SMD RGB LED LTST-S32F1KT-5A Datasheet - Full Color Chip - Voltage 1.6-3.1V - Power 75-80mW - English Technical Document

1. Product Overview

The LTST-S32F1KT-5A is a compact, side-looking, full-color Surface Mount Device (SMD) LED lamp. It integrates three distinct semiconductor chips within a single package: an AlInGaP chip for red emission, and two InGaN chips for green and blue emission. This configuration enables the generation of a broad spectrum of colors through individual or combined control of the three channels. The device is designed for automated printed circuit board (PCB) assembly processes, featuring a tin-plated termination for enhanced solderability and compatibility with lead-free (Pb-free) reflow soldering profiles.

The primary design objective is to provide a reliable, high-brightness RGB light source for space-constrained applications where status indication, backlighting, or symbolic illumination is required. Its miniature footprint and side-emitting lens profile make it particularly suitable for integration into slim consumer electronics, communication devices, and industrial control panels where frontal space is limited but side visibility is crucial.

1.1 Features

• Compliant with RoHS (Restriction of Hazardous Substances) directives.
• Side-viewing optical design with a water-clear lens.
• Utilizes ultra-bright InGaN (for Green/Blue) and AlInGaP (for Red) semiconductor technology.
• Packaged on 8mm tape housed on standard 7-inch diameter reels for automated pick-and-place equipment.
• Conforms to EIA (Electronic Industries Alliance) standard package outlines.
• Input logic compatible (I.C. compatible) for easy interface with microcontroller and driver circuits.
• Fully compatible with high-volume infrared (IR) reflow solder processes.

1.2 Applications

• Telecommunication equipment (e.g., cellular base stations, routers).
• Office automation devices (e.g., printers, scanners, multifunction devices).
• Home appliance indicator panels and control interfaces.
• Industrial equipment status and fault indicators.
• Keypad and keyboard backlighting in portable devices.
• General-purpose status and power indicators.
• Micro-displays and icon illumination.
• Signal and symbolic luminaries in control panels.

2. Technical Parameters: In-Depth Objective Interpretation

This section provides a detailed analysis of the device's operational limits and performance characteristics under defined test conditions. All data is specified at an ambient temperature (Ta) of 25°C unless otherwise noted.

2.1 Absolute Maximum Ratings

These ratings define the stress limits beyond which permanent damage to the device may occur. Continuous operation at or near these limits is not advised.

• Power Dissipation (Pd): Red: 75 mW, Green/Blue: 80 mW. This is the maximum allowable power loss as heat within the package.
• Peak Forward Current (I_F(PEAK)): Red: 80 mA, Green/Blue: 100 mA. Applicable only under pulsed conditions (1/10 duty cycle, 0.1ms pulse width) to prevent thermal overload.
• DC Forward Current (I_F): Red: 30 mA, Green/Blue: 20 mA. The maximum continuous forward current recommended for reliable long-term operation.
• Operating Temperature Range: -20°C to +80°C. The ambient temperature range over which the device is designed to function.
• Storage Temperature Range: -30°C to +100°C. The allowable temperature range when the device is not powered.
• Infrared Soldering Condition: Withstands 260°C peak temperature for 10 seconds, defining its Moisture Sensitivity Level (MSL) and reflow capability.

2.2 Electrical & Optical Characteristics

These are the typical performance parameters measured under standard test conditions (I_F = 5mA, Ta=25°C).

• Luminous Intensity (I_V): Measured in millicandelas (mcd). Minimum values: Red: 18.0 mcd, Green: 45.0 mcd, Blue: 11.2 mcd. Maximum values: Red: 45.0 mcd, Green: 180.0 mcd, Blue: 45.0 mcd. This wide range is managed through a binning system.
• Viewing Angle (2θ_1/2): Typically 130 degrees. This is the full angle at which the luminous intensity is half of the peak intensity, defining the beam width.
• Peak Emission Wavelength (λ_p): Typical: Red: 632 nm, Green: 520 nm, Blue: 468 nm. The wavelength at which the spectral power distribution is maximum.
• Dominant Wavelength (λ_d): The single wavelength perceived by the human eye that matches the color of the LED. Range: Red: 617-631 nm (Typ. 624 nm), Green: 520-540 nm (Typ. 527 nm), Blue: 463-477 nm (Typ. 470 nm).
• Spectral Line Half-Width (Δλ): Typical: Red: 17 nm, Green: 35 nm, Blue: 26 nm. The spectral bandwidth measured at half the maximum intensity, indicating color purity.
• Forward Voltage (V_F): At I_F=5mA. Range: Red: 1.6 - 2.3 V, Green: 2.7 - 3.1 V, Blue: 2.7 - 3.1 V. This parameter is also binned.
• Reverse Current (I_R): Maximum 10 µA at V_R = 5V. LEDs are not designed for reverse bias operation; this test is for quality assurance only.

3. Binning System Explanation

To ensure consistent color and brightness in production, LEDs are sorted into performance bins. The LTST-S32F1KT-5A uses separate binning for Forward Voltage (V_F) and Luminous Intensity (I_V).

3.1 Forward Voltage (V_F) Binning

For Green and Blue chips (tested at I_F=5mA):
- Bin Code E7: V_F = 2.70V to 2.90V.
- Bin Code E8: V_F = 2.90V to 3.10V.
Tolerance on each bin is ±0.1V. Red chip V_F is specified but not binned in this document.

3.2 Luminous Intensity (I_V) Binning

Measured at I_F=5mA. Tolerance on each bin is ±15%.
Blue: L (11.2-18.0 mcd), M (18.0-28.0 mcd), N (28.0-45.0 mcd).
Green: P (45.0-71.0 mcd), Q (71.0-112.0 mcd), R (112.0-180.0 mcd).
Red: M (18.0-28.0 mcd), N (28.0-45.0 mcd).
The bin code is marked on the packaging, allowing designers to select LEDs with matched brightness for multi-LED arrays.

4. Performance Curve Analysis

Typical performance curves illustrate the relationship between key parameters. These are essential for circuit design and thermal management.

• Relative Luminous Intensity vs. Forward Current: Shows the non-linear relationship between drive current and light output for each color. Operating above the recommended DC current leads to diminishing returns and increased heat.
• Relative Luminous Intensity vs. Ambient Temperature: Demonstrates the thermal quenching effect, where light output decreases as junction temperature rises. Proper heat sinking or current derating is necessary for high-temperature environments.
• Forward Voltage vs. Forward Current: Displays the diode's I-V characteristic. The dynamic resistance can be inferred from the slope of the curve above the turn-on voltage.
• Spectral Distribution: Graphs showing the relative radiant power versus wavelength for each chip, highlighting the peak (λ_p) and spectral width (Δλ).

5. Mechanical & Package Information

5.1 Package Dimensions

The device conforms to a standard SMD outline. Critical dimensions include body length, width, and height, as well as the land pattern (footprint) recommendations for PCB design. All dimensions are in millimeters with a standard tolerance of ±0.1mm unless specified otherwise. A detailed diagram specifies the pin assignment: Pin 1 for the Red anode, Pin 2 for the Green anode, and Pin 3 for the Blue anode. The cathodes for all three chips are internally connected to Pin 4.

5.2 Recommended PCB Pad Design & Polarity

A land pattern diagram is provided to ensure proper solder joint formation during reflow. The design accommodates solder fillets and prevents tombstoning. The polarity is clearly indicated by a marking on the device body (typically a dot or a chamfered corner) corresponding to Pin 1 (Red).

6. Soldering & Assembly Guidelines

6.1 Recommended IR Reflow Profile (Pb-Free Process)

A time-temperature graph defines the suggested reflow soldering profile:
- Preheat: 150-200°C for up to 120 seconds.
- Reflow: Peak temperature not exceeding 260°C.
- Time above 260°C: Maximum 10 seconds.
- Number of passes: Maximum of two reflow cycles.
For hand soldering with an iron: Temperature ≤300°C, time ≤3 seconds, only one time.

6.2 Cleaning

If cleaning is necessary post-solder, only specified alcohol-based solvents like ethyl alcohol or isopropyl alcohol should be used. Immersion should be at normal temperature for less than one minute. Unspecified chemicals may damage the epoxy lens or package.

6.3 Storage & Handling

• ESD Precautions: The device is sensitive to electrostatic discharge (ESD). Handling must involve grounded wrist straps, anti-static mats, and properly grounded equipment.
• Moisture Sensitivity: Packaged as MSL 3. Once the original moisture-barrier bag is opened, the components should be reflow-soldered within one week (168 hours) under factory floor conditions (≤30°C/60% RH). For longer storage out of the bag, use a dry cabinet or desiccated container. Components exposed beyond one week require baking (e.g., 60°C for 20 hours) before reflow to prevent popcorning.

7. Packaging & Ordering Information

7.1 Tape and Reel Specifications

The device is supplied in embossed carrier tape with a protective cover tape, wound onto 7-inch (178mm) diameter reels.
- Quantity per reel: 3000 pieces.
- Minimum order quantity for remnants: 500 pieces.
- Tape width: 8mm.
- Pocket spacing and reel dimensions conform to ANSI/EIA-481 standards.
- The maximum allowed number of consecutive missing components in the tape is two.

8. Application Suggestions

8.1 Typical Application Circuits

Each color channel (Red, Green, Blue) must be driven independently via a current-limiting resistor or, preferably, a constant-current driver. The forward voltage differs per color (Red ~2.0V, Green/Blue ~3.0V), so separate current-setting calculations are required if using a common voltage supply with series resistors. For PWM (Pulse Width Modulation) dimming or color mixing, ensure the driver can handle the required frequency and current.

8.2 Design Considerations

• Thermal Management: Although power dissipation is low, ensure adequate PCB copper area or thermal vias under the device's thermal pad (if applicable) to conduct heat away, especially when driving at or near maximum current.
• Current Derating: For operation near the upper end of the temperature range (+80°C), reduce the forward current to maintain reliability and prevent accelerated lumen depreciation.
• Optical Design: The side-emitting profile is ideal for light-pipe or waveguide applications. Consider the 130-degree viewing angle when designing light guides to ensure uniform illumination.

9. Technical Comparison & Differentiation

The LTST-S32F1KT-5A's key differentiators lie in its specific combination of features:
- Side-Looking vs. Top-View: Unlike common top-emitting LEDs, this device emits light from the side, enabling unique mechanical integration for edge-lit panels or status indicators on the vertical surface of a PCB.
- Full-Color in One Package: Integrates three primary-color chips, saving board space compared to using three discrete single-color LEDs.
- Technology Mix: Uses the optimal semiconductor material for each color: high-efficiency AlInGaP for red and high-brightness InGaN for green/blue, resulting in good overall luminous efficacy.
- Robust Construction: Tin-plated leads and compatibility with harsh IR reflow profiles make it suitable for modern, high-volume manufacturing.

10. Frequently Asked Questions (Based on Technical Parameters)

Q1: Can I drive all three colors from a single 5V supply?
A: Yes, but you must use separate current-limiting resistors for each channel. Calculate the resistor value as R = (V_supply - V_F) / I_F. Use the maximum V_F from the datasheet for a safe design. For example, for the Blue channel at 20mA: R = (5V - 3.1V) / 0.02A = 95 Ohms (use 100 Ohms).

Q2: Why is the maximum DC current different for Red (30mA) vs. Green/Blue (20mA)?
A: This is primarily due to differences in the internal quantum efficiency and thermal characteristics of the AlInGaP (Red) and InGaN (Green/Blue) semiconductor materials. The Red chip can typically handle higher current densities within the same package thermal constraints.

Q3: How do I achieve white light with this RGB LED?
A: White light is created by simultaneously driving the Red, Green, and Blue chips at specific current ratios. The exact ratio depends on the desired white point (e.g., cool white, warm white) and the specific bin of LEDs used. This requires calibration or the use of a color sensor feedback loop for precise results.

Q4: What is the significance of the bin codes?
A: Bin codes ensure color and brightness consistency. For applications using multiple LEDs (like a light bar), specifying and using LEDs from the same V_F and I_V bins is critical to avoid visible differences in color hue or brightness between adjacent devices.

11. Practical Use Case

Scenario: Status Indicator for a Network Router
A designer needs a multi-color status indicator for a router showing power (steady green), activity (blinking green), error (red), and setup mode (blue). Using the LTST-S32F1KT-5A saves space compared to three separate LEDs. The side-emitting design allows the light to be coupled into a light pipe that runs to the front panel of the slim router enclosure. A microcontroller's GPIO pins, each with a series resistor (calculated for 5-10mA drive), control the individual colors. The wide viewing angle ensures the indicator is visible from various angles in a room.

12. Operating Principle Introduction

Light Emitting Diodes (LEDs) are semiconductor p-n junction devices. When a forward voltage is applied, electrons from the n-type region recombine with holes from the p-type region within the active layer, releasing energy in the form of photons (light). The wavelength (color) of the emitted light is determined by the energy bandgap of the semiconductor material. The LTST-S32F1KT-5A uses:
- AlInGaP (Aluminium Indium Gallium Phosphide): A material system with a bandgap corresponding to red and amber light. It offers high efficiency in the red-orange spectrum.
- InGaN (Indium Gallium Nitride): A material system with a tunable bandgap capable of emitting light from ultraviolet through blue to green, depending on the indium content. It is the standard for high-brightness blue and green LEDs.

13. Technology Trends

The general trajectory for SMD LEDs like this one includes:
- Increased Efficiency: Ongoing improvements in epitaxial growth and chip design lead to higher lumens per watt (lm/W), reducing power consumption for the same light output.
- Miniaturization: Continued reduction in package size while maintaining or increasing optical power.
- Improved Color Rendering & Consistency: Tighter binning tolerances and new phosphor technologies (for white LEDs) yield more consistent color points and higher Color Rendering Index (CRI).
- Integrated Intelligence: Growth of "smart LED" modules with built-in drivers, controllers, and communication interfaces (e.g., I2C, SPI) for simplified system design. While the LTST-S32F1KT-5A is a discrete component, the industry is moving towards more integrated solutions for complex lighting tasks.