Dual Color SMD LED LTST-C195KRKSKT Datasheet - Red & Yellow - 20mA - 75mW - English Technical Document

1. Product Overview

The LTST-C195KRKSKT is a dual-color, surface-mount device (SMD) LED incorporating two distinct semiconductor chips within a single package: one emitting red light and the other emitting yellow light. This component is designed for applications requiring status indication, backlighting, or decorative lighting in two colors from a single, compact footprint. It utilizes Ultra Bright AlInGaP (Aluminum Indium Gallium Phosphide) chip technology, which is known for its high luminous efficiency and stability. The device is packaged in industry-standard 8mm tape on 7-inch reels, making it fully compatible with high-speed automated pick-and-place assembly equipment used in modern electronics manufacturing.

Key advantages of this LED include its compliance with RoHS (Restriction of Hazardous Substances) directives, classifying it as a green product. It is designed to be compatible with common soldering processes, including infrared (IR) and vapor phase reflow, which are standard for surface-mount technology (SMT) assembly lines. The EIA (Electronic Industries Alliance) standard package ensures mechanical compatibility with other components and design libraries.

2. Technical Parameters Deep Analysis

2.1 Absolute Maximum Ratings

Operating the device beyond these limits may cause permanent damage. The ratings are specified at an ambient temperature (Ta) of 25°C. For both the red and yellow chips, the maximum continuous DC forward current is 30 mA. The maximum power dissipation for each chip is 75 mW. A derating factor of 0.4 mA/°C applies linearly from 25°C, meaning the permissible continuous current decreases as ambient temperature increases to prevent overheating. The device can withstand a peak forward current of 80 mA under pulsed conditions (1/10 duty cycle, 0.1ms pulse width). The maximum reverse voltage is 5 V. The operational and storage temperature range is specified from -55°C to +85°C, indicating suitability for industrial and extended environmental applications.

2.2 Electrical & Optical Characteristics

These characteristics are measured at Ta=25°C with a forward current (IF) of 20 mA, which is the standard test condition. For the red chip, the typical luminous intensity (Iv) is 45.0 millicandelas (mcd), with a minimum of 18.0 mcd. The yellow chip is typically brighter, with an Iv of 75.0 mcd (min. 28.0 mcd). Both chips have a very wide viewing angle (2θ1/2) of 130 degrees, providing a broad, diffuse light emission pattern suitable for panel indicators.

The red chip's typical peak emission wavelength (λP) is 639 nm, with a dominant wavelength (λd) of 631 nm, placing it in the standard red region of the visible spectrum. The yellow chip emits at a typical peak wavelength of 591 nm and a dominant wavelength of 589 nm. The spectral line half-width (Δλ) for both is approximately 15 nm, indicating relatively pure color emission. The typical forward voltage (VF) for both chips at 20mA is 2.0 V, with a maximum of 2.4 V. The maximum reverse current (IR) at 5V is 10 µA, and the typical junction capacitance (C) is 40 pF.

3. Binning System Explanation

The product is sorted into bins based on luminous intensity to ensure consistency in application brightness. Separate bin codes are defined for the red and yellow chips.

Red Chip Binning (at 20mA):

- Bin Code M: 18.0 - 28.0 mcd

- Bin Code N: 28.0 - 45.0 mcd

- Bin Code P: 45.0 - 71.0 mcd

- Bin Code Q: 71.0 - 112.0 mcd

Yellow Chip Binning (at 20mA):

- Bin Code N: 28.0 - 45.0 mcd

- Bin Code P: 45.0 - 71.0 mcd

- Bin Code Q: 71.0 - 112.0 mcd

- Bin Code R: 112.0 - 180.0 mcd

A tolerance of +/-15% is applied to each intensity bin. Designers should specify the required bin code(s) when ordering to guarantee the desired brightness level for their application, especially when multiple LEDs are used together and uniform appearance is critical.

4. Performance Curve Analysis

While specific graphical curves are referenced in the datasheet (e.g., Fig.1 for spectral distribution, Fig.6 for viewing angle), the provided data allows for key performance understandings. The relationship between forward current (IF) and luminous intensity (Iv) is generally linear within the operating range; driving the LED at the maximum 30mA DC current would yield proportionally higher light output than the 20mA standard test point, though thermal management becomes more important. The forward voltage (VF) shows minimal variation between the two chips, simplifying driver circuit design. The wide 130-degree viewing angle is a consistent characteristic, not significantly affected by typical current or temperature variations within the specified range. The derating curve implied by the 0.4 mA/°C factor is linear, indicating a predictable reduction in maximum allowable current as ambient temperature rises.

5. Mechanical & Packaging Information

The device conforms to an industry-standard SMD LED package outline. The pin assignment is crucial for correct circuit design: Pins 1 and 3 are assigned to the red LED chip, while pins 2 and 4 are assigned to the yellow LED chip. This configuration typically allows for independent control of each color. All dimensions are provided in millimeters with a standard tolerance of ±0.10 mm unless otherwise noted. The component is supplied on embossed carrier tape with a width of 8mm, wound onto reels with a 7-inch (178mm) diameter. Each full reel contains 4000 pieces. A top cover tape seals the component pockets for protection during handling and shipping.

6. Soldering & Assembly Guidelines

6.1 Reflow Soldering Profiles

The datasheet provides suggested infrared (IR) reflow profiles for both normal (tin-lead) and Pb-free solder processes. For Pb-free assembly (using SnAgCu solder paste), the recommended profile includes a preheat stage, a controlled ramp to a peak temperature, and a cooling phase. The critical parameters are: a peak body temperature not exceeding 260°C, and the time above 240°C being limited to a maximum of 10 seconds. Wave soldering and hand soldering with an iron are also addressed, with strict limits on temperature (260°C max for wave, 300°C max for iron) and exposure time (10 sec max for wave, 3 sec max per joint for iron).

6.2 Storage & Handling

LEDs should be stored in an environment not exceeding 30°C and 70% relative humidity. Once removed from their original, moisture-protective packaging, components intended for reflow soldering should be processed within one week. If storage beyond one week is necessary, they must be stored in a dry atmosphere (e.g., a sealed container with desiccant or a nitrogen desiccator) and baked at approximately 60°C for at least 24 hours prior to soldering to remove absorbed moisture and prevent \"popcorning\" during reflow.

6.3 Cleaning

If cleaning after soldering is required, only specified alcohol-based solvents should be used. The LED can be immersed in ethyl alcohol or isopropyl alcohol at room temperature for less than one minute. The use of unspecified or aggressive chemical cleaners can damage the LED's epoxy lens or package.

7. Application Recommendations

7.1 Typical Application Scenarios

This dual-color LED is ideal for multi-status indicators on consumer electronics, industrial control panels, automotive interior lighting, and signage. Examples include power/charge status lights (red for charging, yellow for full), mode indicators on appliances, or decorative accent lighting where color switching is desired.

7.2 Circuit Design Considerations

LEDs are current-driven devices. To ensure uniform brightness, especially when connecting multiple LEDs in parallel, it is strongly recommended to use a current-limiting resistor in series with each LED chip (Circuit Model A). Driving multiple LEDs in parallel without individual resistors (Circuit Model B) is not recommended, as slight variations in the forward voltage (VF) characteristics between individual LEDs can cause significant differences in current sharing and, consequently, brightness. The typical VF of 2.0V at 20mA must be considered when designing the driving circuit's voltage supply.

7.3 ESD (Electrostatic Discharge) Precautions

The LED is sensitive to electrostatic discharge. Proper ESD control measures must be implemented during handling and assembly: use grounded wrist straps and work surfaces, employ ionizers to neutralize static charge, and ensure all equipment is properly grounded. The plastic lens can develop a static charge through friction, which an ion blower can help dissipate safely.

8. Technical Comparison & Differentiation

The primary differentiation of this component lies in its dual-color capability within a single, standard SMD package, saving board space compared to using two separate LEDs. The use of AlInGaP technology for both colors offers higher efficiency and better temperature stability compared to older technologies like standard GaP. The wide 130-degree viewing angle is a significant advantage over narrower-angle LEDs when broad, even illumination is needed. The explicit compatibility with Pb-free, high-temperature reflow profiles makes it suitable for modern, RoHS-compliant manufacturing processes.

9. Frequently Asked Questions (FAQs)

Q: Can I drive both the red and yellow chips simultaneously at their maximum current?

A: The maximum ratings are per chip. However, simultaneous operation at 30mA each means a total power dissipation of up to 150mW for the package. The designer must ensure the PCB layout and ambient conditions allow for adequate heat dissipation to keep the junction temperature within safe limits.

Q: What is the difference between peak wavelength and dominant wavelength?

A: Peak wavelength (λP) is the wavelength at which the emission spectrum has its highest intensity. Dominant wavelength (λd) is derived from the color coordinates on the CIE chromaticity diagram and represents the perceived color of the light. λd is often more relevant for color-indication applications.

Q: How do I interpret the bin code when ordering?

A: You must specify a bin code for each color (e.g., Red: P, Yellow: Q). This ensures you receive LEDs where both chips fall within the specified luminous intensity ranges, guaranteeing brightness consistency in your product.

10. Design-in Case Study

Consider a portable device needing a multi-state battery indicator. A single LTST-C195KRKSKT can serve this function: the red chip illuminates when battery is low (<20%), the yellow chip illuminates when charging, and both chips driven at a lower current could create an orange hue for an intermediate state (e.g., battery medium). This design saves space, reduces component count, and simplifies assembly compared to using two discrete LEDs. The circuit would require two independent driver channels (e.g., from a microcontroller) with their own current-limiting resistors connected to the correct pin pairs (1&3 for red, 2&4 for yellow). The wide viewing angle ensures the indicator is visible from various angles.

11. Operating Principle

An LED is a semiconductor diode. When a forward voltage exceeding its characteristic forward voltage (Vf) is applied, electrons and holes recombine at the p-n junction within the AlInGaP material. This recombination releases energy in the form of photons (light). The specific composition of the Aluminum, Indium, Gallium, and Phosphide in the semiconductor crystal lattice determines the bandgap energy, which directly dictates the wavelength (color) of the emitted light. The dual-color package contains two physically separate semiconductor chips, each engineered with a different material composition to emit red and yellow light, respectively.

12. Technology Trends

The optoelectronics industry continues to focus on increasing luminous efficacy (lumens per watt), improving color rendering and saturation, and enhancing reliability. There is a trend towards higher power density in smaller packages. The move to Pb-free and high-temperature soldering is now standard. Furthermore, integration is a key trend, with multi-chip packages (like this dual-color LED) and even LED drivers being integrated into modules to simplify end-product design and assembly. The underlying AlInGaP technology remains a high-performance choice for red, orange, and yellow LEDs due to its efficiency and stability.