LTD-5723AJF LED Display Datasheet - 0.56-inch Digit Height - Yellow-Orange Color - 2.6V Forward Voltage - 70mW Power Dissipation - English Technical Documentation

1. Product Overview

The LTD-5723AJF is a high-performance, two-digit, 7-segment LED display module. Its primary function is to provide clear, bright numeric and limited alphanumeric information in electronic devices. The core technology is based on Aluminium Indium Gallium Phosphide (AlInGaP) semiconductor material, which is specifically engineered to emit light in the yellow-orange spectrum. This material choice is key to the device's high brightness and efficiency. The display features a gray face and white segment color, which enhances contrast and readability under various lighting conditions. It is categorized for luminous intensity, ensuring consistent brightness levels across production batches. The device is designed as a common cathode type, which is a standard configuration for simplifying drive circuitry in multi-digit displays.

2. Technical Parameters Deep Objective Interpretation

2.1 Photometric and Optical Characteristics

The optical performance is central to this display's functionality. The average luminous intensity (Iv) is specified from a minimum of 320 µcd to a typical 900 µcd at a forward current (IF) of 1mA. This parameter indicates the amount of visible light emitted and is crucial for determining display visibility. The dominant wavelength (λd) is 605 nm, and the peak emission wavelength (λp) is 611 nm at IF=20mA, firmly placing the output in the yellow-orange region of the visible spectrum. The spectral line half-width (Δλ) is 17 nm, which describes the purity or narrowness of the emitted color; a smaller value indicates a more monochromatic light source. Luminous intensity matching between segments is guaranteed to be within a 2:1 ratio, ensuring uniform appearance across all illuminated segments of a character.

2.2 Electrical Parameters

The electrical specifications define the operating boundaries and conditions for reliable use. The absolute maximum ratings set hard limits: a continuous forward current per segment of 25 mA (derating linearly from 25°C at 0.33 mA/°C), a peak forward current of 60 mA under pulsed conditions, and a maximum reverse voltage of 5 V per segment. The typical forward voltage (VF) per segment is 2.6 V at IF=20mA, with a minimum of 2.05 V. This forward voltage is a critical parameter for designing the current-limiting circuitry. The reverse current (IR) is a maximum of 100 µA at VR=5V, indicating the level of leakage when the LED is reverse-biased. Power dissipation per segment is limited to 70 mW, which influences thermal design.

2.3 Thermal and Environmental Specifications

The device is rated for an operating temperature range of -35°C to +85°C and an identical storage temperature range. This wide range makes it suitable for applications in challenging environments, from industrial controls to automotive interiors. The solder temperature specification is critical for assembly: the device can withstand 260°C for 3 seconds at a point 1/16 inch (approximately 1.6 mm) below the seating plane. Adhering to this reflow profile is essential to prevent damage to the internal semiconductor chips and wire bonds during the surface-mount assembly process.

3. Binning System Explanation

The datasheet explicitly states that the device is "categorized for luminous intensity." This indicates the implementation of a binning or sorting process post-manufacturing. LEDs are tested and grouped (binned) based on their measured luminous output at a standard test current (likely 1mA or 20mA as per the datasheet). This ensures that customers receive displays with consistent and predictable brightness levels. While the specific bin code structure is not detailed in this excerpt, such systems typically use alphanumeric codes to denote predefined ranges of luminous intensity, forward voltage, and sometimes wavelength. Designers must consult the manufacturer's full binning documentation to select the appropriate grade for their application's brightness uniformity requirements.

4. Performance Curve Analysis

The datasheet references "Typical Electrical / Optical Characteristic Curves" which are essential for in-depth design analysis. Although the specific graphs are not provided in the text, standard curves for such devices typically include:

• Luminous Intensity vs. Forward Current (I-V Curve): This graph shows how light output increases with current. It is typically non-linear, with efficiency (lumens per watt) often decreasing at very high currents due to thermal effects.
• Forward Voltage vs. Forward Current: This shows the diode's I-V characteristic, crucial for selecting the correct series resistor or designing constant-current drivers.
• Luminous Intensity vs. Ambient Temperature: This curve demonstrates how brightness decreases as the junction temperature rises. Understanding this derating is vital for applications operating at high ambient temperatures.
• Spectral Distribution: A plot of relative intensity versus wavelength, showing the peak at 611 nm and the 17 nm half-width, confirming the color characteristics.

These curves allow engineers to optimize drive conditions for a balance of brightness, efficiency, and longevity.

5. Mechanical and Packaging Information

The device is presented with a detailed package dimension drawing (not fully rendered in text). Key mechanical features inferred and standard for such packages include: a 0.56-inch (14.22 mm) digit height, which defines the character size. The package is a dual-digit, side-by-side configuration in a single housing. It features 18 pins for electrical connection, arranged in a standard DIP (Dual In-line Package) or similar footprint. The "Rt. Hand Decimal" note in the part description suggests the inclusion of a right-hand decimal point for each digit. The gray face and white segment color are part of the package design to enhance contrast. Precise dimensions, lead spacing, and overall package outline are contained in the dimensional drawing, with tolerances of ±0.25mm unless otherwise specified.

6. Pin Connection and Internal Circuit

The pin connection table is provided. It details a 18-pin configuration where pins 1-12 and 15-18 are anodes for specific segments (A-G and DP) for Digit 1 and Digit 2. Pins 13 and 14 are the common cathodes for Digit 2 and Digit 1, respectively. This common cathode architecture means all the LED segments for a single digit share a common ground (cathode) connection. The internal circuit diagram, referenced but not shown, would illustrate how the 14 segments (7 per digit, plus decimal points) are connected to these anode and cathode pins. This structure allows multiplexing, where digits are illuminated one at a time rapidly by switching their common cathodes, reducing the total number of driver pins required.

7. Soldering and Assembly Guidelines

The primary assembly guideline provided is the solder temperature specification: 260°C for 3 seconds at a point 1/16 inch (approx. 1.6mm) below the seating plane. This is a standard reflow profile for many lead-free soldering processes. Key considerations include:

• Reflow Profile: Engineers must ensure the oven profile does not exceed this temperature/time at the component body to prevent damage to the epoxy package and internal die.
• ESD Protection: Although not stated, AlInGaP LEDs are semiconductor devices and should be handled with standard ESD (Electrostatic Discharge) precautions.
• Cleaning: If cleaning is required after soldering, use methods compatible with the display's epoxy material.
• Storage: Store in the specified range of -35°C to +85°C in a dry, anti-static environment to prevent moisture absorption and degradation.

8. Application Suggestions

8.1 Typical Application Scenarios

This display is ideal for applications requiring clear, medium-sized numeric readouts. Common uses include: test and measurement equipment (multimeters, oscilloscopes), industrial control panels, point-of-sale terminals, automotive dashboard displays (for non-critical information), consumer appliances (microwaves, ovens, audio equipment), and medical devices. The yellow-orange color is often chosen for its high visibility and lower perceived glare compared to pure red or green, especially in variable lighting conditions.

8.2 Design Considerations

• Drive Circuitry: Use constant-current drivers or appropriate current-limiting resistors for each anode line. Calculate resistor values based on the supply voltage (Vcc), the typical forward voltage (Vf ~2.6V), and the desired forward current (e.g., 10-20 mA for good brightness).
• Multiplexing: For multi-digit displays like this one, a multiplexed drive scheme is efficient. This involves sequentially enabling each digit's common cathode via a transistor switch while presenting the segment data for that digit on the anode lines. The refresh rate must be high enough (>60 Hz) to avoid visible flicker.
• Viewing Angle: The datasheet claims a "wide viewing angle," but for optimal placement, consider the primary user's sight line relative to the display surface.
• Brightness Control: Brightness can be adjusted by varying the forward current (within limits) or by using pulse-width modulation (PWM) on the drive current.

9. Technical Comparison and Differentiation

The key differentiators of the LTD-5723AJF are rooted in its AlInGaP technology compared to older technologies like standard GaAsP (Gallium Arsenide Phosphide) LEDs:

• Higher Brightness and Efficiency: AlInGaP material systems are significantly more efficient at converting electrical energy to light in the red, orange, and yellow spectra, resulting in higher luminous intensity for the same drive current.
• Better Temperature Stability: AlInGaP LEDs generally exhibit less variation in luminous output and wavelength with temperature changes compared to older technologies.
• Color Saturation: The spectral half-width of 17 nm indicates a relatively pure color, which can be more visually appealing and distinct than broader-spectrum emitters.
• Contrast: The combination of a gray face and white segments is designed to maximize contrast when the segments are off, improving overall readability compared to displays with black faces or differently colored segments.

10. Frequently Asked Questions Based on Technical Parameters

Q: What is the purpose of the "Luminous Intensity Matching Ratio" of 2:1?
A: This guarantees that the dimmest segment in a character will be no less than half as bright as the brightest segment under the same conditions. This ensures visual uniformity, preventing some segments from appearing noticeably dimmer than others, which is critical for legibility.

Q: Can I drive this display with a 5V supply?
A: Yes, but you must use a current-limiting resistor in series with each anode. For example, to achieve a typical IF of 20mA with a 5V supply and a VF of 2.6V, the resistor value would be R = (5V - 2.6V) / 0.02A = 120 Ohms. Always verify power dissipation in the resistor as well.

Q: What does "Common Cathode" mean for my circuit design?
A: It means all the cathodes (negative terminals) of the LEDs for one digit are connected together internally to a single pin (Pin 14 for Digit 1, Pin 13 for Digit 2). To illuminate a digit, you apply a positive voltage to the desired segment anodes while connecting that digit's common cathode pin to ground (0V). This simplifies multiplexing.

Q: How do I interpret the "Peak Forward Current" rating of 60mA?
A: This is the maximum instantaneous current the LED can handle under very short pulse conditions (0.1ms pulse width, 1/10 duty cycle). It is NOT for continuous operation. Exceeding the continuous forward current (25 mA) can cause rapid degradation or failure.

11. Practical Design and Usage Case

Consider designing a simple two-digit counter using a microcontroller. The microcontroller's I/O pins would be connected to the 12 anode lines (segments A-G and DP for two digits) via current-limiting resistors. Two additional microcontroller pins would control NPN transistors, whose collectors are connected to the common cathode pins (13 & 14) and emitters to ground. The software would implement a multiplexing routine: it turns off both cathode transistors, sets the I/O pins to display the segments for "Digit 1," then briefly turns on the transistor for Digit 1's cathode. It then repeats the process for Digit 2. This cycle runs continuously at a high frequency. The average current per segment is determined by the peak current and the duty cycle (e.g., 20mA peak with a 50% duty cycle per digit gives an average of 10mA). This approach minimizes component count and power consumption.

12. Principle Introduction

The operating principle is based on electroluminescence in a semiconductor p-n junction. The AlInGaP (Aluminium Indium Gallium Phosphide) crystal structure forms the active region. When a forward voltage exceeding the diode's turn-on voltage (approximately 2.0-2.2V) is applied, electrons from the n-type region and holes from the p-type region are injected into the active region. When these charge carriers recombine, they release energy. In AlInGaP, a significant portion of this energy is released as photons (light) with a wavelength corresponding to the material's bandgap energy, which is engineered to be around 605-611 nm (yellow-orange). The non-transparent GaAs substrate helps reflect light upward, improving the external light extraction efficiency. Each segment of the 7-segment display contains one or more of these tiny AlInGaP LED chips.

13. Development Trends

While this specific device represents mature technology, the broader field of display LEDs continues to evolve. Trends relevant to such indicator and segment displays include:

• Increased Efficiency: Ongoing material science research aims to improve the internal quantum efficiency (more photons generated per electron) and light extraction efficiency (more photons escaping the chip), leading to displays that are brighter at lower power.
• Miniaturization: There is a constant drive for smaller pixel pitches and higher resolution, even in segment displays, allowing for more information in the same space.
• Integration: Trends include integrating the LED driver ICs directly into the display package or module, simplifying the end-user's circuit design.
• New Materials: While AlInGaP dominates the red-orange-yellow spectrum, other material systems like InGaN (for blue/green/white) are also advancing. The trend is towards full-color capability in small-format displays.
• Flexible Substrates: Research into placing LED chips on flexible circuits could lead to novel display form factors, though this is more relevant to dot-matrix than traditional segment displays.

The LTD-5723AJF, with its proven AlInGaP technology, offers a reliable and high-performance solution for applications where its specific characteristics of color, brightness, and size are required.