SMD LED LTST-N683GBEW Datasheet - Multi-Color (Red/Green/Blue) - 20mA/30mA Forward Current - 80mW Power Dissipation - English Technical Document

1. Product Overview

This document provides the complete technical specifications for the LTST-N683GBEW, a surface-mount device (SMD) LED. This component is designed for automated printed circuit board (PCB) assembly and is suitable for space-constrained applications. It is a multi-color LED package containing individual Red, Green, and Blue LED chips within a single housing, allowing for versatile color indication or potential color mixing applications.

1.1 Features

• Compliant with RoHS (Restriction of Hazardous Substances) directives.
• Packaged in 8mm tape on 7-inch diameter reels for automated pick-and-place machinery.
• Standard EIA (Electronic Industries Alliance) package footprint.
• IC (Integrated Circuit) compatible logic levels.
• Fully compatible with standard automatic placement equipment used in high-volume manufacturing.
• Designed to withstand infrared (IR) reflow soldering processes common in SMT (Surface Mount Technology) assembly lines.
• Preconditioned to accelerate to JEDEC (Joint Electron Device Engineering Council) Moisture Sensitivity Level 3, indicating a floor life of 168 hours at ≤30°C/60% RH after the dry pack is opened.

1.2 Applications

The LTST-N683GBEW is engineered for a broad range of electronic equipment where reliable, multi-color status indication is required in a compact form factor. Typical application sectors include:

• Telecommunications: Status indicators in cordless phones, cellular phones, routers, and network switches.
• Office Automation: Backlighting for keys or status lights on printers, scanners, and multifunction devices.
• Consumer Electronics & Home Appliances: Power, mode, or function indicators in audio/video equipment, kitchen appliances, and smart home devices.
• Industrial Equipment: Panel indicators for machinery, control systems, and test equipment.
• Signage & Indoor Display: Low-resolution informational displays, decorative lighting, and backlighting for signs.

2. Technical Parameters: In-Depth Objective Interpretation

This section provides a detailed, objective analysis of the LED's key performance parameters as defined in the datasheet.

2.1 Absolute Maximum Ratings

These ratings define the limits beyond which permanent damage to the device may occur. Operation under these conditions is not guaranteed and should be avoided in circuit design.

• Power Dissipation (Pd): 80 mW for Blue and Green chips; 72 mW for the Red chip. This parameter is crucial for thermal management and directly influences the maximum allowable forward current under DC conditions.
• Peak Forward Current (I_F(PEAK)): 100 mA for Blue/Green, 80 mA for Red, at a 1/10 duty cycle with 0.1ms pulse width. This rating is for pulsed operation only and is significantly higher than the DC rating.
• DC Forward Current (I_F): The recommended continuous operating current is 20 mA for Blue and Green LEDs, and 30 mA for the Red LED. Exceeding this value increases junction temperature and accelerates lumen depreciation.
• Operating & Storage Temperature: The device is rated for an ambient temperature (T_a) range of -40°C to +85°C. The storage temperature range is wider, from -40°C to +100°C.

2.2 Electrical & Optical Characteristics

These are the typical performance parameters measured at an ambient temperature of 25°C and a forward current of 20mA, unless otherwise specified.

• Luminous Intensity (I_V): Measured in millicandelas (mcd). The Green LED is the brightest (710-1400 mcd min-max), followed by Red (355-710 mcd), and then Blue (180-355 mcd). Intensity is measured with a filter approximating the CIE photopic eye-response curve.
• Viewing Angle (2θ_1/2): The typical full viewing angle is 120 degrees. This is the angle at which the luminous intensity drops to half of its axial (on-axis) value. A 120-degree angle indicates a wide, diffuse emission pattern suitable for status indicators.
• Wavelength Parameters:
  • Peak Wavelength (λ_P): The wavelength at which the spectral power distribution is maximum. Typical values are 468 nm (Blue), 518 nm (Green), and 632 nm (Red).
  • Dominant Wavelength (λ_d): The single wavelength perceived by the human eye that defines the color. Typical ranges are 465-475 nm (Blue), 520-530 nm (Green), and 617-630 nm (Red).
  • Spectral Line Half-Width (Δλ): The bandwidth of the emitted light at half its peak intensity. Typical values are 25 nm (Blue), 35 nm (Green), and 20 nm (Red), indicating relatively narrowband emission for each color.
• Forward Voltage (V_F): The voltage drop across the LED at the specified current. Ranges are 2.8-3.8V for Blue/Green and 1.8-2.6V for Red. The lower V_F for Red is characteristic of AlInGaP materials compared to the InGaN used for Blue/Green.
• Reverse Current (I_R): Maximum leakage current of 10 μA when a reverse voltage (V_R) of 5V is applied. Important Note: The datasheet explicitly states the device is not designed for reverse operation; this test is for IR (Infrared) qualification only.

3. Binning System Explanation

To ensure color and brightness consistency in production, LEDs are sorted into "bins" based on measured parameters. The LTST-N683GBEW uses a two-dimensional binning system for Luminous Intensity and Dominant Wavelength.

3.1 Luminous Intensity (I_V) Binning

Each color has specific intensity bins with an 11% tolerance on each bin.

• Blue: Bins S1 (180-224 mcd), S2 (224-280 mcd), T1 (280-355 mcd).
• Green: Bins V1 (710-900 mcd), V2 (900-1120 mcd), W1 (1120-1400 mcd).
• Red: Bins T2 (355-450 mcd), U1 (450-560 mcd), U2 (560-710 mcd).

3.2 Dominant Wavelength (λ_d) Binning

Each color has specific wavelength bins with a +/- 1nm tolerance.

• Blue: Bins AC1 (465.0-467.5 nm), AC2 (467.5-470.0 nm), AD1 (470.0-472.5 nm), AD2 (472.5-475.0 nm).
• Green: Bins AP1 (520.0-522.5 nm), AP2 (522.5-525.0 nm), AQ1 (525.0-527.5 nm), AQ2 (527.5-530.0 nm).
• Red: The Red LED's dominant wavelength is specified as a single range (617-630 nm) without sub-bins in the wavelength table.

3.3 Combined Bin Code on Tag

The datasheet provides a cross-reference table that combines intensity and (for Blue/Green) wavelength bins into a single alphanumeric "Bin Code on Tag." This code, printed on the product reel or packaging, allows manufacturers to select LEDs with tightly matched performance characteristics for their application. For example, code "C4" corresponds to a Blue LED from intensity bin T1, a Green LED from intensity bin V2, and a Red LED from intensity bin T2.

4. Performance Curve Analysis

While specific graphical data is referenced in the datasheet (e.g., Fig.1, Fig.6), typical curves for such LEDs would include:

• I-V (Current-Voltage) Curve: Shows the nonlinear relationship between forward current and forward voltage. The curve will have a distinct "knee" voltage (approximately the min V_F) below which very little current flows. Driving the LED with a constant current source is the recommended method to ensure stable light output regardless of V_F variations.
• Luminous Intensity vs. Forward Current (I_V vs. I_F): Light output generally increases linearly with current in the normal operating range but will saturate at very high currents due to thermal effects and efficiency droop.
• Luminous Intensity vs. Ambient Temperature (I_V vs. T_a): Light output typically decreases as junction temperature rises. The rate of decrease varies by semiconductor material (AlInGaP for Red is generally more temperature-sensitive than InGaN for Blue/Green).
• Spectral Distribution: A plot of relative radiant power versus wavelength, showing the characteristic peak and half-width for each color chip.

5. Mechanical & Package Information

5.1 Package Dimensions and Pin Assignment

The LED uses a standard SMD package. Key dimensional tolerances are ±0.2 mm unless otherwise noted. The pin assignment for the multi-color package is clearly defined:

• Pin 1: Not specified in the provided excerpt (often Cathode common or No Connect).
• Pin 2: Anode for the Red (AlInGaP) LED chip.
• Pin 3: Anode for the Blue (InGaN) LED chip.
• Pin 4: Anode for the Green (InGaN) LED chip.

Critical Design Note: The common cathode configuration is typical for such packages, but the datasheet must be consulted for the exact schematic. Each anode must be driven independently with its own current-limiting resistor or constant-current driver.

5.2 Recommended PCB Attachment Pad

A land pattern (footprint) diagram is provided to ensure proper solder joint formation and mechanical stability during and after reflow soldering. Adhering to this recommended pattern is essential for reliable assembly.

6. Soldering & Assembly Guidelines

6.1 IR Reflow Soldering Profile

The datasheet includes a suggested IR reflow profile compliant with J-STD-020B for lead-free (Pb-free) solder processes. This profile typically defines key parameters:

• Preheat/Ramp-up Rate: To slowly heat the board and components, minimizing thermal shock.
• Soak Zone: A temperature plateau to activate flux and ensure uniform heating across the PCB.
• Reflow Zone: The peak temperature, which must be high enough to melt the solder paste but not exceed the LED's maximum temperature tolerance (implied by its JEDEC Level 3 rating and storage temp).
• Cooling Rate: Controlled cooling to form reliable solder joints.

6.2 Cleaning

If post-solder cleaning is necessary, the only recommended agents are ethyl alcohol or isopropyl alcohol. The LED should be immersed at normal room temperature for less than one minute. Unspecified chemical cleaners may damage the LED's plastic lens or package.

6.3 Storage Conditions

To preserve solderability and device integrity, the LEDs should be stored in their sealed, moisture-barrier bags at conditions of 30°C or less and 70% relative humidity or less. Once the bag is opened, the "floor life" based on the JEDEC MSL 3 rating applies.

7. Packaging and Ordering Information

7.1 Tape and Reel Specifications

The product is supplied in industry-standard embossed carrier tape for automated handling.

• Tape Width: 8 mm.
• Reel Diameter: 7 inches.
• Quantity per Reel: 2000 pieces.
• Minimum Order Quantity (MOQ): 500 pieces for remainder quantities.
• Packaging conforms to ANSI/EIA-481 specifications. The tape has a cover tape to seal component pockets.

8. Application Suggestions & Design Considerations

8.1 Typical Application Circuits

Each LED chip (Red, Green, Blue) requires an independent current-limiting circuit. The simplest method is a series resistor for each anode, calculated as R = (V_supply - V_F) / I_F. For better consistency across temperature and unit-to-unit V_F variation, a constant current driver (e.g., a dedicated LED driver IC or transistor-based circuit) is recommended, especially for the higher-current Red LED or if precise brightness matching is critical.

8.2 Thermal Management

Although power dissipation is low, proper thermal design extends LED life and maintains stable light output. Ensure the PCB pad design provides adequate thermal relief according to the datasheet recommendation. Avoid operating the LED at absolute maximum ratings for extended periods.

8.3 Optical Design

The 120-degree viewing angle provides wide visibility. For applications requiring a more focused beam, external secondary optics (lenses) can be used. The diffused lens helps in achieving a uniform appearance when viewed off-axis.

9. Technical Comparison & Differentiation

The primary differentiating factor of the LTST-N683GBEW is its integration of three distinct LED chips (Red, Green, Blue) into a single, compact SMD package. This offers significant advantages over using three separate single-color LEDs:

• Space Savings: Reduces PCB footprint and component count.
• Simplified Assembly: Only one component needs to be placed instead of three, improving manufacturing throughput and reliability.
• Pre-aligned Emitters: The chips are fixed in position relative to each other, which can be beneficial for applications where color mixing or closely spaced multi-color indicators are needed.
• Consistent Package: Uniform optical characteristics (viewing angle, lens appearance) across all three colors.

10. Frequently Asked Questions (Based on Technical Parameters)

Q: Can I drive all three LEDs simultaneously at their maximum DC current?

A: No. The power dissipation ratings (80/72 mW) and thermal design of the package must be considered. Driving all three at max current (20mA Blue/Green + 30mA Red) simultaneously may exceed the total thermal capacity of the package if the forward voltages are at the high end of their range. Derating or pulsed operation is advised for full-color, full-brightness use.

Q: What does the Bin Code on the tag mean for my design?

A: For applications where color or brightness consistency is critical (e.g., multi-device panels, displays), you should specify and use LEDs from the same bin code. This ensures minimal variation from one unit to the next. For less critical status indicators, any standard bin may be acceptable.

Q: Can I use this LED for reverse voltage protection or as a rectifier?

A: Absolutely not. The datasheet explicitly states the device is not designed for reverse operation. Applying a reverse bias exceeding 5V may cause immediate failure.

Q: How do I achieve white light or other colors with this LED?

A: This is an RGB LED. By independently controlling the intensity of the Red, Green, and Blue chips using PWM (Pulse Width Modulation) or analog dimming, a wide range of colors can be created through additive color mixing. For example, activating Red and Green at similar intensities yields yellow, while activating all three at full intensity produces a form of white light (the quality of white depends on the specific spectral output of each chip).

11. Practical Design and Usage Case

Case: Designing a Multi-Status Indicator for a Network Switch

A designer needs three statuses: Power (Green), Activity (Flashing Green), and Fault (Red). A fourth "Standby" state (Blue) is also desired. Using a single LTST-N683GBEW simplifies the design:

1. PCB Layout: Only one component footprint is needed, saving space.
2. Microcontroller Interface: Three GPIO pins from the system's microcontroller are connected to the Red, Green, and Blue anodes (each via a suitable current-limiting resistor, e.g., 150Ω for Green/Blue @ 3.3V, 75Ω for Red @ 3.3V). The common cathode is connected to ground.
3. Firmware Control: The MCU firmware can easily set the states:
   • Power ON: Green LED pin = HIGH.
   • Activity: Toggle Green LED pin with a timer.
   • Fault: Red LED pin = HIGH.
   • Standby: Blue LED pin = HIGH.
   • Combined states (e.g., Fault during activity) are also possible by driving multiple pins.
4. Manufacturing: The automated pick-and-place machine handles one part instead of three, increasing assembly speed and reducing potential placement errors.

12. Principle Introduction

Light Emitting Diodes (LEDs) are semiconductor devices that emit light when an electric current passes through them. This phenomenon, called electroluminescence, occurs when electrons recombine with electron holes within the device, releasing energy in the form of photons. The color of the emitted light is determined by the energy band gap of the semiconductor material used:

• Red LED (Pin 2): Uses Aluminum Indium Gallium Phosphide (AlInGaP) material, which has a band gap corresponding to red/orange light.
• Blue and Green LEDs (Pins 3 & 4): Use Indium Gallium Nitride (InGaN) material. By varying the indium/gallium ratio, the band gap can be tuned to emit light from ultraviolet through blue to green wavelengths.

The LTST-N683GBEW integrates three such semiconductor junctions into a single package with a common cathode connection and a diffused plastic lens that shapes the light output and provides mechanical and environmental protection.

13. Development Trends

The evolution of multi-chip SMD LEDs like the LTST-N683GBEW follows broader trends in optoelectronics:

• Increased Integration: Moving beyond simple RGB to include white chips or additional colors (e.g., RGBW - Red, Green, Blue, White) in a single package for better color rendering and efficiency.
• Higher Efficiency: Ongoing improvements in internal quantum efficiency (IQE) and light extraction techniques lead to higher luminous intensity (mcd) for the same input current, reducing power consumption.
• Miniaturization: Continued reduction in package size while maintaining or improving optical performance, enabling LEDs in ever-smaller consumer devices.
• Improved Binning & Consistency: Advances in manufacturing process control yield tighter parameter distributions, reducing the need for extensive binning and providing more consistent performance straight from production.
• Enhanced Thermal Performance: Development of package materials and structures with lower thermal resistance, allowing for higher drive currents and greater light output without compromising reliability.

These trends aim to provide designers with more versatile, efficient, and reliable lighting solutions for an expanding range of applications.