LTST-C295KGKFKT Dual Color SMD LED Datasheet - 0.55mm Height - 2.0V Typical Forward Voltage - Green & Orange - English Technical Document

1. Product Overview

The LTST-C295KGKFKT is a dual-color, surface-mount device (SMD) LED designed for modern electronic applications requiring compact size and reliable performance. This product utilizes advanced AlInGaP (Aluminum Indium Gallium Phosphide) chip technology for both its green and orange light sources, housed within an extra-thin package measuring only 0.55mm in height. It is packaged on 8mm tape wound onto 7-inch diameter reels, making it fully compatible with high-speed automated pick-and-place assembly equipment. The device is classified as a green product, meeting RoHS (Restriction of Hazardous Substances) compliance standards, and is suitable for use in a wide range of consumer and industrial electronics.

1.1 Core Advantages

The primary advantages of this LED stem from its combination of advanced materials and a miniaturized form factor. The use of AlInGaP semiconductor material provides high luminous efficiency, resulting in bright output from a small chip area. The dual-color capability within a single package saves valuable PCB (Printed Circuit Board) real estate compared to using two separate single-color LEDs. Its ultra-thin profile is critical for applications with strict height limitations, such as in ultra-slim displays, mobile devices, and backlighting modules. Furthermore, its compatibility with infrared (IR) reflow soldering processes allows it to be integrated using standard surface-mount technology (SMT) assembly lines, ensuring high manufacturing yield and reliability.

2. In-Depth Technical Parameter Analysis

This section provides a detailed, objective interpretation of the key electrical, optical, and thermal parameters specified in the datasheet, explaining their significance for design engineers.

2.1 Absolute Maximum Ratings

These ratings define the stress limits beyond which permanent damage to the device may occur. They are not intended for normal operation.

• Power Dissipation (P_D): 75 mW per color. This is the maximum amount of power the LED can dissipate as heat. Exceeding this value, typically by driving at too high a current or in a high ambient temperature, can lead to overheating, accelerated degradation of the semiconductor material, and ultimately, failure.
• Peak Forward Current (I_FP): 80 mA (at 1/10 duty cycle, 0.1ms pulse width). This rating is for pulsed operation, often used in multiplexing circuits or for achieving brief periods of very high brightness. The low duty cycle and short pulse width are essential to prevent the junction temperature from rising excessively during the pulse.
• DC Forward Current (I_F): 30 mA. This is the maximum continuous current recommended for reliable long-term operation. Designing the drive circuit to operate at or below this current is crucial for ensuring the LED's specified lifetime and maintaining stable optical characteristics.
• Reverse Voltage (V_R): 5 V. LEDs are not designed to withstand significant reverse bias. Exceeding this voltage can cause a sudden breakdown of the PN junction, leading to immediate and catastrophic failure. Proper circuit design must ensure the LED is not subjected to reverse voltages, often by using series protection diodes in AC or bipolar drive scenarios.
• Operating & Storage Temperature: -30°C to +85°C and -40°C to +85°C, respectively. These ranges define the environmental conditions the device can endure during use and while powered off. Operating near or beyond the upper limit will reduce luminous output and lifespan.

2.2 Electrical & Optical Characteristics

These parameters are measured under standard test conditions (Ta=25°C) and represent the typical performance of the device.

• Luminous Intensity (I_V): For the green LED, the typical value is 35.0 mcd at 20mA, with a minimum of 18.0 mcd. For the orange LED, the typical value is 90.0 mcd at 20mA, with a minimum of 28.0 mcd. The orange emitter is inherently more efficient in the AlInGaP material system, resulting in higher typical output. The minimum values are critical for designers who must guarantee a certain brightness level in their application.
• Viewing Angle (2θ_1/2): 130 degrees (typical for both colors). This wide viewing angle indicates a Lambertian or near-Lambertian radiation pattern, where the light intensity is relatively uniform across a broad area. This is ideal for general indicator lights and backlighting where visibility from multiple angles is required, as opposed to a narrow-beam LED used for focusing light.
• Peak & Dominant Wavelength (λ_P, λ_d): The green LED has a typical peak wavelength of 574 nm and a dominant wavelength of 571 nm. The orange LED has a typical peak wavelength of 611 nm and a dominant wavelength of 605 nm. The dominant wavelength is the single wavelength perceived by the human eye and is the key parameter for color specification. The slight difference between peak and dominant wavelength is due to the shape of the emission spectrum.
• Spectral Line Half-Width (Δλ): Approximately 15 nm for green and 17 nm for orange. This parameter, also known as Full Width at Half Maximum (FWHM), describes the spectral purity of the light. A narrower width indicates a more monochromatic (pure) color. These values are typical for AlInGaP LEDs and provide good color saturation.
• Forward Voltage (V_F): 2.0 V typical, 2.4 V maximum at 20mA for both colors. This low forward voltage is beneficial as it reduces power consumption and thermal load. The driver circuit (usually a constant current source or a current-limiting resistor) must be designed to accommodate the maximum V_F to ensure the desired current is delivered under all conditions, including device-to-device variation and temperature effects.
• Reverse Current (I_R): 10 µA maximum at 5V. This is the small leakage current that flows when the device is reverse-biased within its maximum rating. A value significantly higher than this could indicate a damaged junction.

3. Binning System Explanation

The datasheet includes bin codes for luminous intensity and dominant wavelength, which are essential for applications requiring color or brightness consistency.

3.1 Luminous Intensity Binning

LEDs are sorted (binned) after manufacture based on their measured light output. For the green LED, bins range from \"M\" (18.0-28.0 mcd) to \"Q\" (71.0-112.0 mcd). For the orange LED, bins range from \"N\" (28.0-45.0 mcd) to \"R\" (112.0-180.0 mcd). Each bin has a tolerance of +/-15%. When ordering, specifying a tighter bin (e.g., only \"P\" and \"Q\") ensures more uniform brightness across multiple units in an assembly, which is vital for multi-LED displays or backlight arrays. Using LEDs from a single bin is recommended for optimal visual consistency.

3.2 Dominant Wavelength Binning (Green Only)

The green LEDs are also binned by dominant wavelength into codes \"C\" (567.5-570.5 nm), \"D\" (570.5-573.5 nm), and \"E\" (573.5-576.5 nm), with a +/-1 nm tolerance per bin. This allows designers to select LEDs with a very specific shade of green, which is important for color-coded indicators or when matching a specific corporate or product color scheme. The orange LED's wavelength is specified as typical only, indicating less variation or that binning is not offered for this parameter.

4. Performance Curve Analysis

While specific graphical curves are referenced in the datasheet (e.g., Fig.1, Fig.6), their implications are standard for LED technology.

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

The I-V characteristic of an LED is exponential. A small increase in forward voltage beyond the \"turn-on\" point results in a large increase in current. This is why LEDs must be driven by a constant current source or with a series current-limiting resistor; a constant voltage supply would lead to thermal runaway and destruction. The typical V_F of 2.0V at 20mA provides the operating point for this design.

4.2 Luminous Intensity vs. Forward Current

Luminous intensity is approximately proportional to forward current in the normal operating range. However, efficiency (lumens per watt) often decreases at very high currents due to increased heat and other non-radiative recombination processes. Operating at or below the recommended 20mA DC ensures optimal efficiency and longevity.

4.3 Temperature Dependence

LED performance is highly temperature-dependent. As the junction temperature increases: Forward Voltage (V_F) decreases slightly. Luminous Intensity decreases significantly. For AlInGaP LEDs, the light output can drop by approximately 0.5-1.0% per °C rise in junction temperature. Dominant Wavelength may shift slightly (typically to longer wavelengths for AlInGaP). Effective thermal management on the PCB, such as using thermal vias or a copper pour, is critical to maintain stable optical performance, especially in high-power or high-ambient-temperature applications.

4.4 Spectral Distribution

The referenced spectral graph would show a single, relatively narrow peak for each color, characteristic of AlInGaP material. The absence of secondary peaks or a broad spectrum confirms the color purity of the device, which is desirable for applications requiring saturated colors.

5. Mechanical & Package Information

5.1 Package Dimensions and Polarity

The device conforms to an EIA standard package outline. The key mechanical feature is its height of 0.55mm. The pin assignment is clearly defined: Pins 1 and 3 are for the green LED, and pins 2 and 4 are for the orange LED. This four-pad design allows independent control of the two colors. The polarity is indicated by the pin numbering; typically, the anode is connected to the positive supply via the driver circuit, and the cathode is connected to ground or the current sink.

5.2 Recommended Solder Pad Design

The datasheet provides suggested solder pad dimensions. Following these recommendations is crucial for achieving reliable solder joints during reflow. The pad design affects the solder fillet shape, which influences mechanical strength and thermal conduction away from the LED. A well-designed pad ensures proper self-alignment during reflow and prevents tombstoning (where one end of the component lifts off the pad).

6. Soldering & Assembly Guidelines

6.1 Infrared Reflow Soldering Profile

The device is fully compatible with infrared (IR) or convection reflow soldering processes, which is the standard for SMT assembly. The datasheet provides a suggested profile compliant with JEDEC standards for lead-free (Pb-free) solder. Key parameters include: A pre-heat zone (150-200°C) to slowly ramp temperature and activate flux. A peak temperature not exceeding 260°C. A time above liquidus (typically 217°C for SnAgCu solder) of 10 seconds maximum. The total time from room temperature to peak and back should be controlled to minimize thermal stress on the plastic package and the semiconductor die.

6.2 Hand Soldering

If hand soldering is necessary for repair or prototyping, extreme care must be taken. The recommendation is to use a soldering iron at a maximum temperature of 300°C and limit the contact time to 3 seconds per pad. Excessive heat or prolonged contact can melt the plastic lens, damage the wire bonds inside the package, or delaminate the die attach material.

6.3 Storage and Handling Conditions

LEDs are moisture-sensitive devices (MSD). The plastic package can absorb moisture from the air, which can turn to steam during the high-temperature reflow process, causing internal cracking or \"popcorning.\" The datasheet specifies: Sealed packages should be stored at ≤30°C and ≤90% RH and used within one year. Once opened, LEDs should be stored at ≤30°C and ≤60% RH. Components exposed to ambient air for more than one week should be baked at 60°C for at least 20 hours before soldering to drive out moisture. Proper handling also includes precautions against electrostatic discharge (ESD). Although not as sensitive as some ICs, LEDs can be damaged by ESD. Using grounded wrist straps, anti-static mats, and properly grounded equipment is recommended.

6.4 Cleaning

Post-solder cleaning, if required, should only be performed with specified solvents. The datasheet recommends ethyl alcohol or isopropyl alcohol at normal temperature for less than one minute. Harsh or unspecified chemicals can attack the plastic lens material, causing clouding, cracking, or discoloration, which would severely degrade optical performance.

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. Standard reel quantity is 4000 pieces. A minimum order quantity of 500 pieces is specified for remainder reels. The tape dimensions and pocket spacing conform to ANSI/EIA-481 specifications, ensuring compatibility with standard SMT feeders. The tape design includes orientation features and sprocket holes for precise mechanical advancement.

8. Application Recommendations

8.1 Typical Application Scenarios

The dual-color capability and thin profile make this LED suitable for numerous applications: Status Indicators: A single component can show two states (e.g., green for \"on/ready,\" orange for \"standby/warning\"). Backlighting for Keypads and Switches: Its wide viewing angle and brightness are ideal for illuminating symbols on control panels. Consumer Electronics: Used in smartphones, tablets, wearables, and remote controls where space is at a premium. Automotive Interior Lighting: For dashboard indicators or ambient lighting (subject to qualification for specific automotive grades). Portable Devices: Battery-powered devices benefit from its low forward voltage, which minimizes power drain.

8.2 Design Considerations

Current Limiting: Always use a constant current driver or a series resistor calculated based on the supply voltage and the LED's maximum V_F. Thermal Management: Ensure the PCB layout provides a adequate thermal path, especially if driving near maximum current. Consider the thermal resistance from the LED junction to the ambient environment. ESD Protection: Incorporate ESD protection diodes on signal lines driving the LED if they are exposed to user interfaces. Optical Design: The wide viewing angle may require light guides or diffusers if a specific beam pattern is needed. For color mixing (if both LEDs are driven simultaneously), understand that the human eye's perception of the mixed color (e.g., a yellow-ish hue from green+orange) is non-linear.

9. Technical Comparison & Differentiation

Compared to older LED technologies like standard GaP (Gallium Phosphide) or GaAsP (Gallium Arsenide Phosphide), the AlInGaP chip offers significantly higher luminous efficiency, resulting in brighter light output for the same drive current. Compared to some white LEDs based on blue chips with phosphor, these monochromatic LEDs offer superior color purity and typically higher efficacy within their specific color band. The key differentiator of this specific part is the combination of two distinct, efficient colors in an industry-standard, ultra-thin package that supports full reflow assembly. This integration reduces part count, assembly time, and board space versus using two discrete LEDs.

10. Frequently Asked Questions (Based on Technical Parameters)

Q: Can I drive both the green and orange LEDs at the same time?
A: Yes, they are electrically independent. However, you must ensure that the total power dissipation (I_F * V_F for each LED, plus any driver losses) does not exceed the thermal capacity of the PCB and the device's own limits. Driving both at full 20mA simultaneously dissipates approximately 80mW, which is above the 75mW per-color rating but may be acceptable if the duty cycle is low or thermal management is excellent. Consult thermal calculations for your specific layout.

Q: What is the difference between \"Peak Wavelength\" and \"Dominant Wavelength\"?
A: Peak Wavelength (λ_P) is the wavelength at which the spectral power distribution is maximum. Dominant Wavelength (λ_d) is the single wavelength of monochromatic light that would appear to have the same color to a standard human observer. λ_d is calculated from the CIE chromaticity coordinates and is the more relevant parameter for specifying the perceived color.

Q: How do I interpret the bin codes when placing an order?
A: To ensure consistency, specify the desired luminous intensity bin (e.g., \"P\") and, for green, the dominant wavelength bin (e.g., \"D\"). This tells the manufacturer to supply parts that fall within those specific performance ranges. Not specifying bins may result in receiving parts from any production bin, leading to potential variation in your end product.

Q: Is a heat sink required?
A: For operation at the maximum continuous current (20mA) in a typical indoor ambient environment (25°C), a dedicated heat sink is usually not required if the PCB has a modest copper area connected to the LED's thermal pads. However, for high ambient temperatures, enclosed spaces, or if driving with pulses that exceed the DC rating, thermal analysis is necessary. The junction temperature must be kept as low as possible for maximum light output and lifespan.

11. Practical Design and Usage Examples

Example 1: Dual-State Power Indicator: In a wall adapter, the LED can be connected to show green when a device is fully charged and drawing minimal current (controlled by the charging IC), and orange when the device is actively charging. A simple microcontroller or logic circuit can switch between driving pin pairs (1,3) and (2,4).

Example 2: Backlighting with Animation: In a gaming peripheral, multiple LTST-C295KGKFKT LEDs can be arranged in an array. By independently pulse-width modulating (PWM) the green and orange channels of each LED, a microcontroller can create dynamic color-changing and breathing lighting effects, all within a very thin profile constraint.

Example 3: Signal Strength Indicator: In a wireless module, the green LED could indicate strong signal (driven at full current), the orange LED could indicate weak signal (driven at full current), and both LEDs driven simultaneously at reduced currents could create an intermediate yellow color to indicate a medium signal level, providing three distinct states from one component.

12. Operating Principle Introduction

Light Emitting Diodes (LEDs) are semiconductor devices that emit light through a process called electroluminescence. When a forward voltage is applied across the PN junction of the semiconductor material (in this case, AlInGaP), electrons from the N-type region and holes from the P-type region are injected into the active region. When these charge carriers (electrons and holes) recombine, they release energy. In a direct bandgap semiconductor like AlInGaP, this energy is released primarily in the form of photons (light). The specific wavelength (color) of the emitted light is determined by the bandgap energy of the semiconductor material, which is engineered during the crystal growth process. The green and orange colors in this device are achieved by slightly varying the composition of the Aluminum, Indium, Gallium, and Phosphide atoms in the respective chips, which changes the bandgap energy and thus the color of the emitted light.

13. Technology Trends

The general trend in SMD LED technology continues toward higher efficiency (more lumens per watt), increased power density, and further miniaturization. There is also a strong drive toward improved color rendering and color consistency for lighting applications. For indicator and backlight LEDs, the trend includes integrating more features into the package, such as built-in current-limiting resistors, IC drivers for addressability (like WS2812-style \"smart LEDs\"), and even multiple colors beyond dual (e.g., RGB). The push for ultra-thin and flexible displays is also driving the development of even thinner package profiles and LEDs on flexible substrates. The use of advanced materials like GaN-on-Si (Gallium Nitride on Silicon) and micro-LED technology represents the cutting edge for future high-brightness, miniaturized displays.