LTST-C195TGKRKT Dual Color SMD LED Datasheet - Size 2.0x1.25x0.55mm - Green 3.5V / Red 2.4V - 76mW - English Technical Document

1. Product Overview

The LTST-C195TGKRKT is a dual-color, surface-mount device (SMD) LED designed for modern electronic applications requiring compact size and reliable performance. This component integrates two distinct semiconductor chips within a single 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 high-brightness, color-indicating solution in an exceptionally thin form factor, making it suitable for space-constrained designs such as ultra-thin consumer electronics, wearable devices, and advanced panel indicators.

The core advantage of this LED lies in its dual-color capability from a single EIA-standard package, eliminating the need for two separate components. It is a RoHS-compliant green product, ensuring environmental friendliness. The package is supplied on 8mm tape mounted on 7-inch diameter reels, which is fully compatible with high-speed automatic pick-and-place equipment used in volume manufacturing. Furthermore, it is designed to withstand standard infrared (IR) reflow soldering processes, facilitating easy integration into automated PCB assembly lines.

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. For reliable operation, conditions should not exceed these values. The ratings are specified at an ambient temperature (Ta) of 25°C.

• Power Dissipation (Pd): 76 mW for the Green chip, 75 mW for the Red chip. This parameter indicates the maximum power the LED can dissipate as heat without degradation.
• Peak Forward Current (I_FP): 100 mA for Green, 80 mA for Red. This is the maximum allowable pulsed current, typically specified at a 1/10 duty cycle and 0.1ms pulse width, used for brief, high-intensity flashes.
• DC Forward Current (I_F): 20 mA for Green, 30 mA for Red. This is the recommended continuous operating current for standard brightness operation.
• Temperature Ranges: Operating from -20°C to +80°C; Storage from -30°C to +100°C.
• IR Reflow Condition: Withstands 260°C peak temperature for 10 seconds, which is a standard condition for lead-free (Pb-free) solder processes.

2.2 Electrical & Optical Characteristics

These are the typical performance parameters measured at Ta=25°C and I_F=20mA, unless otherwise noted.

• Luminous Intensity (I_V): The Green chip has a minimum of 112 mcd and a maximum of 450 mcd. The Red chip has a minimum of 112 mcd and a maximum of 280 mcd. The typical value is not specified, indicating performance is managed through the binning system.
• Viewing Angle (2θ_1/2): A typical wide viewing angle of 130 degrees for both colors, defined as the off-axis angle where intensity drops to half its on-axis value.
• Peak Wavelength (λ_P): Typically 525 nm (Green) and 639 nm (Red). This is the wavelength at the highest point in the emission spectrum.
• Dominant Wavelength (λ_d): Typically 525 nm (Green) and 631 nm (Red). This is the single wavelength perceived by the human eye, derived from the CIE chromaticity diagram, and is crucial for color definition.
• Spectral Line Half-Width (Δλ): Typically 35 nm (Green) and 20 nm (Red). This indicates the spectral purity; a narrower half-width means a more saturated, pure color.
• Forward Voltage (V_F): Typically 3.30V (max 3.50V) for Green and 2.00V (max 2.40V) for Red at 20mA. This is a critical parameter for driving circuit design and power supply selection.
• Reverse Current (I_R): Maximum 10 µA for both at a reverse voltage (V_R) of 5V. The datasheet explicitly states the device is not designed for reverse operation; this test is for leakage characterization only.

3. Binning System Explanation

The product uses a binning system to categorize LEDs based on key optical parameters, ensuring consistency within a batch. The tolerance for each intensity bin is ±15%, and for dominant wavelength bins is ±1 nm.

3.1 Luminous Intensity Binning

Green Color (@20mA):
Bin Code R: 112.0 – 180.0 mcd
Bin Code S: 180.0 – 280.0 mcd
Bin Code T: 280.0 – 450.0 mcd

Red Color (@20mA):
Bin Code R: 112.0 – 180.0 mcd
Bin Code S: 180.0 – 280.0 mcd

3.2 Dominant Wavelength Binning (Green only)

Bin Code AP: 520.0 – 525.0 nm
Bin Code AQ: 525.0 – 530.0 nm
Bin Code AR: 530.0 – 535.0 nm

4. Performance Curve Analysis

While specific graphical curves are referenced in the datasheet (e.g., Fig.1 for spectral distribution, Fig.6 for viewing angle), their typical interpretations are crucial for design.

• IV Curve: The forward voltage (V_F) vs. forward current (I_F) relationship is non-linear. For both chips, V_F will increase with I_F and decrease with rising junction temperature. A constant current driver is strongly recommended over a constant voltage source to ensure stable luminous output.
• Temperature Characteristics: Luminous intensity typically decreases as the junction temperature increases. The operating temperature range of -20°C to +80°C defines the ambient conditions where the specified performance is guaranteed. Designers must consider thermal management on the PCB to prevent excessive temperature rise at high currents or in enclosed spaces.
• Spectral Distribution: The Green (InGaN) chip has a broader spectral half-width (35nm) compared to the Red (AlInGaP) chip (20nm). This influences color mixing if used with other LEDs and affects the perceived color saturation.

5. Mechanical & Package Information

5.1 Package Dimensions

The device conforms to an EIA standard package outline. Key dimensions include a body size of approximately 2.0mm x 1.25mm, with a critically low profile height of 0.55mm (typical). All dimensional tolerances are ±0.10mm unless otherwise specified. The package features a water-clear lens, which is optimal for achieving the specified wide viewing angle and does not color the emitted light.

5.2 Pin Assignment & Polarity

The LED has four terminals. The Green chip is connected between pins 1 and 3. The Red chip is connected between pins 2 and 4. This configuration allows independent control of each color. The cathode/anode designation for each chip must be verified from the recommended soldering pad layout diagram to ensure correct orientation during PCB design and assembly.

5.3 Suggested Soldering Pad Dimensions

The datasheet provides a recommended land pattern (footprint) for PCB design. Adhering to these dimensions is essential for achieving reliable solder joints, proper alignment, and effective heat dissipation during the reflow process. The pad design also helps prevent tombstoning (component standing up on one end) during soldering.

6. Soldering & Assembly Guidelines

6.1 Reflow Soldering Profile

A suggested IR reflow profile for Pb-free processes is provided. Key parameters include:
- Pre-heat: 150°C to 200°C.
- Pre-heat Time: Maximum 120 seconds to gradually heat the board and components, activating the flux and minimizing thermal shock.
- Peak Temperature: Maximum 260°C.
- Time Above Liquidus: The component should be exposed to the peak temperature for a maximum of 10 seconds, and this reflow cycle should not be performed more than twice.

The profile is based on JEDEC standards to ensure reliability. However, the datasheet correctly notes that the optimal profile depends on the specific board design, components, solder paste, and oven, so characterization is recommended.

6.2 Hand Soldering

If hand soldering is necessary, use a soldering iron with a temperature not exceeding 300°C, and limit the contact time to a maximum of 3 seconds per joint. This should be done only once to avoid thermal damage to the LED chip and plastic package.

6.3 Storage Conditions

LEDs are moisture-sensitive devices (MSD).
- Sealed Package: Store at ≤ 30°C and ≤ 90% RH. Use within one year from the date the moisture-proof bag is opened.
- Opened Package: Store at ≤ 30°C and ≤ 60% RH. It is recommended to complete IR reflow within one week of opening. For longer storage out of the original bag, use a sealed container with desiccant or a nitrogen desiccator. Components stored for more than a week should be baked at approximately 60°C for at least 20 hours before soldering to remove absorbed moisture and prevent \"popcorning\" (package cracking due to vapor pressure during reflow).

6.4 Cleaning

Only use specified cleaning agents. Unspecified chemicals may damage the plastic package. If cleaning is required post-soldering, immerse the LED in ethyl alcohol or isopropyl alcohol at room temperature for less than one minute. Do not use ultrasonic cleaning unless its compatibility is verified, as it may cause mechanical stress.

7. Packaging & Ordering Information

7.1 Tape and Reel Specifications

The device is supplied in embossed carrier tape with a protective top cover tape, wound on 7-inch (178mm) diameter reels. Standard reel quantity is 4000 pieces. A minimum packing quantity of 500 pieces is available for remainder quantities. The packaging conforms to ANSI/EIA 481-1-A-1994 specifications. A maximum of two consecutive missing components (empty pockets) is allowed per reel.

7.2 Part Number Interpretation

The part number LTST-C195TGKRKT follows the manufacturer's internal coding system, which typically encodes information about the series, size, color, bin codes, and packaging. In this case, \"TG\" and \"KR\" likely indicate the green and red color/binning combinations, respectively.

8. Application Suggestions

8.1 Typical Application Scenarios

• Status Indicators: Dual-color capability allows for multiple status signals (e.g., Green=OK/On, Red=Fault/Alert, Both=Standby/Warning) from a single component point.
• Backlighting for Keypads & Icons: Its thin profile is ideal for backlighting thin buttons or symbols in consumer electronics, appliances, and automotive interiors.
• Panel Mount Indicators: For industrial control panels, network equipment, and instrumentation where space is limited and clear color differentiation is needed.
• Portable & Wearable Devices: Smartwatches, fitness trackers, and medical monitors benefit from the low height and dual-function indicator.

8.2 Design Considerations

• Current Limiting: Always use a series current-limiting resistor or a constant-current driver for each color channel. Calculate the resistor value based on the supply voltage (V_CC), the LED's typical V_F at the desired current, and the desired I_F (e.g., 20mA). Example for Green: R = (V_CC - 3.3V) / 0.020A.
• ESD Protection: LEDs are sensitive to electrostatic discharge (ESD). Implement ESD protection measures on the PCB (e.g., TVS diodes) near the LED connections if the trace length is significant or the environment is prone to ESD. Always handle components with proper ESD precautions (wrist straps, grounded workstations).
• Thermal Management: Although power dissipation is low, ensure adequate copper area around the thermal pads (if any) or leads to conduct heat away, especially if operating at high ambient temperatures or near maximum current.
• Optical Design: The water-clear lens and 130-degree viewing angle provide wide, diffuse light. For directed light, external lenses or light guides may be necessary.

9. Technical Comparison & Differentiation

The primary differentiation of the LTST-C195TGKRKT lies in its combination of features:
1. Ultra-Thin Profile (0.55mm): Thinner than many standard dual-color LEDs, enabling design in increasingly slim products.
2. Chip Technology: Uses high-efficiency InGaN for green and AlInGaP for red, offering good brightness and color performance.
3. Dual-Chip Integration: Combines two colors in one industry-standard package footprint, saving PCB space and assembly cost compared to using two separate LEDs.
4. Manufacturing Compatibility: Full compatibility with tape-and-reel, auto-placement, and Pb-free IR reflow processes makes it ideal for high-volume, automated production.

10. Frequently Asked Questions (Based on Technical Parameters)

Q1: Can I drive both the Green and Red LEDs simultaneously at their maximum DC current?
A: The Absolute Maximum Ratings specify power dissipation per chip (76mW Green, 75mW Red). Simultaneous operation at 20mA (Green) and 30mA (Red) results in approximate power draws of 66mW (3.3V*0.02A) and 60mW (2.0V*0.03A) respectively, which are within limits. However, the total heat generated in the tiny package must be considered, and derating may be necessary at high ambient temperatures.

Q2: What is the difference between Peak Wavelength and Dominant Wavelength?
A: Peak Wavelength (λ_P) is the physical wavelength at the highest intensity point of the emitted spectrum. Dominant Wavelength (λ_d) is a calculated value based on human color perception (CIE diagram) that represents the \"color\" we see. For monochromatic LEDs, they are often close, but for broader spectra (like the Green chip here), they can differ slightly. λ_d is more relevant for color specification.

Q3: Why is the Reverse Current test done at 5V if the device is not for reverse operation?
A: The I_R test at V_R=5V is a quality and leakage test for the semiconductor junction. It verifies the integrity of the chip. Applying a reverse voltage in an actual circuit is not recommended and can quickly damage the LED, as it is not designed to block significant reverse voltage.

Q4: How do I select the appropriate bin code for my application?
A: For applications requiring consistent brightness across multiple units (e.g., status indicators on a panel), specify a tighter intensity bin (e.g., Bin S or T). For color-critical applications (e.g., color mixing), specify the dominant wavelength bin (AP, AQ, AR for Green). Consult with the supplier during procurement to ensure the delivered batch meets your binning requirements.

11. Practical Use Case

Scenario: Designing a Dual-Status Indicator for a IoT Sensor Module
A compact IoT sensor module needs to indicate power (Green) and data transmission activity (Red) using a single LED due to space constraints. The LTST-C195TGKRKT is selected.
1. PCB Layout: The recommended solder pad footprint is used. Pins 1&3 (Green) are connected to a GPIO pin set to output high for \"ON\" via a 100Ω resistor (for a 3.3V supply: (3.3V-3.3V)/0.02A ≈ 0Ω, so a small resistor limits inrush current). Pins 2&4 (Red) are connected to another GPIO pin via a 68Ω resistor (for 3.3V supply: (3.3V-2.0V)/0.02A = 65Ω).
2. Firmware: The Green LED is turned on continuously when power is good. The Red LED is blinked briefly during data transmission packets.
3. Result: The module provides clear, dual-status indication from one 2.0x1.25mm point, consuming minimal board space and height, and is assembled using standard SMT processes.

12. Principle Introduction

Light emission in LEDs 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 specific wavelength (color) of the emitted light is determined by the bandgap energy of the semiconductor material used in the active region.
- The Green LED uses an InGaN (Indium Gallium Nitride) compound semiconductor. Adjusting the ratio of Indium to Gallium allows tuning of the bandgap to produce green light (~525 nm).
- The Red LED uses an AlInGaP (Aluminum Indium Gallium Phosphide) compound semiconductor. This material system is efficient for producing red, orange, and amber light. Here, it is tuned for red emission (~631-639 nm).
Both chips are housed in a single plastic package with a water-clear epoxy lens that protects the chips, provides mechanical stability, and shapes the light output pattern.

13. Development Trends

The market for SMD LEDs like the LTST-C195TGKRKT continues to evolve driven by several key trends:
1. Miniaturization: The demand for thinner and smaller components persists, pushing package heights below 0.5mm and footprints even smaller.
2. Increased Integration: Beyond dual-color, trends include integrating RGB (three chips) or RGBW (three chips + white) into single packages, and even incorporating driver ICs within the LED package (\"smart LEDs\").
3. Higher Efficiency & Luminance: Ongoing improvements in epitaxial growth and chip design yield higher luminous efficacy (more light output per electrical watt), allowing for lower power consumption or higher brightness at the same current.
4. Improved Reliability & Thermal Performance: Advancements in packaging materials (mold compounds, leadframes) enhance resistance to moisture, high temperature, and thermal cycling, extending operational lifetime, especially in automotive and industrial applications.
5. Color Consistency & Advanced Binning: Tighter binning tolerances for luminous flux, chromaticity coordinates (x, y on CIE diagram), and forward voltage are becoming standard requirements for applications like display backlighting and architectural lighting, driving more sophisticated production testing and sorting.