LTST-C194KGKT SMD LED Datasheet - Dimensions 1.6x0.8x0.3mm - Voltage 1.8-2.4V - Green Color - 75mW Power - English Technical Documentation

1. Product Overview

The LTST-C194KGKT is a surface-mount device (SMD) chip LED designed for modern, compact electronic applications. Its primary positioning is as a high-brightness, ultra-low-profile indicator or backlighting component. The core advantage of this product lies in its exceptionally thin package height of only 0.30 millimeters, enabling its use in space-constrained designs such as ultra-thin mobile devices, wearables, and edge-lit panels. It is a green LED utilizing AlInGaP (Aluminum Indium Gallium Phosphide) semiconductor technology, which is known for high efficiency and good color purity. The target market includes consumer electronics, industrial control panels, automotive interior lighting, and general-purpose indicator applications where reliable performance and RoHS compliance are mandatory.

2. In-Depth Technical Parameter Analysis

2.1 Absolute Maximum Ratings

The device is rated for a maximum power dissipation of 75 mW at an ambient temperature (Ta) of 25°C. The absolute maximum DC forward current is 30 mA, while a higher peak forward current of 80 mA is permissible under pulsed conditions (1/10 duty cycle, 0.1ms pulse width). This distinction is critical for design: the 30mA limit is for continuous operation, while the 80mA rating allows for brief, high-intensity pulses in multiplexed driving schemes. The maximum reverse voltage is 5V, which is a standard protection level. The operating and storage temperature ranges are -30°C to +85°C and -40°C to +85°C, respectively, indicating robust performance across a wide environmental range. The infrared soldering condition is specified as 260°C for 10 seconds, which is a standard profile for lead-free (Pb-free) reflow processes.

2.2 Electro-Optical Characteristics

Measured at Ta=25°C and a standard test current (IF) of 20mA, the key parameters define the LED's performance. The luminous intensity (Iv) has a typical range from 18.0 to 112.0 millicandelas (mcd). This wide range is managed through a binning system. The viewing angle (2θ1/2) is 130 degrees, providing a very wide, diffuse emission pattern suitable for area illumination rather than focused beams. The peak emission wavelength (λP) is typically 574 nm. The dominant wavelength (λd), which defines the perceived color, ranges from 567.5 nm to 576.5 nm at 20mA, corresponding to a pure green hue. The spectral line half-width (Δλ) is 15 nm, indicating a relatively narrow spectral bandwidth and good color saturation. The forward voltage (VF) ranges from 1.80V to 2.40V at 20mA, which is important for calculating series resistor values and power supply design. The reverse current (IR) is a maximum of 10 μA at a reverse voltage (VR) of 5V, indicating good junction characteristics.

3. Binning System Explanation

The product employs a two-dimensional binning system to ensure color and brightness consistency within an application. This is crucial for applications using multiple LEDs where visual uniformity is required.

3.1 Luminous Intensity Binning

Luminous intensity is categorized into four bins (M, N, P, Q) measured in mcd at 20mA. Each bin has a minimum and maximum value: M (18.0-28.0), N (28.0-45.0), P (45.0-71.0), Q (71.0-112.0). A tolerance of +/-15% is applied to each intensity bin. Designers must specify the required bin code to guarantee the brightness level for their application.

3.2 Dominant Wavelength Binning

The color (dominant wavelength) is also binned into three codes: C (567.5-570.5 nm), D (570.5-573.5 nm), and E (573.5-576.5 nm). A tight tolerance of +/- 1 nm is maintained for each wavelength bin. By combining an intensity bin code and a wavelength bin code, a specific, consistent performance subset of the LTST-C194KGKT product can be selected.

4. Performance Curve Analysis

While specific graphical curves are referenced in the datasheet (e.g., Fig.1, Fig.6), their typical behavior can be described based on the technology. The relationship between forward current (IF) and luminous intensity (Iv) is generally linear within the operating range, meaning brightness increases proportionally with current up to the maximum rating. The forward voltage (VF) has a negative temperature coefficient; it decreases slightly as the junction temperature increases. The dominant wavelength (λd) may also experience a slight shift (typically towards longer wavelengths) with increasing junction temperature, a common characteristic of semiconductor LEDs. The wide 130-degree viewing angle curve implies a near-Lambertian emission pattern, where intensity is highest at the center and decreases gradually towards the edges.

5. Mechanical and Package Information

5.1 Package Dimensions

The LED features an EIA standard package footprint. Key dimensions include a typical length and width, with the defining characteristic being the ultra-thin height of 0.30 mm. All dimensional tolerances are typically ±0.10 mm unless otherwise specified. The lens material is water-clear, which allows the native green color of the AlInGaP chip to be emitted without color filtering or diffusion, maximizing light output.

5.2 Soldering Pad Design and Polarity

The datasheet includes suggested soldering pad dimensions to ensure proper solder joint formation and mechanical stability during reflow. A recommended stencil thickness of 0.10mm maximum is provided for solder paste application. The component has anode and cathode markings; correct polarity must be observed during placement to ensure proper operation. The pad design facilitates good solder wetting and helps self-align the component during reflow.

6. Soldering and Assembly Guidelines

6.1 Reflow Soldering Profile

A suggested infrared (IR) reflow profile is provided, compliant with JEDEC standards for Pb-free processes. Key parameters include a pre-heat zone (150-200°C), a pre-heat time (max 120 sec), a peak temperature (max 260°C), and a time above liquidus (specific time at peak temperature, max 10 sec). This profile is critical to prevent thermal shock, ensure proper solder reflow, and avoid damaging the LED package or the semiconductor die.

6.2 Storage and Handling Conditions

The LEDs are moisture-sensitive. When in the sealed factory packaging with desiccant, they should be stored at ≤30°C and ≤90% RH and used within one year. Once the moisture-proof bag is opened, the storage environment must not exceed 30°C and 60% RH. Components exposed to ambient conditions for more than 672 hours (28 days) are recommended to be baked at approximately 60°C for at least 20 hours before soldering to remove absorbed moisture and prevent "popcorning" during reflow.

6.3 Cleaning

If cleaning after soldering is necessary, only specified solvents should be used. Immersing the LED in ethyl alcohol or isopropyl alcohol at normal temperature for less than one minute is recommended. Unspecified chemical cleaners may damage the epoxy package material or the lens.

7. Packaging and Ordering Information

The product is supplied in tape-and-reel packaging compatible with automated pick-and-place equipment. The tape width is 8mm, wound on 7-inch (178mm) diameter reels. Each reel contains 5000 pieces. For smaller quantities, a minimum packing quantity of 500 pieces is available for remainder lots. The tape and reel specifications follow ANSI/EIA 481-1-A-1994 standards. The packaging includes a top cover tape to seal empty pockets, and the maximum number of consecutive missing components in the tape is two.

8. Application Recommendations

8.1 Typical Application Scenarios

This LED is ideal for status indicators on ultra-thin laptops, tablets, and smartphones. It serves well as backlighting for membrane switches, keypads, and small graphic displays in industrial controls or medical devices. Its wide viewing angle makes it suitable for general panel illumination where even, diffuse light is needed.

8.2 Drive Circuit Design Considerations

LEDs are current-driven devices. To ensure uniform brightness, especially when multiple LEDs are connected in parallel, it is strongly recommended to use a individual current-limiting resistor in series with each LED. Driving LEDs directly from a voltage source without a current limit is not advised, as minor variations in forward voltage can lead to significant differences in current and, consequently, brightness. The series resistor value (R) can be 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 (≤30mA DC).

9. Technical Comparison and Differentiation

The primary differentiating factor of the LTST-C194KGKT is its 0.30mm height, which is significantly thinner than many standard chip LEDs (often 0.6mm or taller). This allows integration into next-generation slim devices. The use of AlInGaP technology for green light offers higher efficiency and better temperature stability compared to older technologies like traditional GaP. The combination of a wide 130-degree viewing angle and water-clear lens provides a bright, pure green spot with good visibility from off-axis angles, unlike diffused lenses which scatter light more but reduce peak intensity.

10. Frequently Asked Questions (FAQ)

Q: What is the difference between peak wavelength and dominant wavelength?
A: Peak wavelength (λP) is the wavelength at which the optical output power is maximum. Dominant wavelength (λd) is the single wavelength perceived by the human eye, calculated from the CIE chromaticity diagram. λd is more relevant for color specification.

Q: Can I drive this LED at 30mA continuously?
A: Yes, 30mA is the maximum rated continuous DC forward current. For optimal longevity and reliability, operating at a lower current, such as 20mA (the test condition), is often recommended.

Q: Why is binning important?
A: Manufacturing variations cause slight differences in brightness and color. Binning sorts LEDs into groups with tightly controlled characteristics. Specifying a bin code ensures visual consistency when using multiple LEDs in a single product.

Q: How do I interpret the "Q" bin for luminous intensity?
A: The "Q" bin contains LEDs with the highest brightness, ranging from 71.0 to 112.0 mcd at 20mA. You are guaranteed that any LED from the Q bin will fall within this range (with a +/-15% tolerance on individual units).

11. Practical Design and Usage Case

Consider designing a status indicator panel for a network router that requires ten green LEDs. To ensure all ten lights appear identical in brightness and color, the designer would specify the LTST-C194KGKT with a specific bin combination, for example, intensity bin "P" and wavelength bin "D". Each LED would be driven by a 5V supply through a separate series resistor. Calculating the resistor value using the maximum VF (2.4V) and a target IF of 20mA: R = (5V - 2.4V) / 0.020A = 130 Ohms. A standard 130Ω or 150Ω resistor could be used. The ultra-thin profile allows the PCB to be placed very close to the router's thin plastic housing. The wide viewing angle ensures the indicator is visible from various angles in a room.

12. Technology Principle Introduction

This LED is based on AlInGaP (Aluminum Indium Gallium Phosphide) semiconductor material grown on a substrate. When a forward voltage is applied, electrons and holes recombine in the active region of the semiconductor, releasing energy in the form of photons (light). The specific composition of the AlInGaP alloy determines the bandgap energy, which directly corresponds to the wavelength (color) of the emitted light—in this case, green. The water-clear epoxy package acts as a lens, shaping the light output and providing environmental protection for the delicate semiconductor chip and wire bonds.

13. Industry Trends and Developments

The trend in SMD LEDs continues towards miniaturization, higher efficiency, and greater reliability. Package heights are decreasing to enable thinner end products. Efficiency improvements (more lumens per watt) reduce power consumption and heat generation. There is also a focus on tighter binning tolerances and improved color consistency across production batches. Furthermore, compatibility with automated assembly processes and high-temperature, lead-free soldering profiles remains a fundamental requirement for broad market adoption in global electronics manufacturing.