LTST-C195TBTGKT Dual Color SMD LED Datasheet - Size 1.6x0.8x0.55mm - Blue 3.8V / Green 2.4V - 76mW - English Technical Document

1. Product Overview

The LTST-C195TBTGKT is a dual-color, surface-mount device (SMD) light-emitting diode (LED) designed for modern, space-constrained electronic applications. It integrates two distinct semiconductor chips within a single, ultra-compact package: an InGaN (Indium Gallium Nitride) chip for blue emission and an InGaN chip for green emission. This configuration allows for the generation of two primary colors from one component, enabling status indication, backlighting, and decorative lighting in a minimal footprint.

The core advantages of this product include its exceptionally thin profile of only 0.55mm, which is critical for applications like ultra-slim displays, mobile devices, and wearable technology. It is manufactured as a green product, meeting ROHS (Restriction of Hazardous Substances) compliance standards, ensuring it is free from substances like lead, mercury, and cadmium. The device is packaged on 8mm tape wound onto 7-inch diameter reels, making it fully compatible with high-speed, automated pick-and-place assembly equipment used in volume manufacturing. Its design is also compatible with infrared (IR) reflow soldering processes, the standard for surface-mount technology (SMT) assembly lines.

1.1 Pin Assignment and Lens

The device features a water-clear lens, which does not diffuse or color the light, allowing the pure chip color (blue or green) to be emitted. The pin assignment is crucial for proper circuit design. For the LTST-C195TBTGKT, the blue LED chip is connected to pins 1 and 3, while the green LED chip is connected to pins 2 and 4. This independent anode/cathode configuration allows each color to be controlled separately by the driving circuit.

2. Technical Parameter Deep-Dive

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. For both the blue and green chips:

• Power Dissipation (Pd): 76 mW. This is the maximum allowable power loss as heat. Exceeding this can lead to overheating and accelerated degradation.
• Peak Forward Current (I_FP): 100 mA. This is permissible only under pulsed conditions with a 1/10 duty cycle and a 0.1ms pulse width. It is used for brief, high-intensity flashes.
• DC Forward Current (I_F): 20 mA. This is the recommended continuous forward current for normal operation, balancing brightness and longevity.
• Operating Temperature Range (T_opr): -20°C to +80°C. The device is guaranteed to function within this ambient temperature range.
• Storage Temperature Range (T_stg): -30°C to +100°C.
• Infrared Soldering Condition: Withstands 260°C peak temperature for 10 seconds, which aligns with typical lead-free (Pb-free) reflow profiles.

2.2 Electrical and Optical Characteristics

These are the typical performance parameters measured at an ambient temperature (T_a) of 25°C and a forward current (I_F) of 20 mA, unless otherwise stated.

• Luminous Intensity (I_V): A measure of perceived light power. For Blue: Minimum 28.0 mcd, Typical value not specified, Maximum 180 mcd. For Green: Minimum 45.0 mcd, Typical value not specified, Maximum 280 mcd. The green chip is inherently more efficient in terms of human eye sensitivity.
• Viewing Angle (2θ_1/2): 130 degrees (typical for both colors). This wide viewing angle indicates a Lambertian-like emission pattern, suitable for applications requiring broad area illumination rather than a focused beam.
• Peak Emission Wavelength (λ_P): The wavelength at which the spectral power distribution is maximum. Blue: 468 nm (typical). Green: 525 nm (typical).
• Dominant Wavelength (λ_d): The single wavelength that defines the perceived color on the CIE chromaticity diagram. Blue: 470 nm (typical). Green: 530 nm (typical). This value is more relevant for color specification than peak wavelength.
• Spectral Line Half-Width (Δλ): The bandwidth of the emitted spectrum at half its maximum intensity. Blue: 25 nm (typical). Green: 17 nm (typical). A narrower half-width indicates a more spectrally pure color.
• Forward Voltage (V_F): The voltage drop across the LED when operating at the specified current. Blue: Typical 3.30V, Maximum 3.80V. Green: Typical 2.00V, Maximum 2.40V. This difference is due to the different bandgap energies of the semiconductor materials. It is critical for driver design, especially when powering both colors from the same voltage rail.
• Reverse Current (I_R): Maximum 10 μA at a Reverse Voltage (V_R) of 5V. LEDs are not designed for reverse bias operation; this parameter is for leakage characterization only.

3. Binning System Explanation

To ensure consistency in mass production, LEDs are sorted into performance bins based on luminous intensity. This allows designers to select a brightness grade suitable for their application.

3.1 Luminous Intensity Binning

The bin code is a single letter defining a min/max intensity range. Tolerance within each bin is +/-15%.

For the Blue Chip (measured in mcd @ 20mA):

• Bin N: 28.0 – 45.0 mcd
• Bin P: 45.0 – 71.0 mcd
• Bin Q: 71.0 – 112.0 mcd
• Bin R: 112.0 – 180.0 mcd

For the Green Chip (measured in mcd @ 20mA):

• Bin P: 45.0 – 71.0 mcd
• Bin Q: 71.0 – 112.0 mcd
• Bin R: 112.0 – 180.0 mcd
• Bin S: 180.0 – 280.0 mcd

The specific bin for a given production lot would be indicated on the packaging or in order documentation.

4. Performance Curve Analysis

The datasheet references typical performance curves which are essential for understanding device behavior under non-standard conditions. While the specific graphs are not reproduced in the text, their implications are standard.

• I-V (Current-Voltage) Curve: Would show the exponential relationship between forward voltage and current. The knee voltage is around the typical V_F values. This curve is vital for designing current-limiting circuits.
• Luminous Intensity vs. Forward Current: Would show that intensity increases approximately linearly with current up to a point, after which efficiency drops due to heating and other effects. Operating at the recommended 20mA ensures optimal efficiency and lifetime.
• Luminous Intensity vs. Ambient Temperature: Would demonstrate thermal quenching, where light output decreases as the junction temperature rises. This is a critical consideration for high-power or high-ambient-temperature applications.
• Spectral Distribution: Would plot relative intensity against wavelength, showing the peak and dominant wavelengths and the spectral half-width.

5. Mechanical and Packaging Information

5.1 Package Dimensions

The device conforms to an EIA standard package outline. Key dimensions (all in mm, tolerance ±0.10mm unless noted) include the overall length (1.6mm), width (0.8mm), and the critical height of 0.55mm. Detailed dimensional drawings would show pad locations, lens shape, and marking orientation.

5.2 Suggested Soldering Pad Layout

A recommended land pattern (footprint) for the PCB is provided to ensure reliable solder joint formation during reflow. Adhering to this pattern prevents tombstoning (component standing on end) and ensures proper alignment and thermal relief.

5.3 Tape and Reel Packaging

The LEDs are supplied in embossed carrier tape with a protective cover tape, wound onto 7-inch (178mm) diameter reels. This is the standard for automated assembly.

• Pocket pitch: 8mm.
• Quantity per reel: 4000 pieces.
• Minimum order quantity for remnants: 500 pieces.
• Packaging conforms to ANSI/EIA-481 specifications.

6. Soldering and Assembly Guidelines

6.1 IR Reflow Soldering Profile

A suggested temperature profile for lead-free (Pb-free) solder process is provided. Key parameters include:

• Pre-heat: 150-200°C.
• Pre-heat Time: Maximum 120 seconds to allow for uniform heating and flux activation.
• Peak Temperature: Maximum 260°C.
• Time Above Liquidus: 10 seconds maximum (and maximum two reflow cycles).

The profile is based on JEDEC standards, ensuring component reliability. The exact profile must be characterized for the specific PCB design, solder paste, and oven used.

6.2 Hand Soldering

If manual repair is necessary:

• Soldering Iron Temperature: Maximum 300°C.
• Soldering Time: Maximum 3 seconds per joint.
• Limit: One-time only for hand soldering to prevent thermal damage.

6.3 Cleaning

If cleaning after soldering is required, only specified solvents should be used to avoid damaging the plastic package. Recommended agents are ethyl alcohol or isopropyl alcohol (IPA). The LED should be immersed at normal temperature for less than one minute.

6.4 Electrostatic Discharge (ESD) Precautions

LEDs are sensitive to static electricity and voltage surges. Handling precautions are mandatory:

• Use a grounded wrist strap or anti-static gloves.
• Ensure all equipment, workstations, and tools are properly grounded.

7. Storage and Handling

• Sealed Package (Moisture Barrier Bag): Store at ≤30°C and ≤90% Relative Humidity (RH). Shelf life is one year when stored in the original bag with desiccant.
• Opened Package: Storage ambient should not exceed 30°C / 60% RH. Components removed from the sealed bag should be reflow-soldered within one week.
• Extended Storage (Out of Bag): Store in a sealed container with desiccant or in a nitrogen desiccator.
• Baking: If components have been exposed to ambient conditions for more than one week, they must be baked at approximately 60°C for at least 20 hours prior to soldering to remove absorbed moisture and prevent \"popcorning\" during reflow.

8. Application Suggestions

8.1 Typical Application Scenarios

• Status Indicators: Dual-color capability allows for multiple states (e.g., blue for \"on/active,\" green for \"standby/complete,\" both on for a third state).
• Backlighting for Keypads and Icons: In mobile phones, remote controls, and consumer electronics, where space is extremely limited.
• Decorative Lighting: In wearable devices, where the thin profile is essential.
• Panel Indicators: In industrial control equipment, networking hardware, and automotive interiors.

8.2 Design Considerations

• Current Driving: Always use a series current-limiting resistor or a constant-current driver. Calculate the resistor value separately for each color due to their different forward voltages (e.g., R_limit = (V_supply - V_F) / I_F).
• Thermal Management: Although power dissipation is low, ensure adequate PCB copper area or thermal vias if operating at high ambient temperatures or at maximum current, to maintain junction temperature within limits.
• PCB Layout: Follow the suggested soldering pad dimensions to ensure mechanical stability and proper solder fillet formation.
• Reverse Voltage Protection: As the device is not designed for reverse bias, ensure circuit design prevents reverse voltage application, which could exceed the 5V test condition and cause immediate failure.

9. Technical Comparison and Differentiation

The primary differentiating factors of the LTST-C195TBTGKT compared to generic single-color or thicker dual-color LEDs are:

• Ultra-Thin Profile (0.55mm): Enables design in next-generation slim devices where vertical space is at a premium.
• Dual InGaN Chips: Provides blue and green from efficient, modern semiconductor materials, offering good brightness and color purity.
• Full SMT Compatibility: Designed for compatibility with automated placement and standard Pb-free reflow profiles, reducing assembly cost and complexity.
• Standardized Binning: Provides predictable luminous performance, aiding in design for consistent visual output across production runs.

10. Frequently Asked Questions (Based on Technical Parameters)

Q1: Can I drive the blue and green LEDs simultaneously from the same power source?
A: Yes, but they must be driven independently with separate current-limiting paths (e.g., two resistors) because their forward voltages differ significantly (3.3V vs. 2.0V). Connecting them in parallel directly would cause most of the current to flow through the green LED due to its lower V_F.

Q2: What is the difference between peak wavelength and dominant wavelength?
A: Peak wavelength (λ_P) is the physical wavelength of highest spectral emission. Dominant wavelength (λ_d) is a calculated value from the CIE color chart that represents the perceived color. λ_d is more relevant for color specification in design.

Q3: Why is the storage condition for opened packages stricter than for sealed ones?
A: The plastic LED package can absorb moisture from the air. During the high-temperature reflow soldering process, this trapped moisture can rapidly vaporize, creating internal pressure and potentially cracking the package (\"popcorning\" or \"delamination\"). The sealed bag with desiccant prevents moisture absorption.

Q4: Can I use this LED for automotive exterior lighting?
A: The datasheet specifies the LED is for \"ordinary electronic equipment.\" Applications requiring exceptional reliability, such as automotive exterior lighting (subject to extreme temperatures, vibration, and humidity), require consultation with the manufacturer for qualified products designed and tested to automotive-grade standards (e.g., AEC-Q102).

11. Practical Design and Usage Case

Case: Designing a Dual-Status Indicator for a Portable Bluetooth Speaker
The speaker requires a single, tiny indicator to show power (blue) and Bluetooth pairing status (flashing green when searching, solid green when connected). The LTST-C195TBTGKT is ideal due to its 0.55mm height fitting behind a thin plastic diffuser. The microcontroller (MCU) has two GPIO pins configured as open-drain outputs. Each pin is connected to the anode of one LED color via a current-limiting resistor. The cathodes are connected to ground. The resistor values are calculated based on the MCU's 3.3V supply: R_Blue = (3.3V - 3.3V) / 0.02A ≈ 0Ω (use a small resistor like 10Ω for safety). R_Green = (3.3V - 2.0V) / 0.02A = 65Ω (use a standard 68Ω resistor). The MCU firmware controls the pins to create the required lighting sequences.

12. Operating Principle Introduction

Light Emitting Diodes (LEDs) are semiconductor devices that emit light through electroluminescence. When a forward voltage is applied across the p-n junction, electrons from the n-type material recombine with holes from the p-type material. This recombination event releases energy. In indirect bandgap semiconductors, this energy is primarily released as heat. In direct bandgap semiconductors like InGaN (used in this device), the energy is released as photons (light). The specific 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, where h is Planck's constant and c is the speed of light. The InGaN material system allows for bandgap engineering to produce light across the blue, green, and ultraviolet spectrum. The water-clear epoxy lens encapsulates the chip, providing mechanical protection and shaping the light output pattern.

13. Technology Trends

The development of LEDs like the LTST-C195TBTGKT follows several key industry trends:

• Miniaturization: Continuous drive towards smaller package sizes (e.g., 01005, micro-LEDs) to enable higher-density electronics and new form factors like flexible and rollable displays.
• Increased Efficiency: Ongoing improvements in internal quantum efficiency (IQE) and light extraction techniques to deliver higher luminous intensity (mcd) at the same or lower drive current, improving battery life in portable devices.
• Advanced Packaging: Development of package-on-package (PoP) and chip-scale packaging (CSP) for LEDs to further reduce thickness and improve thermal performance.
• Color Mixing and Smart Lighting: Integration of multiple color chips (RGB, RGBW) or phosphor-converted white LEDs with integrated control ICs into single packages, enabling tunable white light and dynamic color effects for advanced human-machine interfaces and ambient lighting.
• Reliability and Standardization: Enhanced testing standards (like JEDEC) for moisture sensitivity, thermal cycling, and ESD to ensure reliability in demanding applications, including automotive and industrial environments.