LTST-C194TGKT SMD LED Datasheet - 0.30mm Height - 3.2V - 76mW - Green - English Technical Document

1. Product Overview

The LTST-C194TGKT is a surface-mount device (SMD) chip LED designed for modern, space-constrained electronic applications. It is an extra-thin component with a profile height of only 0.30 mm, making it suitable for slim devices like smartphones, tablets, ultra-thin displays, and wearable technology. The device emits green light using an InGaN (Indium Gallium Nitride) semiconductor material housed in a water-clear lens package. It is compliant with RoHS (Restriction of Hazardous Substances) directives and is classified as a green product. The LED is supplied in industry-standard 8mm tape on 7-inch diameter reels, compatible with high-speed automated pick-and-place equipment and infrared (IR) reflow soldering processes, facilitating efficient mass production.

2. In-Depth Technical Parameter Analysis

2.1 Absolute Maximum Ratings

These ratings define the stress limits beyond which permanent damage to the device may occur. Operation under these conditions is not guaranteed. Key limits include a maximum power dissipation of 76 mW, a DC forward current of 20 mA, and a peak forward current of 100 mA under pulsed conditions (1/10 duty cycle, 0.1ms pulse width). The device can withstand a reverse voltage of 5V, but continuous operation under reverse bias is prohibited. The operating temperature range is from -20°C to +80°C, with a wider storage range of -30°C to +100°C. The component is rated for infrared reflow soldering at a peak temperature of 260°C for a maximum of 10 seconds.

2.2 Electrical and Optical Characteristics

These parameters are specified at an ambient temperature (Ta) of 25°C and a standard test current (IF) of 20 mA, providing the baseline performance data. The luminous intensity (Iv) has a typical value of 450 millicandelas (mcd) with a minimum of 71 mcd, indicating a bright output. It features a wide viewing angle (2θ1/2) of 130 degrees, providing broad, even illumination. The dominant wavelength (λd) is 525 nm, defining its green color perception, while the peak emission wavelength (λp) is 530 nm. The spectral bandwidth (Δλ) is 35 nm. The forward voltage (VF) typically measures 3.2V, with a range from 2.8V to 3.6V. The reverse current (IR) is a maximum of 10 μA at the full 5V reverse bias.

3. Binning System Explanation

To ensure consistency in production, LEDs are sorted into performance bins. The LTST-C194TGKT uses a three-dimensional binning system covering forward voltage (Vf), luminous intensity (Iv), and dominant wavelength (λd). This allows designers to select components that match their specific circuit and brightness/color requirements.

3.1 Forward Voltage Binning

Forward voltage is binned in 0.2V steps. Bin codes D7 (2.80-3.00V), D8 (3.00-3.20V), D9 (3.20-3.40V), and D10 (3.40-3.60V) are available. A tolerance of ±0.1V is applied within each bin. Selecting LEDs from the same Vf bin helps maintain uniform current distribution when multiple LEDs are connected in parallel.

3.2 Luminous Intensity Binning

Luminous intensity bins provide a range of brightness levels. The bins are Q (71.0-112.0 mcd), R (112.0-180.0 mcd), S (180.0-280.0 mcd), and T (280.0-450.0 mcd). A tolerance of ±15% applies to each bin. This allows for cost-effective selection where maximum brightness is not critical, or for tiered product features.

3.3 Dominant Wavelength Binning

Dominant wavelength bins ensure color consistency. The available bins are AP (520.0-525.0 nm), AQ (525.0-530.0 nm), and AR (530.0-535.0 nm), with a tight tolerance of ±1 nm per bin. This is crucial for applications where precise color matching is required, such as in multi-color indicators or display backlighting.

4. Performance Curve Analysis

While specific graphical curves are referenced in the datasheet (e.g., Figure 1 for spectral distribution, Figure 6 for viewing angle), the provided data allows for analysis of key relationships. The forward voltage is specified at a single current (20mA). In practice, Vf has a logarithmic relationship with forward current (If) and a negative temperature coefficient, meaning Vf decreases as the junction temperature increases. The luminous intensity is also temperature-dependent, typically decreasing as temperature rises. The wide 130-degree viewing angle suggests a Lambertian or near-Lambertian radiation pattern, where light intensity is approximately proportional to the cosine of the viewing angle.

5. Mechanical and Packaging Information

5.1 Package Dimensions

The LED conforms to EIA (Electronic Industries Alliance) standard package outlines. The defining feature is its ultra-low profile height of 0.30 mm. Detailed dimensional drawings specify the length, width, lead spacing, and other critical mechanical tolerances, typically with a standard tolerance of ±0.10 mm unless otherwise noted. These dimensions are essential for PCB (Printed Circuit Board) footprint design and ensuring proper placement by automated machinery.

5.2 Solder Pad Design

The datasheet includes suggested solder pad land pattern dimensions. Adhering to these recommendations is vital for achieving reliable solder joints during reflow. A key note is the recommendation for a maximum stencil thickness of 0.10mm to control solder paste volume and prevent bridging or tombstoning of the small component.

5.3 Polarity Identification

Like most LEDs, this device is polarity-sensitive. The cathode is typically marked, often by a notch, a green dot, or a different lead shape. Correct orientation must be verified against the package drawing to ensure proper circuit operation and prevent damage from reverse bias.

6. Soldering and Assembly Guidelines

6.1 Reflow Soldering Profile

A suggested infrared (IR) reflow profile for lead-free (Pb-free) solder processes is provided. This profile is compliant with JEDEC standards. It includes critical parameters: a pre-heat stage (typically 150-200°C for up to 120 seconds), a ramp-up, a peak temperature zone (maximum 260°C), and a time above liquidus (the temperature where solder melts). The component must not be exposed to the peak temperature for more than 10 seconds. This profile ensures reliable solder joint formation without subjecting the LED package to excessive thermal stress.

6.2 Handling and Storage

The LED is sensitive to electrostatic discharge (ESD). Handling precautions such as using grounded wrist straps, anti-static mats, and conductive containers are mandatory. For storage, unopened moisture-barrier bags (with desiccant) should be kept at ≤30°C and ≤90% RH, with a shelf life of one year. Once opened, components should be stored at ≤30°C and ≤60% RH. If exposed to ambient conditions for more than 672 hours (28 days), a bake-out at approximately 60°C for at least 20 hours is recommended before soldering to remove absorbed moisture and prevent \"popcorning\" during reflow.

6.3 Cleaning

If post-solder cleaning is necessary, only specified solvents should be used. The datasheet recommends immersion in ethyl alcohol or isopropyl alcohol at normal temperature for less than one minute. Unspecified chemical cleaners may damage the plastic lens or the package material.

7. Packaging and Ordering Information

The standard packaging is 8mm wide embossed carrier tape wound on 7-inch (178mm) diameter reels. Each reel contains 5000 pieces. Empty pockets in the tape are sealed with a cover tape. The packaging complies with ANSI/EIA 481-1-A-1994 specifications. For production continuity, the maximum allowed number of consecutive missing components in the tape is two. Minimum order quantities for remainder reels are 500 pieces. The part number LTST-C194TGKT follows a specific coding system where elements likely indicate the series, package, color, and bin codes.

8. Application Recommendations

8.1 Typical Application Scenarios

This ultra-thin green LED is ideal for status indicators, backlighting for keys or symbols, and decorative lighting in consumer electronics where height is a critical constraint. Examples include indicator lights in smartphones, tablets, laptops, ultrabooks, wearable devices (smartwatches, fitness bands), and thin control panels. Its compatibility with automatic placement and reflow soldering makes it perfect for high-volume manufacturing.

8.2 Design Considerations

Current Limiting: An external current-limiting resistor is always required when driving the LED from a voltage source higher than its forward voltage. The resistor value is calculated using Ohm's Law: R = (Vcc - Vf) / If, where Vf is the forward voltage (use max value for worst-case design), If is the desired forward current (≤20 mA DC), and Vcc is the supply voltage.
Thermal Management: Although power dissipation is low, ensuring adequate PCB copper area or thermal vias can help dissipate heat, especially when operating at high ambient temperatures or at maximum current, thereby maintaining luminous output and longevity.
ESD Protection: In environments prone to ESD, consider adding transient voltage suppression (TVS) diodes or other protection circuits on the LED lines.

9. Technical Comparison and Differentiation

The primary differentiating factor of the LTST-C194TGKT is its 0.30mm height, which is significantly thinner than many standard SMD LEDs (e.g., 0603 or 0805 packages which are often 0.6-0.8mm tall). This allows for design in applications where z-height is severely limited. Compared to older through-hole LEDs, it offers massive space savings and enables automated assembly. The use of InGaN technology provides high efficiency and bright green light output. Its compliance with lead-free reflow profiles aligns it with modern environmental regulations and manufacturing processes.

10. Frequently Asked Questions (FAQ)

Q: Can I drive this LED at 30 mA for higher brightness?
A: No. The absolute maximum DC forward current is 20 mA. Exceeding this rating can cause irreversible damage due to overheating and accelerated degradation of the semiconductor junction.
Q: What is the difference between dominant wavelength and peak wavelength?
A: Dominant wavelength (λd) is the single wavelength perceived by the human eye that matches the LED's color, derived from the CIE chromaticity diagram. Peak wavelength (λp) is the actual wavelength at which the emitted optical power is highest. They often differ slightly.
Q: Can I use hand soldering?
A: Hand soldering with an iron is possible but requires extreme care. The recommendation is a maximum iron tip temperature of 300°C and a soldering time not exceeding 3 seconds per lead, for one time only. Reflow soldering is the preferred and more reliable method.
Q: How do I interpret the bin code in the part number?
A: The suffix \"TGKT\" likely contains coded information for the specific forward voltage (T?), luminous intensity (G?), and dominant wavelength (K?) bins. One must cross-reference the full bin list with the ordering information to select the exact performance grade required.

11. Practical Design and Usage Case

Scenario: Designing a status indicator for a smartwatch.
The design requires a green charging indicator. The smartwatch's internal height is extremely limited. The LTST-C194TGKT is selected for its 0.30mm profile. The designer chooses bin D8 for Vf (3.0-3.2V) and bin T for luminous intensity (280-450 mcd) to ensure visibility. The LED is driven from the watch's 3.3V rail. Using the maximum Vf of 3.6V for a conservative design, the current-limiting resistor is calculated: R = (3.3V - 3.6V) / 0.02A = -15 Ohms. This negative value indicates that with a worst-case Vf higher than the supply, the LED may not turn on. Therefore, the designer uses the typical Vf of 3.2V: R = (3.3V - 3.2V) / 0.02A = 5 Ohms. A standard 5.1Ω resistor is selected, resulting in a current of ~19.6 mA. The PCB layout uses the recommended solder pad dimensions and includes a small thermal relief connection to a ground plane.

12. Technology Introduction

The LTST-C194TGKT is based on InGaN (Indium Gallium Nitride) semiconductor technology. InGaN is a compound semiconductor whose bandgap energy can be tuned by varying the ratio of indium to gallium. For green LEDs, a specific indium content is used to create a bandgap that corresponds to the emission of photons in the green wavelength range (around 525 nm). When a forward voltage is applied, electrons and holes recombine in the active region of the semiconductor, releasing energy in the form of light—a process called electroluminescence. The water-clear lens epoxy is formulated to efficiently extract this light from the semiconductor chip with minimal absorption, while also providing mechanical and environmental protection.

13. Technology Trends

The trend in SMD LEDs for consumer electronics continues toward miniaturization, higher efficiency, and greater integration. Package heights are decreasing further to enable ever-thinner end products. Efficiency improvements (more lumens per watt) reduce power consumption, which is critical for battery-operated devices. There is also a trend toward more precise color control and tighter binning to meet the demands of high-quality displays and consistent multi-LED arrays. Furthermore, the integration of control electronics (like constant-current drivers) directly into the LED package is becoming more common, simplifying circuit design for the end user. The underlying materials science continues to advance, with ongoing research into improving the efficiency of green InGaN LEDs, which has historically been lower than that of blue LEDs.