LTST-T680VSWT SMD LED Specification Sheet - Diffused Yellow AlInGaP - 50mA - 130mW - Technical Documentation

1. Product Overview

This document provides the complete technical specifications for the LTST-T680VSWT, a Surface-Mount Device (SMD) Light-Emitting Diode (LED). This component belongs to the miniature LED series, designed for automated Printed Circuit Board (PCB) assembly processes and space-constrained applications. The LED utilizes Aluminum Indium Gallium Phosphide (AlInGaP) semiconductor material to produce yellow light output, which is diffused through its lens for a wider, more uniform illumination pattern. Its primary function is to serve as a status indicator, signal light, or backlight for various electronic device front panels.

1.1 Core Advantages and Target Market

LTST-T680VSWT yana ba da fa'idodi masu mahimmanci da yawa ga ƙirƙirar lantarki na zamani. Ya cika ka'idojin RoHS (Ƙuntata Abubuwa Masu Cutarwa), yana dacewa da kasuwanni na duniya masu ƙaƙƙarfan dokokin muhalli. Ana samar da kayan a cikin daidaitaccen masana'antu na 8mm mai ɗaure, faifan inci 7, don sauƙin ɗauka da haɗawa ta atomatik cikin sauri. Ɗayan ƙirarsa ya dace da tsarin IR (infrared) reflow, wanda shine daidaitaccen tsarin haɗa PCB mara gubar (Pb-free). Na'urar kuma ta dace da haɗewar lantarki, ma'ana halayenta na lantarki suna ba da damar haɗa kai tsaye da fil ɗin fitarwa na yau da kullun na haɗewar lantarki. Waɗannan halaye sun sa ya zama zaɓi mai kyau don aikace-aikacen da ke buƙatar masu nuni na gani masu aminci da ƙanƙanta kamar na'urorin sadarwa, na'urori masu sarrafa ofis, na'urorin gida, tsarin sarrafa masana'antu, kwamfutocin hannu da kayan aikin cibiyar sadarwa.

2. In-depth Technical Parameter Analysis

Fahimtar cikakke na sigogi na lantarki da na gani yana da mahimmanci don ƙirar da'ira mai aminci da cimma aiki mai daidaito.

2.1 Absolute Maximum Ratings

Viwango hivi vinabainisha mipaka ya mkazo inayoweza kusababisha uharibifu wa kudumu wa kifaa. Hakuna uhakikisho wa uendeshaji chini ya hali hizi. Viwango vya Juu Kabisa vinabainishwa kwa joto la mazingira (Ta) la 25°C.

• Power Dissipation (Pd):130 mW. This is the maximum power that the LED package can dissipate as heat without exceeding its thermal limits.
• Peak Forward Current (I_FP):100 mA. This is the maximum permissible instantaneous forward current, allowed only under pulse conditions with a duty cycle of 1/10 and a pulse width of 0.1ms. It should not be used for continuous DC operation.
• DC Forward Current (I_F):50 mA. This is the maximum continuous forward current recommended for long-term reliable operation.
• Operating Temperature Range:-40°C to +85°C. The device is designed to operate over this ambient temperature range.
• Storage Temperature Range:-40°C to +100°C. The device can be stored within this range without applying power.

2.2 Electrical and Optical Characteristics

These parameters define the typical performance of the LED under normal operating conditions, measured at Ta=25°C with a standard test current (I_F) of 20mA.

• Luminous intensity (I_V):710.0 - 1800.0 mcd (millicandela). This is an indicator that measures the perceived power of visible light emitted in a specific direction (axial). The wide range is managed through a binning system (see Section 3). Intensity is measured using a sensor filtered to match the human eye's photopic response (CIE curve).
• Viewing angle (2θ_1/2):120 degrees (typical). This is the full angle at which the luminous intensity drops to half of its axial value. The diffused lens creates this wide viewing angle, making the LED suitable for applications where off-axis visibility is important.
• Peak Emission Wavelength (λ_P):592 nm (typical). This is the wavelength at which the spectral power distribution of the emitted light reaches its maximum.
• Dominant Wavelength (λ_d):584.5 - 594.5 nm. This is the single wavelength that best represents the perceived color of the light, derived from the CIE chromaticity diagram. It is a key parameter for color specification.
• Spectral line half-width (Δλ):15 nm (typical value). This is the spectral bandwidth measured at half of the maximum intensity (Full Width at Half Maximum - FWHM). A value of 15nm indicates a relatively pure yellow.
• Forward voltage (V_F):2.1V (typical value), at I_FMaximum 2.6V at =20mA. This is the voltage drop across the LED when it is conducting current. It is a key parameter for designing current-limiting circuits.
• Reverse Current (I_R):At V_RMaximum 10 μA at =5V. This parameter is for quality assurance testing only. The device is not designed to operate under reverse bias; applying reverse voltage may damage it. In circuits where reverse voltage may occur, external protection (e.g., a diode in parallel) may be required.

3. Explanation of the Binning System

To ensure consistency in mass production, LEDs are categorized into performance groups or "bins" based on key parameters. This allows designers to select components that meet specific requirements for color and brightness uniformity in their applications.

3.1 Forward Voltage (V_f) Binning

LEDs are binned according to their forward voltage at 20mA. The bin codes, minimum and maximum values are as follows. The tolerance within each bin is ±0.1V.

• D2:1.8V (Min) - 2.0V (Max)
• D3:2.0V (Minimum) - 2.2V (Maximum)
• D4:2.2V (Minimum) - 2.4V (Maximum)
• D5:2.4V (Minimum) - 2.6V (Maximum)

3.2 Luminous Intensity (I_V) Binning

LEDs are binned according to their axial luminous intensity at 20mA. The tolerance within each bin is ±11%.

• V1:710.0 mcd (min) - 900.0 mcd (max)
• V2:900.0 mcd (min) - 1120.0 mcd (max)
• W1:1120.0 mcd (min) - 1400.0 mcd (max)
• W2:1400.0 mcd (Minimum) - 1800.0 mcd (Maximum)

3.3 Dominant Wavelength (W_d) Binning

LEDs are binned according to their dominant wavelength at 20mA to ensure color consistency. The tolerance within each bin is ±1nm.

• H:584.5 nm (minimum) - 587.0 nm (maximum)
• J:587.0 nm (minimum) - 589.5 nm (maximum)
• K:589.5 nm (minimum) - 592.0 nm (maximum)
• L:592.0 nm (minimum) - 594.5 nm (maximum)

4. Performance Curve Analysis

The graphical data provides in-depth insights into how LED characteristics change with operating conditions. The datasheet contains typical curves for the following relationships (at 25°C unless otherwise noted).

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

This curve shows the nonlinear relationship between the current flowing through an LED and the voltage across its terminals. It is crucial for selecting the appropriate current-limiting method (resistor or constant current driver). The curve will show the "turn-on" voltage and how V_Fchanges with I_F.

increases.

4.2 Luminous Intensity vs. Forward Current

This curve illustrates how the light output (in mcd) scales with the drive current. It is typically linear within a certain range but saturates at higher currents. This helps designers balance brightness requirements with power consumption and thermal management.

4.3 Luminous Intensity vs. Ambient Temperature

This curve illustrates the thermal derating of light output. As the ambient temperature increases, the luminous efficacy of the LED decreases, resulting in reduced intensity at the same drive current. This is a critical consideration for applications operating in high-temperature environments.

4.4 Relative Spectral Power Distribution_PThe chart plots the intensity of emitted light within the visible spectrum. It shows the peak wavelength (λ

~592nm) and the spectral full width at half maximum (Δλ~15nm), confirming the narrow-band yellow light emission characteristic of AlInGaP technology.

5. Mechanical and Packaging Information

5.1 Package Dimensions

This LED conforms to the EIA standard SMD package outline. All critical dimensions, including length, width, height, and lead pitch, are provided in the datasheet drawing, with a general tolerance of ±0.2mm. The lens is described as "diffused," which scatters light to achieve the specified 120-degree viewing angle.

5.2 Polarity Identification and PCB Pad Design

This component has an anode and a cathode. The datasheet contains recommended PCB pad patterns (footprints) for infrared or vapor phase reflow soldering. Adhering to this pad layout is crucial for achieving reliable solder joints, proper alignment, and managing heat dissipation during the soldering process. Polarity is typically indicated by a marking on the component body or an asymmetric feature in the package.

6. Soldering, Assembly and Operation Guide

6.1 Recommended Infrared Reflow Profile (Lead-Free)

• This device is qualified for lead-free soldering processes per J-STD-020B. An example reflow temperature profile is provided, including the following key parameters:Preheat Temperature:
• 150-200°CZamanin shiryawo:
• Mafi tsawon dakika 120.Matsakaicin zafin jiki:
• Maximum 260°C.Time Above Liquidus (TAL):
• It is recommended to follow JEDEC guidelines, typically 60-150 seconds.Maximum number of passes:

Due to variations in PCB design, solder paste, and oven characteristics, this profile should serve as a target and be fine-tuned according to the specific assembly line.

6.2 Manual Soldering

• If manual soldering is necessary, extreme caution must be exercised:Soldering iron temperature:
• Maximum 300°C.Welding time:
• Maximum 3 seconds per pin.Times:

Only once. Repeated heating will damage the package and semiconductor.

6.3 Cleaning

If post-solder cleaning is required, only specified solvents should be used to avoid damaging the plastic package. Acceptable methods include immersion in ethanol or isopropyl alcohol at room temperature for no more than one minute. The use of unspecified chemical cleaners must be avoided.

6.4 Storage and Moisture Sensitivity

LEDs are packaged in moisture barrier bags with desiccant. When sealed, they should be stored at ≤30°C and ≤70% relative humidity (RH) and used within one year. Once the bag is opened, the components are exposed to ambient moisture. Their Moisture Sensitivity Level (MSL) is Level 3, which means they must undergo infrared reflow soldering within 168 hours (7 days) after exposure to factory floor conditions (≤30°C/60% RH). If this time is exceeded, the components require a baking procedure (approximately 60°C, for at least 48 hours) prior to soldering to remove absorbed moisture and prevent "popcorn" effect or package cracking during reflow.

7. Packaging and Ordering Information

7.1 Tape and Reel Specifications

LTST-T680VSWT is supplied in standard 8mm wide embossed carrier tape, 7-inch (178mm) diameter reels. Each reel contains 2000 pieces. The carrier tape pockets are sealed with a cover tape. The packaging conforms to ANSI/EIA-481 specification. The maximum allowable number of consecutive missing components in the tape is two.

8. Application Notes and Design Considerations

8.1 Driving Method_FLED is a current-driven device. To ensure uniform brightness, especially when multiple LEDs are connected in parallel, each LED should be driven by its own current-limiting resistor, or preferably by a constant current source. It is not recommended to drive LEDs directly in parallel from a voltage source because the forward voltage (V

) varies between different units, which can lead to significant differences in current and brightness.

8.2 Thermal Management

Although the power consumption is relatively low (maximum 130mW), proper thermal design can extend LED lifespan and maintain stable light output. Ensure the PCB pad design provides sufficient heat dissipation, and avoid continuously operating the LED at the absolute maximum current (50mA) under high ambient temperatures without evaluation.

8.3 Application Scope and Reliability

This LED is designed for standard commercial and industrial electronic equipment. It is not specifically designed or tested for applications where failure could directly endanger life or health, such as critical medical, aviation, transportation, or security systems. For such high-reliability applications, it is necessary to consult the component manufacturer for specific qualification data.

9. Technology and Principle Introduction

LTST-T680VSWT is based on aluminum indium gallium phosphide (AlInGaP) semiconductor technology. This material system is highly efficient in producing light in the red, orange, amber, and yellow regions of the spectrum. When a forward voltage is applied, electrons and holes recombine in the semiconductor active region, releasing energy in the form of photons. The specific composition of the AlInGaP layer determines the bandgap energy, thereby determining the wavelength (color) of the emitted light. No yellow phosphor is used; the color is inherent to the semiconductor material, resulting in high color purity and stability. A diffused epoxy resin lens encapsulates the semiconductor chip, providing mechanical protection, shaping the light output beam, and improving the viewing angle.

10. Practical Design and Usage Examples

10.1 Example: Network Switch Status Indicator

1. In a 24-port network switch, each port may have multiple LEDs (e.g., link, activity, speed). The LTST-T680VSWT with a 120-degree wide viewing angle is an excellent choice for front-panel status indicators. Designers will:_VDetermine the required brightness based on viewing distance and ambient light. Select the appropriate I
2. grade (e.g., medium brightness selects V2).
3. Select the drive current, typically 10-20mA, to balance brightness and power consumption. Using a constant current drive IC for all LEDs ensures perfect uniformity.
4. Strictly follow the datasheet recommendations to design the PCB footprint to ensure proper soldering.

Follow the MSL-3 handling guidelines: store opened reels in a dry cabinet and ensure board assembly is completed within 168 hours after opening the reel.

10.2 Example: Membrane Switch Panel Backlight

1. For illuminating symbols on control panels, uniform off-axis visibility is crucial. The diffused lens of this LED offers an advantage.
2. The LED will be installed behind translucent or laser-etched icons on the panel.
3. Faɗin kusurwar gani yana tabbatar da cewa ko da LED ba ta daidai a tsakiyar alamar ba, alamar za ta yi haske daidai.
4. Don cimma takamaiman launin rawaya, masu zane za su ƙayyade matakin tsayin daka mai tsauri (misali, K: 589.5-592.0nm), don dacewa da sauran fitilun nuni ko launin alama.

If powering one or two LEDs from a single regulated supply rail, a simple series resistor can be used for current limiting.

11. Frequently Asked Questions (Based on Technical Specifications)
Q1: Can I drive this LED with a 3.3V logic level without using a resistor?No.A:_FTypical V

It is 2.1V, but can be as high as 2.6V. Connecting it directly to 3.3V will force a current limited only by the LED's dynamic resistance and the power supply, likely exceeding the absolute maximum DC current of 50mA and damaging the device. A current-limiting resistor or regulator is always required.
Q2: What is the difference between peak wavelength and dominant wavelength?A:_P)Peak wavelength (λ) is the single wavelength at which an LED emits the most optical power._d)Dominant Wavelength (λ_d) is the single wavelength of monochromatic light that appears to the human eye to be the same color as the LED light. λ

is a parameter used for color specification and binning.
Q3: Why is there a 168-hour floor life limit after opening the bag?

A: Plastic LED packages absorb moisture from the air. During high-temperature reflow soldering, this trapped moisture rapidly evaporates, creating steam pressure inside the package, which can lead to delamination or cracking ("popcorn"). The 168-hour limit and baking procedure are safety measures against this failure mode.
Q4: How to interpret the bin code when ordering?_fA: You need to specify the part number LTST-T680VSWT, followed by your specific required V_V, I_d And W bin codes (e.g., for medium brightness and specific yellow hue). Please consult the manufacturer's ordering guide for the exact format. If no bin is specified, you will receive parts from the standard production bin.