LTST-C195TGKSKT Dual-Color SMD LED Datasheet - EIA Standard Package - Green/Yellow Light - 20mA/30mA - Technical Documentation

1. Product Overview

LTST-C195TGKSKT is a bicolor surface-mount LED designed for modern electronic applications requiring compact size and reliable performance. It integrates two different semiconductor chips within a standard EIA package: an InGaN chip for emitting green light and an AlInGaP chip for emitting yellow light. This configuration enables bicolor indication or simple color mixing in an extremely small space. The device is supplied in 8mm tape on 7-inch reels, fully compatible with high-speed automated pick-and-place equipment. Its design complies with the RoHS directive, ensuring it is free from hazardous substances such as lead, mercury, and cadmium.

1.1 Core Advantages

• Bicolor Light Source:Combining green and yellow light emission in a single package saves PCB space and simplifies multi-state indicator design.
• High brightness:Utilizes advanced InGaN and AlInGaP chip technology to deliver high luminous intensity.
• Sturdy Packaging:EIA standard packaging ensures mechanical compatibility and reliable soldering performance.
• Process Compatibility:Suitable for standard infrared (IR) reflow, vapor phase reflow, and wave soldering processes, including lead-free (Pb-free) assembly temperature profiles.
• Automation Ready:Packaged in tape and reel for efficient, high-volume production.

2. In-depth Technical Parameter Analysis

Unless otherwise specified, all parameters are specified at an ambient temperature (Ta) of 25°C. Understanding these specifications is crucial for reliable circuit design and achieving the intended performance.

2.1 Absolute Maximum Ratings

These ratings define the stress limits that may cause permanent damage to the device. Operation at or beyond these limits is not guaranteed.

• Power Dissipation (Pd):Green: 76 mW, Yellow: 75 mW. This is the maximum power the LED can dissipate as heat.
• Peak Forward Current (I_FP):Green light: 100 mA, Yellow light: 80 mA. Applicable only under pulse conditions (1/10 duty cycle, 0.1ms pulse width).
• Direct forward current (I_F):Green light: 20 mA, Yellow light: 30 mA. Recommended continuous operating current.
• Derating:Green light: 0.25 mA/°C, Yellow light: 0.4 mA/°C. When the ambient temperature exceeds 25°C, the maximum forward current must be linearly reduced according to this coefficient.
• Reverse voltage (V_R):Both colors are 5 V. Exceeding this voltage under reverse bias may cause junction breakdown.
• Temperature range:Operating temperature: -20°C to +80°C; Storage temperature: -30°C to +100°C.
• Welding Temperature:Can withstand 260°C for 5 seconds (IR/Wave Soldering) or 215°C for 3 minutes (Vapor Phase Soldering).

2.2 Electrical and Optical Characteristics

These are typical performance parameters under normal operating conditions (I_F= 20mA).

• Luminous intensity (I_V):is a key indicator for measuring brightness.
  • Green light: Typical value 180 mcd (Minimum value 45 mcd, see binning code).
  • Yellow light: typical value 75 mcd (minimum value 28 mcd, see binning code).
  • Measured using a filtered sensor matching the photopic response of the human eye (CIE curve).
• Viewing Angle (2θ_1/2):Both colors are 130 degrees (typical). This is the full angle at which the luminous intensity drops to half of the axial value, indicating a wide viewing pattern.
• Peak Wavelength (λ_P):Green light: 525 nm (typical), yellow light: 591 nm (typical). Wavelength at which the emitted optical power reaches its maximum value.
• Dominant wavelength (λ_d):Green light: 530 nm (typical), yellow light: 589 nm (typical). The single wavelength perceived by the human eye, defining the color point on the CIE chromaticity diagram.
• Spectral bandwidth (Δλ):Green light: 35 nm (typical), Yellow light: 15 nm (typical). The width of the emission spectrum at Full Width at Half Maximum (FWHM). The spectrum of yellow AlInGaP LEDs is typically narrower than that of green InGaN LEDs.
• Forward voltage (V_F):
  • Green light: typical 3.30 V, maximum 3.50 V @ 20mA. The higher voltage is characteristic of InGaN-based blue/green/white LEDs.
  • Yellow light: typical 2.00 V, maximum 2.40 V @ 20mA. The lower voltage is characteristic of AlInGaP-based red/yellow/orange LEDs.
• Reverse Current (I_R):Two colors at V_R=5V maximum 10 µA.
• Capacitance (C):Typical value for yellow LED chip is 40 pF @ V_F=0V, f=1MHz. Not specified for green LED.

3. Explanation of the Grading System

To ensure brightness consistency, LEDs are binned according to their performance. The LTST-C195TGKSKT employs a luminous intensity binning system.

3.1 Luminous Intensity Grading

Intensity is measured at a standard test current of 20mA. The tolerance for each bin is ±15%.

Green Light Bin:

• P Bin:45.0 mcd (minimum) to 71.0 mcd (maximum)
• Q bin:71.0 mcd to 112.0 mcd
• R bin:112.0 mcd to 180.0 mcd
• S gear:180.0 mcd to 280.0 mcd

Yellow Light Sorting:

• N Grade:28.0 mcd to 45.0 mcd
• P Bin:45.0 mcd to 71.0 mcd
• Q bin:71.0 mcd to 112.0 mcd
• R bin:112.0 mcd to 180.0 mcd

The designer should specify the required bin code when ordering to ensure brightness uniformity among multiple devices in the application.

4. Performance Curve Analysis

Although specific graphs (Figure 1, Figure 6) are referenced in the datasheet, the following trends are standard characteristics for this type of LED and can be inferred from the provided data:

4.1 Relationship Between Forward Current and Forward Voltage (I-V Curve)

The I-V relationship exhibits exponential characteristics. The specified V at 20mA_FIt provides an operating point. For the same current, the green LED has a higher V_Frequires a higher driving voltage than the yellow LED. The current-limiting resistor is crucial for correctly setting the operating point and preventing thermal runaway.

4.2 Relationship between Luminous Intensity and Forward Current

Within the normal operating range (up to I_F), The luminous intensity is roughly proportional to the forward current. Operating above the recommended DC current increases brightness but also increases power consumption and junction temperature, which may shorten lifespan and cause color shift.

4.3 Temperature Dependence

The derating factor (0.25-0.4 mA/°C) indicates that the maximum allowable current decreases as the ambient temperature rises. Furthermore, the luminous intensity of most LEDs decreases with increasing junction temperature. For AlInGaP (yellow), this thermal quenching effect may be more pronounced than for InGaN (green). For high-reliability applications, proper thermal management on the PCB is recommended.

5. Mechanical and Packaging Information

5.1 Pin Assignment

This device has four pins (1, 2, 3, 4).

• Green light chip: Connected to pin 1 and 3.
• Yellow light chip: Connected to pin 2 and 4.

This configuration typically allows independent control of each color. The package lens is water white.

5.2 Package Dimensions and Pad Layout

This LED conforms to the EIA standard SMD package outline. Unless otherwise specified, all dimensions are in millimeters with a standard tolerance of ±0.10mm. The datasheet includes detailed dimensional drawings of the component itself and the recommended pad layout to ensure proper soldering and mechanical stability. Adhering to the recommended pad layout is crucial for achieving reliable solder joints and correct alignment during the reflow soldering process.

6. Soldering and Assembly Guide

6.1 Reflow soldering temperature profile

The datasheet provides two recommended infrared (IR) reflow soldering temperature profiles:

1. For conventional processes:Standard profile for tin-lead (SnPb) solder.
2. For lead-free processes:Profile specifically designed for high-temperature lead-free solder alloys (e.g., SAC305). This profile typically features a higher peak temperature (meeting the rating of 260°C for 5 seconds).

Temperature curve includes preheat zone, soak zone, reflow zone, and cooling zone. Controlling time above liquidus and peak temperature is crucial to prevent damage to LED package or internal wire bonds.

6.2 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. Unspecified chemicals may damage the epoxy lens or package material.

6.3 Storage and Handling

• ESD Precautions:LEDs are sensitive to electrostatic discharge (ESD). When handling, use a grounded wrist strap, anti-static gloves, and a properly grounded workbench. It is recommended to use an ionizing blower to neutralize static charges.
• Humidity Sensitivity:Although there is no explicit classification (e.g., MSL), the datasheet recommends that LEDs removed from their original moisture barrier packaging should undergo reflow soldering within one week. For longer-term storage, they should be kept in a sealed container with desiccant or in a nitrogen environment. If stored unpackaged for more than one week, it is recommended to bake them at 60°C for 24 hours before assembly to remove absorbed moisture and prevent the "popcorn" effect during reflow soldering.

7. Packaging and Ordering Information

7.1 Tape and Reel Specifications

Products are supplied in standard embossed carrier tape format:

• Reel dimensions:Diameter 7 inches.
• Quantity per roll:4000 pieces.
• Minimum Order Quantity (MOQ):The remaining quantity is 500 pieces.
• Carrier tape width: 8mm.
• The carrier tape is sealed with a cover tape. Specifications comply with ANSI/EIA 481-1-A-1994.

8. Application Description and Design Considerations

8.1 Drive Circuit Design

LED is a current-driven device.The most critical design rule is to connect a current-limiting resistor in series with each LED chip.

• Recommended Circuit (Model A):Each LED (or each color chip within a bi-color LED) has its own dedicated current-limiting resistor connected to the drive voltage. This ensures uniform brightness by compensating for the natural differences in forward voltage (V_F) between different LEDs.
• Not Recommended (Model B):It is not recommended to directly connect multiple LEDs in parallel and share a single resistor. V_FMinor variations in Vf can lead to significant current imbalance, resulting in uneven brightness and causing the LED with the lowest V_F.

to potentially experience overcurrent._supply- V_F) / I_F. Use the maximum V from the datasheet for conservative design to ensure that even for LEDs with lower V, their I_Ffor conservative design to ensure that even for LEDs with lower V, their I_Flower LEDs, their I_F part.

E le sili atu foi i le tapulaa.

• 8.2 Typical Application ScenariosFa'ailoga tulaga lanu lua:
• Used in consumer electronics, industrial control panels, and automotive dashboards to display different system statuses (e.g., power on = green, standby = yellow, fault = alternating flash).Symbol/Icon backlighting:
• Used for illuminating multifunction buttons or displays, where color indicates function.Decorative Lighting:

In compact devices with limited space for installing multiple monochromatic LEDs.

9. Technical Comparison and Differentiation

The key differentiation of this component lies in the integration of two chemically distinct semiconductor materials (InGaN and AlInGaP) within a single package. This provides clear separation of green and yellow light, which can be more difficult to achieve with LEDs using a single phosphor conversion. Independent control of each chip offers design flexibility not available with common-anode/common-cathode pre-mixed bicolor LEDs. The EIA package ensures broad industry pad compatibility.

10. Frequently Asked Questions (FAQ)

10.1 Can the green and yellow chips be driven simultaneously at full rated current?

Yes, but total power dissipation must be considered. If both chips are driven at maximum DC current (Green: 20mA @ ~3.3V = 66mW, Yellow: 30mA @ ~2.0V = 60mW), the total power dissipation is approximately 126mW. This exceeds their respective Pd ratings (76mW, 75mW) and may also exceed the total package rating. For continuous simultaneous operation, it is recommended to reduce the current to keep the total power dissipation within a safe range, especially at higher ambient temperatures.

10.2 Why are the forward voltages different for the two colors?

Forward voltage is a fundamental property of a semiconductor material's bandgap energy. The bandgap of InGaN (green light, ~2.4 eV corresponding to 525nm) is wider than that of AlInGaP (yellow light, ~2.1 eV corresponding to 589nm). A wider bandgap requires electrons to overcome more energy, which manifests as a higher forward voltage at the same current.

10.3 How to interpret the binning code in the model number?

The luminous intensity binning code is not embedded in the base part number LTST-C195TGKSKT. Specific intensity bins (e.g., green light R bin, yellow light Q bin) are typically indicated on the reel label or ordering documents. You must negotiate with the supplier to specify and confirm the required bin in your order.

11. Practical Design Case AnalysisScenario:

Design a dual-state indicator light for a 5V USB-powered device. Green indicates "operational," and yellow indicates "charging."

1. Design steps:Select operating current:_FSelect I for both colors
2. = 20mA, to achieve good brightness and lifespan.
   • Calculate the current-limiting resistor:_FFor green light (using maximum V_{= 3.5V): R}Green light
   • = (5V - 3.5V) / 0.020A = 75Ω. Use the closest standard value (e.g., 75Ω or 82Ω)._F= 2.4V): R_{Yellow light}= (5V - 2.4V) / 0.020A = 130Ω. Use 130Ω or 120Ω.
3. Resistor power rating:P = I²R. P_{Green light}= (0.02^2)*75 = 0.03W. A standard 1/10W (0.1W) resistor is sufficient.
4. Microcontroller drive:Connect the cathode pin (through a resistor) to a microcontroller GPIO pin configured as open-drain/open-source. Pull the pin low to turn on the LED. Ensure the MCU GPIO can sink/source 20mA current.
5. PCB Layout:Follow the recommended pad dimensions in the datasheet. Ensure sufficient clearance between pads. Place the LED away from major heat sources.

12. Working Principle

LED light emission is based on the electroluminescence of 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 carriers recombine, they release energy in the form of photons (light). The wavelength (color) of the emitted light is determined by the bandgap energy of the semiconductor material. InGaN materials are used for shorter wavelengths (blue, green), while AlInGaP materials are used for longer wavelengths (red, orange, yellow). The chip is encapsulated in a water-clear epoxy resin lens, providing mechanical protection and shaping the light output beam.

13. Teknoloji Trendleri

The development of such SMD LEDs is driven by trends toward miniaturization, higher efficiency, and greater integration. Future directions may include:

• Efficiency Enhancement:Continuous improvements in epitaxial growth and chip design lead to higher luminous efficacy (more light output per watt of electrical power).
• Color Tuning:Advances in phosphor technology and multi-chip designs enable more precise and stable color points, including tunable white light.
• Improved Thermal Management:New packaging materials and structures provide better heat dissipation, allowing for higher drive currents and maintaining performance at elevated temperatures.
• Intelligent Integration:The potential for integrating control ICs (for constant current, color mixing, or addressing) directly with the LED package within a System-in-Package (SiP) module.