LTS-546AKF Seven Segment LED Display Datasheet - Digit Height 13.2mm - Yellow Orange Color - English Technical Document

1. Product Overview

The LTS-546AKF is a single-digit, seven-segment alphanumeric display module designed for applications requiring clear, bright numeric readouts. Its primary function is to visually represent digits (0-9) and some letters using individually controlled LED segments. The core technology utilizes AlInGaP (Aluminum Indium Gallium Phosphide) semiconductor material to produce a distinct yellow-orange light emission. This device is characterized by a 0.52-inch (13.2 mm) digit height, offering a balance between readability and compact size. It features a gray faceplate with white segment markings, which enhances contrast and legibility under various lighting conditions. The display employs a common anode configuration, simplifying the driving circuitry in many microcontroller-based systems.

1.1 Core Advantages and Target Market

The key advantages of this display stem from its AlInGaP LED technology and design. It offers high brightness and excellent contrast, ensuring visibility even in well-lit environments. The wide viewing angle allows the displayed information to be read from various positions. Furthermore, it boasts solid-state reliability with a long operational lifespan and low power consumption compared to older display technologies like incandescent or vacuum fluorescent displays. The device is categorized for luminous intensity and is offered in a lead-free package compliant with RoHS directives. Its primary target markets include industrial control panels, test and measurement equipment, consumer appliances, automotive dashboards (for secondary displays), and any embedded system requiring a reliable, low-maintenance numeric indicator.

2. In-Depth Technical Parameter Analysis

This section provides a detailed, objective interpretation of the key electrical and optical parameters listed in the datasheet, explaining their significance for design engineers.

2.1 Photometric and Optical Characteristics

The optical performance is central to the display's functionality. The Average Luminous Intensity (Iv) is specified with a typical value of 1400 µcd at a forward current (IF) of 1mA. This parameter, measured using a filter approximating the CIE photopic eye-response curve, indicates the perceived brightness. The wide range (Min: 500, Max: unspecified) suggests a binning process for intensity. The Peak Emission Wavelength (λp) is 611 nm, and the Dominant Wavelength (λd) is 605 nm at IF=20mA. These values define the yellow-orange color point. The Spectral Line Half-Width (Δλ) of 17 nm indicates the spectral purity of the emitted light; a narrower width would mean a more saturated color. The Luminous Intensity Matching Ratio of 2:1 (max) for similar light areas is crucial for uniform appearance across all segments of a digit, ensuring no one segment appears noticeably dimmer or brighter than its neighbors.

2.2 Electrical and Thermal Parameters

The electrical specifications define the operating limits and conditions. The Forward Voltage per Segment (VF) has a typical value of 2.6V at IF=20mA. Designers must ensure the driving circuit can provide this voltage. The Absolute Maximum Ratings set hard limits: a maximum power dissipation of 70mW per segment and a peak forward current of 60mA (at 1kHz, 10% duty cycle). The continuous forward current per segment is derated from 25mA at 25°C by 0.33 mA/°C, meaning the safe operating current decreases as ambient temperature rises to prevent thermal damage. The Operating and Storage Temperature Range is -35°C to +85°C, defining the environmental robustness of the device. The Reverse Current (IR) is specified as a maximum of 100 µA at VR=5V, but the datasheet explicitly notes that reverse voltage operation is not continuous.

3. Binning System Explanation

While the provided datasheet excerpt does not detail a formal multi-parameter binning system common in white LEDs, it implies categorization based on key performance metrics. The primary binning appears to be for Luminous Intensity, as the device is "Categorized for Luminous Intensity." This means units are sorted and sold based on their measured light output at a standard test current (likely 1mA or 20mA), ensuring consistency within a purchased batch. Although not explicitly stated for this model, AlInGaP LEDs may also be binned for Forward Voltage (VF) to simplify current-limiting resistor design in parallel drive configurations and for precise Dominant Wavelength (λd) to guarantee a consistent color appearance across all digits in a multi-digit display. Designers should consult the manufacturer for specific binning codes and available ranges.

4. Performance Curve Analysis

The datasheet references "Typical Electrical / Optical Characteristic Curves." Although the specific graphs are not provided in the text, we can infer their standard content and utility. A typical Relative Luminous Intensity vs. Forward Current (IV-IF) curve would show how light output increases with current, usually in a sub-linear fashion, helping to optimize the drive current for desired brightness versus efficiency. A Forward Voltage vs. Forward Current (VF-IF) curve is essential for designing the correct series resistor or constant-current driver. The Relative Luminous Intensity vs. Ambient Temperature curve would illustrate the thermal derating of light output, which is critical for applications operating in high-temperature environments. Finally, a Spectral Power Distribution graph would visually represent the peak wavelength and spectral half-width. These curves are vital tools for predicting performance under non-standard conditions.

5. Mechanical and Package Information

The mechanical drawing defines the physical form factor. The display has a digit height of 13.2mm (0.52 inches). The package dimensions are provided in millimeters with a standard tolerance of ±0.25mm. The device features 10 pins on a 0.1-inch (2.54mm) pitch, a common standard for through-hole components. The drawing would typically show the overall length, width, and height of the package, the seating plane, and the recommended PCB keep-out area. Clear polarity identification is provided through the pin connection table and the internal circuit diagram, which shows the common anode configuration. The "gray face and white segments" description confirms the aesthetic design of the front panel.

5.1 Pin Connection and Internal Circuit

The pinout is clearly defined: Pins 3 and 8 are the Common Anodes. The cathodes for segments E, D, C, Decimal Point (D.P.), B, A, F, and G are connected to pins 1, 2, 4, 5, 6, 7, 9, and 10 respectively. The internal circuit diagram confirms a common anode structure, where all the anodes of the LED segments are connected internally to the two common anode pins. To illuminate a segment, its corresponding cathode pin must be driven low (connected to ground or a current sink) while a positive voltage is applied to the common anode pin(s). This configuration is advantageous when using microcontroller ports configured as open-drain or when using low-side driver transistors.

6. Soldering and Assembly Guidelines

The datasheet specifies soldering conditions: "1/16 inch below seating plane for 3 seconds at 260°C." This is a critical parameter for wave soldering processes. It indicates that the leads should be immersed in the solder wave to a depth of approximately 1.6mm (1/16") below the plastic body of the display for no more than 3 seconds, with the solder pot temperature at 260°C. Exceeding these limits can damage the internal wire bonds or the plastic package. For manual soldering, a controlled-temperature iron should be used with minimal contact time. For reflow soldering, a standard lead-free profile with a peak temperature around 260°C would be applicable, but the component's specific thermal mass must be considered. The storage temperature range (-35°C to +85°C) should also be observed before assembly to prevent moisture absorption.

7. Packaging and Ordering Information

The primary ordering code is LTS-546AKF. The "AKF" suffix likely encodes specific attributes like color (Yellow-Orange), digit height, and package type. The datasheet header mentions it is a "Lead-Free Package (according to RoHS)." Standard packaging for such through-hole components is typically in anti-static tubes or trays, and then placed in larger boxes or reels for bulk shipment. The quantity per tube or reel is a standard value (e.g., 50 or 100 pieces) but would be confirmed with the distributor or manufacturer. Labels on the packaging would include the part number, quantity, date code, and possibly the luminous intensity bin code.

8. Application Recommendations

8.1 Typical Application Scenarios

This display is ideal for any application requiring a single, highly readable digit. Common uses include: panel meters for voltage, current, or temperature; digital clocks and timers; scoreboards; production counters; setting dials on industrial machinery; and status indicators on consumer electronics (e.g., channel number on an older radio). Its wide temperature range makes it suitable for both indoor and some protected outdoor environments.

8.2 Design Considerations and Circuitry

When integrating the LTS-546AKF, several factors must be considered. Current Limiting: A series resistor must be used for each segment or for the common anode to limit the forward current to a safe value (e.g., 10-20mA for a balance of brightness and longevity). The resistor value is calculated using R = (Vcc - VF) / IF. Drive Method: It can be driven directly by microcontroller GPIO pins if they can sink sufficient current (check the MCU's port sink capability). For higher currents or multiplexing multiple digits, dedicated driver ICs (e.g., 74HC595 shift registers with current-limiting, or dedicated LED driver chips like the MAX7219) are recommended. Multiplexing: While this is a single-digit part, the principle applies if using multiple units. Multiplexing saves I/O pins by lighting one digit at a time rapidly. The common anode design is well-suited for this, where anodes are switched by transistors and cathodes are driven by a persistent pattern.

9. Technical Comparison and Differentiation

Compared to other seven-segment technologies, AlInGaP LEDs offer distinct advantages. Versus older Red GaAsP or GaP LEDs, AlInGaP provides significantly higher efficiency and brightness, resulting in better visibility. Compared to Blue/White GaN-based LEDs with filters to achieve other colors, AlInGaP has a narrower spectrum, leading to higher color purity and often higher efficacy for its target color (yellow-orange). Versus LCD displays, this LED display is emissive, meaning it generates its own light and is therefore easily visible in darkness without a backlight, and has a much wider viewing angle and faster response time. Its main trade-off is higher power consumption per segment compared to an LCD.

10. Frequently Asked Questions (Based on Technical Parameters)

Q: What resistor value should I use to drive a segment at 20mA with a 5V supply?
A: Using the typical VF of 2.6V: R = (5V - 2.6V) / 0.020A = 120 Ohms. A standard 120Ω resistor would be appropriate.

Q: Can I connect the two common anode pins together?
A: Yes, internally they are connected. Connecting both to the drive circuit can help distribute current and improve reliability.

Q: The max continuous current is 25mA at 25°C. What is it at 70°C?
A: Derating is 0.33 mA/°C. Temperature rise is 70 - 25 = 45°C. Current reduction = 45 * 0.33mA ≈ 14.85mA. Max current ≈ 25mA - 14.85mA = 10.15mA. You should operate well below this at high temperatures.

Q: Why is the reverse current test condition (VR=5V) specified if I cannot operate it in reverse?
A: This is a quality and leakage test parameter. A high reverse current could indicate a damaged junction. It ensures device integrity, not a functional operating mode.

11. Practical Design and Usage Example

Consider designing a simple digital thermometer display using a microcontroller. The temperature sensor (e.g., a thermistor or digital sensor like DS18B20) provides a value to the MCU. The MCU converts this to a digit (0-9) and activates the corresponding segments of the LTS-546AKF via its GPIO ports. A current-limiting resistor is placed in series with the common anode connection. The MCU code would contain a lookup table that maps the digit value (0-9) to a 7-bit pattern controlling the cathode pins (A-G). The decimal point (pin 5) could be used to indicate tenths of a degree if needed. This showcases a straightforward, reliable display solution for embedded systems.

12. Operating Principle Introduction

The seven-segment display is an assembly of seven light-emitting diodes (LEDs) arranged in a figure-eight pattern. Each LED forms one segment (labeled A through G). By selectively turning on specific combinations of these segments, the patterns for numerals 0-9 and some letters can be formed. The LTS-546AKF uses AlInGaP semiconductor material. When a forward voltage exceeding the diode's junction potential (VF) is applied, electrons and holes recombine in the active region, releasing energy in the form of photons. The specific bandgap energy of the AlInGaP alloy determines the wavelength of the emitted light, which in this case is in the yellow-orange range (~605-611 nm). The common anode configuration means all the LED anodes are connected together internally.

13. Technology Trends and Context

While discrete seven-segment LED displays remain relevant for specific applications, the broader trend in display technology is towards integration and miniaturization. Surface-mount device (SMD) LED packages and integrated multi-digit modules with built-in controllers are becoming more common, saving board space and assembly time. Furthermore, for new designs requiring more complex information (text, graphics), small OLED or TFT LCD modules are often chosen. However, the classic seven-segment LED retains key advantages for simple numeric readouts: extreme simplicity, robustness, high brightness, low cost for single digits, and ease of interfacing. The move to AlInGaP from older materials like GaAsP represents an ongoing trend towards higher efficiency and more reliable solid-state light sources across all LED applications.