SMD LED LTST-008TGVFWT Datasheet - White Diffused Lens - Green/Orange Source - 20-30mA - 68-84mW - English Technical Document

1. Product Overview

This document details the specifications for a surface-mount device (SMD) LED featuring a white diffused lens and two distinct light-emitting sources within a single package. The device is designed for automated printed circuit board (PCB) assembly processes and is suitable for applications where space is a critical constraint. Its compact form factor and compatibility with standard industry processes make it a versatile component for modern electronics.

1.1 Features

• Compliant with RoHS (Restriction of Hazardous Substances) directives.
• Packaged on 12mm tape wound onto 7-inch diameter reels for automated handling.
• Conforms to EIA (Electronic Industries Alliance) standard package outlines.
• Input is compatible with integrated circuit (IC) logic levels.
• Designed for compatibility with automated pick-and-place assembly equipment.
• Withstands infrared (IR) reflow soldering processes commonly used in surface-mount technology.
• Preconditioned to accelerate to JEDEC (Joint Electron Device Engineering Council) Moisture Sensitivity Level 3, indicating a floor life of 168 hours at <30°C/60% RH after the sealed bag is opened.

1.2 Applications

The dual-color capability and diffused lens make this LED suitable for a variety of indication and backlighting purposes. Primary application areas include:

• Telecommunication Equipment: Status indicators on routers, modems, and handsets.
• Office Automation: Power, connectivity, or function status lights on printers, scanners, and monitors.
• Home Appliances: Control panel indicators for microwaves, washing machines, and audio systems.
• Industrial Equipment: Machine status or fault indication on control panels.
• Signage & Indoor Display: Low-level illumination or color-coded indicators in informational displays.

2. Technical Parameters Deep Dive

This section provides a detailed, objective analysis of the device's electrical, optical, and thermal characteristics. Understanding these parameters is crucial for reliable circuit design and achieving desired performance.

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 (P_D): 68 mW for the Green chip, 84 mW for the Orange chip. This is the maximum power the LED can dissipate as heat at an ambient temperature (T_a) of 25°C.
• Peak Forward Current (I_FP): 80 mA for both colors. This is the maximum allowable current under pulsed conditions (1/10 duty cycle, 0.1ms pulse width). It is significantly higher than the DC rating, useful for brief, high-intensity flashes.
• DC Forward Current (I_F): 20 mA for Green, 30 mA for Orange. This is the maximum continuous current recommended for reliable long-term operation.
• Operating Temperature Range: -40°C to +85°C. The device is guaranteed to function within this ambient temperature range.
• Storage Temperature Range: -40°C to +100°C. The device can be stored without applied power within this range.

2.2 Electrical & Optical Characteristics

These are the typical performance parameters measured at T_a=25°C under specified test conditions. They are used for design calculations and performance expectations.

• Luminous Flux (Φ_v): The total visible light output measured in lumens (lm).
  • Green (I_F=5mA): Min 0.95 lm, Max 2.30 lm.
  • Orange (I_F=20mA): Min 1.25 lm, Max 3.75 lm.
• Luminous Intensity (I_v): The light output in a specific direction, measured in millicandelas (mcd). This is provided for reference, measured with a CIE eye-response filter.
  • Green (I_F=5mA): Min 330 mcd, Max 775 mcd.
  • Orange (I_F=20mA): Min 450 mcd, Max 1350 mcd.
• Viewing Angle (2θ_1/2): Approximately 130 degrees (typical). This is the full angle at which the luminous intensity is half of the intensity measured on-axis (0 degrees). The white diffused lens creates a wide, uniform viewing pattern.
• Peak Emission Wavelength (λ_P): The wavelength at which the spectral output is strongest.
  • Green: 518 nm (typical).
  • Orange: 611 nm (typical).
• Dominant Wavelength (λ_d): The single wavelength that best represents the perceived color.
  • Green: Ranges from 527 nm to 537 nm, binned (see Section 3).
  • Orange: 605 nm (typical).
• Spectral Line Half-Width (Δλ): The bandwidth of the emitted spectrum at half its maximum intensity.
  • Green: 35 nm (typical).
  • Orange: 20 nm (typical). The orange source has a narrower, more pure spectral output.
• Forward Voltage (V_F): The voltage drop across the LED when operating at the specified current.
  • Green (I_F=5mA): Min 2.4V, Max 3.4V.
  • Orange (I_F=20mA): Min 1.8V, Max 2.8V.
  • Tolerance is +/- 0.1V per note.
• Reverse Current (I_R): Max 10 μA at V_R=5V. The device is not designed for reverse bias operation; this parameter is for IR test reference only.

3. Binning System Explanation

To ensure color and brightness consistency in production, LEDs are sorted into bins based on key parameters. This device uses a combined binning system.

3.1 Luminous Intensity (I_V) Bins

LEDs are grouped based on their light output at the standard test current.

Green (@ 5mA):

G1: 0.95-1.26 lm (330-440 mcd)

G2: 1.26-1.70 lm (440-585 mcd)

G3: 1.70-2.30 lm (585-775 mcd)

Orange (@ 20mA):

O1: 1.25-1.80 lm (450-650 mcd)

O2: 1.80-2.60 lm (650-930 mcd)

O3: 2.60-3.75 lm (930-1350 mcd)

Tolerance on each luminous bin is +/- 11%.

3.2 Dominant Wavelength (WD) Bins for Green

Only the green source is binned for wavelength to control hue variation.

AQ: 527 - 532 nm

AR: 532 - 537 nm

Tolerance is +/- 1 nm per bin.

3.3 Combined Bin Code

A single alphanumeric code on the product tag combines both intensity bins. For example, code "A1" corresponds to a Green G1 bin and an Orange O1 bin. This cross-table (A1-A9) allows for precise selection of brightness combinations for the two colors within the same package.

4. Mechanical & Package Information

4.1 Device Dimensions & Pinout

The SMD package has specific footprint dimensions critical for PCB layout. All dimensions are in millimeters with a standard tolerance of ±0.2 mm unless otherwise noted. The pin assignment for the LTST-008TGVFWT is as follows: Pins (0,1) and 2 are assigned to the Green (InGaN) source. Pins 3 and 4 are assigned to the Orange (AlInGaP) source. Pins 5, 6, and 7 are null (no connection). Designers must refer to the detailed dimensional drawing in the original datasheet for exact pad spacing, component height, and lens size to ensure proper fit and soldering.

4.2 Recommended PCB Attachment Pad

A recommended land pattern (footprint) is provided to ensure reliable solder joint formation during reflow. Using this pattern helps achieve proper solder fillets, mechanical stability, and thermal dissipation. The pad design accounts for solder mask and paste application.

4.3 Tape and Reel Packaging

The components are supplied in embossed carrier tape for automated assembly. Key packaging specifications include:

- Tape width: 12 mm.

- Reel diameter: 7 inches.

- Quantity per reel: 4000 pieces.

- Minimum order quantity for remnants: 500 pieces.

- Packaging conforms to ANSI/EIA-481 specifications.

- The tape has a cover seal to protect components, and a maximum of two consecutive empty pockets are allowed.

5. Soldering & Assembly Guidelines

5.1 IR Reflow Soldering Profile

The device is compatible with lead-free (Pb-free) soldering processes. A suggested IR reflow profile is provided, conforming to J-STD-020B. Key parameters include:

- Pre-heat Temperature: 150-200°C.

- Pre-heat Time: Maximum 120 seconds.

- Peak Body Temperature: Maximum 260°C.

- Time Above Liquidus: Should be controlled according to the profile graph to ensure proper solder joint formation without thermal damage to the LED.

5.2 Hand Soldering (If Necessary)

If manual rework is required:

- Soldering iron temperature: Maximum 300°C.

- Soldering time per pad: Maximum 3 seconds.

- Important: Hand soldering should be limited to one time only to prevent excessive thermal stress.

5.3 Storage & Handling

Sealed Package: Store at ≤30°C and ≤70% Relative Humidity (RH). The shelf life is one year when stored in the original moisture-barrier bag with desiccant.

Opened Package: For components removed from the sealed bag, the storage ambient should not exceed 30°C and 60% RH. It is strongly recommended to complete the IR reflow process within 168 hours (1 week) of exposure. For storage beyond 168 hours, components should be rebaked at approximately 60°C for at least 48 hours before soldering to remove absorbed moisture and prevent "popcorning" during reflow.

5.4 Cleaning

If post-solder cleaning is necessary, use only approved solvents. Immersing the LED in ethyl alcohol or isopropyl alcohol at normal temperature for less than one minute is acceptable. Do not use unspecified chemical cleaners as they may damage the epoxy lens or package.

6. Application Notes & Design Considerations

6.1 Current Limiting

An external current-limiting resistor is mandatory for driving an LED. The resistor value (R) can be calculated using Ohm's Law: R = (V_supply - V_F) / I_F. Always use the maximum V_F from the datasheet for a conservative design to ensure the current does not exceed the desired I_F. For the Green LED (V_{F_max}=3.4V @5mA) with a 5V supply: R = (5V - 3.4V) / 0.005A = 320Ω. A standard 330Ω resistor would be suitable. For pulsed operation at the peak current (80mA), ensure the driver circuit can safely deliver the required pulse.

6.2 Thermal Management

While SMD LEDs are efficient, they still generate heat. Exceeding the maximum junction temperature degrades light output and lifespan. Considerations:

- Do not exceed the absolute maximum power dissipation (68/84 mW).

- Ensure the PCB pad design provides adequate thermal relief, especially if operating at high ambient temperatures or near maximum current.

- Avoid placing other heat-generating components in close proximity.

6.3 Optical Design

The white diffused lens provides a wide, Lambertian-like emission pattern (130° viewing angle). This is ideal for applications requiring wide-angle visibility without secondary optics. For directed light, external lenses or light guides would be necessary. The diffused lens also helps blend the light from the two discrete color chips into a more uniform appearance when both are illuminated.

7. Technical Comparison & Differentiation

This device offers specific advantages in particular application contexts:

vs. Single-Color SMD LEDs: The primary advantage is the integration of two distinct colors (green and orange) in one package. This saves PCB space, reduces part count, and simplifies assembly compared to using two separate LEDs. It enables dual-status indication (e.g., green for "on/ok," orange for "standby/warning") from a single point.

vs. RGB LEDs: This is not an RGB LED. It offers only two specific, saturated colors (green and orange) with potentially higher efficiency and simpler 2-channel drive circuitry compared to a 3-channel RGB driver. It is a solution for applications that specifically require only these two indicator colors.

Key Differentiator: The combination of a white diffused lens with colored chip sources is notable. The diffused lens softens the appearance of the discrete emitter dies, creating a more uniform, aesthetically pleasing illuminated area compared to a clear lens which might show distinct die images.

8. Frequently Asked Questions (Based on Technical Parameters)

Q1: Can I drive both the Green and Orange LEDs simultaneously at their maximum DC current?

A: The datasheet provides ratings per color source. The power dissipation ratings (68mW for Green, 84mW for Orange) are independent. Therefore, you can drive both simultaneously at their respective max I_F (20mA Green, 30mA Orange), provided the total heat generated can be dissipated by the package and PCB. It is generally good practice to derate and operate below absolute maximums for enhanced reliability.

Q2: Why is the test current different for the Green (5mA) and Orange (20mA) sources?

A: This reflects typical operating points chosen to achieve target brightness levels and efficiency for each semiconductor material (InGaN for Green, AlInGaP for Orange). The specified luminous intensity values are only valid at these test currents. Interpolating or extrapolating performance to other currents requires consulting the typical characteristic curves.

Q3: What does "binning" mean for my design?

A: Binning ensures consistency. If your design requires a specific shade of green or a minimum brightness, you must specify the corresponding bin codes (e.g., AR for green wavelength, G3/O3 for highest brightness). For less critical applications, a wider bin or "any" bin may be acceptable, potentially reducing cost.

Q4: Is a reverse protection diode needed?

A: The datasheet states the device is not designed for reverse operation and specifies a reverse current (I_R) only for test reference. In circuits where reverse voltage transients are possible (e.g., inductive loads, hot-plugging), external protection such as a series diode or a TVS diode across the LED is recommended to prevent damage.

9. Practical Design Case Study

Scenario: Designing a status indicator for a network switch. Requirements: A single indicator that can show three states: Off (no link), Solid Green (1 Gbps link), Blinking Orange (100 Mbps link activity).

Implementation with LTST-008TGVFWT:

1. PCB Footprint: Use the recommended land pattern. Route traces to pins for Green (e.g., pins 0,1) and Orange (pins 3,4).

2. Drive Circuit: Use two GPIO pins from a microcontroller. Each pin drives a transistor or a dedicated LED driver channel. Calculate separate current-limiting resistors for Green (target ~5-10mA) and Orange (target ~15-20mA).

3. Firmware: Control the states: GPIO_Green=HIGH for solid green; GPIO_Orange toggled with a timer for blinking orange.

4. Benefits: Saves space vs. two separate LEDs. The diffused lens creates a clean, uniform indicator dot. The distinct green and orange colors are easily distinguishable.

10. Operating Principle

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 releases energy in the form of photons (light). The specific wavelength (color) of the emitted light is determined by the energy bandgap of the semiconductor material used.

- The Green light is produced by an Indium Gallium Nitride (InGaN) semiconductor. Its bandgap corresponds to photons in the green wavelength region (~518-537 nm).

- The Orange light is produced by an Aluminum Indium Gallium Phosphide (AlInGaP) semiconductor, which has a smaller bandgap suitable for orange/red wavelengths (~605-611 nm).

The white diffused lens is made of an epoxy or silicone material impregnated with scattering particles. It does not change the color but spatially diffuses the light from the small, bright semiconductor dies, creating a wider, more uniform, and less glaring emission pattern.

11. Technology Trends

The field of SMD LEDs continues to evolve. General trends observable in the industry, which provide context for devices like this one, include:

Increased Efficiency: Ongoing material science and chip design improvements lead to higher lumens per watt (lm/W), allowing brighter output at lower currents or reduced power consumption.

Miniaturization: The drive for smaller end-products pushes LED packages to ever-smaller footprints (e.g., from 0603 to 0402 to 0201 metric sizes), while maintaining or improving optical performance.

Enhanced Color Mixing & Control: Multi-chip packages (like this dual-color LED) are becoming more sophisticated, with tighter binning for color consistency and integrated drivers for better color mixing in RGB or tunable white applications.

Improved Reliability & Thermal Performance: Advances in packaging materials, such as high-temperature silicones and ceramic substrates, enhance the ability to withstand higher reflow temperatures and improve long-term lumen maintenance, especially for high-power applications.

Intelligent Integration: A growing trend is the integration of control circuitry (like constant-current drivers or simple logic) within the LED package itself, simplifying system design for the end-user.