LTST-C19GD2WT Full Color SMD Chip LED Datasheet - Dimensions 3.2x2.8x0.4mm - Voltage 2.0-3.8V - Power 0.075-0.08W - English Technical Document

1. Product Overview

The LTST-C19GD2WT is a full-color surface-mount device (SMD) chip LED designed for modern electronic applications requiring compact, multi-color indication or lighting. This component integrates three distinct semiconductor light sources within a single, ultra-thin package, enabling the generation of a wide spectrum of colors through individual or combined control of the red, green, and blue (RGB) elements.

The core advantage of this device lies in its combination of a minimal footprint, standardized EIA package geometry, and compatibility with high-volume automated assembly processes, including infrared (IR) and vapor phase reflow soldering. It is classified as a green product, meeting RoHS (Restriction of Hazardous Substances) compliance standards, making it suitable for environmentally conscious designs. Its primary target markets include consumer electronics, instrumentation panels, decorative lighting, status indicators in communication equipment, and backlighting modules where space is at a premium and color flexibility is desired.

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 at or near these limits is not recommended for reliable long-term performance.

• Power Dissipation (Pd): Varies by color diode: 80 mW for Blue and Green, 75 mW for Red. This parameter indicates the maximum power the LED junction can safely dissipate as heat at an ambient temperature (Ta) of 25°C.
• Peak Forward Current (I_F(PEAK)): Specified under a 1/10 duty cycle with a 0.1ms pulse width. Blue/Green: 100 mA, Red: 80 mA. This rating is crucial for pulsed operation, such as in multiplexed displays.
• DC Forward Current (I_F): Two conditions are specified. Note 1: Maximum for driving each color individually (Blue: 20mA, Red: 30mA, Green: 20mA). Note 2: Maximum for driving all three colors simultaneously (Red, Green, Blue: 10mA each). This distinction is critical for circuit design to prevent thermal overstress.
• Derating: The DC forward current must be linearly reduced from its 25°C value as ambient temperature rises. Derating factors are 0.25 mA/°C for Blue/Green and 0.4 mA/°C for Red.
• Reverse Voltage (V_R): 5V for all colors. Exceeding this voltage in reverse bias can cause junction breakdown.
• Temperature Ranges: Operating: -20°C to +80°C. Storage: -30°C to +100°C.
• Soldering Condition: Withstands infrared reflow soldering at 260°C for 5 seconds.

2.2 Electrical & Optical Characteristics

These are typical performance parameters measured at Ta=25°C under specified test conditions.

• Luminous Intensity (I_V): Measured in millicandelas (mcd) at I_F=20mA. Typical values: Blue: 40.0 mcd, Red: 100.0 mcd, Green: 150.0 mcd. Minimum values ensure a baseline brightness.
• Viewing Angle (2θ_1/2): Typically 130 degrees. This wide viewing angle is characteristic of a diffused lens, providing a broad, even light distribution rather than a narrow beam.
• Peak Emission Wavelength (λ_P): The wavelength at which the spectral output is maximum. Typical: Blue: 468 nm, Red: 632 nm, Green: 520 nm.
• Dominant Wavelength (λ_d): Derived from the CIE chromaticity diagram, it represents the perceived color. Ranges: Blue: 465-477 nm, Red: 618-630 nm, Green: 519-540 nm.
• Spectral Line Half-Width (Δλ): The bandwidth of the emitted light at half its maximum intensity. Typical: Blue: 26 nm, Red: 17 nm, Green: 35 nm. A narrower width indicates a more spectrally pure color.
• Forward Voltage (V_F): Typical at I_F=20mA: Blue: 3.5V, Red: 2.0V, Green: 3.5V (Max: 3.8V, 2.4V, 3.8V respectively). The lower V_F of the red LED is due to its different semiconductor material (AlInGaP vs. InGaN for Blue/Green).
• Reverse Current (I_R): Maximum 10 µA at V_R=5V, indicating good junction quality.

3. Binning System Explanation

The product uses a binning system to categorize LEDs based on their luminous intensity, ensuring consistency within a batch. The tolerance for each intensity bin is +/-15%.

• Blue Luminous Intensity Bins: N (28.0-45.0 mcd), P (45.0-71.0 mcd), Q (71.0-112.0 mcd).
• Red Luminous Intensity Bins: Q (71.0-112.0 mcd), R (112.0-180.0 mcd).
• Green Luminous Intensity Bins: R (112.0-180.0 mcd), S (180.0-280.0 mcd), T (280.0-450.0 mcd).

This system allows designers to select parts that meet specific brightness requirements for color mixing or uniform appearance in an array.

4. Performance Curve Analysis

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

• I-V (Current-Voltage) Characteristic: LEDs are diodes with an exponential I-V relationship. The forward voltage (V_F) has a negative temperature coefficient, meaning it decreases slightly as junction temperature increases.
• Luminous Intensity vs. Forward Current: Intensity is approximately proportional to forward current in the normal operating range. However, efficiency may drop at very high currents due to thermal effects.
• Luminous Intensity vs. Ambient Temperature: Light output generally decreases as ambient (and thus junction) temperature increases. This is particularly important for high-power or high-density applications.
• Spectral Distribution: Each color LED emits light in a characteristic bell-shaped curve centered around its peak wavelength (λ_P). The half-width (Δλ) defines the curve's breadth.

5. Mechanical & Package Information

The device features an extra-thin profile with a height of only 0.40 mm. It conforms to an EIA standard package outline, facilitating compatibility with industry-standard pick-and-place machines and solder stencils.

• Pin Assignment: Pin 1: InGaN Blue, Pin 2: AlInGaP Red, Pin 3: InGaN Green. The lens is white diffused, which helps blend the light from the individual chips to create a more uniform color mix when viewed off-axis.
• Package Dimensions: Detailed mechanical drawings specify the length, width, lead spacing, and tolerances (typically ±0.10 mm).
• Suggested Soldering Pad Layout: A recommended footprint for PCB design is provided to ensure reliable solder joint formation and mechanical stability. The suggested stencil thickness for solder paste application is a maximum of 0.10mm.

6. Soldering & Assembly Guidelines

6.1 Reflow Soldering Profiles

Two suggested infrared (IR) reflow profiles are provided: one for normal (tin-lead) solder process and one for Pb-free solder process. The Pb-free profile is designed for use with SnAgCu (Tin-Silver-Copper) solder paste and accommodates its higher melting point. Key parameters include pre-heat zones, time above liquidus, peak temperature (max 260°C), and time at peak temperature.

6.2 General Soldering Conditions

• Reflow Soldering: Pre-heat: 120-150°C, Pre-heat time: Max 120 sec, Peak temp: Max 260°C, Time at peak: Max 5 sec.
• Wave Soldering: Pre-heat: Max 100°C for Max 60 sec, Solder wave: Max 260°C for Max 10 sec.
• Hand Soldering (Iron): Temperature: Max 300°C, Time: Max 3 sec (one time only).

6.3 Storage & Handling

• Storage: Recommended not to exceed 30°C and 70% relative humidity. LEDs removed from their original, moisture-protective packaging should be reflow-soldered within one week. For longer storage, use a sealed container with desiccant or a nitrogen ambient. Devices stored out of packaging for >1 week should be baked at ~60°C for at least 24 hours before assembly to remove absorbed moisture and prevent \"popcorning\" during reflow.
• Cleaning: Only use specified solvents. Immerse in ethyl alcohol or isopropyl alcohol at normal temperature for less than one minute if cleaning is necessary. Unspecified chemicals may damage the plastic package.
• ESD (Electrostatic Discharge) Precautions: LEDs are sensitive to ESD and surge damage. Handling recommendations include using a wrist strap or anti-static gloves, and ensuring all equipment is properly grounded.

7. Packaging & Ordering Information

The LTST-C19GD2WT is supplied in tape-and-reel packaging compatible with automated assembly equipment.

• Tape Specifications: 8mm tape width.
• Reel Specifications: 7-inch diameter reels.
• Quantity: 5000 pieces per standard reel. A minimum packing quantity of 500 pieces is available for remainder orders.
• Packaging Quality: Conforms to ANSI/EIA 481-1-A-1994. Empty component pockets are sealed with cover tape. The maximum allowed number of consecutive missing components in the tape is two.

8. Application Recommendations

8.1 Typical Application Scenarios

This LED is suited for ordinary electronic equipment, including but not limited to: status indicators on consumer devices (routers, printers, chargers), backlighting for small displays or icons, decorative accent lighting, and multi-color alert systems in office automation or communication equipment.

8.2 Drive Circuit Design

A critical design note is that LEDs are current-operated devices. To ensure uniform brightness when driving multiple LEDs in parallel, it is strongly recommended to use a current-limiting resistor in series with each LED (Circuit Model A). Driving multiple LEDs in parallel directly from a voltage source with a single shared resistor (Circuit Model B) is discouraged. Variations in the forward voltage (V_F) characteristics between individual LEDs—even from the same batch—will cause unequal current sharing, leading to significant differences in brightness and potential overcurrent in some devices.

8.3 Thermal Management

Despite its low power, proper thermal consideration is necessary, especially when driving at maximum current or in high ambient temperatures. Adhere to the power dissipation and current derating specifications. Ensure the PCB layout provides adequate copper area for heat sinking, particularly for the thermal pad if specified in the package footprint.

9. Technical Comparison & Differentiation

The primary differentiating factors of this component are its ultra-thin 0.4mm height, which is advantageous for space-constrained applications like ultra-slim displays or wearable devices, and its full RGB integration in a single, standardized SMD package. Compared to using three discrete single-color LEDs, this integrated approach saves board space, simplifies assembly, and improves color mixing uniformity due to the co-located light sources under a common diffused lens. Its compatibility with standard IR reflow processes makes it a drop-in solution for modern SMT lines.

10. Frequently Asked Questions (FAQ)

Q: Can I drive the Red, Green, and Blue LEDs all at their individual maximum DC current (20mA, 30mA, 20mA) simultaneously?

A: No. The datasheet specifies two different maximum DC forward current conditions. When driving all three colors at once, the maximum current for each color is limited to 10mA (Note 2). This is a thermal limit to prevent the total power dissipation in the tiny package from exceeding safe levels.

Q: Why is the forward voltage of the Red LED (2.0V) lower than the Blue and Green LEDs (3.5V)?

A: This is due to the different semiconductor materials used. The Red LED uses AlInGaP (Aluminum Indium Gallium Phosphide), which has a lower bandgap energy than the InGaN (Indium Gallium Nitride) used for the Blue and Green LEDs. A lower bandgap translates to a lower forward voltage required for conduction and light emission.

Q: How do I achieve white light with this RGB LED?

A: White light is created by mixing the three primary colors (Red, Green, Blue) in appropriate intensities. This typically requires a microcontroller or dedicated LED driver IC to independently pulse-width modulate (PWM) the current to each diode. By varying the duty cycle for each color, you can mix them to produce not only white but any color within the gamut defined by the three LEDs' specific wavelengths.

Q: The datasheet mentions a \"Pb-Free Process\" profile. Must I use this if my assembly is lead-free?

A: Yes, it is highly recommended. Lead-free solder alloys (like SAC305) generally have higher melting points than traditional tin-lead solder. The suggested Pb-free reflow profile is engineered to reach a sufficient peak temperature (while staying within the LED's 260°C, 5-second limit) to properly melt the solder paste and form reliable joints, without subjecting the component to excessive thermal stress.

11. Design-in Case Study

Scenario: Designing a compact status indicator for a smart home hub. The device needs a single, multi-color LED to show network status (red for error, green for connected, blue for pairing mode, white for normal operation). The LTST-C19GD2WT is selected for its thin profile (fitting a slim bezel) and integrated RGB capability.

Implementation: The LED is placed on the main PCB. A small microcontroller GPIO pin is connected to each cathode (R, G, B) via a current-limiting resistor (calculated based on desired brightness and the LED's V_F at the chosen drive current, e.g., 8mA per color for simultaneous white). The anodes are connected to the supply voltage. The microcontroller firmware controls the pins to turn individual colors on/off or uses PWM to create white and other shades. The wide 130-degree viewing angle ensures the indicator is visible from various angles in a room.

Key Design Checks: Verify total power dissipation (P = V_{F_R}*I_R + V_{F_G}*I_G + V_{F_B}*I_B) is within the 75-80mW limit at the operating ambient temperature, applying derating if needed. Ensure the PCB layout follows the suggested pad dimensions for reliable soldering.

12. Operating Principle

Light Emitting Diodes (LEDs) are semiconductor p-n junction devices that emit light through a process called 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 within the active region. This recombination releases energy. In conventional diodes, this energy is primarily released as heat. In LED materials, the bandgap energy of the semiconductor is such that a significant portion of this energy is released in the form of photons (light). The specific wavelength (color) of the emitted light is directly determined by the bandgap energy of the semiconductor material used. The AlInGaP material system produces red and amber light, while the InGaN system is used for blue, green, and, with a phosphor coating, white LEDs.

13. Technology Trends

The field of SMD LEDs continues to evolve towards higher efficiency (more lumens per watt), smaller package sizes, and greater integration. Trends relevant to components like the LTST-C19GD2WT include the development of even thinner packages for next-generation flexible and foldable displays, improved color rendering and gamut for more vivid and accurate color mixing, and the integration of driver ICs or control logic within the LED package itself (\"smart LEDs\") to simplify system design. Furthermore, advancements in materials science aim to increase reliability and maximum operating temperature ranges, expanding applications into more demanding environments. The drive for energy efficiency across all electronics continues to push for lower operating currents while maintaining or increasing light output.