Dual Color SMD LED LTST-C195KGJSKT Datasheet - Package 3.2x2.8x1.9mm - Voltage 2.0-2.4V - Power 75mW - Green & Yellow - English Technical Document

1. Product Overview

This document provides the complete technical specifications for the LTST-C195KGJSKT, a dual-color Surface-Mount Device (SMD) LED. This component integrates two distinct light-emitting chips within a single, compact package designed for automated assembly processes. It is engineered for applications where space is at a premium and reliable, high-visibility status indication or backlighting is required.

1.1 Core Advantages

The primary advantages of this LED stem from its design and material technology. The use of Ultra Bright AlInGaP (Aluminum Indium Gallium Phosphide) semiconductor material for both chips results in high luminous efficiency and excellent color purity. The dual-color capability in one package saves valuable PCB real estate compared to using two separate single-color LEDs. Its compatibility with infrared reflow soldering processes aligns with modern, high-volume manufacturing lines, ensuring reliable and consistent attachment to circuit boards.

1.2 Target Market and Applications

This LED is suitable for a broad spectrum of electronic equipment. Its miniature size and reliability make it ideal for portable and compact devices. Key application areas include:

• Telecommunication Equipment: Status indicators on routers, modems, and handsets.
• Computer Peripherals: Keyboard backlighting and status lights on laptops, notebooks, and external drives.
• Consumer Electronics: Indicator lights on home appliances, audio/video equipment, and gaming devices.
• Industrial Controls: Panel indicators on machinery and control systems.
• Microdisplays and Signage: Low-level illumination for symbols or small informational displays.

2. Technical Parameters: In-Depth Objective Interpretation

The performance of the LED is defined by a set of electrical, optical, and thermal parameters measured under standard conditions (Ta=25°C). Understanding these parameters is crucial for proper circuit design and application.

2.1 Absolute Maximum Ratings

These ratings define the stress limits beyond which permanent damage to the device may occur. They are not intended for normal operation.

• Power Dissipation (Pd): 75 mW per chip. Exceeding this can lead to overheating and accelerated degradation.
• DC Forward Current (IF): 30 mA continuous. The standard test and operating condition is 20 mA.
• Peak Forward Current: 80 mA, permissible only under pulsed conditions (1/10 duty cycle, 0.1ms pulse width) to handle brief surges.
• Reverse Voltage (VR): 5 V. Applying a higher reverse voltage can cause junction breakdown.
• Operating & Storage Temperature: -30°C to +85°C and -40°C to +85°C, respectively, defining the environmental limits for functionality and non-operational storage.
• Soldering Temperature: Withstands 260°C for 10 seconds, compatible with lead-free (Pb-free) reflow profiles.

2.2 Electro-Optical Characteristics

These are the typical performance values under normal operating conditions (IF=20mA).

• Luminous Intensity (Iv): A key measure of brightness. For the Green chip, the typical value is 35.0 mcd (millicandela), with a minimum of 18.0 mcd. The Yellow chip is brighter, with a typical value of 75.0 mcd and a minimum of 28.0 mcd. This difference is inherent to the semiconductor materials and human eye sensitivity.
• Forward Voltage (VF): Typically 2.0 V, with a maximum of 2.4 V at 20mA. This parameter is critical for designing the current-limiting resistor in series with the LED. A higher VF requires a lower resistor value to achieve the same current, affecting power dissipation in the resistor.
• Viewing Angle (2θ1/2): 130 degrees. This wide viewing angle indicates the LED emits light over a broad cone, making it suitable for applications where the indicator needs to be visible from various angles, not just head-on.
• Peak Wavelength (λP) & Dominant Wavelength (λd): The Green chip has a typical peak at 574 nm and a dominant wavelength of 571 nm. The Yellow chip peaks at 591 nm with a dominant wavelength of 589 nm. The dominant wavelength is the single wavelength perceived by the human eye and is used for color binning.
• Spectral Line Half-Width (Δλ): 15.0 nm for both colors. This defines the color purity; a narrower width means a more saturated, pure color.
• Reverse Current (IR): Maximum 10 μA at 5V reverse bias, indicating a very low leakage current in the off-state.

3. Binning System Explanation

To ensure color and brightness consistency in production, LEDs are sorted into bins based on measured parameters. This allows designers to select parts that meet specific aesthetic or functional requirements.

3.1 Luminous Intensity (Brightness) Binning

LEDs are categorized into bins with defined minimum and maximum luminous intensity values. The tolerance within each bin is +/-15%.

• Green Chip Bins: M (18.0-28.0 mcd), N (28.0-45.0 mcd), P (45.0-71.0 mcd), Q (71.0-112.0 mcd).
• Yellow Chip Bins: N (28.0-45.0 mcd), P (45.0-71.0 mcd), Q (71.0-112.0 mcd), R (112.0-180.0 mcd).

Selecting a higher bin code (e.g., Q or R) guarantees a brighter LED, which may be necessary for high-ambient-light conditions or longer viewing distances.

3.2 Hue (Dominant Wavelength) Binning

For the Green chip, color consistency is managed through dominant wavelength binning with a tolerance of +/-1 nm per bin.

• Green Chip Hue Bins: C (567.5-570.5 nm), D (570.5-573.5 nm), E (573.5-576.5 nm).

This ensures that all Green LEDs in an assembly appear the same shade of green. The product datasheet or specific order should specify the combined bin code (e.g., intensity bin + hue bin) for the desired performance.

4. Performance Curve Analysis

Graphical data provides deeper insight into LED behavior under varying conditions, which is essential for robust design.

4.1 Current vs. Voltage (I-V) Characteristic

The I-V curve is non-linear, similar to a standard diode. The forward voltage increases logarithmically with current. Operating significantly above the recommended 20mA will cause a disproportionate increase in VF and power dissipation (Pd = IF * VF), leading to excessive heat. Designers must use a current-limiting resistor or constant-current driver to maintain IF within safe limits.

4.2 Luminous Intensity vs. Forward Current

Luminous intensity is approximately proportional to forward current in the normal operating range. However, efficiency may drop at very high currents due to increased heat. Derating the current (e.g., operating at 15mA instead of 20mA) can significantly improve long-term reliability and lumen maintenance with only a modest reduction in perceived brightness.

4.3 Temperature Dependence

LED performance is temperature-sensitive. As the junction temperature (Tj) rises:

• Luminous Intensity Decreases: Output can drop by 10-20% over the operating temperature range.
• Forward Voltage Decreases: VF has a negative temperature coefficient (typically -2 mV/°C). In a simple resistor-driven circuit, this can lead to a slight increase in current as the LED warms up, which may require thermal management consideration.
• Wavelength Shifts: The dominant wavelength may shift slightly (usually towards longer wavelengths) with increasing temperature, causing a subtle color change.

5. Mechanical and Package Information

5.1 Package Dimensions

The LED conforms to an EIA standard package outline. Key dimensions are approximately 3.2mm in length, 2.8mm in width, and 1.9mm in height, with a tolerance of ±0.1mm. The package features a water-clear lens that does not tint the emitted light, allowing the pure chip color (Green or Yellow) to be visible.

5.2 Pin Assignment and Polarity Identification

The device has four pins. For the LTST-C195KGJSKT variant:

• Pins 1 and 3 are the anode and cathode for the Green AlInGaP chip.
• Pins 2 and 4 are the anode and cathode for the Yellow AlInGaP chip.

The polarity is indicated by the physical package marking (typically a dot or a chamfered corner near pin 1). Correct polarity is mandatory; applying reverse bias can damage the LED.

5.3 Recommended PCB Attachment Pad Layout

A suggested land pattern (footprint) is provided to ensure proper soldering and mechanical stability. The pad design accommodates the package dimensions and allows for a good solder fillet to form during reflow. Following this recommendation helps prevent tombstoning (one end lifting) and ensures reliable electrical connection.

6. Soldering and Assembly Guidelines

6.1 Infrared Reflow Soldering Parameters

The LED is compatible with lead-free (Pb-free) soldering processes. A suggested reflow profile is provided, typically adhering to JEDEC standards such as J-STD-020. Key parameters include:

• Pre-heat: 150-200°C for up to 120 seconds to gradually heat the board and components, activating the flux and preventing thermal shock.
• Peak Temperature: Maximum of 260°C.
• Time Above Liquidus (TAL): The time the solder is molten, critical for joint formation. The profile suggests a maximum of 10 seconds at peak temperature.
• Limit: The LED should not be subjected to more than two reflow cycles.

Important: The actual profile must be characterized for the specific PCB design, solder paste, and oven used.

6.2 Hand Soldering with Iron

If manual soldering is necessary, extreme care is required:

• Iron Temperature: Maximum 300°C.
• Soldering Time: Maximum 3 seconds per joint.
• Limit: Only one soldering cycle is permitted to prevent thermal damage to the plastic package and the wire bonds inside.

6.3 Storage and Handling Conditions

• ESD Sensitivity: LEDs are sensitive to electrostatic discharge (ESD). Handling must occur in an ESD-protected area using grounded wrist straps and conductive mats.
• Moisture Sensitivity Level (MSL): The device is rated MSL 3. This means:
  • Once the original moisture-barrier bag is opened, the components must be soldered within 168 hours (1 week) under factory floor conditions (<30°C/60% RH).
  • If exposed for longer, a bake-out at approximately 60°C for at least 20 hours is required before soldering to remove absorbed moisture and prevent \"popcorning\" (package cracking during reflow).
• Long-Term Storage: Unopened bags should be stored below 30°C and 90% RH. Opened parts should be stored in a dry environment, preferably in a sealed container with desiccant.

6.4 Cleaning

If post-solder cleaning is required, only specified solvents should be used. Isopropyl alcohol (IPA) or ethyl alcohol at room temperature for less than one minute is recommended. Harsh or unspecified chemicals can damage the plastic lens or the package material, leading to discoloration or cracking.

7. Packaging and Ordering Information

7.1 Tape and Reel Specifications

The LEDs are supplied in industry-standard embossed carrier tape on 7-inch (178mm) diameter reels, facilitating automated pick-and-place assembly. Key details:

• Pocket Pitch: The distance between component pockets in the tape.
• Reel Capacity: 4000 pieces per full reel.
• Minimum Order Quantity (MOQ): 500 pieces for remainder quantities.
• Quality: The tape is sealed with a cover tape. The maximum allowed number of consecutive missing components is two, ensuring feed reliability.

The packaging conforms to ANSI/EIA-481 standards.

8. Application Suggestions and Design Considerations

8.1 Typical Application Circuits

The most common drive method is a simple series resistor. The resistor value (R) is calculated using Ohm's Law: R = (Vcc - VF) / IF, where Vcc is the supply voltage, VF is the LED forward voltage (use max value for worst-case current calculation), and IF is the desired forward current (e.g., 20mA). The resistor power rating should be at least IF² * R. For microcontroller GPIO drive, ensure the GPIO can sink/source the required current (IF plus any resistor current). For driving both colors independently, use two separate current-limiting circuits.

8.2 Design Considerations for Reliability

• 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 Derating: For applications requiring high reliability or operating in elevated ambient temperatures, consider driving the LED at a current lower than the maximum rating (e.g., 15-18 mA).
• Reverse Voltage Protection: In circuits where the LED might be exposed to reverse bias (e.g., in AC-coupled or inductive load scenarios), a protection diode in parallel with the LED (cathode to anode) is recommended.

9. Technical Comparison and Differentiation

The LTST-C195KGJSKT offers specific advantages in its category:

• Dual Color in One Package: Compared to placing two separate 0603 or 0805 sized single-color LEDs, this 4-pin package saves space and reduces placement time/cost.
• Material Technology: The use of AlInGaP for both green and yellow offers higher efficiency and better temperature stability compared to some older technologies like traditional GaP.
• Wide Viewing Angle: The 130-degree viewing angle is broader than many \"top-view\" LEDs, providing better off-axis visibility, which is crucial for panel indicators.
• Standardized Packaging: Compliance with EIA and ANSI/EIA-481 standards ensures compatibility with automated assembly equipment from various manufacturers.

10. Frequently Asked Questions (Based on Technical Parameters)

Q1: Can I drive the Green and Yellow chips simultaneously at 20mA each?
A1: Yes, but you must consider the total power dissipation. Each chip dissipates up to 75mW. If both are on continuously at 20mA and typical VF (2.0V), each dissipates 40mW (P=IV), totaling 80mW, which is within the combined thermal capacity of the package if properly mounted. However, always check the actual VF and ensure adequate PCB cooling.

Q2: Why is the typical luminous intensity different for Green and Yellow?
A2: This is primarily due to the human eye's photopic response curve (CIE curve), which peaks in the green-yellow region (~555 nm). The yellow chip's wavelength (589 nm) is closer to this peak sensitivity than the green chip's (571 nm), so the same radiant power (light energy) from the yellow chip is perceived as brighter in lumens or candela.

Q3: What does \"Water Clear\" lens mean for the color?
A3: A water-clear (non-diffused, non-tinted) lens allows the intrinsic color of the semiconductor chip to pass through unaltered. This results in a more saturated and potentially narrower beam of light compared to a diffused lens, which scatters light for a wider, softer appearance but reduces peak intensity.

Q4: How do I interpret the bin code for ordering?
A4: You would typically specify the part number (LTST-C195KGJSKT) along with the desired luminous intensity and hue bin codes for each color (e.g., Green: P/D, Yellow: Q). Consult the manufacturer or distributor for available bin combinations.

11. Practical Application Example

Scenario: Dual-Status Indicator for a Network Device.
A router design requires a single indicator to show two states: \"Power On/System OK\" (steady Green) and \"Data Activity\" (blinking Yellow). Using the LTST-C195KGJSKT simplifies this design.

• Circuit: Two GPIO pins from the system microcontroller are used. Each pin connects to the anode of one LED color via a current-limiting resistor (e.g., (3.3V - 2.4V)/0.02A = 45Ω, use 47Ω standard value). The cathodes are connected to ground.
• Software: The firmware drives the Green GPIO high for a steady state. For data activity, it toggles the Yellow GPIO at a suitable blink rate (e.g., 2 Hz).
• Benefits: Saves one PCB footprint compared to two discrete LEDs. Provides clear, distinct color states from a single point on the panel. The wide viewing angle ensures visibility from various angles in an office or home environment.

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 in the active region. This recombination releases energy in the form of photons (light particles). The specific wavelength (color) of the emitted light is determined by the bandgap energy of the semiconductor material. AlInGaP (Aluminum Indium Gallium Phosphide) is a compound semiconductor whose bandgap can be tuned by adjusting the ratios of its constituents to produce high-efficiency light in the red, orange, amber, yellow, and green spectral regions. In this dual-color LED, two separate semiconductor chips, each engineered with a slightly different bandgap (one for green, one for yellow), are housed within a single epoxy package with independent electrical connections.

13. Technology Trends

The general trend in SMD indicator LEDs continues towards higher efficiency, smaller package sizes, and greater integration. While AlInGaP remains dominant for amber through green colors, InGaN (Indium Gallium Nitride) technology is prevalent for blue, white, and true green LEDs. Future developments may include:

• Further Miniaturization: Packages smaller than 2.0x1.0mm for ultra-compact devices.
• Integrated Components: LEDs with built-in current-limiting resistors, protection diodes, or even driver ICs in the same package to simplify circuit design.
• Enhanced Optical Control: Packages with integrated lenses or reflectors for specific beam patterns without external optics.
• Improved Thermal Performance: Package designs that more effectively transfer heat from the semiconductor junction to the PCB, allowing for higher drive currents or improved longevity at standard currents.

These trends aim to provide designers with more versatile, reliable, and space-efficient lighting solutions for an ever-expanding range of electronic products.