LTD-5250JD LED Display Datasheet - 0.52-inch Digit Height - Hyper Red Color - 2.6V Forward Voltage - English Technical Document

1. Product Overview

The LTD-5250JD is a dual-digit, seven-segment light-emitting diode (LED) display module. Its primary function is to provide a clear, legible numeric readout for various electronic devices and instrumentation. The core technology utilizes Aluminum Indium Gallium Phosphide (AlInGaP) semiconductor material to produce a hyper red emission. This device features a gray faceplate with white segment markings, enhancing contrast and readability under various lighting conditions. It is categorized based on luminous intensity, ensuring consistency in brightness levels for batch applications.

1.1 Core Advantages and Target Market

The display offers several key advantages that make it suitable for industrial, consumer, and instrumentation applications. Its low power requirement makes it energy-efficient, while the high brightness and excellent contrast ratio ensure visibility from a wide viewing angle. The solid-state construction provides inherent reliability and long operational life compared to other display technologies. The continuous uniform segments contribute to a pleasing and professional character appearance. This combination of features targets applications such as test equipment, point-of-sale terminals, industrial control panels, clock displays, and any device requiring a reliable, bright numeric readout.

2. Technical Specifications Deep Dive

This section provides a detailed, objective analysis of the device's key technical parameters as defined in the datasheet.

2.1 Optical Characteristics

The optical performance is central to the display's function. The primary emission is in the hyper red spectrum.

• Luminous Intensity (I_V): The average luminous intensity per segment is specified with a minimum of 320 µcd, a typical value of 700 µcd, and no stated maximum under a test condition of I_F = 1mA. This parameter is crucial for determining the display's brightness in the final application. The matching ratio between segments is specified as 2:1 maximum, which defines the allowable variation in brightness between different segments of the same digit.
• Wavelength Characteristics: The device features a peak emission wavelength (λ_p) of 650 nm (nanometers) and a dominant wavelength (λ_d) of 639 nm, both measured at I_F = 20mA. The spectral line half-width (Δλ) is 20 nm. These values precisely define the color point of the \"hyper red\" output, which is a deep, saturated red color.

2.2 Electrical Parameters

Understanding the electrical limits and operating points is essential for safe and reliable circuit design.

• Absolute Maximum Ratings: These are stress limits that must not be exceeded under any conditions. Key limits include: Power dissipation per segment (70 mW), peak forward current per segment (90 mA at 1/10 duty cycle, 0.1ms pulse width), and continuous forward current per segment (25 mA at 25°C, derating linearly at 0.33 mA/°C). The maximum reverse voltage per segment is 5V.
• Forward Voltage (V_F): The voltage drop across an illuminated segment is typically 2.6V, with a range from 2.1V to the maximum, when driven at 20mA. This value is necessary for calculating current-limiting resistor values and power supply requirements.
• Reverse Current (I_R): The maximum leakage current when a reverse bias of 5V is applied is 100 µA.

2.3 Thermal and Environmental Specifications

The device's performance is specified within defined environmental limits.

• Operating Temperature Range: The display is rated for continuous operation from -35°C to +85°C ambient temperature (T_a).
• Storage Temperature Range: It can be stored in non-operating conditions from -35°C to +85°C.
• Solder Temperature: For assembly, the maximum allowable soldering temperature is 260°C for a maximum duration of 3 seconds, measured 1.6mm below the seating plane of the component. This is critical for wave or reflow soldering processes.

3. Binning System Explanation

The datasheet indicates the device is \"categorized for luminous intensity.\" This implies a binning or sorting process post-manufacturing.

• Luminous Intensity Binning: LEDs are tested and grouped (binned) based on their measured luminous output at a standard test current (likely 1mA or 20mA). Devices within the same bin will have very similar brightness, ensuring visual uniformity when multiple displays are used in a single product. The 2:1 luminous intensity matching ratio is the performance guarantee within a single device.
• Wavelength Binning: While not explicitly detailed in the provided content, AlInGaP LEDs are often also binned by dominant or peak wavelength to ensure consistent color output. The specified 639 nm dominant wavelength likely represents a target or nominal value for this product.

4. Performance Curve Analysis

The datasheet references \"Typical Electrical/Optical Characteristic Curves.\" While the specific graphs are not provided in the text, standard curves for such devices typically include:

• I-V (Current-Voltage) Curve: This graph shows the relationship between forward current (I_F) and forward voltage (V_F). It is non-linear, with a characteristic \"knee\" voltage (around the typical 2.6V) above which current increases rapidly with small voltage increases. This curve is vital for designing the drive circuitry.
• Luminous Intensity vs. Forward Current: This curve shows how light output increases with drive current. It is generally linear over a wide range but may saturate at very high currents. It helps designers choose an operating current to achieve desired brightness while considering efficiency and heat.
• Luminous Intensity vs. Ambient Temperature: This curve illustrates how light output decreases as the ambient temperature rises. AlInGaP LEDs exhibit less thermal quenching than some other materials, but output still typically declines. This is crucial for applications operating in high-temperature environments.
• Spectral Distribution: A graph showing the relative intensity of light emitted across different wavelengths, centered around the peak wavelength of 650 nm with a defined half-width of 20 nm.

5. Mechanical and Package Information

The physical construction defines how the device integrates into a product.

5.1 Dimensions and Outline Drawing

The package drawing is referenced. The key specification is a 0.52-inch (13.2 mm) digit height. All dimensions are in millimeters with a standard tolerance of ±0.25 mm unless otherwise noted. The exact footprint and overall dimensions would be taken from the referenced drawing for PCB layout.

5.2 Pin Connection and Polarity

The device has an 18-pin configuration and uses a common anode circuit topology. This means the anodes (positive terminals) for all segments of a digit are connected together internally. Each segment cathode (negative terminal) is brought out to a separate pin, and there is a separate common anode pin for each of the two digits (Digit 1 and Digit 2). The pinout table provides a complete map, specifying which pin controls each segment (A-G and decimal point) for each digit. Correct identification of pin 1 is essential for proper orientation.

5.3 Internal Circuit Diagram

The referenced diagram visually represents the common anode structure, showing the two independent common anode nodes (one per digit) and the individual cathodes for the seven segments and decimal point of each digit. This clarifies the electrical architecture for multiplexing or direct drive.

6. Soldering and Assembly Guidelines

Proper handling ensures reliability and prevents damage during manufacturing.

• Reflow Soldering Parameters: Adhere strictly to the maximum rating: 260°C peak temperature for no more than 3 seconds, measured at the specified point below the package. A standard lead-free reflow profile should be used with appropriate ramp-up and cool-down rates to minimize thermal stress.
• Precautions: Avoid mechanical stress on the pins. Ensure the device is stored in a dry, anti-static environment prior to use. Clean the PCB of any flux residues that could affect optical clarity or cause corrosion.
• Storage Conditions: Store within the specified temperature range (-35°C to +85°C) in a low-humidity environment. The original moisture barrier bag is recommended for long-term storage.

7. Application Suggestions

7.1 Typical Application Scenarios

This display is ideal for any application requiring two bright, easy-to-read digits. Common uses include: digital multimeters and test equipment, frequency counters, timer and clock displays, scoreboards, simple control panel readouts (e.g., temperature, speed), point-of-sale terminal displays, and household appliances.

7.2 Design Considerations

• Drive Circuitry: As a common anode device, it is typically driven by connecting the common anode to a positive supply voltage (via a current-limiting resistor or a regulated current source) and sinking current through the individual cathode pins to ground, usually via a transistor or a driver IC. Multiplexing the two digits is straightforward by toggling the two common anode pins.
• Current Limiting: External current-limiting resistors are mandatory for each segment cathode (or for the common anode in a multiplexed setup) to set the operating current. The resistor value is calculated using R = (V_supply - V_F) / I_F. Use the maximum V_F from the datasheet for a conservative design to ensure current does not exceed limits.
• Viewing Angle and Contrast: The wide viewing angle and high contrast make it suitable for panels where the user may not be directly in front of the display. The gray face/white segments enhance readability in both dim and brightly lit environments.
• Thermal Management: While the device has a power dissipation rating, ensuring adequate ventilation in the enclosure is good practice, especially if driven at high currents or in high ambient temperatures, to maintain long-term luminous output and reliability.

8. Technical Comparison and Differentiation

Compared to other seven-segment display technologies, the LTD-5250JD's use of AlInGaP offers specific advantages:

• vs. Standard GaAsP or GaP Red LEDs: AlInGaP technology generally provides higher luminous efficiency (more light output per mA of current), better temperature stability, and a more saturated, deeper red color (hyper red vs. standard red).
• vs. LCD Displays: LEDs are emissive, meaning they produce their own light, making them clearly visible in darkness without a backlight. They also have a much faster response time and a wider operating temperature range. However, they typically consume more power than reflective LCDs.
• vs. VFD (Vacuum Fluorescent Displays): LEDs are solid-state, more rugged, have lower operating voltages, and do not require a filament or high-voltage driver circuits. VFDs can offer a different aesthetic and very wide viewing angles but are generally more complex to drive.

9. Frequently Asked Questions (Based on Technical Parameters)

Q: What is the purpose of the \"luminous intensity matching ratio\" of 2:1?
A: This specification guarantees that within a single display unit, the dimmest segment will be no less than half as bright as the brightest segment. This ensures visual uniformity of the displayed number, preventing some segments from appearing noticeably dimmer than others.

Q: Can I drive this display directly from a 5V microcontroller pin?
A: No, you cannot connect it directly. The microcontroller pin cannot source or sink enough current (typically 20-25mA needed per segment) and would be damaged. You must use external transistors (e.g., NPN transistors on the cathode side or PNP on the anode side) or a dedicated LED driver IC. Furthermore, a current-limiting resistor is always required.

Q: How do I control the two digits independently?
A> The device has separate common anode pins for Digit 1 (pin 14) and Digit 2 (pin 13). To display different numbers on each digit simultaneously, you must multiplex them. This involves rapidly switching (e.g., at 100Hz or faster) which digit's anode is powered while presenting the corresponding segment data on the shared cathode lines. Persistence of vision makes both digits appear to be on continuously.

Q: What does \"Hyper Red\" mean compared to standard red?
A> Hyper Red refers to LEDs with a dominant wavelength typically between 620nm and 645nm, producing a deeper, more orange-tinted red compared to the brighter, more pinkish standard red LEDs which are often around 630nm or below. It is a specific color point within the red spectrum.

10. Design and Usage Case Study

Scenario: Designing a Simple Digital Timer with Two Digits.
The goal is to build a countdown timer displaying minutes from 00 to 99. The microcontroller (e.g., an Arduino or PIC) has limited I/O pins. Using the LTD-5250JD in a multiplexed configuration is efficient. Two NPN transistors (or one dual transistor) would be used to switch the +5V supply to the two common anode pins (pins 13 & 14) under microcontroller control. The eight segment cathodes (7 segments + decimal point, though the DP may not be used) would be connected to the microcontroller via eight current-limiting resistors (calculated for ~15-20mA drive) and possibly through a single 8-channel sink driver IC (like a 74HC595 shift register or a ULN2003 array) to reduce pin count further. The firmware would maintain a counter, convert the tens and units digits to 7-segment patterns, and alternately enable Digit 1 and Digit 2 while outputting the corresponding segment pattern, creating a stable two-digit display.

11. Technology Principle Introduction

The LTD-5250JD is based on Aluminum Indium Gallium Phosphide (AlInGaP) semiconductor technology. This material is a direct bandgap semiconductor grown epitaxially on a Gallium Arsenide (GaAs) substrate, which is non-transparent in this case. When a forward voltage exceeding the material's bandgap energy is applied across the p-n junction, electrons and holes recombine, releasing energy in the form of photons (light). The specific composition of the AlInGaP alloy determines the bandgap energy and thus the wavelength (color) of the emitted light, which is in the hyper red region (~639-650 nm). The gray faceplate acts as a contrast-enhancing filter, and the segments are formed by the patterned LED chips behind the white markings. The common anode configuration is a standard design that simplifies the drive electronics for multi-digit displays.

12. Technology Trends

While seven-segment LED displays remain a robust and cost-effective solution for numeric readouts, broader trends in display technology continue to evolve. There is a general move towards higher integration, with driver electronics increasingly embedded within display modules. The efficiency of AlInGaP and related materials (like InGaN for blue/green) continues to improve, allowing for brighter displays at lower currents or the use of smaller chips. Surface-mount device (SMD) packages are becoming more prevalent for automated assembly, though through-hole displays like this one persist for prototyping, repair, and certain industrial applications due to their robustness and ease of hand-soldering. Furthermore, the rise of organic LED (OLED) and flexible display technologies offers alternative form factors, though for simple, high-brightness, low-cost numeric displays, traditional LED technology like the AlInGaP used here remains highly competitive and reliable.