LTST-E683RGBW SMD LED Datasheet - 3.2x2.8x1.9mm - Red 2.4V/Green 3.8V/Blue 3.8V - 72-80mW - English Technical Documentation

1. Product Overview

The LTST-E683RGBW is a surface-mount device (SMD) LED integrating three distinct semiconductor light sources within a single, compact package. It combines an AlInGaP (Aluminum Indium Gallium Phosphide) chip for red emission with two InGaN (Indium Gallium Nitride) chips for green and blue emission, all covered by a diffused lens. This configuration allows for the generation of a broad spectrum of colors, including white light when all three colors are mixed at appropriate intensities. The primary application is in backlighting, status indicators, decorative lighting, and full-color display modules where space-saving and automated assembly are critical. Its core advantages include compatibility with standard infrared and reflow soldering processes, lead-free construction compliant with RoHS directives, and packaging suitable for high-volume, automated pick-and-place equipment on 8mm tape reels.

2. In-Depth Technical Parameter Analysis

2.1 Absolute Maximum Ratings

These ratings define the stress limits beyond which permanent damage to the device may occur. Operating the LED continuously at or near these limits is not recommended. Key parameters include:

• Power Dissipation (Pd): Red: 72mW, Green/Blue: 80mW. This is the maximum allowable power the LED can dissipate as heat under continuous DC operation at 25°C ambient. Exceeding this limit risks thermal runaway and reduced lifespan.
• Peak Forward Current (Ifp): Red: 80mA, Green/Blue: 100mA. This is the maximum permissible pulsed current, specified at a 1/10 duty cycle and 0.1ms pulse width. It is significantly higher than the DC rating, allowing for brief, high-intensity flashes.
• DC Forward Current (If): Red: 30mA, Green/Blue: 20mA. This is the recommended maximum continuous forward current for reliable long-term operation. Driving the LED above this value will increase light output but also generate more heat, potentially degrading the semiconductor material and phosphors (if present) over time.
• Temperature Range: Operating: -40°C to +85°C; Storage: -40°C to +100°C. These ranges ensure the LED's mechanical and electrical integrity during use and non-operational periods.

2.2 Electrical & Optical Characteristics

These are the typical performance parameters measured under standard test conditions (Ta=25°C, If=20mA).

• Luminous Intensity (Iv): Measured in millicandelas (mcd), it represents the perceived brightness of the LED as seen by the human eye (using a CIE photopic filter). The specified ranges are: Red: 71-224 mcd, Green: 355-900 mcd, Blue: 140-355 mcd. The green chip typically exhibits the highest luminous efficacy.
• Viewing Angle (2θ1/2): A typical value of 120 degrees indicates a wide, diffused light emission pattern. This angle is defined as the full angle at which the luminous intensity drops to half of its value at the central axis (0 degrees).
• Peak Wavelength (λp) & Dominant Wavelength (λd): λp (Red: 639nm, Green: 518nm, Blue: 468nm) is the wavelength at which the spectral power distribution is maximum. λd (Red: 631nm, Green: 525nm, Blue: 470nm) is the single wavelength perceived by the human eye to match the LED's color, derived from the CIE chromaticity diagram. They are closely related but not identical, especially for broad-spectrum sources.
• Spectral Line Half-Width (Δλ): This parameter, typically 20nm (Red), 35nm (Green), and 25nm (Blue), indicates the spectral purity or bandwidth of the emitted light. A smaller value means a more monochromatic light source.
• Forward Voltage (Vf): The voltage drop across the LED when driven at 20mA. Ranges are: Red: 1.8-2.4V, Green: 2.8-3.8V, Blue: 2.8-3.8V. The higher Vf for green and blue InGaN chips compared to the red AlInGaP chip is due to their different semiconductor bandgap energies. A current-limiting resistor or constant-current driver is essential for proper operation.
• Reverse Current (Ir): Maximum 10μA at VR=5V. This LED is not designed for reverse bias operation. Applying a reverse voltage can cause immediate and catastrophic failure due to the low reverse breakdown voltage of the semiconductor junction.

3. Binning System Explanation

To ensure color and brightness consistency in production, LEDs are sorted into performance bins. The datasheet provides bin codes for luminous intensity only for each color.

• Red Luminous Intensity Bins: Q1 (71-90 mcd), Q2 (90-112 mcd), R1 (112-140 mcd), R2 (140-180 mcd), S1 (180-224 mcd). Tolerance within each bin is ±11%.
• Green Luminous Intensity Bins: T2 (355-450 mcd), U1 (450-560 mcd), U2 (560-710 mcd), V1 (710-900 mcd). Tolerance within each bin is ±11%.
• Blue Luminous Intensity Bins: R2 (140-180 mcd), S1 (180-224 mcd), S2 (224-280 mcd), T1 (280-355 mcd). Tolerance within each bin is ±11%.

When ordering or designing, specifying the required bin code(s) is crucial for achieving uniform appearance in an array or display. Mixing bins can lead to visible brightness or color variations.

4. Performance Curve Analysis

While the PDF references typical characteristic curves on page 5, the specific graphs are not provided in the text. Based on standard LED behavior, these curves would typically include:

• Forward Current vs. Forward Voltage (I-V Curve): Shows the exponential relationship. The "knee" voltage is where conduction begins, after which current increases rapidly with small voltage increases.
• Luminous Intensity vs. Forward Current (I-L Curve): Generally linear at lower currents, but may saturate at higher currents due to thermal and efficiency droop effects.
• Luminous Intensity vs. Ambient Temperature: Shows how light output decreases as junction temperature rises. Red AlInGaP LEDs typically have a more pronounced thermal quenching effect compared to blue/green InGaN LEDs.
• Spectral Power Distribution: Graphs showing the relative intensity of light emitted across the wavelength spectrum for each color chip.

These curves are vital for understanding the LED's behavior under non-standard conditions (different drive currents, temperatures) and for thermal management design.

5. Mechanical & Package Information

5.1 Package Dimensions

The LED conforms to an EIA standard SMD package footprint. Key dimensions (in mm, tolerance ±0.2mm unless noted) define its placement on a PCB. The pin assignment is: Pin 1: Anode for Red, Pin 4: Anode for Green, Pin 3: Anode for Blue. The common cathode is likely connected internally to another pin or the thermal pad (specific connection needs verification from the dimensional drawing). The diffused lens helps in achieving a wider and more uniform viewing angle.

5.2 Recommended PCB Pad Design

A land pattern diagram is suggested for infrared or vapor phase reflow soldering. Following this recommendation ensures proper solder joint formation, good thermal conduction away from the LED junction, and mechanical stability. The pad design accounts for solder fillet formation and prevents tombstoning during reflow.

6. Soldering & Assembly Guidelines

6.1 Reflow Soldering Profile

For the lead-free process, a profile compliant with J-STD-020B is suggested. Key parameters include:

• Pre-heat: 150-200°C for a maximum of 120 seconds to gradually heat the board and activate flux.
• Peak Temperature: Maximum 260°C. The time above liquidus (typically ~217°C for lead-free solder) should be controlled to form reliable joints without overheating the LED.
• Total Soldering Time: Maximum 10 seconds at peak temperature, with a maximum of two reflow cycles allowed.

Adherence to this profile prevents thermal shock, which can crack the epoxy lens or the semiconductor die, and prevents excessive intermetallic growth at the solder joints.

6.2 Hand Soldering

If necessary, hand soldering with a soldering iron is permissible with strict limits: iron tip temperature not exceeding 300°C, and soldering time not exceeding 3 seconds per joint. Only one hand-soldering cycle is allowed. Applying the iron directly to the LED body must be avoided; heat should be applied to the PCB pad.

6.3 Cleaning

If post-solder cleaning is required, only specified alcohol-based solvents like ethyl alcohol or isopropyl alcohol should be used at normal temperature for less than one minute. Harsh or unspecified chemicals can damage the epoxy lens material, causing clouding, cracking, or discoloration.

6.4 Storage & Moisture Sensitivity

The LED package is moisture-sensitive. If the original sealed moisture-proof bag (with desiccant) is unopened, storage should be at ≤30°C and ≤70% RH, with a recommended use-within period of one year. Once the bag is opened, the components should be stored at ≤30°C and ≤60% RH. Components exposed to ambient humidity for more than 168 hours (7 days) should be baked at approximately 60°C for at least 48 hours before reflow soldering to remove absorbed moisture and prevent "popcorning" (package cracking due to rapid vapor expansion during reflow).

7. Packaging & Ordering Information

The product is supplied in industry-standard packaging for automated assembly:

• Tape & Reel: Components are placed in 8mm wide carrier tape.
• Reel Size: 7 inches (178mm) in diameter.
• Quantity per Reel: 2000 pieces.
• Minimum Order Quantity (MOQ): 500 pieces for remainder quantities.
• Cover Tape: Empty pockets are sealed with a top cover tape.
• Missing Components: A maximum of two consecutive missing LEDs is allowed per reel specification.
• Standard: Packaging conforms to EIA-481-1-B specifications.

The part number LTST-E683RGBW follows the manufacturer's internal coding system, where "RGBW" indicates the color combination capable of producing white light.

8. Application Suggestions

8.1 Typical Application Scenarios

• Full-Color Display Panels: Used as individual pixels or sub-pixels in large video walls or indoor signage.
• Backlighting: For LCD panels in consumer electronics, automotive dashboards, or industrial controls, often combined with light guides and diffusers.
• Status & Indicator Lights: In networking equipment, appliances, and instrumentation where multi-color status coding is needed.
• Decorative & Architectural Lighting: In strips or modules for color-changing effects.

8.2 Design Considerations

• Current Driving: Always use a constant current driver or a current-limiting resistor in series with each color channel. Calculate the resistor value using R = (Vsupply - Vf_LED) / If. Use the maximum Vf from the datasheet to ensure the current does not exceed the limit even with a high-Vf LED.
• Thermal Management: Although power dissipation is low, proper PCB layout with adequate copper area (thermal pads) is essential to conduct heat away from the LED junction, especially when driven at high currents or in high ambient temperatures. This maintains light output and longevity.
• Color Mixing & Control: To achieve specific colors or white points, pulse-width modulation (PWM) is the preferred method for intensity control of each channel, as it maintains a consistent forward voltage and color chromaticity unlike analog dimming.
• ESD Protection: LEDs are sensitive to electrostatic discharge. Implement ESD safe handling procedures during assembly.

9. Technical Comparison & Differentiation

While a direct comparison with other models is not in the PDF, the LTST-E683RGBW's key differentiators can be inferred:

• Integrated RGB Package: Combines three chips in one 3.2x2.8mm footprint, saving PCB space compared to using three discrete single-color LEDs.
• Diffused Wide-Angle Lens: The 120-degree viewing angle provides a broad, uniform emission pattern suitable for applications requiring wide viewing cones without secondary optics.
• Process Compatibility: Explicit compatibility with standard infrared/reflow soldering and automatic placement makes it suitable for high-volume, cost-effective manufacturing.
• Material Choice: Use of AlInGaP for red offers higher efficiency and better temperature stability compared to older technologies like GaAsP on GaP.

10. Frequently Asked Questions (Based on Technical Parameters)

10.1 Can I drive the red LED at 30mA and the green/blue at 20mA simultaneously?

Yes, you can drive each channel independently at their respective maximum DC forward currents. However, the total power dissipation for the package must be considered. If all three are on at max current, calculate total power: Pred = 30mA * 2.4V(max) = 72mW; Pgreen = 20mA * 3.8V(max) = 76mW; Pblue = 20mA * 3.8V(max) = 76mW. The sum (224mW) likely exceeds the package's total dissipation capability. Therefore, simultaneous full-power operation may require derating or enhanced thermal management. Consult the detailed thermal resistance data if available.

10.2 Why is the forward voltage different for each color?

The forward voltage is primarily determined by the bandgap energy of the semiconductor material. AlInGaP (red) has a lower bandgap (~1.9-2.0 eV) than InGaN (green/~2.4 eV, blue/~2.7 eV). A higher bandgap requires more energy for electrons to cross, resulting in a higher forward voltage drop.

10.3 How do I achieve white light with this RGB LED?

White light is created by mixing the three primary colors (red, green, blue) in specific intensity ratios. There is no single "correct" ratio, as it depends on the target white point (e.g., cool white, warm white). You will need to experiment with different current levels or PWM duty cycles for each channel. Using a microcontroller with PWM outputs is the most flexible approach. Note that RGB mixing often produces white light with a lower Color Rendering Index (CRI) compared to phosphor-converted white LEDs.

10.4 What happens if I connect the polarity incorrectly?

Applying a reverse voltage, even a small one (like 5V as in the Ir test condition), can cause a high reverse current to flow, potentially leading to immediate and irreversible damage (junction breakdown). Always verify polarity before applying power. Incorporating a series diode for reverse polarity protection on the supply line is a good practice for the overall circuit.

11. Practical Design Case Study

Scenario: Designing a multi-color status indicator for a portable device. The indicator must show red (error), green (ok), blue (active), and cyan (active+ok) using a single LTST-E683RGBW to save space.

Implementation:

1. Driver Circuit: Use a microcontroller with three PWM-capable GPIO pins. Each pin connects to the base of a small-signal NPN transistor (e.g., 2N3904). The collector of each transistor connects to the cathode (common) of the respective LED color via a current-limiting resistor. The LED anodes are connected to a 3.3V supply rail.
2. Resistor Calculation (for Green, worst-case Vf=3.8V): R = (3.3V - 3.8V) / 0.02A = Negative value. This indicates 3.3V is insufficient to forward bias the green/blue LEDs at their typical Vf. Solution: Use a higher supply voltage (e.g., 5V) for the LED circuit. Recalculate for Green at 5V: R = (5.0V - 3.8V) / 0.02A = 60 Ohms. Use a standard 62-ohm resistor. For Red: R = (5.0V - 2.4V) / 0.03A ≈ 87 Ohms, use 91 ohms.
3. Software Control: Program the microcontroller to set PWM duty cycles: 100% for solid colors. For cyan (blue+green), set both blue and green channels to 100%. The intensity balance between green and blue can be adjusted via PWM to tune the cyan hue.
4. Thermal Check: Maximum power scenario is cyan (Green+Blue both at 20mA). Ptotal ≈ (5V-3.8V)*0.02A * 2 = 48mW, well within the package limits. Ensure the PCB has a small copper pour under the LED for heat spreading.

12. Operating Principle Introduction

Light emission in LEDs is based on electroluminescence in a semiconductor p-n junction. When a forward voltage is applied, electrons from the n-type region and holes from the p-type region are injected into the active region (the junction). When an electron recombines with a hole, it releases energy. In direct bandgap semiconductors like AlInGaP and InGaN, this energy is released primarily in the form of a photon (light particle). The wavelength (color) of the emitted photon is determined by the bandgap energy (Eg) of the semiconductor material, according to the equation λ ≈ 1240 / Eg (where λ is in nm and Eg is in eV). The diffused epoxy lens serves to protect the semiconductor die, shape the light output beam, and enhance light extraction from the chip.

13. Technology Trends

The field of SMD RGB LEDs is driven by several key trends:

• Increased Efficiency & Luminance: Ongoing improvements in epitaxial growth, chip design, and light extraction techniques continue to boost luminous efficacy (lumens per watt), allowing for brighter displays or lower power consumption.
• Miniaturization: Packages are becoming smaller (e.g., 2.0x1.6mm, 1.6x1.6mm) while maintaining or improving optical performance, enabling higher resolution displays.
• Improved Color Consistency & Binning: Tighter binning tolerances for luminous intensity, dominant wavelength, and forward voltage are becoming standard, reducing the need for calibration in end-products.
• Integrated Drivers & Smart LEDs: A growing trend is the integration of control circuitry (like I2C or SPI interfaces) within the LED package itself, creating addressable "smart" RGB LEDs that simplify system design and wiring.
• Enhanced Reliability & Lifetime: Improvements in packaging materials (e.g., high-temperature silicones instead of epoxy) and die attach techniques are increasing the maximum operating temperature and overall lifespan of LEDs, especially for automotive and industrial applications.