Dual Color Side Looking SMD LED LTST-S326TGKFKT-5A Datasheet - Package Dimensions - Green 2.8V / Orange 1.9V - 76mW / 75mW - English Technical Document

1. Product Overview

This document provides the complete technical specifications for a dual-color, side-looking surface-mount device (SMD) LED. The component integrates two distinct semiconductor chips within a single package: an InGaN-based chip for green emission and an AlInGaP-based chip for orange emission. This design enables compact solutions for status indication, backlighting, and decorative lighting where multiple color signals are required from a single point. The device is constructed with a water-clear lens, maximizing light output, and features tin-plated terminations for enhanced solderability and RoHS compliance.

The LED is supplied in industry-standard 8mm tape on 7-inch reels, making it fully compatible with high-speed automated pick-and-place assembly equipment. Its design is also compatible with infrared (IR) reflow soldering processes, facilitating its integration into modern printed circuit board (PCB) manufacturing lines.

2. Technical Parameters Deep Analysis

2.1 Absolute Maximum Ratings

The absolute maximum ratings define the stress limits beyond which permanent damage to the device may occur. For reliable operation, these limits should never be exceeded, even momentarily.

• Power Dissipation (Pd): The maximum allowable power dissipation is 76 mW for the green chip and 75 mW for the orange chip at an ambient temperature (Ta) of 25°C. Exceeding this limit risks thermal degradation of the semiconductor junction.
• Forward Current: The maximum continuous DC forward current (IF) is 20 mA for the green chip and 30 mA for the orange chip. For pulsed operation, a peak forward current of 100 mA (green) and 80 mA (orange) is permitted under a strict 1/10 duty cycle with a 0.1ms pulse width. This parameter is critical for driving circuit design to prevent current-induced failure.
• Temperature Ranges: The operating temperature range is specified from -20°C to +80°C. The storage temperature range is wider, from -30°C to +100°C. These ranges ensure the LED's mechanical and chemical integrity under various environmental conditions.
• Soldering Condition: The device can withstand infrared reflow soldering with a peak temperature of 260°C for a maximum duration of 10 seconds. This is a standard condition for lead-free (Pb-free) solder processes.

2.2 Electrical and Optical Characteristics

These characteristics are measured at a standard test condition of Ta=25°C and a forward current (IF) of 5 mA, unless otherwise noted. They define the typical performance of the device.

• Luminous Intensity (Iv): This is the primary measure of light output. For the green chip, the typical luminous intensity ranges from a minimum of 28.0 mcd to a maximum of 180.0 mcd. For the orange chip, the range is from 11.2 mcd to 71.0 mcd. The actual value for a specific unit depends on its assigned bin code.
• Viewing Angle (2θ1/2): Both chips feature a wide viewing angle of 130 degrees (typical). This is defined as the full angle at which the luminous intensity drops to half of its value measured on the central axis. This wide angle ensures good visibility from various perspectives, which is essential for side-looking indicators.
• Wavelength: The green chip has a typical peak emission wavelength (λP) of 530 nm and a typical dominant wavelength (λd) of 527 nm. The orange chip has a typical peak emission wavelength of 611 nm and a dominant wavelength of 605 nm. The spectral line half-width (Δλ) is 35 nm for green and 17 nm for orange, indicating the spectral purity of the emitted light.
• Forward Voltage (VF): At 5 mA, the typical forward voltage is 2.8 V for the green chip (max 3.2 V) and 1.9 V for the orange chip (max 2.3 V). This parameter is crucial for calculating the series resistor value in a constant-voltage driving circuit to set the desired current.
• Reverse Current (IR): The maximum reverse current is 10 μA for both chips when a reverse voltage (VR) of 5V is applied. It is explicitly noted that the device is not designed for reverse operation; this test is for leakage characterization only.

3. Binning System Explanation

To manage production variations and allow designers to select LEDs with consistent performance, the devices are sorted into bins based on luminous intensity.

3.1 Green Chip Intensity Binning

The green LEDs are categorized into four bins (N, P, Q, R) with the following minimum and maximum luminous intensity values at 5 mA:
Bin N: 28.0 - 45.0 mcd
Bin P: 45.0 - 71.0 mcd
Bin Q: 71.0 - 112.0 mcd
Bin R: 112.0 - 180.0 mcd
A tolerance of +/-15% is applied to each intensity bin.

3.2 Orange Chip Intensity Binning

The orange LEDs are categorized into four bins (L, M, N, P) with the following ranges:
Bin L: 11.2 - 18.0 mcd
Bin M: 18.0 - 28.0 mcd
Bin N: 28.0 - 45.0 mcd
Bin P: 45.0 - 71.0 mcd
A tolerance of +/-15% is also applied to these bins.

This binning system allows for precise selection based on application brightness requirements, ensuring visual consistency in multi-LED arrays or products.

4. Performance Curve Analysis

While specific graphical curves are referenced in the datasheet (e.g., Fig.1, Fig.5), their typical implications are analyzed here based on standard LED physics and the provided parameters.

4.1 Forward Current vs. Luminous Intensity (I-Iv Curve)

The luminous intensity of an LED is approximately proportional to the forward current over a significant range. Operating the green chip at its maximum DC current of 20 mA would typically yield significantly higher light output than the 5 mA test condition, though the exact relationship should be verified from the characteristic curve. The same applies to the orange chip at 30 mA. Designers must ensure the increased power dissipation at higher currents remains within the absolute maximum rating.

4.2 Forward Voltage vs. Forward Current (V-I Curve)

The forward voltage has a logarithmic relationship with current. The specified VF at 5 mA provides a key operating point. As current increases, VF will increase slightly. This non-linear relationship is important for designing efficient constant-current drivers versus simple resistor-limited circuits.

4.3 Temperature Dependence

LED performance is temperature-sensitive. Typically, luminous intensity decreases as the junction temperature increases. The forward voltage also decreases with rising temperature. While specific curves are not provided, the specified operating temperature range of -20°C to +80°C indicates the limits within which the published characteristics are reasonably valid. For applications near the extremes, derating or thermal management may be necessary.

4.4 Spectral Distribution

The peak and dominant wavelengths, along with the spectral half-width, define the color point. The green emission (centered ~527-530 nm) and orange emission (centered ~605-611 nm) are distinct. The narrower half-width of the orange chip (17 nm vs. 35 nm for green) suggests a more spectrally pure, saturated orange color.

5. Mechanical and Package Information

5.1 Package Dimensions and Pin Assignment

The device conforms to an EIA standard package outline. Detailed dimensional drawings are provided in the datasheet, with all measurements in millimeters. Key tolerances are typically ±0.10 mm. The pin assignment is clearly defined: Cathode 1 (C1) is for the orange chip, and Cathode 2 (C2) is for the green chip. The common anode configuration is implied, allowing independent control of each color.

5.2 Suggested Soldering Pad Layout

The datasheet includes a recommended soldering pad pattern for PCB design. Adhering to these dimensions ensures proper solder joint formation, mechanical stability, and heat dissipation during the reflow process. A suggested soldering direction is also indicated to promote uniform solder flow.

6. Soldering and Assembly Guidelines

6.1 Reflow Soldering Profile

A detailed suggestion for an IR reflow profile suitable for Pb-free processes is provided. This profile typically includes:
1. A pre-heat zone to gradually raise the PCB temperature and activate the flux.
2. A soak zone to equalize temperature across the board.
3. A reflow zone where the temperature peaks at a maximum of 260°C for no more than 10 seconds.
4. A cooling zone. The profile is based on JEDEC standards to ensure reliability.

6.2 Manual Soldering

If manual soldering with an iron is necessary, the maximum recommended tip temperature is 300°C, with a soldering time not exceeding 3 seconds per joint. This should be performed only once to minimize thermal stress on the LED package.

6.3 Cleaning

If cleaning is required after soldering, only specified solvents should be used. The datasheet recommends immersing the LED in ethyl alcohol or isopropyl alcohol at normal temperature for less than one minute. Unspecified chemicals may damage the epoxy lens or package.

6.4 Electrostatic Discharge (ESD) Precautions

The LED is sensitive to static electricity and voltage surges. Proper ESD controls must be implemented during handling and assembly. This includes the use of grounded wrist straps, anti-static mats, and ensuring all equipment is properly grounded.

7. Packaging and Ordering Information

7.1 Tape and Reel Specifications

The device is packaged in 8mm wide embossed carrier tape. The tape is wound onto standard 7-inch (178 mm) diameter reels. Each full reel contains 3000 pieces. For quantities less than a full reel, a minimum packing quantity of 500 pieces is specified for remainders. The packaging conforms to ANSI/EIA-481 specifications.

7.2 Storage Conditions

Sealed Package: LEDs in the original moisture-proof bag with desiccant should be stored at ≤30°C and ≤90% Relative Humidity (RH). The recommended shelf life under these conditions is one year.
Opened Package: Once the moisture barrier bag is opened, the storage environment should not exceed 30°C and 60% RH. Components removed from the original packaging should ideally undergo IR reflow within one week. For longer storage outside the original bag, they should be kept in a sealed container with desiccant or in a nitrogen desiccator. If stored for more than a week, a bake-out at approximately 60°C for at least 20 hours is recommended before soldering to remove absorbed moisture and prevent "popcorning" during reflow.

8. Application Suggestions

8.1 Typical Application Scenarios

• Status Indicators: Ideal for equipment panels requiring multi-state indication (e.g., power on=green, standby=orange, fault=both blinking).
• Consumer Electronics: Backlighting for buttons or logos in devices like routers, audio equipment, or gaming peripherals.
• Automotive Interior Lighting: For non-critical interior ambient lighting or status displays, noting the operating temperature range.
• Industrial Control Panels: Providing clear, color-coded operational status in control systems.

8.2 Design Considerations

• Current Limiting: Always use a series resistor or constant-current driver for each chip. Calculate the resistor value using R = (Vcc - VF) / IF, where VF is the forward voltage at the desired current (IF). Use the maximum VF from the datasheet for a conservative design that ensures current never exceeds the limit.
• Thermal Management: While the power dissipation is low, continuous operation at maximum current in high ambient temperatures may require attention to PCB layout for heat sinking, especially if multiple LEDs are clustered.
• Visual Design: The wide 130-degree viewing angle facilitates off-axis visibility. Consider the lens color (water clear) and the surrounding bezel design to achieve the desired visual effect and light mixing if both colors are used simultaneously.

9. Technical Comparison and Differentiation

This dual-color side-looking LED offers specific advantages compared to alternatives:

• vs. Two Discrete LEDs: Saves PCB space, reduces component count, and simplifies pick-and-place assembly with a single part number.
• vs. RGB LEDs: Provides a simpler, often more cost-effective solution when only two specific colors (green and orange) are needed, without the complexity of a three-channel driver.
• vs. Through-Hole LEDs: The SMD package enables fully automated assembly, lower profile designs, and better reliability by eliminating manual soldering and lead bending.
• Key Features: The combination of InGaN (for efficient green) and AlInGaP (for efficient orange) technologies in one package provides good luminous efficacy for both colors. RoHS compliance and compatibility with lead-free reflow are essential for modern manufacturing.

10. Frequently Asked Questions (FAQs)

10.1 Can I drive both colors simultaneously at their maximum DC current?

Yes, but you must consider the total power dissipation. If both chips are driven at their max DC current (Green: 20mA @ ~3.2V, Orange: 30mA @ ~2.3V), the approximate power is (0.02A * 3.2V) + (0.03A * 2.3V) = 0.064W + 0.069W = 0.133W or 133 mW. This exceeds the individual Pd ratings (76mW, 75mW) and requires careful thermal evaluation of the PCB and ambient conditions to ensure the junction temperature does not exceed safe limits, potentially affecting longevity.

10.2 What is the difference between peak wavelength and dominant wavelength?

Peak wavelength (λP) is the wavelength at which the emission spectrum has its highest intensity. Dominant wavelength (λd) is derived from the CIE chromaticity diagram and represents the single wavelength of a pure monochromatic light that would match the perceived color of the LED. λd is more closely related to human color perception, while λP is a physical measurement of the spectrum.

10.3 How do I interpret the bin code when ordering?

The part number LTST-S326TGKFKT-5A likely includes or implies specific bin codes for intensity. To ensure consistency in your application's brightness, you should specify the desired bin codes (e.g., Green: Bin R for highest output, Orange: Bin P) when ordering. Consult the manufacturer's full product ordering guide for the exact coding system.

10.4 Is a reverse protection diode necessary?

While the LED can tolerate a 5V reverse bias with only 10 μA leakage, it is not designed for reverse operation. In circuits where reverse voltage transients are possible (e.g., inductive loads, hot-plugging), external protection such as a series diode or a bridge rectifier configuration is strongly recommended to prevent damage.

11. Practical Design and Usage Examples

11.1 Dual-State Network Router Indicator

Scenario: Designing a status LED for a router to indicate "Active/Data Transfer" (green) and "Idle/Standby" (orange).
Implementation: Connect the common anode to a 3.3V rail via a current-limiting resistor sized for each color. Use two GPIO pins from the router's microcontroller, each connected to the cathode of one color via a small-signal NPN transistor or a MOSFET. The firmware can then switch the green LED on during data activity and the orange LED on during idle periods. The wide viewing angle ensures visibility from anywhere in the room.

11.2 Battery Charge Level Indicator

Scenario: A simple 2-stage charger indicator: "Charging" (orange) and "Fully Charged" (green).
Implementation: The charge management IC's status outputs can directly drive the LED cathodes (if capable of sinking the required current) or drive transistors. When charging, the orange LED is illuminated. When the charge cycle completes, the IC switches off the orange drive and switches on the green drive.

12. Technology Principle Introduction

This LED utilizes two different semiconductor material systems:

• InGaN (Indium Gallium Nitride): This material is used for the green-emitting chip. By varying the ratio of indium to gallium in the alloy, the bandgap of the semiconductor can be tuned, which directly determines the wavelength of light emitted when electrons recombine with holes across the bandgap. InGaN is known for its ability to produce efficient blue, green, and white LEDs.
• AlInGaP (Aluminum Indium Gallium Phosphide): This material is used for the orange-emitting chip. Similarly, by adjusting the composition of this quaternary alloy, the bandgap can be engineered to produce light in the red, orange, yellow, and green spectral regions. AlInGaP is particularly efficient in the red to orange range.

In a dual-color package, these two distinct chip structures are mounted on a common lead frame, wire-bonded, and encapsulated in a clear epoxy lens that protects the chips and acts as an optical element.

13. Technology Development Trends

The field of LED technology continues to evolve, with trends impacting components like this one:

• Increased Efficiency: Ongoing research aims to improve the internal quantum efficiency (IQE) and light extraction efficiency (LEE) of both InGaN and AlInGaP materials, leading to higher luminous intensity for the same input current or lower power consumption for the same light output.
• Miniaturization: The drive for smaller electronic devices pushes for ever-smaller LED packages while maintaining or improving optical performance.
• Improved Color Consistency: Advances in epitaxial growth and binning processes lead to tighter tolerances on dominant wavelength and luminous intensity, reducing color and brightness variation between units.
• Enhanced Reliability: Improvements in packaging materials (epoxy, silicones) and die attach technologies enhance the LED's ability to withstand higher temperatures, humidity, and thermal cycling, extending operational lifetime.
• Integrated Intelligence: A broader trend is the integration of control circuitry (like constant-current drivers or simple logic) within the LED package itself, creating "smart LED" components that simplify system design.