LTST-C295TGKRKT Dual Color SMD LED Datasheet - 0.55mm Height - Green 3.8V / Red 2.4V - 76mW / 75mW - English Technical Document

1. Product Overview

The LTST-C295TGKRKT is a dual-color, surface-mount device (SMD) LED designed for modern electronic applications requiring compact size and high-brightness indicators. 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 red emission. Its primary design goal is to provide a reliable, space-saving solution for status indication, backlighting, and panel illumination where color differentiation is essential.

The core advantages of this LED include its exceptionally low profile of 0.55mm, which facilitates use in slim consumer electronics and portable devices. It is compliant with ROHS (Restriction of Hazardous Substances) directives, making it an environmentally conscious choice. The package is standardized according to EIA (Electronic Industries Alliance) norms, ensuring compatibility with automated pick-and-place assembly equipment and standard infrared reflow soldering processes, which streamlines high-volume manufacturing.

The target market encompasses a broad range of electronic equipment, including but not limited to office automation devices, communication hardware, household appliances, and various consumer electronics where dual-color status indication (e.g., power on/standby, charge status, network activity) is required in a minimal footprint.

2. In-Depth Technical Parameter Analysis

2.1 Absolute Maximum Ratings

These ratings define the stress limits beyond which permanent damage to the device may occur. Operation under or at these limits is not guaranteed. For the green chip, the maximum continuous DC forward current is 20mA, with a peak forward current of 100mA permissible under pulsed conditions (1/10 duty cycle, 0.1ms pulse width). The red chip allows for a slightly higher DC current of 30mA but a lower peak current of 80mA. The maximum power dissipation is 76mW for the green chip and 75mW for the red chip, critical for thermal management in densely packed PCBs. The device is rated for an operating temperature range of -20°C to +80°C and can withstand storage temperatures from -30°C to +100°C. It is also qualified for lead-free infrared reflow soldering with a peak temperature of 260°C for up to 10 seconds.

2.2 Electrical and Optical Characteristics

These parameters are measured at a standard ambient temperature of 25°C and a forward current (I_F) of 20mA, which is the typical operating point.

Luminous Intensity (I_V): This is the measure of perceived light power emitted by the LED. For the green chip, the minimum intensity is 112 millicandelas (mcd), with a typical range extending up to a maximum of 450 mcd. The red chip has a minimum of 45 mcd and a maximum of 180 mcd. The wide range indicates the device is available in different brightness bins.

Viewing Angle (2θ_1/2): Both colors feature a very wide viewing angle of 130 degrees (typical). This is the full angle at which the luminous intensity drops to half of its value at the central axis, making the LED suitable for applications where visibility from off-axis angles is important.

Wavelength Characteristics: The green chip's typical peak emission wavelength (λ_P) is 530nm, with a dominant wavelength (λ_d) range from 520.0nm to 535.0nm. The red chip's typical peak is at 639nm, with a dominant wavelength range from 624.0nm to 638.0nm. The spectral line half-width (Δλ) is approximately 35nm for green and 20nm for red, describing the spectral purity of the emitted light.

Forward Voltage (V_F): This is the voltage drop across the LED when operating at the specified current. The green chip's V_F ranges from 2.8V (min) to 3.8V (max). The red chip has a lower V_F, ranging from 1.8V to 2.4V. This difference is crucial for circuit design, especially when driving both colors from a common voltage source, as it may require current-limiting resistors of different values.

Reverse Current (I_R): The maximum reverse leakage current is 10µA for both chips when a reverse voltage (V_R) of 5V is applied. It is explicitly noted that the device is not designed for reverse operation; this parameter is for test purposes only.

3. Binning System Explanation

To ensure consistency in mass production, LEDs are sorted into performance bins. The LTST-C295TGKRKT uses a binning system for luminous intensity and dominant wavelength.

3.1 Luminous Intensity Binning

For the green chip, bins are designated R, S, and T, covering intensity ranges of 112.0-180.0 mcd, 180.0-280.0 mcd, and 280.0-450.0 mcd, respectively. For the red chip, bins P, Q, and R cover 45.0-71.0 mcd, 71.0-112.0 mcd, and 112.0-180.0 mcd. A tolerance of +/-15% is applied to each intensity bin.

3.2 Dominant Wavelength Binning

Applicable to the green chip, wavelength bins AP, AQ, and AR correspond to dominant wavelength ranges of 520.0-525.0nm, 525.0-530.0nm, and 530.0-535.0nm. The tolerance for each wavelength bin is a tight +/-1nm, ensuring precise color consistency within a selected bin.

4. Performance Curve Analysis

While specific graphical curves are referenced in the datasheet (pages 6-7), their implications are standard. The I-V (Current-Voltage) curve would show the exponential relationship typical of diodes, with the forward voltage knee being higher for the green (InGaN) chip than for the red (AlInGaP) chip. The relative luminous intensity vs. forward current curve would demonstrate that light output increases approximately linearly with current up to a point, after which efficiency drops due to heating. The relative luminous intensity vs. ambient temperature curve is critical; for most LEDs, light output decreases as junction temperature rises. Designers must account for this thermal derating, especially when operating near maximum ratings or in high ambient temperatures. The spectral distribution curves would show the narrow emission bands centered around the peak wavelengths, with the green band being broader than the red.

5. Mechanical and Package Information

5.1 Package Dimensions and Polarity

The LED comes in a standard SMD package. The key mechanical feature is its height of 0.55mm. The pin assignment is clearly defined: Pins 1 and 3 are for the green anode/cathode, and Pins 2 and 4 are for the red anode/cathode. The exact footprint and dimensional drawing are provided in the datasheet, which is essential for PCB land pattern design. The lens is water clear, allowing the true chip color to be visible.

5.2 Recommended Solder Pad Design

A suggested solder pad layout is included to ensure reliable soldering and proper mechanical stability. Adhering to these recommendations helps prevent tombstoning (component standing up on one end) during reflow and ensures good solder fillet formation for strong joints.

6. Soldering and Assembly Guidelines

6.1 Reflow Soldering Profile

The device is compatible with infrared reflow soldering processes, which is the standard for SMD assembly. A suggested reflow profile for lead-free solder is provided, conforming to JEDEC standards. Key parameters include a pre-heat stage (typically 150-200°C for up to 120 seconds), a controlled ramp to a peak temperature not exceeding 260°C, and a time above liquidus (TAL) where the peak temperature is maintained for a maximum of 10 seconds. The profile aims to minimize thermal shock while ensuring complete solder joint formation.

6.2 Handling and Storage Precautions

ESD (Electrostatic Discharge) Sensitivity: LEDs are susceptible to damage from static electricity. It is strongly recommended to handle them in an ESD-protected environment using wrist straps and grounded equipment.

Moisture Sensitivity: While the device is shipped in a moisture-proof bag with desiccant, once the bag is opened, the components should be used within one week if stored in ambient conditions (<30°C, <60% RH). For longer storage after opening, they should be kept in a sealed container with desiccant or in a nitrogen atmosphere. Components stored out of the original packaging for more than a week require a baking process (approximately 60°C for at least 20 hours) before soldering to remove absorbed moisture and prevent \"popcorning\" during reflow.

6.3 Cleaning

If cleaning after soldering is necessary, only specified solvents should be used. Immersing the LED in ethyl alcohol or isopropyl alcohol at room temperature for less than one minute is recommended. Unspecified chemicals may damage the plastic package or lens.

7. Packaging and Ordering Information

The LTST-C295TGKRKT is supplied in industry-standard packaging for automated assembly. The components are placed on 8mm wide embossed carrier tape, which is then wound onto 7-inch (178mm) diameter reels. Each full reel contains 4000 pieces. For smaller quantities, a minimum packing of 500 pieces is available. The tape and reel specifications comply with ANSI/EIA-481. The top cover tape seals the component pockets, and the reel includes orientation indicators for correct machine loading.

8. Application Notes and Design Considerations

8.1 Typical Application Circuits

Each color chip (green and red) must be driven independently. A series current-limiting resistor is mandatory for each LED to set the desired forward current (typically 20mA). The resistor value is calculated using Ohm's Law: R = (V_supply - V_F) / I_F. Due to the different forward voltages of the green and red chips, using a common supply voltage will result in different resistor values for each color to achieve the same current. For example, with a 5V supply: R_green = (5V - 3.3V) / 0.02A = 85Ω; R_red = (5V - 2.1V) / 0.02A = 145Ω (using typical V_F values).

8.2 Thermal Management

Although power dissipation is low, proper thermal design on the PCB is still important for longevity and stable performance. Ensure adequate copper area around the solder pads to act as a heat sink, especially if operating at high ambient temperatures or near maximum current ratings. Avoid placing heat-generating components directly adjacent to the LED.

8.3 Optical Design

The wide 130-degree viewing angle makes this LED suitable for applications requiring broad visibility. For more directed light, external lenses or light guides can be used. The water-clear lens provides the purest color from the chip, but diffused lenses or coatings can be applied externally if a softer, more uniform appearance is desired.

9. Technical Comparison and Differentiation

The primary differentiator of the LTST-C295TGKRKT is its dual-color capability in an ultra-thin 0.55mm package. Compared to using two separate single-color LEDs, it saves PCB space and simplifies assembly. The use of InGaN for green offers higher efficiency and brightness compared to older technologies like GaP. The AlInGaP red chip provides high efficiency and excellent color purity. Its compatibility with standard reflow processes and tape-and-reel packaging makes it a cost-effective choice for high-volume manufacturing compared to more exotic or manually assembled solutions.

10. Frequently Asked Questions (FAQ)

Q: Can I drive both the green and red LEDs simultaneously?
A: Yes, but they must be driven by separate circuits (i.e., independent current paths with their own current-limiting resistors). Driving them in parallel from a single resistor is not recommended due to their different forward voltage characteristics, which would cause an uneven current distribution.

Q: What is the meaning of the bin codes (R, S, T, AP, AQ, etc.) in the part number or ordering?
A: These codes specify the performance grade of the LED in terms of luminous intensity and dominant wavelength. For consistent appearance in a product, specifying and using LEDs from the same bin is crucial. Consult the supplier for available bins.

Q: Is a heat sink required for this LED?
A: Generally, no, due to its low power dissipation (≤76mW). However, good PCB thermal design practices, such as using thermal relief pads connected to a ground plane, are recommended for optimal lifetime, especially in high-temperature environments.

Q: Can I use this LED for reverse voltage indication?
A: No. The datasheet explicitly states the device is not designed for reverse operation. Applying a reverse voltage exceeding 5V may cause damage. For reverse polarity protection, an external diode should be used in the circuit.

11. Practical Design and Usage Examples

Case Study 1: Portable Device Status Indicator: In a smartphone or tablet, this LED could be used near a USB port. The green chip could indicate \"fully charged,\" while the red chip could indicate \"charging in progress.\" The ultra-thin profile allows it to fit within the tight mechanical constraints of modern devices.

Case Study 2: Industrial Control Panel: On a machine operator's panel, the dual-color LED can provide clear state information. For example, green for \"system ready,\" red for \"fault or alert.\" The wide viewing angle ensures the status is visible from various positions on the factory floor.

Case Study 3: Automotive Interior Lighting: While not for primary illumination, it could be used for subtle button backlighting or accent lighting, with the color changing based on mode (e.g., normal vs. night mode). The robust packaging and qualified soldering profile make it suitable for automotive electronic modules, though specific automotive-grade qualification may be required.

12. Technology Principle Introduction

The operation of an LED is based on electroluminescence in a semiconductor p-n junction. When a forward voltage is applied, electrons from the n-type region and holes from the p-type region are injected into the active region. When these charge carriers recombine, they release energy in the form of photons (light). The color (wavelength) of the emitted light is determined by the bandgap energy of the semiconductor material. The InGaN material system has a wider bandgap, enabling the emission of green, blue, and white light. The AlInGaP material system is particularly efficient for producing red, orange, and yellow light. By housing two such chips in one package, a compact dual-color source is created.

13. Industry Trends and Development

The trend in SMD LEDs continues toward higher efficiency (more light output per watt), smaller package sizes, and greater integration. Dual-color and RGB (red-green-blue) LEDs are becoming more common as they enable dynamic color mixing and more sophisticated user interfaces. There is also a strong drive toward improved reliability and performance under higher temperature conditions, catering to automotive and industrial markets. Furthermore, the push for miniaturization, as seen in this 0.55mm high package, supports the development of ever-thinner consumer electronics. The underlying semiconductor materials, particularly for green and blue, are seeing ongoing research to improve their efficiency, a challenge historically known as the \"green gap.\"