LTD-5307AG LED Digit Display Datasheet - 0.56 Inch (14.22mm) Digit Height - Green Segment - 2.6V Forward Voltage - English Technical Document

1. Product Overview

The LTD-5307AG is a high-performance, single-digit, 7-segment LED display module. Its primary function is to provide clear, bright numeric or limited alphanumeric character output in electronic devices. The core application areas include instrumentation panels, consumer electronics displays, industrial control readouts, and test equipment where a compact, reliable, and easily readable numeric indicator is required.

The device's key positioning lies in its balance of size, readability, and power efficiency. It is designed for engineers and product developers who need a dependable display component that integrates seamlessly into digital circuits without requiring complex driving electronics, thanks to its straightforward common cathode configuration.

2. Technical Specifications Deep Dive

2.1 Optical Characteristics

The optical performance is central to the display's functionality. The device utilizes Gallium Phosphide (GaP) LED chips on a transparent GaP substrate, which is a proven technology for producing efficient green light emission.

• Average Luminous Intensity (I_V): Ranges from 800 μcd (min) to 2400 μcd (typ) when driven at a forward current (I_F) of 10mA. This parameter defines the perceived brightness. The typical value of 2400 μcd indicates a bright display suitable for well-lit environments.
• Peak Emission Wavelength (λ_p): 565 nm. This is the wavelength at which the LED emits the most optical power, placing it firmly in the green region of the visible spectrum.
• Dominant Wavelength (λ_d): 569 nm. This wavelength corresponds to the perceived color of the light by the human eye, which is a slightly yellowish-green.
• Spectral Line Half-Width (Δλ): 30 nm. This value indicates the spectral purity or bandwidth of the emitted light. A value of 30 nm is typical for standard green GaP LEDs, resulting in a saturated green color.
• Luminous Intensity Matching Ratio (I_V-m): Maximum 2:1. This critical specification ensures visual uniformity across the display. It means the brightness of the dimmest segment will be no less than half the brightness of the brightest segment under the same driving conditions, preventing uneven appearance.

2.2 Electrical Characteristics

The electrical parameters define the interface between the display and the driving circuitry.

• Forward Voltage per Segment (V_F): Typically 2.6V, with a maximum of 2.6V at I_F=20mA. This is a crucial parameter for designing the current-limiting resistor value in series with each segment. Using a standard 5V logic supply, a typical current-limiting resistor value would be (5V - 2.6V) / 0.02A = 120Ω.
• Continuous Forward Current per Segment (I_F): 25 mA maximum. Exceeding this current will degrade the LED's lifespan and luminous output. The datasheet provides a linear derating factor of 0.28 mA/°C above 25°C ambient temperature, meaning the maximum allowable current decreases as temperature rises.
• Peak Forward Current per Segment: 100 mA maximum, but only under pulsed conditions (0.1ms pulse width, 1/10 duty cycle). This allows for brief over-driving to achieve higher instantaneous brightness in multiplexed applications.
• Reverse Voltage per Segment (V_R): 5V maximum. Applying a higher reverse voltage can cause immediate and catastrophic failure of the LED junction.
• Reverse Current per Segment (I_R): 100 μA maximum at V_R=5V. This is the leakage current when the LED is reverse-biased.

2.3 Absolute Maximum Ratings and Thermal Considerations

These ratings define the operational limits beyond which permanent damage may occur. They are not for normal operation.

• Power Dissipation per Segment: 75 mW. This is calculated as V_F * I_F. At the typical V_F of 2.6V, the maximum continuous current is approximately 75mW / 2.6V ≈ 28.8 mA, which aligns with the 25mA continuous current rating.
• Operating Temperature Range: -35°C to +105°C. This wide range makes the device suitable for applications in harsh environments, from industrial freezers to automotive engine compartments.
• Storage Temperature Range: -35°C to +105°C.
• Solder Temperature: The device can withstand a soldering temperature of 260°C for 3 seconds at a point 1/16 inch (≈1.6mm) below the seating plane. This is a standard specification for wave or reflow soldering processes.

3. Binning and Categorization System

The datasheet explicitly states that the devices are "Categorized for Luminous Intensity." This indicates a production binning process. While specific bin codes 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., 10mA). This ensures that designers can select displays with consistent brightness levels for their products, or use displays from the same intensity bin within a single product to maintain uniform appearance across multiple digits.

4. Performance Curve Analysis

The datasheet references "Typical Electrical / Optical Characteristic Curves." Although the specific graphs are not provided in the text, we can infer their standard content and significance based on the parameters listed:

• Forward Current vs. Forward Voltage (I-V Curve): This graph would show the exponential relationship typical of a diode. It is essential for understanding the voltage drop across the LED at various operating currents, crucial for accurate driver design.
• Luminous Intensity vs. Forward Current: This curve shows how brightness increases with current. It is typically linear over a range before efficiency drops at very high currents due to thermal effects.
• Luminous Intensity vs. Ambient Temperature: This graph would demonstrate the derating of light output as the junction temperature rises. LED efficiency decreases with increasing temperature.
• Spectral Distribution: A plot of relative intensity versus wavelength, showing the peak at 565nm and the 30nm half-width, confirming the green color characteristics.

5. Mechanical and Package Information

5.1 Physical Dimensions

The device features a 0.56-inch digit height, which corresponds to 14.22 millimeters. This is a standard size offering a good balance between readability and board space consumption. The package dimensions drawing (referenced but not detailed in text) would typically show the overall length, width, and height of the module, the digit and segment dimensions, and the lead spacing. All dimensions have a standard tolerance of ±0.25mm unless otherwise specified.

5.2 Pin Configuration and Internal Circuit

The LTD-5307AG is a two-digit, common cathode display in a single package. The pin connection table is provided:

• Configuration: Common Cathode. This means all the cathodes (negative terminals) for the segments of each digit are connected together internally. To illuminate a segment, its corresponding anode pin must be driven high (through a current-limiting resistor) while its digit's common cathode pin is pulled low.
• Pinout: The 18-pin device has a specific assignment for anodes of segments A-G and decimal point (D.P.) for two digits (Digit 1 and Digit 2), along with their respective common cathode pins (pins 13 and 14). Pins 1, 2, 16, 17, 18 are marked as "No Connection" (N.C.).
• Internal Circuit Diagram: Referenced in the datasheet, it would visually depict the interconnection of the 14 LED segments (7 per digit) and the two common cathode nodes, clarifying the electrical layout.

6. Soldering and Assembly Guidelines

Based on the absolute maximum ratings:

• Soldering: The device is compatible with standard PCB assembly processes. The critical specification is the 260°C for 3 seconds at 1.6mm below the body. For reflow soldering, a standard lead-free profile with a peak temperature around 260°C is acceptable, provided the time above liquidus is controlled.
• Handling: Standard ESD (Electrostatic Discharge) precautions should be observed during handling and assembly, as LED chips are sensitive to static electricity.
• Cleaning: If cleaning is required after soldering, use methods and solvents compatible with the device's plastic package and epoxy fill.

7. Application Suggestions and Design Considerations

7.1 Typical Application Circuits

The common cathode configuration is directly compatible with standard microcontroller I/O pins or decoder/driver ICs (like the 74HC595 shift register or dedicated LED driver chips). A typical driving circuit involves:

1. Connecting each segment anode to a positive supply voltage (e.g., 3.3V or 5V) through an individual current-limiting resistor.
2. Connecting the common cathode pins to the ground via a low-side switch (e.g., an NPN transistor or a MOSFET). The switch is controlled by a microcontroller to select which digit is active.
3. For two-digit multiplexing, the microcontroller rapidly cycles between activating Digit 1 and Digit 2 while updating the segment patterns accordingly. This reduces the number of required I/O pins significantly.

7.2 Design Considerations

• Current Limiting: Always use series resistors for each segment anode. The resistor value is calculated as R = (V_supply - V_F) / I_F. For a 5V supply, V_F=2.6V, and I_F=10mA: R = (5 - 2.6) / 0.01 = 240Ω. A 220Ω or 270Ω standard resistor would be appropriate.
• Multiplexing Frequency: When multiplexing multiple digits, use a refresh rate high enough to avoid visible flicker, typically above 60 Hz per digit. For two digits, a cycle frequency >120 Hz is recommended.
• Heat Management: While the power dissipation is low, ensure adequate ventilation if multiple displays are used in a confined space, especially near the upper end of the operating temperature range.
• Viewing Angle: The datasheet highlights a "Wide Viewing Angle." This should be considered during mechanical design to ensure the display is oriented correctly for the end-user.

8. Frequently Asked Questions (Based on Technical Parameters)

Q: Can I drive this display directly from a 3.3V microcontroller pin?
A: Possibly, but you must check the forward voltage. The typical V_F is 2.6V. A 3.3V pin might only provide 3.3V - 2.6V = 0.7V across the current-limiting resistor, limiting the maximum current and thus the brightness. It is generally safer to use a driver circuit or a higher supply voltage for the anode side.

Q: What is the difference between peak wavelength and dominant wavelength?
A: Peak wavelength (565nm) is the physical peak of the emitted light spectrum. Dominant wavelength (569nm) is the single wavelength of monochromatic light that would appear to have the same color as the LED's output to the human eye. Dominant wavelength is more relevant for color perception.

Q: How do I achieve uniform brightness across all segments?
A> Use identical current-limiting resistor values for all segments. The built-in luminous intensity matching ratio (2:1 max) ensures that even with identical drive currents, segments will not vary in brightness by more than a factor of two. For critical applications, select displays from the same intensity bin.

9. Operational Principle

The LTD-5307AG operates on the principle of electroluminescence in a semiconductor P-N junction. When a forward voltage exceeding the diode's threshold (approximately 2.1-2.6V for this GaP device) is applied, electrons from the N-type material recombine with holes from the P-type material in the depletion region. In Gallium Phosphide (GaP) LEDs, this recombination event releases energy in the form of photons (light) with a wavelength corresponding to the bandgap energy of the material, which is in the green region of the spectrum. The transparent GaP substrate allows more of this internally generated light to escape, contributing to higher efficiency. The specific segments are illuminated by selectively applying forward bias to the anode of the desired segment while grounding the common cathode of the corresponding digit.

10. Technology Context and Trends

The LTD-5307AG represents a mature and reliable technology based on GaP material. While newer display technologies like OLEDs, micro-LEDs, and high-efficiency InGaN-based LEDs offer advantages in terms of color gamut, efficiency, and resolution for complex graphics, traditional 7-segment LED displays like this one remain highly relevant. Their advantages include extreme simplicity of control, very high reliability and longevity, excellent brightness and contrast, wide operating temperature range, and low cost. They are the optimal choice for applications where only numeric or simple alphanumeric information needs to be displayed clearly and reliably under various environmental conditions, such as in industrial controls, medical devices, automotive dashboards (for secondary functions), and household appliances. The trend in this segment is towards higher efficiency (more light output per mA), lower forward voltages to be more compatible with modern low-voltage logic, and potentially smaller package sizes while maintaining or improving readability.