LTS-3861JS LED Display Datasheet - 0.3-inch Digit Height - AlInGaP Yellow - 2.6V Forward Voltage - 40mW Power Dissipation - English Technical Document

1. Product Overview

The LTS-3861JS is a single-digit, seven-segment alphanumeric display module designed for applications requiring clear, high-visibility numeric or limited alphanumeric readouts. Its primary function is to convert electrical signals into a visible, segmented light pattern representing numbers and some letters. The core technology is based on Aluminium Indium Gallium Phosphide (AlInGaP) semiconductor material, which is specifically engineered to emit light in the yellow wavelength region. This material system is known for its high efficiency and excellent brightness compared to older technologies like standard Gallium Phosphide (GaP). The device features a gray faceplate and white segment markings, which work in conjunction with the yellow emission to create a high-contrast, easily readable character, especially under various ambient lighting conditions.

1.1 Core Advantages and Target Market

The display offers several key advantages that make it suitable for a range of industrial and consumer applications. Its high brightness and excellent contrast ratio ensure readability even in brightly lit environments. The wide viewing angle allows the display to be seen clearly from various positions, which is crucial for panel meters and instrumentation. The solid-state reliability of LED technology means it has a long operational lifetime, is resistant to shock and vibration, and has a fast response time. The low power requirement makes it compatible with battery-powered or low-voltage digital logic circuits. Typical target markets and applications include test and measurement equipment (multimeters, oscilloscopes), industrial control panels, automotive dashboard indicators, consumer appliances, and any electronic device where a compact, reliable numeric display is needed.

2. Technical Parameters and Objective Interpretation

2.1 Photometric and Optical Characteristics

The photometric performance is central to the display's functionality. The Average Luminous Intensity (Iv) is specified between 200 and 600 microcandelas (µcd) at a forward current (If) of 1 mA. This range indicates a categorization or binning process for brightness. The typical value likely falls in the middle of this range. The Peak Emission Wavelength (λp) is 588 nm, and the Dominant Wavelength (λd) is 587 nm, both measured at If=20mA. These values firmly place the output in the pure yellow region of the visible spectrum. The Spectral Line Half-Width (Δλ) of 15 nm indicates a relatively narrow spectral bandwidth, resulting in a saturated, pure yellow color without significant spread into adjacent green or orange wavelengths. The Luminous Intensity Matching Ratio of 2:1 maximum specifies the allowable variation in brightness between different segments of the same digit, ensuring uniform appearance.

2.2 Electrical Parameters

The electrical characteristics define the interface between the display and the driving circuitry. The Forward Voltage per Segment (Vf) has a typical value of 2.6V and a maximum of 2.6V at If=20mA. This is a critical parameter for designing the current-limiting resistors or constant-current driver circuits. The low forward voltage is beneficial for low-voltage system design. The Reverse Current per Segment (Ir) is a maximum of 100 µA at a Reverse Voltage (Vr) of 5V, indicating the leakage current when the LED is reverse-biased, which is important for multiplexing circuits. The Absolute Maximum Ratings provide hard limits: a Continuous Forward Current per Segment of 25 mA (derated above 25°C), a Peak Forward Current of 60 mA under pulsed conditions, and a maximum Power Dissipation per Segment of 40 mW. Exceeding these ratings can cause immediate or gradual degradation of the LED chip.

2.3 Thermal and Environmental Specifications

The device is rated for an Operating Temperature Range of -35°C to +85°C. This wide range makes it suitable for use in harsh environments, both indoors and outdoors. The Storage Temperature Range is identical. The solder temperature rating is crucial for assembly: the device can withstand a maximum temperature of 260°C for a maximum of 3 seconds, measured at a point 1.6mm (1/16 inch) below the seating plane of the package. This defines the reflow soldering profile that must be used during PCB assembly to prevent thermal damage to the internal die, wire bonds, or plastic package.

3. Binning System Explanation

The datasheet explicitly states that the device is \"Categorized for Luminous Intensity.\" This refers to a binning or sorting process performed during manufacturing. Due to inherent variations in the semiconductor epitaxial growth and chip fabrication processes, LEDs from the same production batch can have slightly different optical outputs. To ensure consistency for the end user, the manufactured units are tested and sorted into different \"bins\" based on their measured luminous intensity at a standard test current (likely 1mA or 20mA). The specified range of 200 to 600 µcd represents the spread across bins that are offered for this product. Designers must be aware that the actual brightness of a specific unit will fall within this pre-defined range. The tight spectral specifications (wavelength) suggest that color binning is also tightly controlled, ensuring a consistent yellow hue across all units.

4. Performance Curve Analysis

While the specific graphs are not detailed in the provided text, typical curves for such a device would be essential for in-depth design. These would normally include: Forward Current vs. Forward Voltage (I-V Curve): This non-linear curve shows the relationship between the voltage applied across the LED and the resulting current. It is crucial for determining the appropriate series resistor value to achieve the desired operating current. Luminous Intensity vs. Forward Current (L-I Curve): This graph shows how the light output increases with increasing drive current. It is generally linear over a range but will saturate at high currents. Luminous Intensity vs. Ambient Temperature: This curve shows how light output decreases as the junction temperature of the LED increases. Understanding this derating is vital for applications operating at high ambient temperatures. Spectral Distribution Curve: A plot of relative intensity versus wavelength, visually confirming the narrow 15nm half-width and the peak at 588nm.

5. Mechanical and Packaging Information

The device uses a standard single-digit, 10-pin, side-view DIP (Dual In-line Package) format. The package dimensions are provided in millimeters with a standard tolerance of ±0.25 mm. The 0.3-inch digit height (7.62mm) refers to the physical size of the illuminated character. The gray face and white segments are part of the plastic molding. The Pin Connection diagram is critical: it shows a common anode configuration with two common anode pins (1 and 6) for redundancy or lower current density per pin. The other pins (2, 3, 4, 5, 7, 8, 9, 10) are the cathodes for segments F, G, E, D, Decimal Point, C, B, and A respectively. The internal circuit diagram confirms that all LED segments for the digit share a common positive connection (anode), and each segment has its own negative connection (cathode). This configuration is typically driven by a \"sink\" driver IC that grounds the cathode of the segment to be lit.

6. Soldering and Assembly Guidelines

The key assembly guideline is the solder temperature specification: 260°C maximum for 3 seconds at 1.6mm below the seating plane. This translates to a standard lead-free reflow soldering profile (e.g., IPC/JEDEC J-STD-020). The profile must ensure that the body of the component does not exceed this temperature/time limit to prevent damage to the epoxy resin, the LED chip, or the internal wire bonds. For hand soldering, a temperature-controlled iron should be used, and contact time should be minimized. Standard ESD (Electrostatic Discharge) precautions should be observed during handling and assembly, as LED chips are sensitive to static electricity. Storage should be in a dry, ambient environment within the specified -35°C to +85°C range, preferably in moisture-sensitive device (MSD) bags if the shelf life is extended.

7. Packaging and Ordering Information

The part number is LTS-3861JS. The \"LTS\" prefix likely denotes a Lite-On display product, \"3861\" is the specific series/model, and \"JS\" may indicate the color (Yellow) and package style. The datasheet does not specify bulk packaging details (tubes, trays, or reels), but such displays are commonly supplied in anti-static tubes or ammo packs for automated insertion, or in reels for tape-and-reel automated placement. The label on the packaging would typically include the part number, quantity, date code, and luminous intensity bin code if applicable.

8. Application Recommendations

Typical Application Circuits: The common anode configuration is best driven by a microcontroller or dedicated driver IC with open-drain or open-collector outputs. A current-limiting resistor must be connected in series with each cathode pin (or each driver output). The resistor value is calculated using R = (Vcc - Vf) / If, where Vcc is the supply voltage, Vf is the forward voltage of the LED (use 2.6V for design margin), and If is the desired forward current (e.g., 10-20 mA for full brightness). For multiplexing multiple digits, the common anodes are switched sequentially (scanned) while the appropriate cathodes are driven for each digit. Design Considerations: 1) Current Limiting: Always use series resistors or constant-current drivers. 2) Heat Management: While power dissipation is low, ensure adequate ventilation if operating at high ambient temperatures or high continuous current. 3) Viewing Angle: Mount the display considering the intended user's line of sight relative to the specified wide viewing angle. 4) Brightness Control: Brightness can be adjusted by varying the forward current (within ratings) or by using pulse-width modulation (PWM) on the driver.

9. Technical Comparison and Differentiation

The primary differentiator of the LTS-3861JS is its use of AlInGaP material for yellow emission. Compared to older GaP:Y (Gallium Phosphide doped for yellow) technology, AlInGaP offers significantly higher luminous efficiency, resulting in greater brightness for the same drive current, or similar brightness at lower power. It also provides superior color purity and saturation. Compared to a filtered or phosphor-converted white LED used behind a colored filter to make yellow, the AlInGaP direct-emission yellow is more efficient and has a more stable color point over temperature and current variations. The 0.3-inch digit height is a standard size, offering a good balance between readability and board space consumption, fitting between smaller 0.2-inch and larger 0.5-inch or 0.56-inch displays.

10. Frequently Asked Questions (Based on Technical Parameters)

Q: What resistor value should I use for a 5V supply? A: For a target current of 20mA and a Vf of 2.6V, R = (5V - 2.6V) / 0.02A = 120 Ohms. A standard 120Ω or 150Ω resistor would be suitable. Q: Can I drive it directly from a microcontroller pin? A: It is not recommended to source the current for the common anode from an MCU pin, as the total digit current (e.g., 8 segments * 20mA = 160mA) exceeds pin ratings. Use the MCU to control a transistor or driver IC. Sinking the cathode current (per segment) via an MCU pin may be possible if the pin's current sink rating (e.g., 25mA) is not exceeded per segment. Q: Why are there two common anode pins (1 and 6)? A: For redundancy and to distribute the total anode current. When all segments are lit, the total current flows into the common anode. Having two pins reduces current density per pin, improves reliability, and provides a backup connection. They should be connected together on the PCB. Q: What does the luminous intensity matching ratio of 2:1 mean? A: It means the brightest segment in the digit will be no more than twice as bright as the dimmest segment under the same test conditions, ensuring visual uniformity.

11. Practical Design and Usage Case

Case: Designing a Simple Digital Voltmeter Readout: A designer is creating a 3-digit DC voltmeter display. They choose three LTS-3861JS displays. The microcontroller's ADC reads the voltage, converts it to a value, and drives the displays. A dedicated 7-segment driver IC (like the MAX7219 or a multiplexing shift register) is used to interface between the MCU's few I/O pins and the 24 segment lines (3 digits * 8 segments) and 3 common anode lines. The driver IC handles the multiplexing scan, refreshing each digit sequentially at a high frequency to avoid flicker. The designer calculates the series resistors based on the driver's output voltage and the desired brightness. The PCB layout places the displays in a row, with careful routing to avoid crosstalk. The gray face and yellow segments provide a classic, high-contrast instrument look. The wide operating temperature range assures functionality in a workshop environment.

12. Operating Principle Introduction

The fundamental operating principle is based on electroluminescence in a semiconductor p-n junction. The AlInGaP chip consists of layers of aluminium, indium, gallium, and phosphide compounds grown epitaxially on a non-transparent Gallium Arsenide (GaAs) substrate. When a forward voltage exceeding the junction's built-in potential (around 2V) is applied, 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 specific bandgap energy of the AlInGaP alloy determines the wavelength (color) of the emitted light, which in this case is yellow (~587-588 nm). The non-transparent GaAs substrate absorbs any light emitted downwards, improving contrast by preventing internal reflection that could wash out the segments.

13. Technology Trends and Context

AlInGaP technology represents a significant advancement in visible LED efficiency for red, orange, amber, and yellow colors. It has largely superseded older GaAsP and GaP technologies in performance-critical applications. The trend in display technology is towards higher integration and miniaturization. While discrete 7-segment displays like the LTS-3861JS remain vital for many applications, there is a growing use of dot-matrix LED displays and OLEDs for greater flexibility in showing graphics and text. However, for simple, bright, low-cost, and highly reliable numeric readouts, dedicated 7-segment LEDs like this one, especially with efficient materials like AlInGaP, continue to have a strong and enduring role in electronic design due to their simplicity, robustness, and excellent readability.