LTS-5703AKF 0.56-inch Yellow-Orange 7-Segment LED Display Datasheet - Digit Height 14.22mm - Forward Voltage 2.6V - Power Dissipation 70mW - English Technical Document

1. Product Overview

The LTS-5703AKF is a high-performance, single-digit, seven-segment LED display module designed for applications requiring clear, bright numeric readouts. It features a 0.56-inch (14.22 mm) digit height, making it suitable for medium-sized panels and instrumentation where readability from a moderate distance is essential. The device utilizes advanced Aluminium Indium Gallium Phosphide (AlInGaP) semiconductor technology on a Gallium Arsenide (GaAs) substrate to produce a distinctive yellow-orange light emission. This material system is known for its high efficiency and excellent brightness. The display has a light gray face with white segments, providing high contrast for optimal character appearance under various lighting conditions.

Its core advantages include low power requirement, high brightness, wide viewing angle, and solid-state reliability. The segments are designed to be continuous and uniform, ensuring a consistent and professional visual output. The device is categorized for luminous intensity and is offered in a lead-free package compliant with RoHS (Restriction of Hazardous Substances) directives, making it suitable for modern electronic designs with environmental considerations.

2. Technical Parameter Deep Dive

2.1 Electrical Characteristics

The electrical parameters define the operating limits and conditions for reliable use. The absolute maximum ratings specify the boundaries that must not be exceeded to prevent permanent damage. The continuous forward current per segment is rated at 25 mA at 25°C, with a linear derating factor of 0.33 mA/°C as the ambient temperature rises. The peak forward current, permissible under pulsed conditions (1/10 duty cycle, 0.1ms pulse width), is 60 mA. The maximum power dissipation per segment is 70 mW. The reverse voltage withstand capability is 5 V. The forward voltage (V_F) per segment typically ranges from 2.05V to 2.6V when driven at a standard test current of 20 mA. The reverse current (I_R) is specified at a maximum of 100 µA when a reverse bias of 5V is applied.

2.2 Optical Characteristics

The optical performance is central to its function. The average luminous intensity (I_V) is a key metric, with a minimum of 800 µcd, a typical value of 1667 µcd, and no maximum specified under a test condition of I_F = 1 mA. This high brightness ensures good visibility. The color characteristics are defined by wavelength: the peak emission wavelength (λ_p) is typically 611 nm, and the dominant wavelength (λ_d) is typically 605 nm, both measured at I_F = 20 mA, placing the output firmly in the yellow-orange spectrum. The spectral line half-width (Δλ) is approximately 17 nm, indicating a relatively pure color emission. Luminous intensity matching between segments (for similar lit areas) has a maximum ratio of 2:1, ensuring uniformity across the digit.

2.3 Thermal and Environmental Ratings

The device is rated for an operating temperature range of -35°C to +85°C, and a storage temperature range of -35°C to +85°C. This wide range makes it suitable for use in various environments, from industrial controls to consumer electronics. For assembly, the solder temperature is specified as 260°C for 3 seconds, measured 1/16 inch (approximately 1.59 mm) below the seating plane, which is a standard reference for wave or reflow soldering processes.

3. Binning System Explanation

The datasheet indicates that the device is "Categorized for Luminous Intensity." This implies a binning or sorting process based on measured light output. In LED manufacturing, bins are created to group components with similar performance characteristics, such as luminous intensity (brightness), forward voltage, and dominant wavelength. By purchasing from a specific bin, designers can ensure consistency in brightness across multiple displays in a product, avoiding noticeable variations between digits or units. While the specific bin codes or ranges are not detailed in this document, designers should consult the manufacturer's detailed binning documentation for production planning to guarantee visual uniformity in their application.

4. Performance Curve Analysis

The datasheet references "Typical Electrical / Optical Characteristic Curves." Although the specific graphs are not provided in the text, such curves are standard in LED documentation and are crucial for design. Typically, they include:

• Relative Luminous Intensity vs. Forward Current (I-V Curve): This graph shows how light output increases with drive current. It is typically non-linear, with efficiency dropping at very high currents due to thermal effects.
• Forward Voltage vs. Forward Current: This shows the diode's IV characteristic, essential for designing the current-limiting circuitry.
• Relative Luminous Intensity vs. Ambient Temperature: This curve demonstrates how light output decreases as the junction temperature rises, highlighting the importance of thermal management in high-brightness or high-duty-cycle applications.
• Spectral Distribution: A plot of relative intensity versus wavelength, showing the shape and purity of the emitted color.

Designers should use these curves to select appropriate drive currents, understand thermal derating, and predict performance under non-standard conditions.

5. Mechanical and Package Information

The device comes in a standard LED display package. The package dimensions drawing (referenced but not detailed in the text) would typically show the overall length, width, and height of the module, the segment window dimensions, and the precise spacing and diameter of the ten pins. Key mechanical notes include: all dimensions are in millimeters, with standard tolerances of ±0.25 mm unless otherwise specified. An additional tolerance of ±0.4 mm is allowed for pin tip shift, which is important for PCB footprint design and automated insertion processes. The pin connection diagram is clearly provided, identifying the function of each of the ten pins for segments A-G, the decimal point (D.P.), and the two common cathode pins.

6. Soldering and Assembly Guidelines

The primary assembly guideline provided is the soldering temperature specification: the device can withstand a temperature of 260°C for 3 seconds at a point 1.59 mm (1/16 inch) below the seating plane. This is a critical parameter for reflow soldering profiles. Designers must ensure their reflow oven profile does not exceed this temperature-time combination at the component leads to avoid damaging the internal wire bonds or the LED chip. Standard handling precautions for static-sensitive devices should be observed. The wide storage temperature range (-35°C to +85°C) allows for flexibility in inventory management.

7. Internal Circuit and Pin Configuration

The internal circuit diagram shows a common cathode configuration. This means all the cathodes (negative terminals) of the LED segments are connected together internally. The LTS-5703AKF has two common cathode pins (pin 3 and pin 8), which are internally connected. This allows for flexibility in PCB layout. The anodes (positive terminals) for each segment (A, B, C, D, E, F, G) and the decimal point (D.P.) are brought out to separate pins. The pinout is as follows: Pin 1: E, Pin 2: D, Pin 3: Common Cathode, Pin 4: C, Pin 5: D.P., Pin 6: B, Pin 7: A, Pin 8: Common Cathode, Pin 9: F, Pin 10: G. To illuminate a segment, a positive voltage (through a current-limiting resistor) must be applied to its respective anode pin, while the common cathode pin(s) must be connected to ground.

8. Application Suggestions

8.1 Typical Application Scenarios

This display is ideal for any device requiring a clear, single-digit numeric readout. Common applications include: test and measurement equipment (multimeters, frequency counters), industrial control panels, medical devices, consumer appliances (microwaves, ovens, coffee makers), automotive dashboard displays (for trip computers, climate control), and point-of-sale terminals.

8.2 Design Considerations

• Current Limiting: Always use a series resistor for each segment anode (or a resistor on the common cathode for multiplexing) to set the forward current. Calculate the resistor value based on the supply voltage (V_CC), the LED forward voltage (V_F ~2.6V max), and the desired current (e.g., 10-20 mA for good brightness). Formula: R = (V_CC - V_F) / I_F.
• Multiplexing: For multi-digit displays, a multiplexing scheme is used where digits are illuminated one at a time rapidly. The LTS-5703AKF's common cathode design is well-suited for this. The peak current rating (60 mA) allows for higher pulsed currents during multiplexing to achieve perceived brightness comparable to a continuously driven segment.
• Viewing Angle: The wide viewing angle ensures readability from various positions, which is crucial for panel-mounted equipment.
• Thermal Management: While the device has a good operating range, ensure adequate ventilation if operating at high ambient temperatures or at high continuous currents to maintain longevity and stable light output.

9. Technical Comparison and Differentiation

The key differentiators of the LTS-5703AKF lie in its material technology and specific performance characteristics. Compared to older technologies like standard Gallium Phosphide (GaP) red or green LEDs, AlInGaP offers significantly higher luminous efficiency, resulting in much brighter displays for the same drive current. Compared to some high-brightness white or blue LEDs based on InGaN, the yellow-orange color has distinct aesthetic and functional applications, often chosen for specific panel color schemes or for its perceived warmth and clarity. The 0.56-inch size fills a niche between smaller (0.3-inch) displays for compact devices and larger (1-inch+) displays for long-distance viewing. Its RoHS compliance is a standard but essential feature for modern global markets.

10. Frequently Asked Questions (FAQ)

Q: What is the purpose of having two common cathode pins?
A: The two pins (3 and 8) are internally connected. This provides layout flexibility on the PCB, allowing the ground connection to be made from either side of the package, which can simplify routing, especially in dense designs or when using single-sided PCBs.

Q: Can I drive this display directly from a 5V microcontroller pin?
A: No. You must always use a current-limiting resistor. A microcontroller pin typically cannot source 20 mA safely, and even if it could, without a resistor, the LED would attempt to draw excessive current, potentially damaging both the LED and the microcontroller. Calculate the appropriate series resistor value.

Q: What does "luminous intensity matching ratio of 2:1" mean?
A> It means that the dimmest segment in a device will be no less than half as bright as the brightest segment (under the same test conditions). This ensures visual uniformity across the digit.

Q: Is this display suitable for outdoor use?
A: The operating temperature range extends to -35°C, which covers many outdoor conditions. However, the datasheet does not specify an Ingress Protection (IP) rating against dust and water. For outdoor use, the display would likely need to be behind a sealed window or within a protected enclosure.

11. Practical Design and Usage Case

Case: Designing a Simple Digital Timer Display. A designer is creating a countdown timer with a single-digit display. They choose the LTS-5703AKF for its clarity and size. They use a microcontroller with 5V logic. For a target segment current of 15 mA, they calculate the current-limiting resistor: R = (5V - 2.4V) / 0.015A ≈ 173 ohms. They select a standard 180-ohm resistor. They connect the two common cathode pins to a ground pin on the microcontroller via an NPN transistor (for switching/multiplexing if more digits are added later). The seven segment anode pins are connected to microcontroller I/O pins, each through its own 180-ohm resistor. The decimal point is not used in this design. The software cycles through displaying numbers 9 down to 0. The high contrast and brightness ensure the number is easily read in a well-lit room.

12. Operating Principle Introduction

The LTS-5703AKF is based on a solid-state semiconductor light-emitting diode (LED). The active material is Aluminium Indium Gallium Phosphide (AlInGaP) grown on a Gallium Arsenide (GaAs) substrate. When a forward voltage exceeding the diode's threshold (approximately 2V) is applied, electrons and holes are injected into the active region from the n-type and p-type semiconductor layers, respectively. These charge carriers recombine, releasing energy in the form of photons (light). The specific composition of the AlInGaP alloy determines the bandgap energy of the semiconductor, which directly dictates the wavelength (color) of the emitted light—in this case, yellow-orange (~605-611 nm). Each segment of the display contains one or more of these tiny LED chips. The common cathode configuration internally connects all the negative sides of these chips, simplifying external drive circuitry.

13. Technology Trends and Context

AlInGaP LED technology represents a mature and highly optimized solution for red, orange, amber, and yellow light emission. It has been the dominant material system for these colors in high-brightness applications for decades due to its superior efficiency and reliability compared to older technologies. Current trends in display technology include the development of even more efficient micro-LEDs and the widespread adoption of organic LEDs (OLEDs) for full-color, flexible displays. However, for monochromatic, segmented numeric displays requiring very high brightness, long lifetime, and stability over a wide temperature range—especially in industrial, automotive, and instrumentation contexts—AlInGaP-based LEDs like the one in this datasheet remain a preferred and cost-effective choice. The move to lead-free (RoHS) packaging, as seen here, is a standard industry-wide evolution driven by environmental regulations.