LTS-547AJD 7-Segment LED Display Datasheet - Digit Height 13.2mm - Forward Voltage 2.6V - Hyper Red 650nm - English Technical Document

1. Product Overview

The LTS-547AJD is a single-digit, 7-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 by selectively illuminating its seven individual LED segments. The device is constructed using advanced Aluminium Indium Gallium Phosphide (AlInGaP) semiconductor material for its light-emitting chips, which are mounted on a non-transparent Gallium Arsenide (GaAs) substrate. This combination results in the characteristic \"Hyper Red\" emission. The display features a gray-colored faceplate with white segment markings, enhancing contrast and readability when the segments are illuminated.

1.1 Core Advantages and Target Market

The display offers several key benefits that make it suitable for a wide range of industrial and consumer applications. Its high luminous intensity and excellent contrast ratio ensure legibility even in brightly lit environments. The low power requirement per segment makes it energy-efficient, which is crucial for battery-powered devices. The solid-state construction provides high reliability and long operational life with no moving parts. The continuous, uniform segments contribute to a pleasing and professional character appearance. This combination of features makes the LTS-547AJD ideal for use in instrumentation panels, test equipment, point-of-sale systems, industrial controllers, medical devices, and consumer appliances where reliable and clear numeric indication is required.

2. In-Depth Technical Parameter Analysis

The performance of the LTS-547AJD is defined by a comprehensive set of electrical and optical parameters measured under standard conditions (Ta=25°C). Understanding these parameters is critical for proper circuit design and ensuring optimal display performance.

2.1 Absolute Maximum Ratings

These ratings define the stress limits beyond which permanent damage to the device may occur. They are not intended for normal operation.

• Power Dissipation per Segment: 70 mW. This is the maximum power that can be safely dissipated as heat by a single LED segment.
• Peak Forward Current per Segment: 90 mA. This is the maximum instantaneous current allowed, typically under pulsed conditions (1/10 duty cycle, 0.1ms pulse width).
• Continuous Forward Current per Segment: 25 mA. This is the maximum DC current recommended for continuous operation. A linear derating factor of 0.33 mA/°C applies above 25°C ambient temperature.
• Reverse Voltage per Segment: 5 V. Exceeding this voltage in reverse bias can damage the LED junction.
• Operating & Storage Temperature Range: -35°C to +85°C. The device is rated for reliable operation within this ambient temperature range.
• Solder Temperature: 260°C for 3 seconds at 1/16 inch (approx. 1.6mm) below the seating plane. This defines the reflow soldering profile constraint.

2.2 Electrical & Optical Characteristics

These are the typical performance parameters under specified test conditions.

• Average Luminous Intensity (I_V): 320 μcd (Min), 700 μcd (Typ) at I_F=1mA. This quantifies the perceived brightness of the lit segment.
• Peak Emission Wavelength (λ_p): 650 nm (Typ) at I_F=20mA. This is the wavelength at which the optical output power is greatest.
• Spectral Line Half-Width (Δλ): 20 nm (Typ) at I_F=20mA. This indicates the spectral purity or bandwidth of the emitted light.
• Dominant Wavelength (λ_d): 639 nm (Typ) at I_F=20mA. This is the single wavelength perceived by the human eye, defining the color.
• Forward Voltage per Segment (V_F): 2.1V (Min), 2.6V (Typ) at I_F=20mA. This is the voltage drop across the LED when conducting the specified current.
• Reverse Current per Segment (I_R): 10 μA (Max) at V_R=5V. This is the small leakage current when the LED is reverse-biased.
• Luminous Intensity Matching Ratio (I_V-m): 2:1 (Typ) at I_F=1mA. This specifies the maximum allowable brightness variation between different segments of the same digit to ensure uniform appearance.

3. Binning System Explanation

The LTS-547AJD is categorized for luminous intensity. This means units are tested and sorted (\"binned\") based on their measured brightness at a standard test current (typically 1mA or 20mA). This binning process ensures consistency within a production batch. Designers can specify a particular intensity bin if their application requires tight brightness tolerances. The 2:1 intensity matching ratio is a related parameter that guarantees visual uniformity within a single device, regardless of its absolute intensity bin.

4. Performance Curve Analysis

While the datasheet provides a reference to typical characteristic curves, their general behavior can be inferred from the technology. For AlInGaP LEDs like those used in the LTS-547AJD, key relationships include:

• Current vs. Luminous Intensity (I-V Curve): Luminous intensity increases approximately linearly with forward current in the normal operating range (e.g., up to 20-30mA). Beyond this, efficiency may drop due to heating.
• Forward Voltage vs. Temperature: The forward voltage (V_F) has a negative temperature coefficient, meaning it decreases slightly as the junction temperature increases.
• Luminous Intensity vs. Temperature: The light output of AlInGaP LEDs generally decreases as junction temperature rises. This is an important consideration for high-brightness or high-ambient-temperature applications.
• Spectral Distribution: The emission spectrum is centered around the dominant/peak wavelength (639-650 nm). The half-width of 20 nm indicates a relatively narrow, pure red color emission compared to some other LED technologies.

5. Mechanical and Package Information

The LTS-547AJD comes in a standard 10-pin, single-digit DIP (Dual In-line Package) format. The package dimensions are provided in the datasheet with all measurements in millimeters and standard tolerances of ±0.25 mm unless otherwise specified. The pinout is clearly defined for the common cathode configuration. Pin 3 and Pin 8 are both connected to the common cathode, providing two connection points for flexibility in PCB layout. The other pins (1, 2, 4, 5, 6, 7, 9, 10) are the anodes for segments E, D, C, Decimal Point, B, A, F, and G respectively. An internal circuit diagram shows that all LED segments share the common cathode connection.

6. Soldering and Assembly Guidelines

The absolute maximum rating specifies a critical soldering parameter: the package body temperature must not exceed 260°C for more than 3 seconds during reflow soldering, measured at a point 1.6mm below the seating plane. This guideline is essential to prevent thermal damage to the LED chips, the epoxy encapsulant, and the internal wire bonds. Standard lead-free (SnAgCu) reflow profiles should be evaluated to ensure compliance with this limit. For manual soldering, a temperature-controlled iron should be used, and contact time with the leads should be minimized. Prior to soldering, the devices should be stored in conditions within the specified storage temperature range (-35°C to +85°C) and in low-humidity environments to avoid moisture absorption, which can cause \"popcorning\" during reflow.

7. Application Recommendations

7.1 Typical Application Circuits

As a common-cathode display, the LTS-547AJD is typically driven by connecting the common cathode pin(s) to ground (or a switched low-side driver) and using current-limiting resistors in series with each segment anode. The resistors are then connected to a positive voltage supply via microcontroller I/O pins or dedicated display driver ICs. The resistor value (R) is calculated using Ohm's Law: R = (V_supply - V_F) / I_F, where V_F is the forward voltage of the LED (use 2.6V for design margin) and I_F is the desired operating current (e.g., 10-20 mA for good brightness). For multiplexing multiple digits, the common cathodes of each digit are switched sequentially at a high frequency while the corresponding segment data is presented.

7.2 Design Considerations

• Current Limiting: Always use series resistors or constant-current drivers. Never connect an LED directly to a voltage source.
• Heat Management: While power dissipation is low per segment, ensure adequate ventilation in enclosed spaces, especially when driving multiple segments or multiple displays. Adhere to the current derating above 25°C ambient.
• Viewing Angle: The wide viewing angle is beneficial but consider the primary viewing direction when mounting the display.
• ESD Protection: Although not explicitly stated in this datasheet, standard ESD handling precautions for semiconductor devices should be observed during assembly.

8. Technical Comparison and Differentiation

The LTS-547AJD's use of AlInGaP (Aluminium Indium Gallium Phosphide) technology is a key differentiator. Compared to older technologies like standard GaAsP (Gallium Arsenide Phosphide) red LEDs, AlInGaP offers significantly higher luminous efficiency, resulting in greater brightness for the same drive current. It also provides better temperature stability and color purity (narrower spectral width). The \"Hyper Red\" emission, with its dominant wavelength of ~639 nm, is often perceived as a deeper, more saturated red compared to the orange-red hue of some standard red LEDs. The gray face/white segment design further enhances contrast compared to displays with diffused or tinted faces.

9. Frequently Asked Questions (Based on Technical Parameters)

Q: What is the purpose of having two common cathode pins (Pin 3 and Pin 8)?

A: This provides layout flexibility on the PCB. Both pins are internally connected. The designer can use one or both, depending on routing convenience. Using both can also help reduce the current density in a single PCB trace if driving all segments at high current.

Q: Can I drive this display at 5V?

A: Yes, but you must use a current-limiting resistor. For example, to achieve a typical I_F of 20mA with a 5V supply and a V_F of 2.6V, the resistor value would be R = (5V - 2.6V) / 0.02A = 120 Ohms. A standard 120Ω or 150Ω resistor would be suitable.

Q: What does \"categorized for luminous intensity\" mean for my design?

A: It means the displays are tested and sorted by brightness. If your application does not require precise brightness matching between different units, you can use displays from any intensity bin. If consistency is critical (e.g., in a multi-digit instrument), you should specify that all displays come from the same bin or a tight bin range.

Q: How do I calculate the total power consumption?

A: For a single digit with all 7 segments lit (plus decimal point = 8 segments), each at I_F=20mA and V_F=2.6V, the power per segment is P_seg = V_F * I_F = 2.6V * 0.02A = 52 mW. Total power P_total = 8 * 52 mW = 416 mW. Ensure your power supply and drivers can handle this.

10. Practical Use Case Example

Scenario: Designing a simple digital voltmeter readout. A microcontroller's analog-to-digital converter (ADC) measures a voltage. The digital value is processed and needs to be displayed on a 3-digit readout. Three LTS-547AJD displays would be used. The design would employ multiplexing: the common cathodes of the three digits are connected to three separate low-side driver transistors (e.g., NPN BJTs or N-channel MOSFETs) controlled by the microcontroller. The eight segment/anode lines (A-G + DP) from all three displays are connected in parallel. The microcontroller rapidly cycles through each digit, turning on its cathode driver while outputting the segment pattern for that specific digit on the common anode lines. A refresh rate of 100Hz or higher prevents visible flicker. Current-limiting resistors are placed on each of the eight common anode lines. This approach minimizes the number of required microcontroller I/O pins compared to directly driving each segment of each digit.

11. Technology Principle Introduction

The LTS-547AJD is based on Light Emitting Diode (LED) technology. An LED is a semiconductor p-n junction diode. When forward-biased (positive voltage applied to the p-side relative to the n-side), electrons from the n-region and holes from the p-region are injected into the junction region. When these charge carriers recombine, they release energy. In standard silicon diodes, this energy is released primarily as heat. In direct bandgap semiconductor materials like AlInGaP, a significant portion of this recombination energy is released as photons (light). The specific wavelength (color) of the emitted light is determined by the bandgap energy of the semiconductor material. AlInGaP alloys allow engineers to tune this bandgap to produce light in the red, orange, and yellow regions of the spectrum. The \"Hyper Red\" color is achieved with a specific composition yielding a bandgap corresponding to light around 650 nm.

12. Technology Trends and Context

AlInGaP technology represents a mature and highly optimized solution for high-efficiency red, orange, and yellow LEDs. It has been the dominant material system for these colors in indicator and display applications for decades due to its superior efficiency and brightness compared to earlier technologies. Current trends in display technology for consumer electronics are heavily focused on full-color, high-resolution micro-LED and mini-LED arrays for screens. However, for standalone numeric and alphanumeric displays in industrial, instrumentation, and appliance contexts, discrete 7-segment LEDs like the LTS-547AJD remain highly relevant due to their simplicity, robustness, low cost, excellent readability, and ease of interface. Ongoing developments in this segment focus on further increasing efficiency (lumens per watt), improving high-temperature performance, and offering even wider viewing angles, ensuring their continued use in a vast array of embedded systems.