LTST-S33GBEGK-SN SMD LED Datasheet - 3.2x1.6x0.6mm - Blue/Red/Green - 20mA - English Technical Document

1. Product Overview

This document provides the complete technical specifications for the LTST-S33GBEGK-SN, a side-looking, full-color SMD LED. This component is designed for automated printed circuit board assembly and is suitable for space-constrained applications across a wide range of consumer and industrial electronics.

1.1 Features

• Compliant with RoHS environmental standards.
• Ultra-thin 0.6mm profile side-looking package with tin plating for improved solderability.
• Utilizes high-brightness InGaN (Blue/Green) and AlInGaP (Red) semiconductor chips.
• Packaged on 8mm tape wound onto 7-inch diameter reels for automated pick-and-place.
• Conforms to EIA standard package outlines.
• IC compatible drive logic.
• Fully compatible with standard automatic placement equipment.
• Designed to withstand infrared (IR) reflow soldering processes.

1.2 Applications

This LED is intended for use in various electronic equipment where compact size and reliable performance are critical. Typical application areas include:

• Telecommunication devices and office automation equipment.
• Home appliances and industrial control panels.
• Keypad and keyboard backlighting.
• Status and power indicators.
• Micro-displays and symbol illumination.
• Signal luminaries.

2. Technical Parameters: In-Depth Objective Interpretation

The following sections provide a detailed breakdown of the LED's performance characteristics under standard test conditions (Ta=25°C).

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.

• Power Dissipation (Pd): Blue/Green: 76 mW max; Red: 50 mW max. This parameter is crucial for thermal management design.
• Peak Forward Current (I_FP): Blue/Green: 100 mA (1/10 duty cycle, 0.1ms pulse); Red: 80 mA. For pulsed operation only.
• DC Forward Current (I_F): 20 mA for all colors. This is the recommended continuous operating current.
• Operating Temperature Range (T_opr): -20°C to +80°C.
• Storage Temperature Range (T_stg): -30°C to +100°C.
• Infrared Soldering Condition: Withstands 260°C peak temperature for 10 seconds, suitable for lead-free (Pb-free) reflow processes.

2.2 Electrical and Optical Characteristics

Measured at I_F = 20 mA, Ta = 25°C, unless otherwise noted.

• Luminous Intensity (I_V):
  • Blue: 224 - 450 mcd (min - max).
  • Red: 400 - 750 mcd.
  • Green: 1120 - 1900 mcd.
• Viewing Angle (2θ_1/2): Typical 130 degrees. This wide viewing angle is characteristic of side-emitting packages.
• Peak Emission Wavelength (λ_P): Typical values are Blue: 468 nm, Red: 632 nm, Green: 518 nm.
• Dominant Wavelength (λ_d):
  • Blue: 465 - 475 nm.
  • Red: 618 - 628 nm.
  • Green: 520 - 530 nm.
• Spectral Line Half-Width (Δλ): Typical values are Blue: 25 nm, Red: 17 nm, Green: 35 nm. This indicates the spectral purity of the emitted light.
• Forward Voltage (V_F):
  • Blue/Green: 2.55 - 3.30 V.
  • Red: 1.90 - 2.50 V.
• Reverse Current (I_R): Maximum 10 μA at V_R = 5V. Note: The device is not designed for reverse bias operation; this parameter is for IR test purposes only.

3. Binning System Explanation

The LEDs are sorted into bins based on key electrical and optical parameters to ensure consistency in mass production. This allows designers to select parts that meet specific application requirements for color and brightness uniformity.

3.1 Forward Voltage (V_F) Binning

At I_F = 20 mA. Tolerance on each bin is ±0.1V.

• Blue & Green: Bin 1: 2.55-3.05V; Bin 2: 3.05-3.30V.
• Red: Bin 1: 1.90-2.20V; Bin 2: 2.20-2.50V.

3.2 Luminous Intensity (I_V) Binning

At I_F = 20 mA. Tolerance on each bin is ±15%.

• Blue: S2 (224-280 mcd), T1 (280-355 mcd), T2 (355-450 mcd).
• Red: U1 (400-500 mcd), U2 (500-600 mcd), U3 (600-750 mcd).
• Green: W1 (1120-1380 mcd), W2 (1380-1640 mcd), W3 (1640-1900 mcd).

4. Performance Curve Analysis

While specific graphical data is referenced in the datasheet, the typical relationships are described below based on standard LED physics.

4.1 Current vs. Voltage (I-V) Characteristic

The forward voltage (V_F) exhibits a logarithmic relationship with forward current (I_F). It increases with current but is also temperature-dependent, typically decreasing as junction temperature rises.

4.2 Luminous Intensity vs. Current (I_V-I_F)

Luminous intensity is approximately proportional to the forward current in the normal operating range. However, efficiency may drop at very high currents due to increased thermal effects and droop phenomena in the semiconductor material.

4.3 Temperature Dependence

The performance of LEDs is significantly affected by junction temperature (T_j). Typically, luminous intensity decreases as T_j increases. The forward voltage (V_F) for InGaN-based LEDs (Blue/Green) generally decreases with rising temperature, while for AlInGaP-based LEDs (Red), the decrease is less pronounced. Proper heat sinking and current management are essential for maintaining stable optical output and long-term reliability.

4.4 Spectral Distribution

The emitted light spectrum is characterized by the peak wavelength (λ_P) and the spectral half-width (Δλ). The dominant wavelength (λ_d) is the single wavelength perceived by the human eye. The spectrum can shift slightly with changes in drive current and junction temperature.

5. Mechanical and Package Information

5.1 Package Dimensions

The LTST-S33GBEGK-SN is housed in a side-looking SOP (Small Outline Package). Key dimensions (in millimeters) are as follows, with a general tolerance of ±0.1mm: The package body measures approximately 3.2mm in length, 1.6mm in width, and has a height of 0.6mm, making it an extra-thin component. The pin assignment is: Pin 1: Green cathode, Pin 3: Red anode, Pin 4: Blue anode (specific pin functions should be verified from the package diagram).

5.2 Recommended PCB Pad Layout and Polarity

A recommended land pattern for the PCB is provided to ensure proper solder joint formation and mechanical stability during reflow. The design considers solder fillet formation and tombstoning prevention. Clear polarity marking on the PCB silkscreen corresponding to the LED's pin 1 indicator is essential to prevent incorrect installation.

6. Soldering and Assembly Guidelines

6.1 IR Reflow Soldering Conditions (Pb-Free Process)

The device is qualified for lead-free infrared reflow soldering. A suggested profile includes a preheat stage, a soak zone, a reflow zone with a peak temperature not exceeding 260°C for a duration of 10 seconds, and a controlled cooling phase. Adherence to this profile is critical to prevent thermal damage to the LED package and the internal wire bonds.

6.2 Cleaning

If cleaning is necessary after soldering, only specified solvents should be used. Immersing the LED in ethyl alcohol or isopropyl alcohol at room temperature for less than one minute is acceptable. The use of unspecified or aggressive chemical cleaners can damage the epoxy lens and package material, leading to reduced light output or premature failure.

6.3 Storage and Handling

• ESD Precautions: LEDs are sensitive to electrostatic discharge (ESD). Handling should be performed using grounded wrist straps, anti-static mats, and containers. All equipment must be properly grounded.
• Moisture Sensitivity: The package is rated at MSL 3. When the original moisture-barrier bag is sealed with desiccant, storage should be at ≤30°C and ≤90% RH, with a shelf life of one year. Once opened, components should be stored at ≤30°C and ≤60% RH and should be IR-reflowed within one week. For storage beyond one week out of the original bag, a bake at 60°C for at least 20 hours is required before soldering to remove absorbed moisture and prevent "popcorning" during reflow.

7. Packaging and Ordering Information

7.1 Tape and Reel Specifications

The LEDs are supplied on embossed carrier tape with a width of 8mm. The tape is wound onto a standard 7-inch (178mm) diameter reel. Each reel contains 3000 pieces. The tape pockets are sealed with a protective top cover tape. Packaging conforms to ANSI/EIA-481 specifications. For quantities less than a full reel, a minimum packing quantity of 500 pieces applies for remainders.

8. Application Suggestions

8.1 Design Considerations

• Current Limiting: Always use a series current-limiting resistor or a constant-current driver to set the I_F to the desired level (typically 20mA max DC). The resistor value is calculated as R = (Supply Voltage - V_F) / I_F.
• Thermal Management: Although power dissipation is low, ensure adequate PCB copper area or thermal vias, especially for the Red LED which has a lower Pd rating, to conduct heat away from the LED junction and maintain performance and longevity.
• Optical Design: The side-emitting nature of this package is ideal for edge-lighting light guides, illuminating symbols from the side, or providing status indication on the edge of a PCB. Consider the 130-degree viewing angle when designing light pipes or lenses.

8.2 Typical Application Circuits

For simple indicator use, each color channel (Red, Green, Blue) can be driven independently via a microcontroller GPIO pin through a suitable current-limiting resistor. For multi-color or white light generation (by mixing RGB), more sophisticated PWM (Pulse Width Modulation) control is recommended to achieve color mixing and dimming without shifting chromaticity.

9. Technical Comparison and Differentiation

The primary differentiating factors of this component are its ultra-thin 0.6mm profile and side-looking emission. Compared to top-emitting LEDs, this package enables innovative industrial designs where vertical space is extremely limited, such as in ultra-thin mobile devices, wearable technology, or behind panels. The integration of three distinct high-brightness chips (InGaN Blue/Green, AlInGaP Red) in one compact side-emitting package offers a full-color solution in a form factor typically reserved for single-color side LEDs.

10. Frequently Asked Questions (Based on Technical Parameters)

10.1 Can I drive the LED above 20mA for more brightness?

Operating continuously above the absolute maximum DC forward current of 20mA is not recommended as it will exceed the power dissipation rating, leading to excessive junction temperature, accelerated lumen depreciation, and potential catastrophic failure. For higher brightness, select an LED from a higher luminous intensity bin or consider pulsed operation within the peak current ratings.

10.2 Why is the forward voltage different for each color?

The forward voltage is a fundamental property of the semiconductor material's bandgap. Blue and Green LEDs use InGaN materials with a wider bandgap, resulting in a higher V_F (typically ~3.0V). Red LEDs use AlInGaP material with a narrower bandgap, resulting in a lower V_F (typically ~2.0V). This must be accounted for in circuit design, especially when driving multiple colors from the same voltage rail.

10.3 How do I interpret the binning codes?

The bin codes (e.g., T1 for Blue intensity, U2 for Red intensity, Bin 1 for voltage) are used during manufacturing to sort LEDs based on measured performance. For applications requiring color or brightness consistency (e.g., multi-LED arrays, backlighting), specifying and using LEDs from the same bin code is critical. Consult the bin code tables in sections 3.1 and 3.2 to select the appropriate performance range for your design.

11. Practical Use Case Example

Scenario: Status Indicator on a Thin Consumer Device Motherboard. A designer is developing a smartwatch with a motherboard thickness constraint of 1.0mm. A multi-color status indicator (e.g., charging=Red, fully charged=Green, Bluetooth connected=Blue) is required on the edge of the board. The LTST-S33GBEGK-SN is an ideal choice. Its 0.6mm height fits within the mechanical envelope. The side emission allows the light to be coupled directly into a small light guide that runs to the device's bezel, illuminating a small window. The designer would place three independent driver circuits (microcontroller pin + resistor) for each color channel on the PCB, following the recommended pad layout. They would specify LEDs from the same V_F and I_V bins to ensure uniform brightness and color appearance across all units in production.

12. Operating Principle Introduction

Light Emitting Diodes (LEDs) are semiconductor devices that emit light through electroluminescence. When a forward voltage is applied across the p-n junction, electrons and holes are injected into the active region where they recombine. The energy released during this recombination is emitted as photons (light). The color (wavelength) of the emitted light is determined by the bandgap energy of the semiconductor material used in the active region. The LTST-S33GBEGK-SN integrates three such p-n junctions made from different semiconductor materials (InGaN for blue/green, AlInGaP for red) within a single epoxy-molded package, each with separate electrical connections.

13. Technology Trends

The development of SMD LEDs continues to focus on several key areas: Increased Efficiency (lm/W): Ongoing improvements in epitaxial growth and chip design yield more light output per unit of electrical input power. Miniaturization: Packages are becoming smaller and thinner to enable denser integration and new form factors in consumer electronics. Improved Color Rendering and Consistency: Advances in phosphor technology (for white LEDs) and tighter binning processes allow for more accurate and uniform color production. Higher Reliability and Lifetime: Enhanced packaging materials and thermal management designs are extending operational lifetimes, making LEDs suitable for more demanding applications. The side-looking, multi-chip package represented by this datasheet is a response to the demand for compact, integrated lighting solutions in space-constrained devices.