maximum DC forward current rating (30mA). Operating at or below the typical test currents (25mA Green, 20mA Red, 15mA Blue) is recommended for long-term reliability.

7.2 Thermal Management

While the power dissipation is relatively low, proper thermal design on the PCB is important, especially in high ambient temperature environments or when driving multiple LEDs. The PCB's copper area acts as a heat sink. Ensuring a good thermal path from the LED's solder pads to a larger copper plane can help maintain lower junction temperatures, preserving luminous output and operational life.

7.3 Optical Design with Diffused Lens

The white diffused lens provides a wide, uniform viewing angle (130° typical) by scattering the light from the small, bright chip sources. This makes the LED ideal for status indicators that need to be visible from a wide range of angles. It reduces glare and hotspots, creating a soft, even illumination suitable for panel backlighting. Designers should account for this diffusion when modeling light output for their specific application.

7.4 Independent Color Control

With separate anode/cathode pairs for each color chip, the LTST-008GEBW offers full independent control. This allows for static indication of three different states (Green, Red, Blue) or, by using pulse-width modulation (PWM) on the individual channels, the creation of a multitude of mixed colors. Careful circuit design is needed to manage three separate current-limiting paths.

8. Comparison and Selection Guidance

The LTST-008GEBW occupies a specific niche. Key differentiators include its integrated RGB capability in a single, standard SMD package and its diffused lens for wide-angle viewing. When selecting an LED, engineers should compare:

• Single-color vs. Multi-chip: This device consolidates three indicators into one footprint, saving board space.
• Clear vs. Diffused Lens: Diffused lenses trade off peak axial intensity for wider, more uniform viewing.
• Luminous Flux Binning: For applications requiring consistent brightness across multiple units, specifying a tighter flux bin (e.g., K1) is advisable.
• Color Binning: For color-critical applications, specifying a specific CIE bin code ensures visual consistency between different production batches or adjacent LEDs.

9. Frequently Asked Questions (FAQ)

Q: Can I drive all three colors simultaneously at their maximum DC current?
A: No. The absolute maximum power dissipation for the package must not be exceeded. Simultaneously driving Green (102mW), Red (72mW), and Blue (102mW) at their max ratings would far exceed the package's thermal capacity. Derate currents or use multiplexing/PWM to manage total power.

Q: What is the purpose of the JEDEC Level 3 preconditioning?
A: It indicates the device's moisture sensitivity. Level 3 means the package can be exposed to factory floor conditions (≤30°C/60% RH) for up to 168 hours before it must be baked prior to reflow soldering to prevent "popcorning" (package cracking due to vaporized moisture).

Q: How do I interpret the CIE bin code table?
A: Each bin code (e.g., H2) defines a small quadrilateral region on the CIE 1931 chromaticity diagram. The four (x,y) coordinate pairs in the table are the corners of that region. An LED whose measured color coordinates fall within that region is assigned that bin code.

Q: Is a reverse protection diode necessary?
A> While the device can withstand a 5V reverse voltage for test purposes, it is not designed for operation in reverse bias. In circuits where reverse voltage transients are possible (e.g., inductive loads, hot-plugging), external protection such as a series diode or a TVS diode across the LED is strongly recommended to prevent damage.

10. Technical Principles and Trends

10.1 Operating Principle

Light emission in LEDs is based on electroluminescence in semiconductor materials. When a forward voltage is applied across the p-n junction, electrons and holes recombine, releasing energy in the form of photons. The specific semiconductor compounds (InGaN for green/blue, AlInGaP for red) determine the bandgap energy and thus the wavelength (color) of the emitted light. The white diffused lens is typically made of epoxy or silicone with scattering particles (e.g., titanium dioxide) added to diffuse the point-source light from the chip.

10.2 Industry Trends

The SMD LED market continues to evolve towards higher efficiency (more lumens per watt), improved color rendering, and greater miniaturization. Multi-chip packages like the LTST-008GEBW represent a trend toward functional integration, reducing component count and assembly complexity. Furthermore, there is a growing emphasis on tighter binning tolerances for both flux and color to meet the demands of applications like full-color displays and architectural lighting where consistency is paramount. The drive for higher reliability in automotive and industrial applications also pushes advancements in package materials and thermal performance.