LTST-C295TGKSKT Dual Color SMD LED Datasheet - 0.55mm Height - Green/Yellow - 20mA/30mA - English Technical Document

1. Product Overview

This document provides the complete technical specifications for the LTST-C295TGKSKT, a dual-color, surface-mount device (SMD) light-emitting diode (LED). This component is designed for applications requiring compact, high-brightness indicators in two distinct colors from a single package. Its primary distinguishing feature is an exceptionally low profile, making it suitable for space-constrained modern electronic designs.

The LED integrates two independent semiconductor chips within one standard EIA-compatible package: an Indium Gallium Nitride (InGaN) chip for green emission and an Aluminum Indium Gallium Phosphide (AlInGaP) chip for yellow emission. This dual-chip architecture allows for independent control of each color, enabling status indication, bi-color signaling, or simple color mixing depending on the drive circuit configuration. The device is supplied on industry-standard 8mm tape mounted on 7-inch reels, facilitating high-speed automated pick-and-place assembly processes common in volume electronics manufacturing.

2. Technical Parameters Deep Objective Interpretation

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 and should be avoided in circuit design.

• Power Dissipation (Pd): 76 mW for the Green chip, 75 mW for the Yellow chip. This parameter, combined with the thermal resistance of the package and PCB, determines the maximum allowable continuous forward current to avoid exceeding the junction temperature limit.
• Peak Forward Current (I_FP): 100 mA for Green, 80 mA for Yellow. This is specified under a 1/10 duty cycle with a 0.1ms pulse width. It indicates the LED can handle short, high-current pulses, useful for multiplexed driving or pulsed-brightness applications, but not for DC operation.
• DC Forward Current (I_F): 20 mA for Green, 30 mA for Yellow. This is the recommended maximum continuous current for reliable long-term operation under normal conditions.
• Temperature Ranges: Operating: -20°C to +80°C; Storage: -30°C to +100°C. The operating range is typical for commercial-grade LEDs. Designers must ensure the ambient temperature and self-heating do not cause the LED junction to exceed its maximum rated temperature.
• Infrared Soldering Condition: Withstands 260°C for 10 seconds. This is critical for lead-free (Pb-free) reflow soldering processes and must be adhered to during PCB assembly.

2.2 Electrical & Optical Characteristics

These are the typical performance parameters measured at Ta=25°C under specified test conditions. They are essential for circuit design and optical system integration.

• Luminous Intensity (I_V): Measured in millicandelas (mcd) at I_F=20mA. The Green chip has a range from 45.0 mcd (Min) to 280.0 mcd (Max). The Yellow chip ranges from 28.0 mcd (Min) to 450.0 mcd (Max). The wide range is managed through a binning system (detailed in Section 3). The test uses a filter approximating the CIE photopic eye-response curve.
• Viewing Angle (2θ_1/2): Typically 130 degrees for both colors. This is the full angle at which the luminous intensity drops to half of its on-axis value. A 130-degree angle indicates a very wide viewing pattern, suitable for applications where the LED needs to be visible from a broad range of angles.
• Peak Emission Wavelength (λ_P): Typically 525 nm for Green and 588 nm for Yellow. This is the wavelength at the highest point in the emitted light spectrum.
• Dominant Wavelength (λ_d): Typically 525.0 nm for Green and 587.0 nm for Yellow. Derived from the CIE chromaticity diagram, this is the single wavelength perceived by the human eye that defines the color. It is a more perceptually relevant metric than peak wavelength.
• Spectral Line Half-Width (Δλ): Typically 35 nm for Green and 20 nm for Yellow. This indicates the spectral purity or bandwidth of the emitted light. Yellow AlInGaP LEDs generally have a narrower spectrum than Green InGaN LEDs.
• Forward Voltage (V_F): Maximum of 3.50V for Green and 2.40V for Yellow at I_F=20mA. This is crucial for designing the current-limiting circuitry. The Green chip's higher V_F is characteristic of InGaN technology.
• Reverse Current (I_R): Maximum of 10 μA for both at V_R=5V. Critical Note: The device is not designed for reverse operation. Applying a reverse bias beyond 5V may cause immediate damage. Protection against reverse voltage or incorrect polarity connection in the circuit is strongly advised.

3. Binning System Explanation

To ensure consistent color and brightness in production, LEDs are sorted into performance bins. The LTST-C295TGKSKT uses a luminous intensity binning system for each color.

3.1 Green Color Intensity Bins

Bins are defined by a letter code (P, Q, R, S) with minimum and maximum luminous intensity values in mcd at 20mA. Each bin has a tolerance of +/-15%. For example, Bin 'P' covers 45.0 to 71.0 mcd. Designers should specify the required bin code when ordering to guarantee brightness consistency across multiple units in an assembly.

3.2 Yellow Color Intensity Bins

The yellow chip uses a more extensive binning range with codes N, P, Q, R, S, T, covering intensities from 28.0 mcd (Bin N Min) up to 450.0 mcd (Bin T Max), also with a +/-15% tolerance per bin. The wider range accommodates the higher potential brightness of the AlInGaP material.

4. Performance Curve Analysis

While specific graphical data is referenced in the datasheet (e.g., Fig.1, Fig.6), the provided numerical data allows for analysis of key relationships.

• IV Relationship: The forward voltage (V_F) is specified at a single test current (20mA). In practice, V_F has a logarithmic relationship with I_F and is also temperature-dependent. Driving the LED with a constant current source, rather than a constant voltage, is essential for stable luminous output.
• Temperature Characteristics: The luminous intensity of LEDs typically decreases as junction temperature increases. The specified parameters are at 25°C ambient. In high-temperature environments or at high drive currents, derating of the output should be expected. The maximum operating temperature of 80°C provides the upper limit for reliable operation.
• Spectral Distribution: The typical peak and dominant wavelengths, along with the spectral half-width, define the color point. The green emission (525nm, 35nm FWHM) will appear as a pure green, while the yellow emission (587nm, 20nm FWHM) will be a saturated yellow, distinct from amber (~590nm) or pure green.

5. Mechanical & Packaging Information

5.1 Package Dimensions and Polarity

The device conforms to a standard EIA SMD package footprint. The key mechanical feature is its height of only 0.55 mm, described as "Extra Thin." The pin assignment is clearly defined: Pins 1 and 3 are for the Green anode/cathode, and Pins 2 and 4 are for the Yellow anode/cathode. The exact internal connection (common anode or common cathode) is not explicitly stated in the provided text and must be verified from the detailed package drawing. Proper polarity identification is critical to prevent damage during installation.

5.2 Recommended Soldering Pad Layout

The datasheet includes a suggestion for the soldering pad dimensions on the PCB. Following these recommendations ensures a reliable solder joint, proper thermal relief, and prevents issues like tombstoning during reflow. The pad design also influences the final viewing angle and mechanical stability of the mounted component.

5.3 Tape and Reel Packaging

The LEDs are supplied on 8mm wide embossed carrier tape wound onto 7-inch (178mm) diameter reels. Each reel contains 4000 pieces. This packaging is compliant with ANSI/EIA 481 specifications, ensuring compatibility with automated surface-mount technology (SMT) equipment. The tape has pockets sealed with a top cover tape. Specifications note a maximum of two consecutive missing components and a minimum packing quantity of 500 pieces for remainder orders.

6. Soldering & Assembly Guidelines

6.1 Reflow Soldering Profile

A suggested infrared (IR) reflow profile is provided for Pb-free assembly processes. The key parameters include a pre-heat zone (150-200°C), a specific time above liquidus, and a peak temperature not exceeding 260°C for a maximum of 10 seconds. This profile is based on JEDEC standards and is intended as a generic target. The actual profile must be characterized for the specific PCB design, solder paste, and oven used in production.

6.2 Hand Soldering Notes

If hand soldering is necessary, it should be performed with a soldering iron tip temperature not exceeding 300°C, and the soldering time should be limited to a maximum of 3 seconds for a single operation only. Excessive heat or prolonged contact can damage the LED package or the internal wire bonds.

6.3 Cleaning

If cleaning after soldering is required, 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. The use of unspecified or aggressive chemical cleaners can damage the plastic lens or the package material, leading to reduced light output or premature failure.

6.4 Storage Conditions

Proper storage is vital for maintaining solderability. Unopened, moisture-proof bags with desiccant should be stored at ≤30°C and ≤90% RH, with a shelf life of one year. Once the original packaging is opened, components should be stored at ≤30°C and ≤60% RH. It is recommended to complete IR reflow within one week of opening. For longer storage outside the original bag, components should be kept in a sealed container with desiccant or in a nitrogen desiccator. Components stored for over a week in non-ideal conditions should be baked at approximately 60°C for at least 20 hours before assembly to remove absorbed moisture and prevent "popcorning" during reflow.

7. Application Suggestions

7.1 Typical Application Scenarios

This dual-color LED is ideal for status and indicator applications where space is at a premium and multiple states need to be communicated. Examples include:

• Portable Consumer Electronics: Power/charging status (green=charged, yellow=charging), connectivity indicators (Bluetooth/Wi-Fi), or mode indicators on smartphones, tablets, wearables, and wireless earbuds, benefiting from the ultra-thin profile.
• Industrial Control Panels: Machine status indicators (green=run, yellow=standby/fault), level indicators, or confirmation lights on human-machine interfaces (HMIs).
• Automotive Interior Lighting: Dashboard backlighting for buttons or switches, ambient lighting, or non-critical status indicators (where specific automotive-grade qualifications would be required).
• IoT Devices and Smart Home Gadgets: Network status, sensor activity indication, or battery level warnings.

7.2 Design Considerations

• Current Driving: Always use a series current-limiting resistor or a dedicated constant-current LED driver IC. Calculate the resistor value using R = (V_supply - V_F) / I_F, using the maximum V_F from the datasheet to ensure I_F does not exceed the limit. Remember V_F is different for each color.
• Thermal Management: Although power dissipation is low, ensure adequate PCB copper area or thermal vias, especially if driving near maximum current or in high ambient temperatures, to maintain junction temperature within limits.
• ESD Protection: The datasheet includes a caution regarding electrostatic discharge (ESD). These devices are sensitive. Implement ESD-safe handling procedures (wrist straps, grounded workstations) during assembly and consider adding transient voltage suppression (TVS) diodes or resistors on sensitive lines in the end application if exposed to potential ESD events.
• Optical Design: The 130-degree viewing angle provides wide visibility. For applications requiring a more focused beam, external lenses or light guides may be necessary. The "water clear" lens ensures minimal color distortion.

8. Technical Comparison & Differentiation

The primary differentiation of the LTST-C295TGKSKT lies in its combination of features:

• Ultra-Thin Profile (0.55mm): This is a significant advantage over many standard SMD LEDs (which are often 0.6mm, 0.8mm, or taller), enabling its use in the thinnest modern electronic devices.
• Dual Color in a Single Package: This saves PCB space and simplifies assembly compared to using two separate single-color LEDs to achieve a similar function.
• Chip Technology: The use of InGaN for green and AlInGaP for yellow represents high-efficiency, modern semiconductor materials, offering good brightness and color saturation.
• Compliance: Meeting ROHS and being a Green Product ensures compliance with global environmental regulations.

9. Frequently Asked Questions (Based on Technical Parameters)

Q: Can I drive both the green and yellow LEDs simultaneously at their full DC current?
A: Not necessarily. The Absolute Maximum Ratings specify power dissipation per chip (76mW Green, 75mW Yellow). Simultaneous operation at 20mA (Green) and 30mA (Yellow) would result in approximate power draws of ~70mW (3.5V*20mA) and ~72mW (2.4V*30mA) respectively, which are close to the individual limits. The total heat generated must be managed. It is advisable to consult thermal calculations or derate the currents slightly for simultaneous full-brightness operation.

Q: What is the difference between Peak Wavelength and Dominant Wavelength?
A: Peak Wavelength (λ_P) is the physical wavelength of the highest intensity point in the spectral output. Dominant Wavelength (λ_d) is a calculated value from colorimetry that represents the single wavelength of a pure monochromatic light that would appear to have the same color as the LED to a standard human observer. λ_d is often more useful for color matching in design.

Q: How do I interpret the bin code when ordering?
A: The bin code (e.g., 'S' for Green, 'T' for Yellow) guarantees the luminous intensity will fall within the specified min/max range for that code, with +/-15% tolerance. For consistent appearance in a product, specifying a single bin code for all units in a production run is crucial. If not specified, you may receive LEDs from any bin within the product's overall range.

10. Practical Design Case Study

Scenario: Designing a low-battery indicator for a handheld device powered by a 3.3V regulator. The indicator should be green when battery voltage is above 3.6V and yellow when it drops below 3.5V.

Implementation: A microcontroller with an analog-to-digital converter (ADC) monitors the battery voltage. Two GPIO pins are used to control the LED. The circuit would be configured based on the internal pinout (e.g., if common cathode, the cathode pins would be grounded, and the microcontroller would sink current to turn on each anode via a current-limiting resistor). The resistor values would be calculated separately: R_Green = (3.3V - 3.5V) / 0.020A = ~ -10Ω (invalid). This shows a problem: the Green V_F (max 3.5V) is too close to or exceeds the supply voltage (3.3V).

Solution: 1) Use a lower current (e.g., 10mA) for the green LED, which would lower its V_F. 2) Use a charge pump or boost converter to generate a slightly higher voltage (e.g., 4.0V) for driving the LEDs. 3) Use a different LED with a lower V_F for green. This case highlights the importance of checking V_F against the available supply voltage early in the design process.

11. Operating Principle Introduction

Light Emitting Diodes (LEDs) are semiconductor p-n junction devices that emit light through electroluminescence. When a forward voltage is applied, electrons from the n-type region and holes from the p-type region are injected into the junction region. When these charge carriers recombine, energy is released. In traditional semiconductors like silicon, this energy is primarily thermal. In direct bandgap semiconductors like InGaN and AlInGaP, a significant portion of this energy is released as photons (light). The wavelength (color) of the emitted light is determined by the bandgap energy (E_g) of the semiconductor material, according to the equation λ = hc/E_g. InGaN materials are used for shorter wavelengths (blue, green), while AlInGaP materials are used for longer wavelengths (yellow, orange, red). The dual-color LED package simply houses two such independent semiconductor chips with different bandgaps.

12. Technology Trends

The development of LEDs like the LTST-C295TGKSKT follows several key industry trends:

• Miniaturization: Continuous reduction in package size and height to enable thinner and more compact end products, as seen in the 0.55mm profile.
• Increased Integration: Combining multiple functions (like two colors) into a single package to save board space and simplify assembly.
• Material Efficiency: Ongoing improvements in the epitaxial growth of InGaN and AlInGaP materials lead to higher internal quantum efficiency, allowing for greater brightness at lower currents or reduced power consumption for the same light output.
• Advanced Packaging: Improvements in packaging materials and processes enhance thermal performance, allowing for higher drive currents in smaller packages, and improve reliability under harsh environmental conditions.
• Automation Compatibility: Design for Manufacturing (DFM) principles ensure components are perfectly suited for high-speed, precision automated assembly lines, with features like standardized tape-and-reel packaging.