LTD-5223AJF LED Display Datasheet - 0.56-inch Digit Height - AlInGaP Yellow Orange - 2.6V Forward Voltage - English Technical Document

1. Product Overview

The LTD-5223AJF is a high-performance, seven-segment alphanumeric display module designed for applications requiring clear, bright numeric readouts with low power consumption. Its primary function is to provide a visual numeric output in electronic devices. The core technology utilizes Aluminium Indium Gallium Phosphide (AlInGaP) semiconductor material to produce a distinct yellow-orange light emission. This material system is known for its high efficiency and excellent visibility. The display features a light gray face and white segment color, offering high contrast for optimal legibility under various lighting conditions.

The device is categorized as a common cathode type with a right-hand decimal point configuration. It is engineered for solid-state reliability, ensuring long operational life and consistent performance. The target market includes industrial control panels, test and measurement equipment, consumer appliances, and any embedded system where a compact, reliable, and energy-efficient numeric display is required.

2. In-Depth Technical Parameter Analysis

2.1 Optical Characteristics

The optical performance is central to the display's functionality. The key parameters, measured at an ambient temperature (TA) of 25\u00b0C, are as follows:

• Average Luminous Intensity (I_V): Ranges from a minimum of 320 \u00b5cd to a typical value of 700 \u00b5cd when driven at a forward current (I_F) of 1mA per segment. This high brightness level ensures good visibility.
• Peak Emission Wavelength (\u03bb_p): Typically 611 nanometers (nm). This defines the specific point of highest spectral power output in the yellow-orange region of the visible spectrum.
• Spectral Line Half-Width (\u0394\u03bb): Approximately 17 nm. This parameter indicates the spectral purity or bandwidth of the emitted light; a narrower width suggests a more saturated, pure color.
• Dominant Wavelength (\u03bb_d): Typically 605 nm. This is the single-wavelength perception of the color by the human eye, closely matching the perceived yellow-orange hue.
• Luminous Intensity Matching Ratio (I_V-m): Maximum 2:1. This specifies the allowable variation in brightness between different segments of the same digit when driven under identical conditions (I_F=1mA), ensuring uniform appearance.

All luminous intensity measurements are performed using a sensor and filter combination calibrated to approximate the CIE photopic eye-response curve, ensuring data relevance to human vision.

2.2 Electrical Characteristics

The electrical parameters define the operating conditions and limits for the device:

• Forward Voltage per Segment (V_F): Typically 2.6V, with a maximum of 2.6V at I_F=20mA. This is the voltage drop across an illuminated segment.
• Reverse Current per Segment (I_R): Maximum 100 \u00b5A when a reverse voltage (V_R) of 5V is applied. This indicates the level of leakage current when the LED is reverse-biased.

2.3 Absolute Maximum Ratings

These are stress limits that must not be exceeded under any circumstances to prevent permanent damage:

• Power Dissipation per Segment: 70 mW.
• Peak Forward Current per Segment: 90 mA (at 1/10 duty cycle, 0.1ms pulse width).
• Continuous Forward Current per Segment: 25 mA. This rating derates linearly from 25\u00b0C at a rate of 0.33 mA/\u00b0C.
• Reverse Voltage per Segment: 5 V.
• Operating & Storage Temperature Range: -35\u00b0C to +85\u00b0C.
• Solder Temperature: 260\u00b0C for 3 seconds, measured 1/16 inch (approx. 1.6mm) below the seating plane.

3. Binning System Explanation

The datasheet indicates the device is "Categorized for Luminous Intensity." This implies a binning or sorting process based on measured optical output. While specific bin code details are not provided in this excerpt, typical categorization for such displays involves grouping units based on their measured luminous intensity at a standard test current (e.g., 1mA or 20mA). This ensures designers receive displays with consistent brightness levels for a uniform product appearance. Purchasers should consult the manufacturer's full binning specifications for detailed code definitions related to intensity and potentially forward voltage (V_f) to ensure electrical compatibility in their design.

4. Performance Curve Analysis

The datasheet references "Typical Electrical / Optical Characteristic Curves." These graphical representations are crucial for understanding device behavior beyond single-point specifications. Although the specific curves are not displayed in the provided text, they typically include:

• I-V (Current-Voltage) Curve: Shows the relationship between forward current (I_F) and forward voltage (V_F). This is essential for designing the current-limiting circuitry.
• Luminous Intensity vs. Forward Current: Illustrates how light output increases with drive current, helping to optimize the trade-off between brightness and power consumption.
• Luminous Intensity vs. Ambient Temperature: Demonstrates how brightness decreases as the junction temperature rises, which is critical for applications operating in elevated temperature environments.
• Spectral Distribution: A plot of relative intensity versus wavelength, showing the peak (\u03bb_p) and shape of the emitted light spectrum.

Designers must refer to these curves to predict performance under non-standard conditions and to ensure reliable operation across the specified temperature range.

5. Mechanical and Package Information

5.1 Physical Dimensions

The device has a digit height of 0.56 inches (14.22 mm). The package dimensions drawing (referenced but not shown) provides detailed mechanical outlines, including overall length, width, height, segment dimensions, and lead (pin) spacing. All dimensions are specified in millimeters with a standard tolerance of \u00b10.25mm unless otherwise noted. This information is vital for PCB footprint design and ensuring proper fit within the end product's enclosure.

5.2 Pin Connection and Polarity Identification

The LTD-5223AJF is a two-digit, common cathode display with 18 pins. The pinout is as follows:

• Common Cathode (CC): Pins 13 and 14 are the common cathode terminals for Digit 2 and Digit 1, respectively. In a common cathode configuration, all LED segment cathodes for a given digit are connected internally to this single pin. To illuminate a segment, its corresponding anode pin must be driven high (positive voltage through a current-limiting resistor) while its digit's common cathode is pulled low (ground).
• Segment Anodes: Pins 1-12 and 15-18 are the anode connections for the individual segments (A-G and DP) of both digits. The mapping is clearly defined in the pin connection table (e.g., Pin 1: Anode E for Digit 1).
• Right-Hand Decimal Point: The decimal point anodes are specified for each digit (Pins 4 and 9), confirming its position on the right side of the digit.

The internal circuit diagram (referenced) visually confirms this common cathode architecture and the interconnection of segments within each digit.

6. Soldering and Assembly Guidelines

The absolute maximum ratings specify a critical soldering parameter: the leads can be subjected to a temperature of 260\u00b0C for a maximum of 3 seconds, measured at a point 1/16 inch (1.6mm) below the seating plane (where the package body meets the PCB). This is a standard reflow soldering profile constraint. To ensure reliability:

• Adhere strictly to this time-temperature profile during reflow soldering processes.
• Avoid hand soldering directly to the package body; apply heat only to the leads.
• Allow the device to cool naturally after soldering; avoid thermal shock.
• Follow standard ESD (Electrostatic Discharge) precautions during handling and assembly.
• Store devices within the specified temperature range (-35\u00b0C to +85\u00b0C) in a dry environment prior to use.

7. Application Recommendations

7.1 Typical Application Circuits

For common cathode displays like the LTD-5223AJF, two primary driving methods are used:

1. Static Drive: Each segment anode has a dedicated current-limiting resistor and driver pin. The common cathodes are permanently connected to ground. This method is simple but requires many I/O pins (7 segments + DP per digit).
2. Multiplexed (Dynamic) Drive: This is the most common method for multi-digit displays. All segment anodes for the same segment position across digits are connected together. The common cathode of each digit is controlled independently by a transistor or driver IC. The microcontroller rapidly cycles through turning on one digit's cathode at a time while presenting the segment data for that digit on the common anode lines. This significantly reduces the required I/O pins and is highly efficient. The high brightness and good response time of AlInGaP LEDs make them well-suited for multiplexing.

7.2 Design Considerations

• Current Limiting: Always use a series resistor for each segment anode (or common anode line in multiplexing) to limit the forward current to a safe value, typically between 1mA and 20mA depending on the desired brightness and power budget. Calculate the resistor value using R = (V_supply - V_F) / I_F.
• Low-Current Operation: The datasheet highlights excellent performance at currents as low as 1mA per segment. This is a key advantage for battery-powered or energy-sensitive applications.
• Viewing Angle: The wide viewing angle ensures readability from various positions, which is important for panel-mounted equipment.
• Heat Management: While power dissipation is low, ensure the operating ambient temperature does not exceed 85\u00b0C. In enclosed spaces or high-temperature environments, consider ventilation.

8. Technical Comparison and Differentiation

The LTD-5223AJF's primary differentiators are its material technology and low-current optimization:

• AlInGaP vs. Traditional Materials: Compared to older GaAsP or GaP LED technologies, AlInGaP offers significantly higher luminous efficiency, resulting in greater brightness for the same drive current or equivalent brightness at lower power. It also provides superior color saturation and stability over temperature and lifetime.
• Low-Current Design: Many displays are characterized at higher currents (e.g., 20mA). The LTD-5223AJF is explicitly tested and selected for excellent characteristics at 1mA, making it a standout choice for ultra-low-power designs where every milliamp counts.
• Uniformity: Features like "Continuous Uniform Segments" and a tight luminous intensity matching ratio (2:1) ensure a professional, consistent appearance across all digits and segments, which is not always guaranteed in lower-cost displays.

9. Frequently Asked Questions (Based on Technical Parameters)

Q: What is the minimum current needed to see the segments illuminate?
A: While the device is tested down to 1mA, segments may be visible at even lower currents, though brightness will be very dim. For reliable operation, design for the specified 1mA minimum.

Q: Can I drive this display with a 3.3V or 5V microcontroller directly?
A: Yes, but you must always use a current-limiting resistor. With a typical V_F of 2.6V, a 5V supply would require a resistor value of approximately (5V - 2.6V) / 0.020A = 120\u03a9 for 20mA drive. For 3.3V logic, the headroom is smaller: (3.3V - 2.6V) / 0.020A = 35\u03a9. Always verify the actual forward current.

Q: What does "Common Cathode" mean for my circuit design?
A> It means you sink current to ground to turn on a digit. In practice, you connect the common cathode pin to a microcontroller I/O pin (set as output low) or to the collector of an NPN transistor whose emitter is grounded. The microcontroller then switches the transistor on to enable the digit.

Q: How do I achieve uniform brightness when multiplexing?
A> In multiplexed drive, the instantaneous current per segment is higher than the desired average current because each digit is only on for a fraction of the time (duty cycle). For example, to achieve an average of 5mA per segment in a 2-digit multiplex with equal duty cycle, you would drive each segment with approximately 10mA when its digit is active. The peak current must still stay within the absolute maximum rating of 25mA continuous/90mA pulsed.

10. Design and Usage Case Study

Scenario: Designing a Low-Power Portable Multimeter Display
A designer is creating a handheld digital multimeter that must operate for extended periods on a single 9V battery. Readability in various lighting conditions is critical. The LTD-5223AJF is an ideal candidate.

Implementation: The designer uses a microcontroller with integrated LCD/segment drivers or a dedicated multiplexing driver IC. They choose to drive each segment at an average current of 2mA to conserve power. For a 2-digit multiplex, the peak current during the active time slot is set to 4mA per segment, well within the device's capabilities. The high luminous intensity at low current (320-700 \u00b5cd at 1mA) ensures the display remains clearly visible. The AlInGaP yellow-orange color is chosen for its high contrast against the light gray face and its effectiveness in both dim and bright ambient light. The wide viewing angle allows the user to read the measurement from different angles without losing clarity. The low forward voltage minimizes power loss in the driving circuitry, further extending battery life.

11. Technical Principle Introduction

The core operating principle is based on electroluminescence in a semiconductor P-N junction. The LTD-5223AJF uses AlInGaP (Aluminium Indium Gallium Phosphide) as the active semiconductor material. When a forward voltage exceeding the material's bandgap energy is applied across the junction, electrons from the N-type region recombine with holes from the P-type region. This recombination process releases energy in the form of photons (light). The specific composition of the AlInGaP alloy determines the bandgap energy, which directly corresponds to the wavelength (color) of the emitted light\u2014in this case, yellow-orange (~605-611 nm). The chips are mounted on a non-transparent GaAs substrate, which helps direct light output upwards through the segment, improving efficiency and contrast. The seven individual segments (A-G) and decimal point (DP) are formed by separate LED chips or chip regions, electrically isolated but physically arranged to form a digit pattern. The common cathode configuration internally connects all the cathodes of the segments within a single digit, simplifying external drive circuitry.

12. Technology Trends and Context

While seven-segment LED displays remain a robust and cost-effective solution for numeric readouts, the broader optoelectronics field is evolving. The use of AlInGaP represents an advancement over older III-V semiconductor materials like GaAsP, offering higher efficiency and better color purity. Current trends in display technology for more complex information include a shift towards dot-matrix OLEDs or LCDs, which offer full alphanumeric and graphic capabilities in similarly sized packages. However, for dedicated numeric applications requiring extreme reliability, wide temperature range operation, high brightness, and simplicity, LED seven-segment displays like the LTD-5223AJF continue to be the preferred choice. Future developments may focus on even higher efficiency materials (like improved InGaN for other colors or micro-LED technology), further reducing power consumption for battery-critical applications, and integrating driver electronics directly into the display package to simplify system design.