LTST-C195TBKFKT Dual Color SMD LED Datasheet - Blue & Orange - 20mA/30mA Forward Current - English Technical Document

1. Product Overview

The LTST-C195TBKFKT is a dual-color, surface-mount device (SMD) light-emitting diode (LED). It integrates two distinct semiconductor chips within a single EIA standard package: an InGaN (Indium Gallium Nitride) chip for emitting blue light and an AlInGaP (Aluminum Indium Gallium Phosphide) chip for emitting orange light. This design allows for the creation of two different colors from one compact component, which is valuable for status indicators, backlighting, and decorative lighting where space is at a premium. The device is packaged on 8mm tape wound onto 7-inch diameter reels, making it fully compatible with high-speed automated pick-and-place assembly equipment used in modern electronics manufacturing.

2. Technical Parameters Deep Objective Interpretation

2.1 Absolute Maximum Ratings

These ratings define the limits beyond which permanent damage to the device may occur. For the Blue chip, the maximum continuous DC forward current is 20 mA, with a power dissipation limit of 76 mW. The Orange chip has a slightly higher DC current rating of 30 mA and a 75 mW power dissipation limit. Both chips share a maximum reverse voltage of 5V, but it is noted that continuous operation under reverse bias is not permitted. The device can withstand short-term current surges; the Blue chip handles a peak forward current of 100 mA (at 1/10 duty cycle, 0.1ms pulse), while the Orange chip handles 80 mA under the same conditions. The operating temperature range is specified from -20°C to +80°C, and the storage range is from -30°C to +100°C.

2.2 Electrical and Optical Characteristics

Measured at a standard ambient temperature of 25°C and a forward current (IF) of 20 mA, the key performance metrics are defined. The luminous intensity (Iv) for the Blue chip ranges from a minimum of 28.0 mcd to a maximum of 180 mcd, with typical values falling within this range. The Orange chip has a higher minimum intensity of 45.0 mcd, with the same 180 mcd maximum. The forward voltage (VF) is a critical parameter for circuit design. For the Blue chip, VF typically measures 3.30V, ranging from 2.90V (Min) to 3.50V (Max). The Orange chip operates at a lower voltage, with a typical VF of 2.00V and a range from 1.80V to 2.40V. Both LEDs feature a very wide viewing angle (2θ1/2) of 130 degrees, providing a broad, diffuse light pattern. The Blue chip's light emission is centered around a peak wavelength (λP) of 468 nm and a dominant wavelength (λd) of 470 nm, with a spectral bandwidth (Δλ) of 25 nm. The Orange chip emits at a peak of 611 nm, a dominant wavelength of 605 nm, and a narrower bandwidth of 17 nm.

3. Binning System Explanation

To ensure consistency in mass production, LEDs are sorted into performance bins. This datasheet defines bins for forward voltage and luminous intensity.

3.1 Forward Voltage Binning (Blue Chip)

The Blue chip's forward voltage at 20mA is categorized into bins labeled 12 through 17. Each bin covers a 0.1V range, starting from 2.90-3.00V (Bin 12) up to 3.40-3.50V (Bin 17). The tolerance within each bin is +/-0.1V. This allows designers to select LEDs with closely matched voltage drops for applications requiring uniform brightness in parallel configurations.

3.2 Luminous Intensity Binning

Both Blue and Orange chips are binned for luminous output. For the Blue chip, bins are labeled N, P, Q, and R, with minimum intensities ranging from 28.0 mcd (N) to 112.0 mcd (R). The Orange chip uses bins P, Q, and R, starting from a minimum of 45.0 mcd (P). The maximum for the highest bin (R) is 180 mcd for both colors. A tolerance of +/-15% applies to each intensity bin. This system enables selection based on required brightness levels for different applications.

4. Performance Curve Analysis

While specific graphical curves are referenced in the datasheet (e.g., Figure 1 for spectral output, Figure 6 for viewing angle), their typical characteristics can be described. The relationship between forward current (IF) and forward voltage (VF) is exponential, as per the diode equation. The luminous intensity for both chips is approximately proportional to the forward current within the recommended operating range. However, efficiency may drop at very high currents due to increased heat. The dominant and peak wavelengths are generally stable with current but can experience minor shifts with significant temperature changes. The wide 130-degree viewing angle indicates a Lambertian or near-Lambertian radiation pattern, where intensity is highest at the center and decreases according to the cosine of the viewing angle.

5. Mechanical and Packaging Information

The LED conforms to an industry-standard SMD package outline. Detailed dimensional drawings are provided in the datasheet, specifying the length, width, height, and placement of the solder pads. The device has four pins (1, 2, 3, 4). For the LTST-C195TBKFKT, pins 1 and 3 are assigned to the Blue chip's anode and cathode, while pins 2 and 4 are assigned to the Orange chip. A polarity indicator, such as a notch or a marked cathode pin, is typically included in the package drawing to ensure correct orientation during assembly. The component is supplied in an embossed carrier tape with a protective cover tape, wound on a standard 7-inch reel containing 4000 pieces.

6. Soldering and Assembly Guidelines

6.1 Reflow Soldering Profiles

The datasheet provides suggested infrared (IR) reflow profiles for both normal (tin-lead) and lead-free (Pb-free) solder processes. For lead-free assembly using SAC (Sn-Ag-Cu) solder paste, the profile must ensure the peak package body temperature does not exceed 260°C, and the time above 240°C is limited. A controlled pre-heat and ramp-up stage is crucial to prevent thermal shock. The LED is also rated for wave soldering (260°C max for 5 seconds) and vapor phase soldering (215°C for 3 minutes).

6.2 Storage and Handling

LEDs should be stored in an environment not exceeding 30°C and 70% relative humidity. Once removed from their original moisture-barrier packaging, they should be reflow-soldered within one week. If storage beyond one week is necessary, the devices 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 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 LED's epoxy lens or package.

7. Packaging and Ordering Information

The standard packaging is a 7-inch reel with 4000 pieces. A minimum order quantity of 500 pieces is accepted for remainder quantities. The tape and reel specifications follow ANSI/EIA 481-1-A-1994 standards. The part number LTST-C195TBKFKT follows the manufacturer's internal coding system, where elements likely indicate the series (C195), color (TB for dual color Blue/Orange), lens type (K for water clear), and packaging (FKT for tape and reel).

8. Application Suggestions

8.1 Typical Application Scenarios

This dual-color LED is ideal for applications requiring bi-color status indication, such as power on/standby, charge/full, network activity, or system error/warning signals. It can be used in consumer electronics (routers, chargers, audio equipment), industrial control panels, automotive interior lighting, and signage. The wide viewing angle makes it suitable for front-panel indicators that need to be visible from various angles.

8.2 Design Considerations

Drive Circuit: LEDs are current-driven devices. To ensure uniform brightness, especially when multiple LEDs are connected in parallel, a current-limiting resistor must be placed in series with each LED. Using a single resistor for multiple parallel LEDs (Circuit Model B in the datasheet) is not recommended due to variations in the forward voltage (Vf) of individual LEDs, which would cause significant differences in current and thus brightness. The recommended circuit (Model A) uses one resistor per LED.

Power Dissipation: The maximum power ratings (76 mW for Blue, 75 mW for Orange) must be respected. At the maximum recommended DC current (20mA Blue, 30mA Orange), the power dissipated is Vf * If. Using the typical Vf, this is 66 mW for Blue (3.3V*20mA) and 60 mW for Orange (2.0V*30mA), which are within limits. Designers must consider the derating factor (0.25 mA/°C for Blue, 0.4 mA/°C for Orange from 25°C) when operating at high ambient temperatures.

ESD Protection: These LEDs are sensitive to electrostatic discharge (ESD). All handling and assembly processes must be performed in an ESD-protected area using grounded wrist straps, conductive mats, and properly grounded equipment. The devices themselves may not contain integrated ESD protection diodes.

9. Technical Comparison

The key differentiating feature of this product is the integration of two high-performance, ultra-bright chips (InGaN for Blue, AlInGaP for Orange) in one standard SMD package. Compared to using two separate single-color LEDs, this saves PCB space, reduces component count, and simplifies assembly. The InGaN technology provides high-efficiency blue light, while AlInGaP is known for high-efficiency in the red-orange-amber spectrum. The combination offers a good color contrast between the two states. The wide 130-degree viewing angle is a consistent advantage for indicator applications over narrower-angle LEDs designed for focused beams.

10. Frequently Asked Questions (Based on Technical Parameters)

Q: Can I drive both the Blue and Orange chips simultaneously?

A: The datasheet specifies parameters for each chip independently. While it may be physically possible, driving both at full current simultaneously would likely exceed the total package power dissipation limits and is not specified. Typical use is to alternate between the two colors.

Q: Why is a series resistor necessary for each LED even if the supply voltage matches Vf?

A: The forward voltage (Vf) has a range (e.g., 2.9V to 3.5V for Blue). A "3.3V" supply might be perfect for an LED with a typical 3.3V Vf but would cause excessive current in an LED with a 2.9V Vf, potentially destroying it. The resistor sets the current precisely regardless of small variations in Vf or supply voltage.

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

A> Peak wavelength (λP) is the single wavelength at which the emission spectrum has its maximum intensity. Dominant wavelength (λd) is derived from the color coordinates on the CIE chromaticity diagram and represents the perceived color—the single wavelength that would match the LED's color to the human eye. For monochromatic LEDs, they are often close; for broader spectra, they can differ.

11. Practical Use Case

Scenario: Dual-Status Indicator for a USB Hub

A designer is creating a compact USB hub. They need one LED to indicate power (steady Orange) and another to indicate data activity (blinking Blue). Using the LTST-C195TBKFKT, they can achieve this with one component footprint. The PCB layout includes the four pads and two current-limiting resistors—one calculated for the Orange LED at 30mA (e.g., (5V - 2.0V)/0.03A = 100Ω) and one for the Blue LED at 20mA (e.g., (5V - 3.3V)/0.02A = 85Ω). A microcontroller drives the respective pins to ground to activate each color. This saves space, reduces BOM cost, and provides a clean, professional look with two distinct colors from a single point.

12. Principle Introduction

Light emission in LEDs is based on electroluminescence in semiconductor materials. When a forward voltage is applied across the p-n junction, electrons from the n-type region and holes from the p-type region are injected into the active region. When these charge carriers recombine, they release energy in the form of photons (light). The wavelength (color) of the emitted light is determined by the bandgap energy of the semiconductor material. InGaN has a wider bandgap, producing higher-energy photons in the blue spectrum. AlInGaP has a narrower bandgap, producing lower-energy photons in the red/orange spectrum. The epoxy lens serves to protect the chip, shape the light output beam, and enhance light extraction.

13. Development Trends

The trend in SMD indicator LEDs continues towards higher efficiency (more light output per watt of electrical input), enabling lower power consumption and reduced heat generation. Miniaturization is another key trend, with packages becoming smaller while maintaining or improving optical performance. There is also a growing focus on improved color consistency and tighter binning tolerances to meet the demands of applications requiring uniform appearance, such as full-color displays and architectural lighting. Furthermore, integration is increasing, with more multi-chip packages (like this dual-color LED) and even packages incorporating control ICs (like addressable RGB LEDs) becoming common to simplify system design.