LTST-C19FD1WT Full Color SMD LED Datasheet - Dimensions 3.2x1.6x0.55mm - Voltage 2.0-3.8V - Power 0.08W - English Technical Document

1. Product Overview

The LTST-C19FD1WT is a full-color, surface-mount device (SMD) LED lamp designed for modern, space-constrained electronic applications. It integrates three distinct LED chips within a single, ultra-thin package, enabling the generation of multiple colors from a single component footprint. This design is particularly advantageous for applications requiring status indication, backlighting, or compact display elements without sacrificing color capability.

Its miniature size and compatibility with automated assembly processes make it a versatile choice for high-volume manufacturing. The device is constructed to meet RoHS (Restriction of Hazardous Substances) compliance, ensuring it adheres to global environmental standards for electronic components.

1.1 Core Advantages and Target Market

The primary advantage of this LED is its integration of Blue (InGaN), Green (InGaN), and Orange (AlInGaP) light sources into one EIA-standard package measuring only 0.55mm in height. This multi-chip configuration eliminates the need for multiple discrete LEDs to achieve similar color functionality, saving valuable PCB (Printed Circuit Board) real estate.

The device is specifically targeted at applications within:

• Telecommunications Equipment: Status indicators on routers, modems, and handsets.
• Office Automation: Backlighting for keypads and keyboards in laptops and peripherals.
• Consumer Electronics & Home Appliances: Power, mode, or function indicators.
• Industrial Equipment: Panel indicators and operator interface elements.
• Micro-Displays & Signage: Small-scale informational or symbolic luminaires.

Its compatibility with infrared (IR) reflow soldering processes aligns with standard surface-mount technology (SMT) assembly lines, facilitating efficient and reliable board population.

2. Technical Parameters: In-Depth Objective Interpretation

This section provides a detailed analysis of the electrical, optical, and thermal characteristics defined in the datasheet. Understanding these parameters is critical for proper circuit design and ensuring long-term reliability.

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 and should be avoided in design.

• Power Dissipation (Pd): 80 mW for Blue/Green, 75 mW for Orange. This is the maximum allowable power the LED can dissipate as heat at an ambient temperature (Ta) of 25°C. Exceeding this limit risks thermal runaway and degradation.
• DC Forward Current (IF): 20 mA for Blue/Green, 30 mA for Orange. This is the maximum continuous forward current recommended for normal operation. The higher rating for the Orange chip is typical for AlInGaP technology compared to InGaN.
• Peak Forward Current: 100 mA for Blue/Green, 80 mA for Orange (at 1/10 duty cycle, 0.1ms pulse width). This rating is for brief, pulsed operation only and should not be used for DC design calculations.
• Temperature Ranges: Operating: -20°C to +80°C; Storage: -30°C to +100°C. The device functionality is guaranteed within the operating range. Prolonged storage outside the specified range may affect material properties.
• Infrared Soldering Condition: 260°C peak temperature for a maximum of 10 seconds. This defines the thermal profile tolerance for lead-free (Pb-free) solder reflow processes.

2.2 Electro-Optical Characteristics

These parameters are measured under standard test conditions (Ta=25°C, IF=20mA) and define the device's performance.

• Luminous Intensity (Iv): Measured in millicandelas (mcd). The datasheet provides minimum and maximum values for each color, which are further subdivided into bins (see Section 3). Typical values are: Blue: 28-180 mcd, Green: 71-450 mcd, Orange: 45-180 mcd. The Green chip generally exhibits higher efficiency.
• Viewing Angle (2θ1/2): Typically 130 degrees. This wide viewing angle indicates a diffuse lens, distributing light over a broad area rather than a focused beam, which is ideal for status indicators meant to be seen from various angles.
• Forward Voltage (VF): The voltage drop across the LED when conducting 20mA. Typical/Max: Blue/Green: 3.5V/3.8V; Orange: 2.0V/2.4V. This is a crucial parameter for driver design. The lower VF of the Orange chip requires different current-limiting considerations if colors are driven independently.
• Peak Emission Wavelength (λp) & Dominant Wavelength (λd): λp is the wavelength at the highest point of the emission spectrum. λd is the single wavelength perceived by the human eye. Typical values: Blue: λp=468nm, λd=470nm; Green: λp=520nm, λd=525nm; Orange: λp=611nm, λd=605nm. The difference between λp and λd is due to the shape of the emission spectrum and the eye's photopic response.
• Spectral Line Half-Width (Δλ): The width of the emission spectrum at half its maximum intensity. Typical: Blue: 26nm, Green: 35nm, Orange: 17nm. A narrower Δλ, as seen with Orange, indicates a more spectrally pure color.
• Reverse Current (IR): Maximum 10 µA at VR=5V. LEDs are not designed for reverse bias operation. This test parameter indicates very minor leakage. Applying significant reverse voltage will damage the device.

3. Binning System Explanation

To manage natural variations in semiconductor manufacturing, LEDs are sorted into performance bins. This allows designers to select components that meet specific brightness requirements.

3.1 Luminous Intensity Binning

The LTST-C19FD1WT uses a letter-based binning system for luminous intensity, with a +/-15% tolerance within each bin. The available bins differ per color due to inherent material efficiencies.

• Blue (InGaN): Bins N (28-45 mcd), P (45-71 mcd), Q (71-112 mcd), R (112-180 mcd).
• Green (InGaN): Bins Q (71-112 mcd), R (112-180 mcd), S (180-280 mcd), T (280-450 mcd). Note the higher upper range compared to Blue.
• Orange (AlInGaP): Bins P (45-71 mcd), Q (71-112 mcd), R (112-180 mcd).

When ordering, specifying the bin code ensures consistency in brightness across a production run. For example, specifying "Green, Bin T" guarantees the highest brightness green chips available for this product.

4. Performance Curve Analysis

While the datasheet references typical curves, their general interpretation is based on standard LED physics.

• IV Curve (Current vs. Voltage): The forward voltage (VF) increases logarithmically with current. The curve for the Orange chip (AlInGaP) will typically have a lower knee voltage (~1.8-2.0V) than the Blue/Green chips (InGaN, ~3.0-3.2V). Beyond the knee, the voltage rises more linearly.
• Luminous Intensity vs. Forward Current: Intensity is approximately proportional to forward current up to the maximum rated current. However, efficiency (lumens per watt) often decreases at very high currents due to increased heat.
• Temperature Characteristics: Luminous intensity typically decreases as junction temperature increases. The forward voltage also decreases with rising temperature (negative temperature coefficient for VF).
• Spectral Distribution: Each chip emits light across a narrow band of wavelengths, peaking at λp. The Orange AlInGaP spectrum is typically narrower than the InGaN spectra for Blue and Green.

5. Mechanical and Package Information

5.1 Package Dimensions and Pin Assignment

The device conforms to an industry-standard SMD footprint. Key dimensions include a body size of approximately 3.2mm x 1.6mm with a height of only 0.55mm. The pin assignment is critical for correct orientation: Pin 1: Blue (InGaN) anode, Pin 2: Orange (AlInGaP) anode, Pin 3: Green (InGaN) anode. The cathodes for all three chips are internally connected to the remaining terminal(s). The exact pad layout must be followed as shown in the datasheet's "Recommend Printed Circuit Board Attachment Pad" diagram to ensure proper soldering and thermal relief.

5.2 Polarity Identification

Polarity is typically indicated by a marking on the LED package, such as a dot, notch, or beveled edge near Pin 1. The PCB silkscreen should clearly mirror this marking to prevent assembly errors. Incorrect polarity will prevent the LED from illuminating and may stress the device if a high reverse voltage is applied by the driver circuit.

6. Soldering and Assembly Guidelines

6.1 Reflow Soldering Parameters

The device is rated for lead-free (Pb-free) IR reflow soldering. The recommended profile includes a pre-heat zone (150-200°C), a controlled ramp to a peak temperature of 260°C maximum, and a time above liquidus (TAL) where the peak temperature is maintained for a maximum of 10 seconds. The total pre-heat time should not exceed 120 seconds. These parameters are based on JEDEC standards to prevent thermal shock and damage to the epoxy package and internal wire bonds. The profile should be characterized for the specific PCB assembly.

6.2 Storage and Handling

• ESD (Electrostatic Discharge) Precautions: The LED is sensitive to ESD. Handling should be performed at an ESD-protected workstation using grounded wrist straps and conductive foam.
• Moisture Sensitivity Level (MSL): The device is rated MSL 3. When the original moisture-barrier bag is opened, the components must be soldered within 168 hours (1 week) of exposure to factory floor conditions (<30°C/60% RH). If exceeded, a bake at 60°C for at least 20 hours is required to remove absorbed moisture and prevent "popcorning" during reflow.
• Long-Term Storage: Unopened bags should be stored at ≤30°C and ≤90% RH. Opened devices should be stored in a dry cabinet or sealed container with desiccant.

6.3 Cleaning

Post-solder cleaning, if necessary, should use mild, alcohol-based solvents like isopropyl alcohol (IPA) or ethyl alcohol. Immersion should be brief (less than one minute) at room temperature. Harsh or unspecified chemicals can damage the lens material or package markings.

7. Packaging and Ordering Information

The LTST-C19FD1WT is supplied in industry-standard embossed carrier tape on 7-inch (178mm) diameter reels. Each reel contains 3000 pieces. The tape and reel dimensions conform to ANSI/EIA-481 specifications, ensuring compatibility with automated pick-and-place equipment. For quantities less than a full reel, a minimum packing quantity of 1000 pieces is typical for remainders.

8. Application Suggestions

8.1 Typical Application Circuits

Each color chip must be driven independently with its own current-limiting resistor or constant-current driver. The resistor value (R) is calculated using Ohm's Law: R = (Vsupply - VF_LED) / IF. For example, driving the Blue LED from a 5V supply with a target IF of 20mA and a typical VF of 3.5V: R = (5V - 3.5V) / 0.02A = 75 Ohms. A standard 75Ω or 82Ω resistor would be suitable. The power rating of the resistor should be at least I²R = (0.02)² * 75 = 0.03W, so a 1/10W (0.1W) resistor is sufficient. Microcontrollers or dedicated LED driver ICs can be used for PWM (Pulse Width Modulation) dimming or dynamic color mixing.

8.2 Design Considerations

• Thermal Management: Although power dissipation is low, ensuring adequate PCB copper area around the LED pads helps conduct heat away from the junction, maintaining brightness and longevity.
• Current Matching: For uniform apparent brightness when multiple colors are on simultaneously, the different luminous intensities and human eye sensitivity (photopic response) must be considered. The drive currents may need to be adjusted independently (e.g., lower current for the brighter Green chip) to achieve balanced white light or other color blends.
• Reverse Voltage Protection: In circuits where the LED could be exposed to reverse bias (e.g., in multiplexed arrays), a shunt diode in parallel with each LED string is recommended to protect the devices.

9. Technical Comparison and Differentiation

The key differentiator of the LTST-C19FD1WT is its "full color" capability in an ultra-thin 0.55mm package. Compared to using three separate single-color 0603 or 0402 LEDs, this integrated solution offers significant space savings, simplified pick-and-place (one component vs. three), and potentially better color mixing due to the closer proximity of the light sources. The use of InGaN for blue/green and AlInGaP for orange provides high efficiency and good color saturation across the spectrum. Alternative solutions might use a white LED with color filters or a dedicated RGB LED package, which may be thicker or have different driving voltage requirements.

10. Frequently Asked Questions (Based on Technical Parameters)

10.1 Can I drive all three colors simultaneously to create white light?

Yes, by driving the Red (Orange), Green, and Blue chips at appropriate current ratios, you can mix light to create various colors, including white. However, the specific orange wavelength (605-611nm dominant) is not a deep red, so the resulting "white" may have a slightly warm or limited color gamut compared to an LED using a true red chip. Achieving a specific white point (e.g., D65) requires precise current control and may involve calibration.

10.2 Why is the maximum forward current different for the Orange chip?

The Orange chip uses AlInGaP semiconductor technology, while the Blue and Green use InGaN. These different material systems have inherent differences in current density handling, internal efficiency, and thermal characteristics, leading to the manufacturer specifying a higher safe continuous current (30mA vs. 20mA) for the Orange chip under the same package thermal constraints.

10.3 What happens if I exceed the 260°C for 10 seconds reflow specification?

Exceeding the recommended thermal profile can cause multiple failures: delamination of the epoxy package, cracking of the silicon die or substrate, degradation of the phosphor (if present), or failure of the internal gold wire bonds. This will likely result in immediate failure (no light output) or significantly reduced long-term reliability.

11. Practical Use Case Example

Scenario: Multi-Function Status Indicator for a Network Router. A single LTST-C19FD1WT can replace three separate LEDs to indicate power (steady Orange), network activity (flashing Green), and error status (flashing Blue). A microcontroller's GPIO pins, each with a series current-limiting resistor calculated as in section 8.1, independently control each color. The wide 130-degree viewing angle ensures the indicator is visible from anywhere in a room. The ultra-thin profile allows it to fit behind a slim panel bezel. By using PWM on the microcontroller, the brightness of each color can be adjusted for optimal visibility in different ambient lighting conditions.

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, releasing energy in the form of photons. The wavelength (color) of the emitted light is determined by the energy bandgap of the semiconductor material. The LTST-C19FD1WT utilizes two material systems: Indium Gallium Nitride (InGaN) for the blue and green chips, which has a wider bandgap, and Aluminum Indium Gallium Phosphide (AlInGaP) for the orange chip, which has a narrower bandgap corresponding to longer wavelengths (red/orange). The diffuse white lens encapsulates the chips, providing mechanical protection, shaping the light output beam, and mixing the colors when multiple chips are active.

13. Technology Trends

The development of SMD LEDs like the LTST-C19FD1WT follows broader trends in optoelectronics: increased integration, miniaturization, and efficiency. Future iterations may feature even thinner packages, higher luminous efficacy (more light output per watt), and improved color rendering indices (CRI) for mixed-white applications. There is also a trend towards tighter binning tolerances to provide more consistent color and brightness for high-end display applications. The drive for lower voltage operation to be compatible with advanced low-power digital logic (e.g., 1.8V or 3.3V systems) is another ongoing area of development.