LTST-C193KRKT-2A SMD LED Datasheet - 0.35mm Height - 1.6-2.2V Forward Voltage - Red Color - 75mW Power - English Technical Document

1. Product Overview

This document provides the complete technical specifications for the LTST-C193KRKT-2A, a high-performance, surface-mount chip LED designed for modern electronic applications requiring minimal component height and reliable performance. The device is an extra-thin LED utilizing advanced AlInGaP (Aluminum Indium Gallium Phosphide) semiconductor technology to produce a bright red light output. Its primary design goal is to enable integration into space-constrained assemblies without compromising optical performance or manufacturability.

The core advantages of this component include its exceptionally low profile of 0.35mm, which is a critical parameter for slim consumer electronics, displays, and indicator applications. It is engineered to be compatible with standard automated pick-and-place assembly lines and high-volume reflow soldering processes, including both infrared (IR) and vapor phase methods. The product is classified as a Green Product and complies with RoHS (Restriction of Hazardous Substances) directives, making it suitable for environmentally conscious designs and global markets.

1.1 Key Features and Target Market

The LTST-C193KRKT-2A is characterized by several key features that define its application space. The use of an AlInGaP chip is central to its performance, offering higher luminous efficiency and better temperature stability compared to traditional LED materials for red emission. The package is standardized according to EIA (Electronic Industries Alliance) norms, ensuring broad compatibility with industry design libraries and assembly equipment.

The target market for this LED spans a wide range of electronic equipment. Its primary applications are found in office automation devices (printers, scanners, copiers), communication equipment (routers, modems, switches), and household appliances where status indication, backlighting for buttons, or functional lighting is required. Its thin profile makes it particularly attractive for portable devices, ultra-thin bezels on monitors and TVs, and any application where Z-height is a critical design constraint. The device's compatibility with automatic placement and reflow soldering makes it ideal for high-volume, cost-effective manufacturing.

2. In-Depth Technical Parameter Analysis

A thorough understanding of the electrical, optical, and thermal parameters is essential for reliable circuit design and system integration. All specifications are defined at an ambient temperature (Ta) of 25\u00b0C unless otherwise stated.

2.1 Absolute Maximum Ratings

The Absolute Maximum Ratings define the stress limits beyond which permanent damage to the device may occur. These are not operating conditions.

• Power Dissipation (Pd): 75 mW. This is the maximum amount of power the LED package can dissipate as heat. Exceeding this limit risks thermal damage to the semiconductor junction and the epoxy lens.
• DC Forward Current (IF): 30 mA. The maximum continuous forward current that can be applied. For pulsed operation, a higher Peak Forward Current of 80 mA is allowed under specific conditions (1/10 duty cycle, 0.1ms pulse width).
• Forward Current Derating: 0.4 mA/\u00b0C linear from 25\u00b0C. This is a critical parameter for thermal management. As the ambient temperature rises above 25\u00b0C, the maximum allowable continuous current must be reduced. For example, at 50\u00b0C, the maximum current is 30 mA - [0.4 mA/\u00b0C * (50-25)\u00b0C] = 20 mA.
• Reverse Voltage (VR): 5 V. Applying a reverse bias voltage greater than this can cause junction breakdown.
• Operating & Storage Temperature Range: -55\u00b0C to +85\u00b0C. This wide range ensures reliability in harsh environments.
• Soldering Temperature Tolerance: The device can withstand wave soldering at 260\u00b0C for 5 seconds, IR reflow at 260\u00b0C for 5 seconds, and vapor phase reflow at 215\u00b0C for 3 minutes. These parameters are vital for defining the assembly process window.

2.2 Electrical & Optical Characteristics

These parameters define the typical performance of the LED under normal operating conditions.

• Luminous Intensity (Iv): Ranges from a minimum of 1.80 mcd to a maximum of 11.2 mcd at a test current (IF) of 2 mA. The actual intensity for a specific unit is determined by its Bin Code (see Section 3). The measurement uses a sensor filtered to approximate the CIE photopic eye-response curve.
• Viewing Angle (2\u03b81/2): 130 degrees. This is the full angle at which the luminous intensity drops to half of its value at the central axis (0 degrees). A wide viewing angle like this is suitable for applications requiring broad, diffuse illumination rather than a focused beam.
• Peak Wavelength (\u03bbP): 639 nm. This is the wavelength at which the spectral power output is maximum. It defines the perceived hue of the red light.
• Dominant Wavelength (\u03bbd): 629 nm. Derived from the CIE chromaticity diagram, this is the single wavelength that best represents the color perceived by the human eye. It is typically slightly shorter than the peak wavelength for red AlInGaP LEDs.
• Spectral Line Half-Width (\u0394\u03bb): 20 nm. This indicates the spectral purity or bandwidth of the emitted light. A smaller value indicates a more monochromatic light source.
• Forward Voltage (VF): 1.60 V to 2.20 V at IF = 2 mA. This is the voltage drop across the LED when operating. It is crucial for designing the current-limiting circuitry. The variation is due to normal semiconductor manufacturing tolerances.
• Reverse Current (IR): 10 \u00b5A maximum at VR = 5 V. This is the small leakage current that flows when the device is reverse-biased within its maximum rating.
• Capacitance (C): 40 pF typical at VF = 0V, f = 1 MHz. This parasitic capacitance can be relevant in high-frequency switching applications.
• ESD Threshold (HBM): 1000 V. This Human Body Model rating indicates the LED's sensitivity to electrostatic discharge. It is classified as moderately sensitive; proper ESD handling procedures are mandatory.

3. Binning System Explanation

To manage the natural variation in semiconductor manufacturing, LEDs are sorted into performance bins. The LTST-C193KRKT-2A uses a binning system primarily for Luminous Intensity.

The intensity is measured at the standard test condition of IF = 2 mA. Units are sorted into the following bins:

• Bin G: 1.80 mcd (Min) to 2.80 mcd (Max)
• Bin H: 2.80 mcd to 4.50 mcd
• Bin J: 4.50 mcd to 7.10 mcd
• Bin K: 7.10 mcd to 11.20 mcd

A tolerance of +/-15% is applied to the limits of each bin. This binning allows designers to select LEDs with a guaranteed minimum brightness for their application, ensuring consistency in the final product's appearance, especially when multiple LEDs are used side-by-side. For critical color-matched applications, consulting the manufacturer for specific chromaticity binning information is recommended, as the datasheet primarily details intensity bins.

4. Performance Curve Analysis

While the datasheet provides tabular data, understanding the relationships between parameters through characteristic curves is vital for robust design.

4.1 Forward Current vs. Forward Voltage (I-V Curve)

The relationship between forward current (IF) and forward voltage (VF) is non-linear and exponential in nature, typical of a diode. The specified VF range of 1.6V-2.2V at 2mA provides a key operating point. Designers must note that VF will decrease with increasing temperature for a given current, which can affect the current drawn in a simple resistor-limited circuit if not properly accounted for.

4.2 Luminous Intensity vs. Forward Current

The light output (luminous intensity) is approximately proportional to the forward current in the typical operating range. However, efficiency (lumens per watt) may peak at a certain current and then decrease due to thermal and electrical effects. Operating at or below the recommended DC current ensures optimal efficiency and longevity.

4.3 Temperature Dependence

The performance of an LED is significantly affected by temperature. Key effects include:

• Luminous Intensity: Output decreases as the junction temperature increases. The derating of forward current is directly linked to managing this thermal effect to maintain brightness and reliability.
• Forward Voltage: VF typically decreases with increasing temperature (negative temperature coefficient).
• Wavelength: The peak and dominant wavelengths will shift slightly (usually to longer wavelengths) as temperature increases, which can affect color perception in precision applications.

5. Mechanical & Package Information

5.1 Package Dimensions and Polarity

The LED is housed in a very compact surface-mount package. The defining mechanical feature is its height of only 0.35 mm. Detailed dimensioned drawings are provided in the datasheet, including length, width, and the location of the optical lens. The package follows a standard chip LED footprint. Polarity is indicated by a marking or a chamfered corner on the package. Correct orientation during assembly is critical, as applying reverse bias can damage the device.

5.2 Recommended Solder Pad Design

To ensure reliable solder joints and proper alignment during reflow, a specific solder pad layout (land pattern) is suggested. The datasheet provides these dimensions. Adherence to this pattern helps prevent issues like tombstoning (where one end of the component lifts off the pad) or misalignment. A recommended stencil thickness of 0.10mm maximum is specified to control the volume of solder paste deposited.

6. Soldering & Assembly Guidelines

6.1 Reflow Soldering Profiles

The datasheet provides two suggested infrared (IR) reflow profiles: one for normal (tin-lead) solder process and one for Pb-free solder process. The Pb-free profile typically has a higher peak temperature (e.g., 260\u00b0C) to accommodate the higher melting point of Pb-free alloys like SAC (Sn-Ag-Cu). Both profiles include critical parameters:

• Pre-heat/Ramp-up: A controlled heating phase to gradually bring the board and components to temperature, minimizing thermal shock and preventing solder paste spattering.
• Soak/Pre-reflow: A temperature plateau to allow the flux in the solder paste to activate and volatiles to escape, and to equalize temperatures across the assembly.
• Reflow/Peak: The temperature exceeds the solder's liquidus point, allowing it to melt, wet the pads and component terminations, and form a proper metallurgical joint. The time above liquidus (TAL) and the peak temperature must be controlled within the LED's tolerance (5 sec at 260\u00b0C max).
• Cooling: A controlled cool-down to solidify the joint and minimize thermal stress.

6.2 Storage and Handling Precautions

Proper storage is essential to maintain solderability. LEDs removed from their original moisture-barrier packaging are hygroscopic and can absorb moisture. If stored for extended periods (more than 672 hours or 28 days) outside the dry pack, they must be baked (e.g., at 60\u00b0C for 24 hours) before reflow to drive out moisture and prevent \"popcorning\" or package cracking during the high-temperature soldering process. For long-term storage, use sealed containers with desiccant or a nitrogen atmosphere.

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. Harsh or unspecified chemicals can damage the epoxy lens material, causing clouding, cracking, or discoloration.

7. Packaging and Ordering Information

The LTST-C193KRKT-2A is supplied in industry-standard packaging for automated assembly.

• Tape and Reel: Components are placed in embossed carrier tape, which is then sealed with a cover tape. The tape width is 8mm.
• Reel Size: 7 inches in diameter.
• Quantity per Reel: 5000 pieces.
• Minimum Order Quantity (MOQ): 500 pieces for remainder quantities.
• Packaging Standards: Complies with ANSI/EIA-481-1-A specifications, ensuring compatibility with standard tape feeders on placement machines.

The part number LTST-C193KRKT-2A itself encodes specific product attributes, though the full naming convention details are typically found in a separate product selection guide.

8. Application Design Recommendations

8.1 Drive Circuit Design

LEDs are current-driven devices. The most critical aspect of the drive circuit is current control. A simple series resistor is the most common method, but its design requires care.

Calculating the Series Resistor (R_S):
R_S = (V_SUPPLY - V_F) / I_F
Where:
V_SUPPLY = Power supply voltage
V_F = LED forward voltage (use the maximum value from datasheet, 2.2V, for a conservative design)
I_F = Desired forward current (must be \u2264 30 mA DC)

Example: For a 5V supply and a target current of 20 mA:
R_S = (5V - 2.2V) / 0.020 A = 140 \u03a9. The nearest standard value (e.g., 150 \u03a9) would be selected, resulting in a slightly lower current.

Important Consideration - Parallel Connection: Directly connecting multiple LEDs in parallel with a single current-limiting resistor is not recommended (Circuit B in the datasheet). Due to natural variations in the I-V characteristics of individual LEDs (even from the same bin), one LED may draw significantly more current than others, leading to uneven brightness and potential overstress of one device. The recommended practice is to use a separate series resistor for each LED (Circuit A). For driving multiple LEDs efficiently, constant current driver ICs or dedicated LED driver circuits are preferred.

8.2 Thermal Management

Despite its low power, effective thermal management is important for longevity and stable performance. The 0.4 mA/\u00b0C derating factor must be applied in designs where the ambient temperature near the LED is expected to rise significantly (e.g., inside a sealed enclosure, near other heat-generating components). Ensuring adequate airflow or thermal relief in the PCB layout can help mitigate temperature rise.

8.3 ESD Protection

With an ESD threshold of 1000V (HBM), the LED is susceptible to damage from common electrostatic discharges. Implementation of ESD protection measures is non-negotiable:

• Use grounded workstations, conductive floor mats, and wrist straps.
• Store and transport components in anti-static packaging.
• Consider incorporating transient voltage suppression (TVS) diodes or other protection circuits on PCBs if the LED is connected to external interfaces that could be exposed to ESD events.

9. Technical Comparison and Differentiation

The LTST-C193KRKT-2A differentiates itself in the market primarily through its ultra-thin 0.35mm profile. Compared to standard chip LEDs which are often 0.6mm or 1.0mm in height, this represents a 40-65% reduction, enabling new industrial design possibilities. The use of AlInGaP technology provides advantages over older GaAsP (Gallium Arsenide Phosphide) red LEDs, offering higher efficiency (more light output per mA), better temperature stability, and a more saturated, \"truer\" red color. Its compatibility with lead-free (Pb-free) high-temperature reflow processes makes it future-proof for regulations and modern manufacturing lines.

10. Frequently Asked Questions (FAQs)

Q1: Can I drive this LED directly from a 3.3V microcontroller pin?
A: Possibly, but it requires calculation. With a typical VF of ~1.9V, a series resistor would be needed to limit the current. However, you must ensure the MCU pin can source the required current (e.g., 20mA) without exceeding its own specifications. Using a transistor as a switch is often a safer and more flexible approach.

Q2: Why is the luminous intensity specified at such a low current (2mA)?
A: 2mA is a standard test condition for low-current indicator LEDs. It allows for easy comparison between different products and provides a baseline. The intensity will be higher at higher currents, but the relationship is not perfectly linear, and efficiency may drop.

Q3: The datasheet shows a wide viewing angle (130\u00b0). What if I need a more focused beam?
A: This particular package is designed for wide-angle emission. For a narrower beam, you would need to select an LED in a different package (e.g., one with a smaller lens or a built-in reflector) or use an external secondary optic (like a collimating lens).

Q4: How do I interpret the bin code when ordering?
A: Specify the required intensity bin (G, H, J, or K) based on the minimum brightness needed for your application. For example, if your design requires at least 5.0 mcd, you must order Bin J (4.50-7.10 mcd) or Bin K (7.10-11.20 mcd). Ordering \"standard brightness\" may result in any bin, potentially causing brightness mismatches in your product.

11. Practical Design and Usage Examples

Example 1: Status Indicator on a Portable Device
In a slim smartphone or tablet, space behind the glass or plastic fascia is extremely limited. The 0.35mm height of this LED allows it to be placed directly on the main PCB underneath a thin light guide or diffuser film, indicating charging status, notification alerts, or capacitive button backlighting without increasing the device's thickness.

Example 2: Backlighting for Membrane Switches
For industrial control panels or medical equipment with membrane keypads, even illumination under each key is crucial. Multiple LTST-C193KRKT-2A LEDs can be placed around the edges of the switch panel. Their wide viewing angle helps create uniform backlighting across the key area. The separate-resistor-per-LED drive method ensures all keys have consistent brightness regardless of VF variations.

Example 3: Integration into an Ultra-Thin Bezel Display
Modern monitors and TVs strive for bezels that are only a few millimeters wide. This LED can be mounted on a flexible printed circuit (FPC) that runs along the very edge of the display panel to provide ambient bias lighting or a subtle power indicator, contributing to the sleek aesthetic without compromising the slim profile.

12. Technology Principle Introduction

The LTST-C193KRKT-2A is based on AlInGaP semiconductor technology. This material system is grown epitaxially on a substrate. When a forward voltage is applied across the p-n junction, electrons and holes are injected into the active region where they recombine. In AlInGaP, this recombination primarily releases energy in the form of photons (light) in the red to yellow-orange part of the visible spectrum. The specific ratio of Aluminum, Indium, Gallium, and Phosphide in the crystal lattice determines the bandgap energy and thus the wavelength of the emitted light. The \"water clear\" lens is typically made of epoxy or silicone that is transparent to the emitted wavelength and is molded to shape the light output pattern (in this case, a wide viewing angle).

13. Industry Trends and Developments

The trend in indicator and functional lighting LEDs continues toward miniaturization, higher efficiency, and greater integration. The 0.35mm height of this component represents the ongoing push for thinner packages. Future developments may include even thinner chip-scale packages (CSP) where the LED die is mounted directly without a traditional plastic package. There is also a strong trend toward higher reliability and longer lifetime under higher temperature operating conditions, driven by automotive and industrial applications. Furthermore, the demand for precise color consistency and tighter binning tolerances is increasing for applications in display backlighting and architectural lighting where color matching is critical. The underlying AlInGaP technology continues to be refined for higher efficiency, potentially reducing the power consumption for a given light output in future generations.