LTST-C155TGKFKT Dual Color SMD LED Datasheet - 1.10mm Height - Green 3.3V/Orange 2.0V - 76mW/75mW - English Technical Document

1. Product Overview

This document provides the complete technical specifications for the LTST-C155TGKFKT, a dual-color, surface-mount device (SMD) LED. This component integrates two distinct semiconductor chips within a single, ultra-thin package: an InGaN (Indium Gallium Nitride) chip for green emission and an AlInGaP (Aluminum Indium Gallium Phosphide) chip for orange emission. It is designed for modern electronic assembly processes and applications requiring compact, bi-color indication.

The core advantages of this LED include its exceptionally low profile of 1.10mm, which is crucial for space-constrained designs in consumer electronics, automotive interiors, and portable devices. It is a green product compliant with ROHS (Restriction of Hazardous Substances) directives. The package is supplied on 8mm tape mounted on 7-inch diameter reels, making it fully compatible with high-speed automated pick-and-place equipment used in volume manufacturing. Its design is also compatible with infrared (IR) reflow soldering processes, aligning with lead-free (Pb-free) assembly standards.

The target market encompasses a wide range of electronic equipment where reliable, dual-status indication is needed. This includes office automation equipment, communication devices, household appliances, industrial control panels, and automotive dashboard indicators. The separate anode/cathode pins for each color allow for independent control, enabling status signaling, power indication, or multi-state user interface feedback.

2. In-Depth Technical Parameter Analysis

2.1 Absolute Maximum Ratings

Operating the device beyond these limits may cause permanent damage. The ratings are specified at an ambient temperature (Ta) of 25\u00b0C.

• Power Dissipation (Pd): 76 mW for the Green chip, 75 mW for the Orange chip. This parameter defines the maximum allowable power loss as heat. Exceeding this can lead to excessive junction temperature and accelerated degradation.
• Peak Forward Current (I_FP): 100 mA for Green, 80 mA for Orange. This is the maximum pulsed current allowed under a 1/10 duty cycle with a 0.1ms pulse width. It is significantly higher than the continuous DC rating, useful for brief, high-brightness pulses.
• DC Forward Current (I_F): 20 mA for Green, 30 mA for Orange. This is the recommended continuous operating current for standard brightness and long-term reliability.
• Reverse Voltage (V_R): 5 V for both colors. The device offers limited protection against reverse bias. It is not designed for AC operation or reverse-bias conditions in circuit design.
• Operating Temperature Range: -20\u00b0C to +80\u00b0C. The LED can function within this ambient temperature range.
• Storage Temperature Range: -30\u00b0C to +100\u00b0C.
• Infrared Soldering Condition: Withstands 260\u00b0C peak temperature for 10 seconds, which is a standard condition for Pb-free reflow profiles.

2.2 Electrical & Optical Characteristics

These are the typical performance parameters measured at Ta=25\u00b0C and I_F=20mA, unless otherwise noted.

• Luminous Intensity (I_V): This is the perceived brightness. For Green, it ranges from a minimum of 71.0 mcd to a maximum of 280.0 mcd. For Orange, it ranges from 45.0 mcd to 180.0 mcd. The actual intensity for a specific unit is determined by its bin code (see Section 3). Measurement follows the CIE photopic eye-response curve.
• Viewing Angle (2\u03b8_1/2): Typically 130 degrees for both colors. This wide viewing angle, defined as the full angle where intensity drops to half its on-axis value, makes the LED suitable for applications requiring visibility from a broad range of perspectives.
• Peak Emission Wavelength (\u03bb_P): Typically 525 nm for Green (InGaN) and 611 nm for Orange (AlInGaP). This is the wavelength at the highest point in the emitted spectrum.
• Dominant Wavelength (\u03bb_d): Typically 525 nm for Green and 605 nm for Orange. Derived from the CIE chromaticity diagram, this is the single wavelength that best represents the perceived color of the light.
• Spectral Line Half-Width (\u0394\u03bb): Typically 35.0 nm for Green and 17.0 nm for Orange. The Orange AlInGaP chip has a narrower spectral bandwidth, resulting in a more saturated, pure color compared to the broader Green spectrum.
• Forward Voltage (V_F): Typically 3.3 V (max 3.5 V) for Green at 20mA. Typically 2.0 V (max 2.4 V) for Orange at 20mA. The lower V_F of the Orange chip means it consumes less power for the same drive current. These values are critical for designing current-limiting resistors in the driver circuit.
• Reverse Current (I_R): Maximum 10 \u00b5A for Green and 20 \u00b5A for Orange when a reverse voltage (V_R) of 5V is applied. This test is for characterization only; the device is not intended for reverse operation.

3. Binning System Explanation

The LEDs are sorted (binned) based on their measured luminous intensity to ensure consistency within a production batch. The bin code is a critical part of the ordering information for applications requiring specific brightness levels.

3.1 Green Chip Intensity Bins

• Bin Code Q: Minimum 71.0 mcd, Maximum 112.0 mcd.
• Bin Code R: Minimum 112.0 mcd, Maximum 180.0 mcd.
• Bin Code S: Minimum 180.0 mcd, Maximum 280.0 mcd.

3.2 Orange Chip Intensity Bins

• Bin Code P: Minimum 45.0 mcd, Maximum 71.0 mcd.
• Bin Code Q: Minimum 71.0 mcd, Maximum 112.0 mcd.
• Bin Code R: Minimum 112.0 mcd, Maximum 180.0 mcd.

Tolerance: The intensity within each defined bin has a tolerance of +/-15%. This accounts for minor measurement and production variations.

4. Performance Curve Analysis

The datasheet references typical performance curves which are essential for understanding device behavior under non-standard conditions. While the specific graphs are not reproduced in text, their implications are analyzed below.

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

The I-V curve for each chip (Green/Orange) would show the exponential relationship typical of a diode. The curve for the Orange AlInGaP chip would have a lower knee voltage (around 2.0V) compared to the Green InGaN chip (around 3.3V). This graph is vital for determining the necessary supply voltage and for designing constant-current drivers to ensure stable brightness across units and temperatures.

4.2 Luminous Intensity vs. Forward Current

This curve typically shows a near-linear relationship between drive current and light output within the recommended operating range (up to 20-30mA). Driving the LED above the rated DC current will increase brightness but at the cost of higher power dissipation, reduced efficiency, and potentially shorter lifespan due to increased junction temperature.

4.3 Spectral Distribution

The referenced spectral graphs would illustrate the difference in spectral half-width between the Green (broader, ~35nm) and Orange (narrower, ~17nm) chips. The Orange chip's narrow emission is characteristic of AlInGaP technology, providing high color purity, which is often desirable for indicator applications where color distinction is critical.

4.4 Temperature Dependence

LED performance is temperature-sensitive. While not detailed in the provided text, typical characteristics include: a decrease in luminous intensity as junction temperature rises, a slight shift in dominant wavelength (usually a few nanometers), and a reduction in forward voltage (V_F) with increasing temperature. These factors must be considered in thermal management and circuit design for applications exposed to high ambient temperatures.

5. Mechanical & Package Information

5.1 Package Dimensions

The LED features an industry-standard EIA package outline. The key mechanical feature is its extra-thin profile with a maximum height (H) of 1.10 mm. All other critical dimensions for PCB footprint design, such as length, width, and lead spacing, are provided in the package drawing with a standard tolerance of \u00b10.10 mm unless otherwise specified.

5.2 Pin Assignment

The device has four pins. For the LTST-C155TGKFKT variant:

• Pins 1 and 3 are assigned to the Green InGaN chip (Anode and Cathode).
• Pins 2 and 4 are assigned to the Orange AlInGaP chip (Anode and Cathode).

This configuration allows the two LEDs to be wired and controlled completely independently.

5.3 Suggested Soldering Pad Layout

A recommended land pattern (footprint) for the PCB is provided. Adhering to this pattern is crucial for achieving reliable solder joints during reflow, preventing tombstoning (component standing up), and ensuring proper alignment. The pad design accounts for solder fillet formation and thermal relief.

6. Soldering & Assembly Guidelines

6.1 Reflow Soldering Profile

A suggested infrared (IR) reflow profile for Pb-free processes is included. Key parameters of this profile, which aligns with JEDEC standards, include:

• Pre-heat: 150\u00b0C to 200\u00b0C.
• Pre-heat Time: Maximum 120 seconds to gradually heat the board and component, minimizing thermal shock.
• Peak Temperature: Maximum 260\u00b0C.
• Time Above Liquidus: The component should be exposed to the peak temperature for a maximum of 10 seconds. Reflow should be performed a maximum of two times.

Because board design, components, and pastes vary, this profile serves as a generic target. Board-specific characterization is recommended.

6.2 Hand Soldering

If hand soldering is necessary, use a soldering iron with a temperature not exceeding 300\u00b0C. The soldering time per lead should be limited to a maximum of 3 seconds, and this should be done only once to prevent thermal damage to the plastic package and the internal wire bonds.

6.3 Cleaning

Do not use unspecified chemical cleaners. If cleaning is required after soldering, immerse the LED in ethyl alcohol or isopropyl alcohol at normal room temperature for less than one minute. Aggressive solvents may damage the epoxy lens or the package markings.

6.4 Electrostatic Discharge (ESD) Precautions

LEDs are sensitive to electrostatic discharge and voltage surges. It is recommended to use a grounded wrist strap or anti-static gloves when handling. All assembly equipment and workstations must be properly grounded to prevent ESD damage, which may not be immediately apparent but can degrade long-term reliability.

7. Packaging & Ordering Information

7.1 Tape and Reel Specifications

The components are supplied in embossed carrier tape on 7-inch (178 mm) diameter reels, per ANSI/EIA-481 standards.

• Tape Width: 8 mm.
• Quantity per Reel: 3000 pieces.
• Minimum Order Quantity (MOQ): 500 pieces for remainder quantities.
• Cover Tape: Empty component pockets are sealed with a top cover tape.
• Missing Components: A maximum of two consecutive missing lamps (empty pockets) is allowed per reel specification.

7.2 Storage Conditions

Sealed Package: Store at \u2264 30\u00b0C and \u2264 90% Relative Humidity (RH). The shelf life in the sealed moisture-proof bag with desiccant is one year. Opened Package: For components removed from their original packaging, the storage ambient should not exceed 30\u00b0C / 60% RH. It is recommended to complete IR reflow within one week of opening. Extended Storage (Opened): Store in a sealed container with desiccant or in a nitrogen desiccator. If stored out of the original bag for more than one week, a bake-out at approximately 60\u00b0C for at least 20 hours is recommended before assembly to remove absorbed moisture and prevent \"popcorning\" during reflow.

8. Application Notes & Design Considerations

8.1 Typical Application Circuits

Each LED chip (Green and Orange) requires an external current-limiting resistor when driven from a voltage source (e.g., 5V or 3.3V rail). The resistor value (R) can be calculated using Ohm's Law: R = (V_supply - V_F) / I_F. Use the maximum V_F from the datasheet to ensure the current does not exceed I_F(max) under worst-case conditions. For example, driving the Green LED from a 5V supply with a target I_F of 20mA: R = (5V - 3.5V) / 0.020A = 75 \u03a9. A standard 75\u03a9 or 82\u03a9 resistor would be suitable. For precise control or multiplexing, constant-current drivers are recommended.

8.2 Thermal Management

Although the power dissipation is low (76/75 mW), effective thermal management on the PCB is important for maintaining brightness and longevity, especially in high ambient temperature environments or when driven at higher currents. Ensure the PCB layout provides adequate copper area around the LED pads to act as a heat sink. Avoid placing other heat-generating components in close proximity.

8.3 Optical Design

The water-clear lens provides a wide, diffuse viewing angle. For applications requiring a more directed beam, secondary optics (such as light pipes or lenses) can be mounted above the LED. The dual-color capability allows for creating a third color (e.g., a yellowish hue) by driving both chips simultaneously at adjusted currents, though this requires careful current control to achieve the desired chromaticity.

9. Technical Comparison & Differentiation

The LTST-C155TGKFKT differentiates itself in the market through several key features: Ultra-Thin Profile (1.10mm): This is a significant advantage over many standard SMD LEDs, enabling its use in ultra-slim devices like modern smartphones, tablets, and laptops. Dual-Chip, Independent Control: Unlike some bi-color LEDs that use a common anode or cathode, this device offers fully independent pins. This provides greater design flexibility, allowing for separate drive circuits and more complex signaling patterns without additional multiplexing complexity. Material Technology: The use of InGaN for green and AlInGaP for orange represents a choice of high-efficiency semiconductor materials for their respective colors, offering good brightness and color stability. Manufacturing Readiness: Full compatibility with automated placement and standard Pb-free reflow profiles reduces assembly cost and complexity for high-volume manufacturers.

10. Frequently Asked Questions (FAQs)

Q1: Can I drive both the Green and Orange LEDs at the same time? A: Yes, the pins are independent. You can drive one, the other, or both simultaneously. Ensure your power supply and circuit can provide the combined current (e.g., up to 50mA if both are at 20mA).

Q2: What is the difference between Peak Wavelength and Dominant Wavelength? A: Peak Wavelength (\u03bb_P) is the physical wavelength of the highest intensity point in the spectrum. Dominant Wavelength (\u03bb_d) is a calculated value based on human color perception (CIE chart) that best matches the perceived color. They are often close but not identical, especially for broad spectra.

Q3: Why is the reverse voltage rating only 5V? A: LEDs are not designed to block reverse voltage like rectifier diodes. The 5V rating is a safe limit for occasional accidental reverse bias during handling or testing. In circuit design, always ensure the LED is correctly polarized or protected by a series diode if connected to an AC signal or a bidirectional bus.

Q4: How do I interpret the bin code when ordering? A: The bin code (e.g., \"S\" for Green, \"R\" for Orange) specifies the guaranteed minimum and maximum luminous intensity. For consistent brightness across a product line, specify the required bin code to your distributor. If not specified, you may receive components from any available bin within the product's range.

11. Practical Application Example

Scenario: Dual-Status Power Indicator for a Consumer Device. A portable battery-powered device uses this LED to indicate charging status. The design goal is: Orange for \"Charging,\" Green for \"Fully Charged.\" Implementation: The microcontroller (MCU) has two GPIO pins. Each pin is connected to the anode of one LED color through a current-limiting resistor (calculated as in Section 8.1). The cathodes are connected to ground. The MCU firmware drives the Orange LED pin high during charging. When the battery management IC signals a full charge, the MCU switches off the Orange pin and drives the Green pin high. The ultra-thin package allows it to fit behind a slim bezel. The wide viewing angle ensures the status is visible from various angles. The independent control simplifies the firmware compared to a common-anode type requiring a switched ground.

12. Technology Principle Introduction

Light Emitting Diodes (LEDs) are semiconductor devices that emit light when an electric current passes through them. This phenomenon is called electroluminescence. When a voltage is applied in the forward direction, electrons from the n-type semiconductor and holes from the p-type semiconductor are injected into the active region (the junction). When an electron recombines with a hole, it releases energy in the form of a photon (light particle). The wavelength (color) of the emitted light is determined by the energy bandgap of the semiconductor material used in the active region. In this dual-color LED, two different semiconductor chips are housed in one package: InGaN (Indium Gallium Nitride): This material system has a wider bandgap that can be tuned to emit light in the blue, green, and ultraviolet regions. Here, it is engineered to emit green light (peak ~525 nm). AlInGaP (Aluminum Indium Gallium Phosphide): This material system is known for high efficiency in the red, orange, and yellow spectral regions. Here, it is engineered to emit orange light (peak ~611 nm). Each chip is connected to its own pair of bonding wires, which are attached to the four external pins, allowing for independent electrical operation.

13. Industry Trends

The development of SMD LEDs like the LTST-C155TGKFKT follows several key industry trends: Miniaturization: The drive towards thinner, smaller components continues to enable sleeker and more compact end products. The 1.10mm height represents this trend. Increased Integration: Combining multiple functions (two colors) in a single package saves PCB space and reduces assembly cost compared to using two separate LEDs. Lead-Free and Green Manufacturing: Compliance with ROHS and compatibility with Pb-free, high-temperature reflow profiles are now standard requirements driven by global environmental regulations. Automation Compatibility: Packaging on tape-and-reel and design for pick-and-place are essential for high-volume, cost-effective manufacturing. Performance Standardization: The use of EIA standard packages and JEDEC reflow profiles ensures interoperability and reliability across the electronics supply chain. Future trends may include even thinner packages, higher efficiency materials, and integrated drivers or control logic within the LED package itself.