LTD-5723AJS LED Display Datasheet - 0.56-inch Digit Height - AlInGaP Yellow - 2.6V Forward Voltage - English Technical Document

1. Product Overview

The LTD-5723AJS is a high-performance, low-power seven-segment LED display module. Its primary function is to provide clear, bright numeric and limited alphanumeric information in a wide range of electronic devices. The core technology is based on Aluminium Indium Gallium Phosphide (AlInGaP) semiconductor material, which is renowned for its high efficiency and excellent color purity in the yellow-orange-red spectrum. This device is specifically engineered for applications where power consumption, readability, and reliability are critical factors.

1.1 Core Advantages and Target Market

The display offers several key advantages that make it suitable for demanding applications. Its low power requirement allows it to be driven with currents as low as 1mA per segment, making it ideal for battery-powered or energy-sensitive systems. The use of AlInGaP technology provides high brightness and high contrast, ensuring excellent visibility even in well-lit ambient conditions. The continuous uniform segments and wide viewing angle contribute to superior character appearance and readability from various perspectives. Its solid-state reliability ensures long operational life with no moving parts to wear out. This combination of features targets markets such as portable instrumentation, medical devices, industrial control panels, consumer electronics, and automotive dashboard displays where clear, reliable, and efficient indication is required.

2. Technical Specifications Deep Dive

This section provides a detailed, objective analysis of the device's electrical, optical, and physical parameters as defined in the datasheet.

2.1 Photometric and Optical Characteristics

The optical performance is central to the display's function. The Average Luminous Intensity (Iv) is specified with a typical value of 700 µcd at a forward current (IF) of 1mA, with a minimum of 320 µcd. This measurement is taken using a sensor and filter that approximates the CIE photopic eye-response curve, ensuring the value correlates with human brightness perception. The Peak Emission Wavelength (λp) is 588 nm, and the Dominant Wavelength (λd) is 587 nm, both measured at IF=20mA, firmly placing the output in the yellow region of the visible spectrum. The Spectral Line Half-Width (Δλ) of 15 nm indicates a relatively narrow spectral bandwidth, which contributes to the perceived color purity and saturation of the yellow light. The Luminous Intensity Matching Ratio between segments is specified at a maximum of 2:1, ensuring uniform brightness across the display for a consistent appearance.

2.2 Electrical Parameters

The electrical specifications define the operating limits and conditions for reliable use. The Absolute Maximum Ratings set the boundaries: a maximum power dissipation of 40 mW per segment, a peak forward current of 60 mA (at 1/10 duty cycle, 0.1ms pulse), and a continuous forward current of 25 mA per segment at 25°C, derating linearly by 0.33 mA/°C above that temperature. The maximum reverse voltage per segment is 5V. The key operational parameter is the Forward Voltage (VF), which has a typical value of 2.6V at IF=20mA, with a minimum of 2.05V. This value is crucial for designing the current-limiting circuitry. The Reverse Current (IR) is a maximum of 100 µA at VR=5V, indicating the leakage characteristics of the LED junction.

3. Binning and Categorization System

The datasheet explicitly states that the devices are categorized for luminous intensity. This means the LTD-5723AJS units are tested and sorted (binned) based on their measured light output at a standard test current (implied to be 1mA). This binning process ensures that designers can select displays with consistent brightness levels for their applications, preventing noticeable variations in intensity between different units in a product batch. While the specific bin codes are not listed in this document, the practice guarantees a level of performance uniformity.

4. Performance Curve Analysis

Although the specific graphs are not detailed in the provided text, typical characteristic curves for such a device would be essential for design. These would normally include:

• Relative Luminous Intensity vs. Forward Current (I-V Curve): This graph shows how light output increases with driving current, typically in a sub-linear relationship, helping to optimize the trade-off between brightness and power consumption.
• Forward Voltage vs. Forward Current: Illustrates the diode's I-V characteristic, critical for determining the necessary supply voltage and series resistor value.
• Relative Luminous Intensity vs. Ambient Temperature: Shows how light output decreases as the junction temperature rises, which is vital for thermal management in high-temperature environments.
• Spectral Distribution: A plot of relative intensity versus wavelength, visually confirming the peak and dominant wavelength values and the spectral half-width.

Designers should consult these curves to understand the device's behavior under non-standard conditions (different currents, temperatures) not covered by the tabular data at 25°C.

5. Mechanical and Packaging Information

5.1 Physical Dimensions and Package

The device features a 0.56 inch (14.22 mm) digit height. The package dimensions are provided in a detailed drawing (referenced but not shown in text). All dimensions are in millimeters with a standard tolerance of ±0.25 mm unless otherwise specified. The physical construction includes a gray face and white segment color, which enhances contrast by absorbing ambient light from non-active areas.

5.2 Pin Connection and Internal Circuit

The LTD-5723AJS is a two-digit, common cathode display with a right-hand decimal point for each digit. The pinout is clearly defined across 18 pins. The internal circuit diagram shows that each segment (A-G, DP) of each digit is an independent LED with its own anode. The cathodes for all segments within a single digit are connected together internally, forming the common cathode for that digit (pins 13 and 14). This configuration is optimal for multiplexed driving schemes, where digits are illuminated one at a time in rapid succession.

6. Soldering and Assembly Guidelines

The datasheet provides a critical parameter for assembly: the solder temperature. It specifies that the device can withstand a soldering temperature of 260°C for 3 seconds, measured 1/16 inch (approximately 1.6 mm) below the seating plane. This is a standard wave or reflow soldering condition. To ensure reliability, it is imperative to adhere to this profile to prevent thermal damage to the LED chips, the epoxy encapsulant, or the internal wire bonds. Preheating stages are recommended to minimize thermal shock. The operating and storage temperature range is specified from -35°C to +85°C.

7. Application Suggestions and Design Considerations

7.1 Typical Application Scenarios

This display is well-suited for:
- Portable Multimeters and Test Equipment: Where low power consumption extends battery life.
- Industrial Process Controllers: Where high brightness ensures visibility in factory settings.
- Consumer Appliances: Such as microwave ovens, scales, or audio equipment for clear numeric readouts.
- Automotive Aftermarket Displays: For auxiliary gauges or control units, benefiting from the wide temperature range.

7.2 Design Considerations

• Current Limiting: Always use a series resistor for each segment anode (or a constant current driver) to set the forward current. Calculate the resistor value using R = (Vcc - VF) / IF, where VF is taken from the datasheet at the desired IF.
• Multiplexing: For multi-digit displays, a multiplexed drive is standard. The common cathodes are switched to ground sequentially while the corresponding segment anodes are driven with the pattern for that digit. Refresh rates should be above 60 Hz to avoid visible flicker.
• Thermal Management: While LEDs generate less heat than incandescent bulbs, the derating curve for forward current must be respected in high ambient temperature applications to maintain longevity and brightness.
• ESD Protection: AlInGaP LEDs can be sensitive to electrostatic discharge. Implement standard ESD handling precautions during assembly.

8. Technical Comparison and Differentiation

The primary differentiator of the LTD-5723AJS is its use of AlInGaP material on a non-transparent GaAs substrate. 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. The yellow color produced is also more saturated and pure. Compared to white LEDs (which are typically blue LEDs with a phosphor coating), this monochromatic yellow display has no phosphor-related aging effects and offers a very specific wavelength ideal for certain indicator standards. Its low-current optimization (down to 1mA) is a key advantage over displays designed primarily for higher drive currents.

9. Frequently Asked Questions (Based on Technical Parameters)

Q: Can I drive this display with a 3.3V or 5V microcontroller directly?
A: No. You must use external current-limiting resistors or driver ICs. The typical VF is 2.6V. Connecting an MCU pin (3.3V or 5V) directly would attempt to drive an unlimited current through the LED, damaging both the LED and possibly the MCU pin.

Q: What is the purpose of the luminous intensity matching ratio of 2:1?
A: It guarantees that within a single device, the dimmest segment will be no less than half as bright as the brightest segment. This ensures visual uniformity across all segments of a digit.

Q: How do I interpret the derating for continuous forward current?
A: At 25°C, you can use up to 25 mA per segment. If the ambient temperature rises to 85°C, the maximum allowable current decreases. The derating factor is 0.33 mA/°C. The reduction is (85 - 25) * 0.33 = 19.8 mA. Therefore, the max current at 85°C would be 25 - 19.8 = 5.2 mA per segment.

10. Operating Principle Introduction

The device operates on the principle of electroluminescence in a semiconductor p-n junction. The AlInGaP semiconductor layers are engineered with a specific bandgap energy. When a forward voltage exceeding the junction's threshold (approximately 2V) is applied, electrons and holes are injected across the junction. When these charge carriers recombine, they release energy in the form of photons (light). The specific composition of the AlInGaP alloy determines the bandgap energy, which directly dictates the wavelength (color) of the emitted light—in this case, yellow (~587 nm). The non-transparent GaAs substrate helps reflect light upward, improving the overall light extraction efficiency from the top surface of the chip.

11. Development Trends and Context

While this is a specific component datasheet, it exists within broader industry trends. The use of AlInGaP represents an advancement over earlier LED materials for red-yellow-orange colors. Current trends in display technology are moving towards even higher efficiency materials, broader color gamuts, and the integration of displays with touch sensing or communication capabilities. However, for simple, reliable, low-cost, and low-power numeric indication, dedicated seven-segment LED displays like the LTD-5723AJS remain highly relevant and are often the most practical solution. Their design is mature, offering excellent reliability and a straightforward interface that requires minimal supporting circuitry compared to more complex dot-matrix or OLED displays.