LTD-323JS 0.3-inch Yellow LED Digit Display Datasheet - Digit Height 7.62mm - Forward Voltage 2.6V - Power Dissipation 70mW - English Technical Document

1. Product Overview

The device is a 0.3-inch (7.62 mm) digit height display module. It is designed to provide clear, high-visibility numeric output in a compact form factor. The core technology utilizes AlInGaP (Aluminum Indium Gallium Phosphide) Yellow LED chips. These chips are fabricated on a non-transparent GaAs (Gallium Arsenide) substrate, which contributes to the display's contrast and performance. The visual design features a black face with white segments, optimizing readability by enhancing contrast between illuminated and non-illuminated areas.

1.1 Core Advantages and Target Market

The display offers several key benefits that make it suitable for a range of applications. Its primary advantages include low power requirement, which is essential for battery-operated or energy-efficient devices. It provides high brightness and high contrast, ensuring legibility even in well-lit environments. The wide viewing angle allows the displayed information to be read from various positions. The device boasts solid-state reliability, meaning no moving parts and typically longer operational life compared to other display technologies. It is categorized for luminous intensity, indicating consistent performance and quality control. The continuous uniform segments contribute to an excellent character appearance. This combination of features makes the display ideal for applications such as instrumentation panels, test equipment, consumer electronics, industrial controls, and any device requiring a reliable, clear, and efficient numeric readout.

2. Technical Parameters Deep Objective Interpretation

2.1 Photoelectric Characteristics

The photometric and colorimetric performance is defined under specific test conditions. The average luminous intensity (Iv) is specified with a minimum of 320 \u00b5cd, a typical value of 800 \u00b5cd, and no stated maximum, when measured at a forward current (IF) of 1mA. This parameter indicates the perceived brightness of the lit segments. The peak emission wavelength (\u03bbp) is 588 nm, measured at IF=20mA, placing the output firmly in the yellow region of the visible spectrum. The spectral line half-width (\u0394\u03bb) is 15 nm (at IF=20mA), describing the spectral purity or the narrowness of the emitted light's wavelength band; a smaller value indicates a more monochromatic color. The dominant wavelength (\u03bbd) is 587 nm (at IF=20mA), which is the single wavelength perceived by the human eye to match the color of the light. Luminous intensity is measured using a sensor and filter combination that approximates the CIE photopic eye-response curve, ensuring the measurement correlates with human vision.

2.2 Electrical Parameters

The electrical specifications define the operating limits and conditions. The forward voltage per segment (VF) has a typical value of 2.6V and a maximum of 2.6V when the forward current is 20mA. This is the voltage drop across an LED segment when it is conducting. The reverse current per segment (IR) has a maximum of 100 \u00b5A when a reverse voltage (VR) of 5V is applied, indicating the level of leakage when the LED is reverse-biased. The luminous intensity matching ratio (IV-m) is specified as 2:1 (at IF=1mA). This ratio defines the maximum allowable variation in brightness between different segments of the same digit or between digits, ensuring visual uniformity.

2.3 Absolute Maximum Ratings and Thermal Characteristics

These ratings specify the limits beyond which permanent damage to the device may occur. The maximum power dissipation per segment is 70 mW. The peak forward current per segment is 60 mA, but this is only permissible under pulsed conditions (1/10 duty cycle, 0.1ms pulse width). The continuous forward current per segment is 25 mA at 25\u00b0C. Importantly, this current must be derated linearly by 0.33 mA for every degree Celsius above 25\u00b0C. For example, at 50\u00b0C, the maximum continuous current would be 25 mA - (0.33 mA/\u00b0C * 25\u00b0C) = 16.75 mA. This derating is crucial for reliable operation at elevated temperatures. The maximum reverse voltage per segment is 5 V. The operating and storage temperature range is from -35\u00b0C to +85\u00b0C. The maximum soldering temperature is 260\u00b0C for a maximum of 3 seconds, measured 1.6mm below the seating plane of the device.

3. Grading System Explanation

The datasheet indicates that the device is categorized for luminous intensity. This implies a binning or grading process where units are sorted based on their measured light output at a standard test current (likely 1mA or 20mA). This ensures that customers receive displays with consistent brightness levels. While specific bin codes or ranges are not detailed in this document, such a system typically involves grouping devices into categories (e.g., high-brightness, standard-brightness) to meet different application requirements or to guarantee a minimum performance level. The 2:1 luminous intensity matching ratio is a related specification that controls variation within a single device.

4. Performance Curve Analysis

The datasheet references typical electrical/optical characteristic curves. Although the specific graphs are not provided in the text, standard curves for such devices would typically include: Forward Current vs. Forward Voltage (I-V Curve): This shows the relationship between the current flowing through the LED and the voltage across it. It is non-linear, with a characteristic \"knee\" voltage (around the typical Vf of 2.6V) above which current increases rapidly with small voltage increases. Luminous Intensity vs. Forward Current (L-I Curve): This plot shows how the light output increases with increasing drive current. It is generally linear over a range but can saturate at very high currents. Luminous Intensity vs. Ambient Temperature: This curve demonstrates how light output decreases as the ambient temperature rises, highlighting the importance of thermal management and current derating. Spectral Distribution: A plot of relative intensity versus wavelength, showing the peak at 588 nm and the 15 nm half-width, confirming the yellow color emission.

5. Mechanical and Packaging Information

5.1 Dimensional Drawing

The package dimensions are provided in a drawing (referenced but not detailed in the text). All dimensions are specified in millimeters (mm). The standard tolerance for these dimensions is \u00b10.25 mm (which is equivalent to \u00b10.01 inches) unless a specific feature note states otherwise. This drawing is critical for PCB (Printed Circuit Board) layout, ensuring the footprint and hole patterns match the physical device.

5.2 Pin Connection and Polarity Identification

The device has a 10-pin configuration. It is a duplex (two-digit) common anode display. The pinout is as follows: Pin 1: Cathode G; Pin 2: No Pin (likely a mechanical placeholder or unused); Pin 3: Cathode A; Pin 4: Cathode F; Pin 5: Common Anode (Digit 2); Pin 6: Cathode D; Pin 7: Cathode E; Pin 8: Cathode C; Pin 9: Cathode B; Pin 10: Common Anode (Digit 1). The \"common anode\" configuration means the anodes of the LEDs for each digit are connected together internally. To illuminate a segment, its corresponding cathode pin must be driven low (connected to ground or a current sink) while its digit's common anode pin is driven high (connected to the positive supply through a current-limiting resistor).

5.3 Internal Circuit Diagram

An internal circuit diagram is referenced. For a common anode, two-digit, 7-segment display, this diagram would typically show: Two common anode nodes, one for each digit (pins 10 and 5). Seven cathode lines (A, B, C, D, E, F, G), each connected to the corresponding segment LED in both digits. Each segment LED (e.g., segment \"A\" of digit 1 and segment \"A\" of digit 2) shares the same cathode pin but has its anode connected to its respective digit's common anode. This multiplexing arrangement reduces the total number of pins required to control the display.

6. Soldering and Assembly Guidelines

The key assembly specification provided is for the soldering process. The device can withstand a maximum soldering temperature of 260\u00b0C. This exposure must be limited to a maximum duration of 3 seconds. The temperature is measured 1.6mm below the seating plane of the component on the PCB. This guideline is critical for wave soldering or reflow soldering processes to prevent thermal damage to the LED chips or the plastic package. For manual soldering, a temperature-controlled iron should be used with minimal contact time. Standard ESD (Electrostatic Discharge) precautions should be observed during handling and assembly to protect the semiconductor junctions.

7. Application Suggestions

7.1 Typical Application Scenarios

This display is well-suited for any application requiring clear, reliable numeric indication. Examples include: Digital multimeters and oscilloscopes. Panel meters for voltage, current, or temperature. Consumer appliances like microwave ovens, digital clocks, or audio equipment. Industrial control and automation panels. Test and measurement equipment. Automotive aftermarket gauges (considering the operating temperature range). Portable battery-powered devices due to its low power requirement.

7.2 Design Considerations and Circuit Implementation

When designing a drive circuit, several factors are crucial: Current Limiting: Each segment must have a series current-limiting resistor. The resistor value is calculated based on the supply voltage (Vcc), the LED forward voltage (Vf, typ. 2.6V), and the desired forward current (If). For example, to drive a segment at 20mA with a 5V supply: R = (Vcc - Vf) / If = (5V - 2.6V) / 0.020A = 120 Ohms. Multiplexing: For multi-digit common anode displays, multiplexing is used. The microcontroller sequentially activates one digit's common anode at a time while outputting the segment pattern for that digit on the cathode lines. The switching must be fast enough (typically >60Hz) to avoid visible flicker. Driver ICs: Using dedicated LED display driver ICs (e.g., MAX7219, TM1637) simplifies control, provides constant current drive, and handles multiplexing internally. Thermal Management: Adhere to the current derating curve above 25\u00b0C. Ensure adequate ventilation if the display is in an enclosed space or near other heat-generating components.

8. Technical Comparison and Differentiation

Compared to other numeric display technologies, this AlInGaP yellow LED display offers distinct advantages: vs. Red GaAsP/GaP LEDs: AlInGaP technology generally offers higher efficiency and brightness, and better temperature stability than older red LED materials. The yellow color may offer better visibility or aesthetic preference in some applications. vs. LCDs (Liquid Crystal Displays): LEDs are emissive (produce their own light), making them easily visible in low-light conditions without a backlight, whereas reflective LCDs require ambient light. LEDs have a much wider viewing angle and faster response time. However, LCDs typically consume significantly less power for static displays. vs. VFDs (Vacuum Fluorescent Displays): LEDs are solid-state, more rugged, have a longer lifetime, and require simpler, lower-voltage drive electronics compared to VFDs, which need a relatively high anode voltage. The key differentiators of this specific device are its 0.3-inch digit height, AlInGaP material for yellow emission, common anode configuration, and its specified performance in brightness, contrast, and viewing angle.

9. Frequently Asked Questions Based on Technical Parameters

Q: What is the purpose of the \"no pin\" on pin 2?
A: This is typically a mechanical placeholder used for alignment during the manufacturing process or to ensure the package has a symmetrical pin count for stability on the PCB. It is not electrically connected.

Q: How do I calculate the appropriate current-limiting resistor?
A: Use Ohm's Law: R = (Supply Voltage - LED Forward Voltage) / Desired Forward Current. Always use the maximum forward voltage from the datasheet (2.6V) in your calculation to ensure the current does not exceed safe limits, especially at lower temperatures.

Q: Can I drive this display with a 3.3V microcontroller?
A: Yes, but the headroom is small. With a Vf of 2.6V, only 0.7V remains for the current-limiting resistor. At 20mA, this requires a resistor of only 35 Ohms. The brightness may be slightly lower. It's often better to use a lower drive current (e.g., 10-15mA) or use a driver IC that can provide a higher voltage source.

Q: What does \"categorized for luminous intensity\" mean for my design?
A: It means the displays are tested and sorted by brightness. When purchasing, you may receive units from a specific brightness \"bin.\" For consistent appearance in a product, it's important to specify if you need a particular brightness grade or to source all units for a production run from the same manufacturer batch.

Q: Why is current derating necessary?
A: LED efficiency decreases as temperature increases. Driving an LED at the same current at a higher junction temperature produces more heat, not more light, potentially leading to thermal runaway and failure. Derating the current reduces the power dissipation and heat generation at high ambient temperatures, ensuring long-term reliability.

10. Practical Design and Usage Case

Case: Designing a Two-Digit Voltmeter Readout
A designer is creating a simple 0-99V DC voltmeter display. They select this display for its clarity and size. The system uses a microcontroller with an ADC to measure voltage. The microcontroller's I/O pins cannot source/sink enough current for the LEDs. The designer chooses a dedicated LED driver IC with constant current outputs and multiplexing support. The driver is connected to the display: the driver's segment outputs connect to the display's cathode pins (A-G), and the driver's two digit drivers connect to the common anode pins (10 and 5). The microcontroller communicates with the driver IC via a serial interface (e.g., SPI or I2C), sending the digit values. The driver IC handles the multiplexing, refreshing each digit at 500Hz to avoid flicker. Current-limiting is set within the driver IC to 15mA per segment to balance brightness and power consumption, staying well within the 25mA continuous rating at the expected operating temperature. The PCB layout includes the exact footprint from the dimensional drawing, with thermal relief on the pads for the common anode pins which may carry higher average current.

11. Principle Introduction

The device operates on the principle of electroluminescence in semiconductor materials. The AlInGaP (Aluminum Indium Gallium Phosphide) structure forms a p-n junction. When a forward voltage exceeding the junction's barrier potential (the forward voltage, Vf) is applied, electrons from the n-type region and holes from the p-type region are injected into the junction region. When these charge carriers recombine, they release energy. In a direct bandgap semiconductor like AlInGaP, this energy is released primarily in the form of photons (light). The specific composition of the AlInGaP alloy determines the bandgap energy, which in turn dictates the wavelength (color) of the emitted light. For this device, the composition is tuned to produce photons with a wavelength around 588 nm, which is perceived as yellow light. The non-transparent GaAs substrate helps absorb stray light, improving contrast by preventing internal reflections that could make unlit segments appear faintly illuminated.

12. Development Trends

The evolution of LED display technology like this follows several industry trends: Increased Efficiency: Ongoing material science research aims to improve the internal quantum efficiency (IQE) and light extraction efficiency of AlInGaP and other LED materials, leading to higher brightness at lower currents. Miniaturization: There is a constant drive for smaller pixel/digit pitches and lower profile packages while maintaining or improving optical performance. Enhanced Reliability and Lifetime: Improvements in packaging materials, die attach methods, and phosphor technology (for white LEDs) continue to extend operational lifetimes and stability over temperature and time. Integration: Trends include integrating driver circuitry, current limiters, or even microcontrollers directly with the display module, simplifying the end-user's design process. Broader Color Gamuts and New Materials: While this device uses AlInGaP for yellow, research into materials like GaN (Gallium Nitride) and its alloys (InGaN, AlGaN) has enabled highly efficient blue, green, and white LEDs. The pursuit of efficient red and amber LEDs using other material systems remains active. For numeric displays, the trend is towards flatter, more versatile modules that can be easily integrated into modern product designs.