LTS-547AKS LED Display Datasheet - 0.52-inch Digit Height - Yellow Color - 2.6V Forward Voltage - English Technical Document

1. Product Overview

The LTS-547AKS is a high-performance, single-digit numeric display module designed for applications requiring clear, bright, and reliable numerical readouts. Its primary function is to visually represent a single decimal digit (0-9) along with a decimal point. The device is constructed using advanced AS-AlInGaP (Aluminum Indium Gallium Phosphide) semiconductor technology, specifically engineered to emit a bright yellow light. This material system, grown on a GaAs (Gallium Arsenide) substrate, is known for its high efficiency and excellent color purity in the yellow-orange spectrum. The display features a distinctive appearance with a gray-colored faceplate and white segments, which enhances contrast and readability under various lighting conditions. It is categorized for luminous intensity, ensuring consistency in brightness across production batches.

1.1 Core Advantages and Target Market

The LTS-547AKS offers several key advantages that make it suitable for a wide range of industrial, commercial, and consumer applications. Its low power requirement is a significant benefit, allowing for integration into battery-powered or energy-efficient systems. The high brightness and high contrast ratio ensure excellent visibility even in brightly lit environments. A wide viewing angle provides flexibility in mounting and user positioning. The solid-state reliability of LED technology translates to long operational life, shock resistance, and minimal maintenance compared to older display technologies like incandescent or vacuum fluorescent displays. The device is also offered in a lead-free package, complying with modern environmental regulations such as RoHS (Restriction of Hazardous Substances). Typical target markets include instrumentation panels, test and measurement equipment, industrial controls, medical devices, consumer appliances, and automotive dashboard displays where a single, clear numeric indicator is needed.

2. Technical Parameters Deep Objective Interpretation

This section provides a detailed, objective analysis of the key electrical and optical parameters specified in the datasheet. Understanding these parameters is crucial for proper circuit design and ensuring optimal display performance.

2.1 Photometric and Optical Characteristics

The primary optical characteristic is the Average Luminous Intensity (Iv). Measured at a forward current (IF) of 1 mA, the typical value is 1400 \u00b5cd (microcandelas), with a minimum specified value of 500 \u00b5cd. This parameter defines the perceived brightness of each illuminated segment. The Luminous Intensity Matching Ratio (IV-m) is specified as a maximum of 2:1. This ratio indicates the maximum allowable variation in brightness between the brightest and dimmest segments within a single device, ensuring a uniform appearance when all segments are lit. The color characteristics are defined by wavelength. The Peak Emission Wavelength (\u03bbp) is typically 588 nm (nanometers) at IF=20mA. The Dominant Wavelength (\u03bbd), which more closely correlates with perceived color, has a range of 584 nm to 594 nm. The Spectral Line Half-Width (\u0394\u03bb) is typically 15 nm, describing the spectral purity of the emitted yellow light.

2.2 Electrical Parameters

The key electrical parameter is the Forward Voltage (VF) per segment. At a forward current of 20 mA, the typical VF is 2.6 Volts, with a minimum of 2.05 Volts. This is the voltage drop across the LED when it is conducting current and emitting light. Designers must ensure the driving circuit can provide this voltage. The Reverse Current (IR) is specified as a maximum of 10 \u00b5A at a reverse voltage (VR) of 5V, indicating the very small leakage current when the LED is reverse-biased. Exceeding the Absolute Maximum Rating for reverse voltage (5V) can damage the device.

2.3 Absolute Maximum Ratings and Thermal Considerations

These ratings define the limits beyond which permanent damage to the device may occur. They are not for normal operation. The Continuous Forward Current per segment is 25 mA at 25\u00b0C. A derating factor of 0.33 mA/\u00b0C is provided, meaning the maximum allowable continuous current decreases as ambient temperature rises above 25\u00b0C. For example, at 85\u00b0C, the maximum current would be approximately 25 mA - (0.33 mA/\u00b0C * 60\u00b0C) = 5.2 mA. The Peak Forward Current is 60 mA but is only permissible under pulsed conditions (1 kHz, 25% duty cycle). The Power Dissipation per segment is 70 mW. The operating and storage temperature range is specified from -35\u00b0C to +85\u00b0C, defining the environmental conditions the device can withstand.

3. Binning System Explanation

The datasheet indicates the product 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 wafer processing, LEDs from the same production batch can have slight differences in key parameters like luminous intensity and forward voltage. To ensure consistency for the end user, manufacturers test each device and sort them into different \"bins\" or categories based on measured performance. The LTS-547AKS is binned specifically for luminous intensity (Iv), meaning customers can select devices from a specific intensity range (bin) to guarantee uniform brightness across all digits in a multi-digit display application. The datasheet provides the minimum (500 \u00b5cd) and typical (1400 \u00b5cd) values, but specific bin codes and their corresponding intensity ranges would typically be detailed in a separate binning document or available upon request.

4. Performance Curve Analysis

While the specific graphs are not detailed in the provided text, typical performance curves for such a device would provide invaluable design insight. These curves graphically represent the relationship between key parameters.

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

This curve shows the non-linear relationship between the current flowing through the LED and the voltage across it. It demonstrates the \"turn-on\" voltage (around 2.0-2.1V for AlInGaP) and how the forward voltage increases slightly with current. This information is critical for designing current-limiting circuits, whether using simple resistors or constant-current drivers.

4.2 Luminous Intensity vs. Forward Current

This plot illustrates how the light output (in \u00b5cd or mcd) increases with the forward current. It is generally linear over a range but may saturate at very high currents. This helps designers choose an operating current that delivers the required brightness without exceeding power dissipation limits or accelerating lumen depreciation.

4.3 Temperature Characteristics

Curves showing the variation of forward voltage and luminous intensity with ambient temperature (Ta) or junction temperature (Tj) are essential. Typically, forward voltage decreases with increasing temperature (negative temperature coefficient), while luminous intensity also decreases as temperature rises. Understanding these trends is vital for applications subject to wide temperature swings to ensure stable performance.

5. Mechanical and Package Information

The LTS-547AKS has a digit height of 0.52 inches (13.2 mm). The package dimensions are provided in a drawing with all measurements in millimeters and a standard tolerance of \u00b10.25 mm unless otherwise noted. This drawing is crucial for PCB (Printed Circuit Board) layout, ensuring the footprint and hole patterns are correctly designed. The device has 10 pins in a dual-in-line package configuration.

5.1 Pin Connection and Internal Circuit

The pinout is as follows: Pin 1: Anode E, Pin 2: Anode D, Pin 3: Common Cathode, Pin 4: Anode C, Pin 5: Anode D.P. (Decimal Point), Pin 6: Anode B, Pin 7: Anode A, Pin 8: Common Cathode, Pin 9: Anode F, Pin 10: Anode G. The device uses a common cathode configuration. This means the cathodes (negative terminals) of all LED segments (A-G and DP) are connected internally and brought out to two pins (3 and 8, which are connected). To illuminate a specific segment, its corresponding anode pin must be driven to a positive voltage (through a current-limiting resistor or driver) while the common cathode pin(s) are connected to ground. The internal circuit diagram would show this common cathode connection for all segments.

6. Soldering and Assembly Guidelines

The datasheet specifies a critical soldering parameter: the maximum allowable solder temperature is 260\u00b0C, and this temperature can only be applied for a maximum of 3 seconds. This measurement is taken at a point 1.6 mm (1/16 inch) below the seating plane of the component on the PCB. This guideline is essential for wave soldering or reflow soldering processes. Exceeding these time/temperature limits can cause thermal damage to the LED chips, the epoxy encapsulant, or the internal wire bonds, leading to immediate failure or reduced long-term reliability. It is recommended to follow standard IPC guidelines for LED assembly. For storage, the specified range is -35\u00b0C to +85\u00b0C in a dry environment to prevent moisture absorption, which can cause \"popcorning\" during reflow soldering.

7. Application Suggestions

7.1 Typical Application Scenarios

The LTS-547AKS is ideal for any device requiring a single, highly legible numeric display. Common applications include: digital multimeters and clamp meters, frequency counters, bench power supplies, process timers and counters, medical monitoring equipment (e.g., single parameter displays), household appliances (microwaves, ovens, coffee makers), automotive aftermarket gauges (voltage, temperature), and industrial control panel indicators.

7.2 Design Considerations

• Current Limiting: LEDs are current-driven devices. A current-limiting resistor must be connected in series with each anode (or a constant-current driver used) to set the forward current to the desired value (e.g., 10-20 mA for full brightness). The resistor value is calculated using R = (Vcc - Vf) / If, where Vcc is the supply voltage, Vf is the LED forward voltage, and If is the desired forward current.
• Multiplexing: For driving multiple digits, a multiplexing technique is often used where segments of the same type across digits are connected together, and each digit's common cathode is turned on sequentially at a high frequency. This saves I/O pins on a microcontroller.
• Viewing Angle: The wide viewing angle allows for flexible mounting, but for optimal readability, consider the primary user's sight line relative to the display surface.
• ESD Protection: While not explicitly stated, AlInGaP LEDs can be sensitive to electrostatic discharge (ESD). Standard ESD handling precautions should be observed during assembly.

8. Technical Comparison

Compared to other single-digit display technologies, the LTS-547AKS (AlInGaP Yellow) offers distinct advantages. Versus older red GaAsP or GaP LEDs, AlInGaP provides significantly higher brightness and efficiency for colors in the yellow-orange-red spectrum. Compared to 7-segment LCDs, it offers superior visibility in low-light conditions, a wider operating temperature range, and does not require a backlight. Versus vacuum fluorescent displays (VFDs), it is more rugged, has a lower operating voltage, and consumes less power, though VFDs may offer a different color (often blue-green) and a very wide viewing angle. The choice of yellow is often selected for its high luminous efficacy and its clear, attention-grabbing appearance, which is different from the common red or green displays.

9. Frequently Asked Questions (Based on Technical Parameters)

Q1: What is the purpose of the two common cathode pins (3 and 8)?
A1: They are internally connected. Having two pins provides mechanical symmetry, better current distribution, and improved heat dissipation from the cathode side of the LED chips. In a PCB layout, both should be connected to ground.

Q2: Can I drive this display directly from a 5V microcontroller pin?
A2: No, not directly. The typical forward voltage is 2.6V, and a microcontroller pin outputting 5V would cause excessive current to flow, destroying the LED segment. You must use a series current-limiting resistor. For a 5V supply and a target current of 20 mA, the resistor value would be approximately (5V - 2.6V) / 0.02A = 120 Ohms. A slightly higher value (e.g., 150 Ohms) is often used for safety and longevity.

Q3: What does \"categorized for luminous intensity\" mean for my design?
A3: It means you can order devices from a specific brightness bin. If you are building a multi-unit product or a multi-digit display, specifying the same bin code for all your displays ensures they will all have very similar brightness, resulting in a uniform and professional appearance. If you mix bins, some digits may appear noticeably brighter or dimmer than others.

Q4: How do I interpret the derating factor for forward current?
A4: The derating factor of 0.33 mA/\u00b0C means that for every degree Celsius the ambient temperature rises above 25\u00b0C, you must reduce the maximum continuous forward current by 0.33 mA. This is necessary to prevent the LED junction temperature from exceeding its safe limit, which would drastically reduce its lifespan. In high-temperature environments, you may need to operate the display at a lower current to maintain reliability.

10. Practical Design Case

Scenario: Designing a simple battery-powered digital voltmeter to display 0-9.9V.
Implementation: Use a microcontroller with an analog-to-digital converter (ADC) to measure voltage. The microcontroller will need at least 8 I/O pins to drive the 7 segments and the decimal point of the LTS-547AKS. A current-limiting resistor (e.g., 180-220 Ohms for a 3.3V-5V system) is required on each anode line. The two common cathode pins are connected to ground. The microcontroller firmware will read the ADC value, convert it to a decimal number, and light up the corresponding segments by setting the appropriate anode pins high. For displaying a tenths place (the \"9\" in 9.9), a second digit would be needed, and multiplexing would be employed to drive both digits from the same 8 segment lines, using separate I/O pins to control the common cathode of each digit.

11. Operating Principle Introduction

The LTS-547AKS operates on the principle of electroluminescence in a semiconductor diode. The core of each segment is a tiny chip made of AlInGaP layers grown on a GaAs substrate. This structure forms a p-n junction. When a forward voltage exceeding the junction's built-in potential (roughly 2.0-2.1V) is applied, electrons from the n-type region and holes from the p-type region are injected across the junction. When these charge carriers recombine in the active region of the semiconductor, energy is released in the form of photons (light). The specific composition of the AlInGaP alloy determines the bandgap energy of the semiconductor, which in turn dictates the wavelength (color) of the emitted light\u2014in this case, yellow (~588 nm). The gray face and white segments act as a diffuser and contrast enhancer, respectively, shaping and directing the light for optimal readability.

12. Technology Trends

The development of display technologies is ongoing. For discrete LED numeric displays like the LTS-547AKS, trends focus on several areas. Increased Efficiency: Ongoing material science research aims to improve the internal quantum efficiency (IQE) and light extraction efficiency of AlInGaP and other compound semiconductors, yielding brighter displays at lower currents, which is critical for portable devices. Miniaturization: While 0.52-inch is a standard size, there is demand for both smaller digits for compact devices and larger, brighter digits for long-distance viewing. Integration: There is a trend towards displays with integrated drivers (I2C, SPI) or even microcontrollers, simplifying the interface for the system designer. Color Options: While yellow is highly efficient, advances in blue InGaN LEDs and phosphor conversion have made full-color RGB displays and white displays more accessible, though often at a different cost/performance point. The core advantages of LEDs\u2014reliability, longevity, and solid-state robustness\u2014ensure they remain a dominant choice for many numeric display applications where these attributes are paramount.