LTST-C295TGKSKT Bicolor SMD LED Datasheet - 0.55mm Ultra-Low Profile - Green/Yellow - 20mA/30mA - Technical Documentation

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 two distinct colors, compact size, and high-brightness indication within a single package. Its key distinguishing feature is its extremely low profile height, making it suitable for space-constrained modern electronic designs.

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

2. In-depth and Objective Interpretation of Technical Parameters

2.1 Absolute Maximum Ratings

These ratings define the stress limits that may cause permanent damage to the device. Operation at or near these limits is not guaranteed and should be avoided in circuit design.

• Power Dissipation (Pd):The green chip is 76 mW, and the yellow chip is 75 mW. 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):The green light is 100 mA, and the yellow light is 80 mA. This value is specified at a 1/10 duty cycle and a 0.1ms pulse width. It indicates that the LED can withstand brief high-current pulses, making it suitable for multiplexed driving or pulsed brightness applications, but not for DC operation.
• Direct forward current (I_F):Green light is 20 mA, yellow light is 30 mA. This is the recommended maximum continuous current for reliable long-term operation under normal conditions.
• Temperature range:Operating temperature: -20°C to +80°C; Storage temperature: -30°C to +100°C. The operating range is typical for commercial-grade LEDs. Designers must ensure that ambient temperature and self-heating do not cause the LED junction temperature to exceed its maximum rated temperature.
• Infrared reflow soldering conditions:Can withstand 260°C for 10 seconds. This is crucial for Pb-free reflow soldering processes and must be strictly adhered to during PCB assembly.

2.2 Electrical and Optical Characteristics

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

• Luminous intensity (I_V):Measured in millicandelas (mcd) at I_F=20mA. The green chip ranges from 45.0 mcd (min) to 280.0 mcd (max). The yellow chip ranges from 28.0 mcd (min) to 450.0 mcd (max). This wide range is managed through a binning system (see Section 3 for details). Testing uses a filter approximating the CIE photopic response curve.
• Viewing Angle (2θ_1/2):Both colors typically have a 130-degree angle. This is the full angle at which the luminous intensity drops to half of the axial 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):Green light is typically 525 nm, and yellow light is typically 588 nm. This is the wavelength corresponding to the highest point in the emission spectrum.
• Dominant Wavelength (λ_d):Green light is typically 525.0 nm, and yellow light is typically 587.0 nm. This value is derived from the CIE chromaticity diagram and is the single wavelength that defines the color as perceived by the human eye. It is a more perceptually relevant metric than peak wavelength.
• Spectral Line Half-Width (Δλ):Green light typically has a wavelength of 35 nm, while yellow light typically has a wavelength of 20 nm. This indicates the spectral purity or bandwidth of the emitted light. The spectrum of yellow AlInGaP LEDs is generally narrower than that of green InGaN LEDs.
• Forward voltage (V_F):Measured in millicandelas (mcd) at I_FAt 20mA, the maximum forward voltage for green light is 3.50V, and for yellow light, it is 2.40V. This is crucial for designing current-limiting circuits. The higher V_Fis a characteristic of InGaN technology.
• Reverse current (I_R):In V_R=5V, both have a maximum of 10 μA.Key Considerations:This device is not designed for reverse operation. Applying a reverse bias exceeding 5V may cause immediate damage. It is strongly recommended to implement protective measures in the circuit to prevent reverse voltage or incorrect polarity connections.

3. Binning System Description

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

3.1 Green Light Intensity Grading

The bin is defined by a letter code (P, Q, R, S), with the minimum and maximum luminous intensity values (in mcd) given at 20mA. The tolerance for each bin is +/-15%. For example, bin 'P' covers 45.0 to 71.0 mcd. Designers should specify the required bin code when ordering to ensure brightness uniformity among multiple devices in an assembly.

3.2 Yellow Light Intensity Grading

The yellow LED chip employs a broader binning range, coded as N, P, Q, R, S, T, covering intensities from 28.0 mcd (minimum for bin N) to 450.0 mcd (maximum for bin T), with each bin also having a +/-15% tolerance. The wider range accommodates the higher potential brightness of the AlInGaP material.

4. Performance Curve Analysis

Although the datasheet references specific graphical data (e.g., Figure 1, Figure 6), the provided numerical data allows for the analysis of key relationships.

• IV characteristics:Forward voltage (V_F) is specified at a single test current (20mA). In practice, V_FWith I_Fexhibits a logarithmic relationship and also depends on temperature. Using a constant current source rather than a constant voltage source to drive the LED is crucial for stable light output.
• Temperature Characteristics:The luminous intensity of an LED typically decreases as the junction temperature rises. The specified parameters are measured at an ambient temperature of 25°C. In high-temperature environments or under high drive currents, output derating should be expected. The maximum operating temperature of 80°C provides the upper limit for reliable operation.
• Spectral Distribution:Typical peak wavelength and dominant wavelength, along with spectral half-width, collectively define the color point. Green emission (525nm, 35nm FWHM) will appear as pure green, while yellow emission (587nm, 20nm FWHM) will be a saturated yellow, distinct from amber (~590nm) or pure green.

5. Mechanical and Packaging Information

5.1 Package Dimensions and Polarity

This device conforms to the standard EIA SMD package outline. Its key mechanical feature is a height of only 0.55 mm, described as "ultra-thin". 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. Correct polarity identification is crucial to prevent damage during installation.

5.2 Recommended Pad Layout

The datasheet contains recommendations for pad dimensions on the PCB. Following these recommendations ensures reliable solder joints, proper heat dissipation, and prevents issues like tombstoning during the reflow process. Pad design also affects the viewing angle and mechanical stability of the finally mounted component.

5.3 Tape and Reel Packaging

LED ina toa a cikin sigar tebur mai nisa na 8mm, wanda aka nade akan keke mai diamita na inci 7 (178mm). Kowace keke tana dauke da guda 4000. Wannan marufi ya dace da ka'idar ANSI/EIA 481, yana tabbatar da dacewa da na'urorin sarrafa kai ta atomatik (SMT). Tebur yana dauke da aljihu da aka rufe da tebur na sama. Bayanin sifa ya nuna cewa akwai iyakar guda biyu da ba a samu ba a jere, kuma mafi karancin adadin marufi na sauran odar shine guda 500.

6. Welding and Assembly Guide

6.1 Reflow Soldering Temperature Profile

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

6.2 Manual Soldering Precautions

If manual soldering is necessary, the soldering iron tip temperature should not exceed 300°C, and the soldering time per joint should be limited to a maximum of 3 seconds. Excessive heat or prolonged contact may damage the LED package or internal bonding wires.

6.3 Cleaning

If cleaning is required after soldering, only specified solvents should be used. The datasheet recommends immersing the LED in ethanol or isopropyl alcohol at room temperature for no more than one minute. Using unspecified or highly corrosive chemical cleaners may damage the plastic lens or package material, leading to reduced light output or premature failure.

6.4 Storage Conditions

Proper storage is crucial for maintaining solderability. Unopened moisture barrier bags with desiccant should be stored at ≤30°C and ≤90% relative humidity, with a shelf life of one year. Once the original packaging is opened, components should be stored at ≤30°C and ≤60% relative humidity. It is recommended to complete infrared reflow soldering within one week after opening. For storage outside the original bag for longer periods, components should be kept in sealed containers with desiccant or in nitrogen dry boxes. Components stored under non-ideal conditions for more than one week 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 Recommendations

7.1 Typical Application Scenarios

This bi-color LED is ideal for status and indication applications where space is limited and multiple states need to be communicated. For example:

• Portable Consumer Electronics:Power/charging status (green=fully charged, yellow=charging), connection indicators (Bluetooth/Wi-Fi), or mode indicators on smartphones, tablets, wearables, and wireless earbuds benefit from its ultra-thin profile.
• Industrial Control Panels:Machine status indicator lights (green = running, yellow = standby/fault), level indicator lights, or acknowledgment lights on the Human-Machine Interface (HMI).
• Automotive Interior Lighting:Dashboard backlighting for buttons or switches, ambient lighting, or non-critical status indicator lights (requires specific automotive-grade certification).
• IoT devices and smart home gadgets:Network status, sensor activity indicators, or battery warnings.

7.2 Design Considerations

• Current Drive:Always use a series current-limiting resistor or a dedicated constant-current LED driver IC. Use the formula R = (V_{Power Supply}- V_F) / I_F Calculate the resistance value using the maximum V from the datasheet_Fto ensure I_Fdoes not exceed the limit. Remember the V for each color_FDifferent.
• Thermal Management:Although the power consumption is low, sufficient PCB copper area or thermal vias should be ensured, especially when operating near the maximum drive current or under high ambient temperatures, to keep the junction temperature within the specified limits.
• ESD Protection:The datasheet contains warnings regarding Electrostatic Discharge (ESD). These devices are sensitive. Implement ESD-safe handling procedures (wrist straps, grounded workstations) during assembly, and in the final application, consider adding Transient Voltage Suppression (TVS) diodes or resistors on sensitive lines if they may be exposed to potential ESD events.
• Optical Design:A 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 and Differentiation

The main differentiation of LTST-C295TGKSKT lies in its functional combination:

• Ultra-thin profile (0.55mm):Compared to many standard SMD LEDs (typically 0.6mm, 0.8mm, or higher), this is a significant advantage, enabling its use in the thinnest modern electronic devices.
• Dual-color in a single package:Compared to using two separate single-color LEDs to achieve similar functionality, this saves PCB space and simplifies assembly.
• Chip Technology:The use of InGaN for green light and AlInGaP for yellow light represents modern semiconductor materials with high efficiency, providing excellent brightness and color saturation.
• Compliance:Yana daidai da ma'aunin ROHS kuma samfur ne mai kore, yana tabbatar da bin ka'idojin muhalli na duniya.

9. Frequently Asked Questions (Based on Technical Parameters)

Tambaya: Shin zan iya tuka LED kore da rawaya tare da cikakken igiyar ruwa DC a lokaci guda?
A: Not necessarily. The absolute maximum ratings specify the power consumption per chip (76mW for green, 75mW for yellow). Operating simultaneously at 20mA (green) and 30mA (yellow) will result in power consumption of approximately 70mW (3.5V*20mA) and 72mW (2.4V*30mA) respectively, which is close to their respective limits. The total heat generated must be managed. It is recommended to refer to thermal calculations or slightly reduce the current when performing simultaneous full-brightness operation.

Q: What is the difference between peak wavelength and dominant wavelength?
A: Peak wavelength (λ_P) is the physical wavelength at the highest intensity point in the spectral output. Dominant wavelength (λ_d) is a value calculated based on colorimetry, representing the single wavelength of a pure monochromatic light that appears identical to the LED color for a standard human observer. λ_dIt is generally more useful for color matching in design.

Q: How to interpret the binning code when ordering?
A: The binning code (e.g., 'S' for green, 'T' for yellow) guarantees that the luminous intensity will fall within the specified minimum/maximum range for that code, with a +/-15% tolerance. For consistency in product appearance, it is crucial to specify a single binning code for all devices within a production lot. If not specified, you may receive LEDs from any bin within the overall product range.

10. Case Studies of Practical Design

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

Implementation Plan:A microcontroller with an Analog-to-Digital Converter (ADC) monitors the battery voltage. Two GPIO pins are used to control the LEDs. The circuit will be configured according to the internal pin arrangement (e.g., if it is common cathode, the cathode pin is grounded, and the microcontroller sinks current through a current-limiting resistor to light each anode). The resistor values will be calculated separately: R_{Green Light}= (3.3V - 3.5V) / 0.020A = ~ -10Ω (invalid). This indicates a problem: the 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 will reduce its V_F.2) Use a charge pump or boost converter to generate a slightly higher voltage (e.g., 4.0V) to drive the LED. 3) Use a green LED with a lower V_F. This case highlights the importance of checking V early in the design process based on the available power supply voltage._F.

11. Brief Introduction to Working Principles

Light-emitting diode (LED) is a semiconductor p-n junction device that emits 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 area. When these carriers recombine, energy is released. In traditional semiconductors like silicon, this energy is primarily thermal. In direct bandgap semiconductors such as InGaN and AlInGaP, a significant portion of this energy is released in the form of photons (light). The wavelength (color) of the emitted light is determined by the bandgap energy (E_g) of the semiconductor material, according to the formula λ = hc/E_g. InGaN materials are used for shorter wavelengths (blue, green light), while AlInGaP materials are used for longer wavelengths (yellow, orange, red light). A dual-color LED package simply houses two such independent semiconductor chips with different bandgaps.

12. Technology Trends

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

• Miniaturization:The continuous reduction in package size and height to enable thinner, more compact end products, as indicated by the 0.55mm profile height.
• Integrated Circuit Density Enhancement:Combining multiple functions (such as two colors) into a single package to save PCB space and simplify assembly.
• Material Efficiency:The continuous improvement in the epitaxial growth of InGaN and AlInGaP materials has led to higher internal quantum efficiency, allowing for greater brightness at lower currents or reduced power consumption at the same light output.
• Advanced Packaging:Improvements in packaging materials and processes have enhanced thermal performance, allowing for the use of higher drive currents in smaller packages and improving reliability under harsh environmental conditions.
• Automation Compatibility:Design for Manufacturing (DFM) principles ensure components are fully compatible with high-speed, precision automated assembly lines, featuring standardized tape-and-reel packaging.