LTS-546AJG 0.52-inch Seven-Segment LED Display Datasheet - Digit Height 13.2mm - Green (AlInGaP) - 2.6V Forward Voltage - 70mW Power Dissipation - English Technical Documentation

1. Product Overview

The LTS-546AJG is a single-digit, seven-segment alphanumeric display module. Its primary function is to provide a clear, legible numeric or limited alphanumeric readout in electronic equipment. The core technology is based on Aluminium Indium Gallium Phosphide (AlInGaP) semiconductor material grown on a Gallium Arsenide (GaAs) substrate, which is engineered to emit green light. This material choice is significant as AlInGaP LEDs are known for their high efficiency and brightness in the red to yellow-green part of the spectrum. The device features a gray faceplate with white segment delineations, which enhances contrast and improves character appearance under various lighting conditions. It is categorized by luminous intensity, meaning devices are binned and sorted according to their measured light output to ensure consistency in applications where multiple displays are used side-by-side.

1.1 Key Features and Core Advantages

• Digit Size: A 0.52-inch (13.2 mm) digit height offers a balance between readability and compactness, suitable for panel meters, test equipment, and consumer appliances.
• Optical Quality: The display provides continuous, uniform segments with high brightness and high contrast, resulting in excellent character appearance.
• Viewing Angle: It boasts a wide viewing angle, ensuring the display remains legible even when viewed from off-axis positions.
• Power Efficiency: It has a low power requirement, making it suitable for battery-powered or energy-conscious devices.
• Reliability: As a solid-state device, it offers high reliability and long operational life compared to mechanical or vacuum-based displays.
• Environmental Compliance: The package is lead-free, manufactured in compliance with the RoHS (Restriction of Hazardous Substances) directive.

1.2 Device Identification and Configuration

The part number LTS-546AJG specifies a device with AlInGaP green LED chips in a common anode configuration. The "Rt. Hand Decimal" notation indicates the inclusion of a right-hand decimal point. In a common anode display, all the anodes (positive terminals) of the LED segments are connected together internally. To illuminate a specific segment, its corresponding cathode (negative terminal) pin must be driven low (connected to ground or a low voltage) while the common anode is held at a positive voltage. This configuration is common and often simplifies circuit design when using microcontroller or transistor sink drivers.

2. Technical Parameters: In-Depth Objective Interpretation

2.1 Absolute Maximum Ratings

These ratings define the stress limits beyond which permanent damage to the device may occur. Operation under or at these limits is not guaranteed.

• Power Dissipation per Segment: 70 mW maximum. Exceeding this can cause overheating and catastrophic failure.
• Peak Forward Current per Segment: 60 mA under pulsed conditions (1/10 duty cycle, 0.1ms pulse width). This rating is for brief, high-current pulses used in multiplexing.
• Continuous Forward Current per Segment: 25 mA at 25°C. This current must be derated linearly by 0.33 mA/°C as ambient temperature (Ta) rises above 25°C. For example, at 50°C, the maximum continuous current would be approximately 25 mA - (0.33 mA/°C * 25°C) = 16.75 mA.
• Temperature Ranges: Operating and storage temperature range is -35°C to +85°C.
• Solder Condition: Wave or reflow soldering should be performed with the solder point 1/16 inch (≈1.6mm) below the seating plane for 3 seconds at 260°C maximum.

2.2 Electrical and Optical Characteristics

These are the typical performance parameters measured under specified test conditions (Ta=25°C).

• Average Luminous Intensity (I_V): Ranges from 200 µcd (minimum) to 577 µcd (typical) at a forward current (I_F) of 1 mA. Luminous intensity is measured with a filter matching the CIE photopic eye-response curve, with a tolerance of ±15%.
• Wavelength Parameters:
  • Peak Emission Wavelength (λ_p): 571 nm (at I_F=20mA).
  • Dominant Wavelength (λ_d): 572 nm (at I_F=20mA), with a tolerance of ±1 nm. This is the single wavelength perceived by the human eye to match the color of the LED.
  • Spectral Line Half-Width (Δλ): 15 nm (at I_F=20mA). This indicates the spectral purity; a smaller value means a more monochromatic light.
• Forward Voltage per Chip (V_F): 2.1V to 2.6V at I_F=20mA, with a tolerance of ±0.1V. This is a critical parameter for driver circuit design.
• Reverse Current (I_R): Maximum 100 µA at a reverse voltage (V_R) of 5V. This test is for characterization only; continuous reverse bias operation is prohibited.
• Luminous Intensity Matching Ratio: 2:1 maximum for segments within the same display. This means the brightest segment should be no more than twice as bright as the dimmest segment under the same drive conditions, ensuring uniformity.
• Cross Talk: Specified as ≤ 2.5%. This refers to unwanted illumination of a segment when an adjacent segment is driven, caused by internal optical or electrical leakage.

3. Binning System Explanation

The datasheet explicitly states the device is "Categorized for Luminous Intensity." This implies a binning process where manufactured LEDs are tested and sorted into groups (bins) based on their measured light output at a standard test current. This is crucial for applications using multiple displays, as it prevents noticeable brightness differences between units. Designers should specify or ensure they receive displays from the same or adjacent bins to maintain visual consistency across a product. While not detailed in this excerpt, binning may also apply to forward voltage (V_F) and dominant wavelength (λ_d), the latter having a stated tolerance of ±1 nm.

4. Performance Curve Analysis

The datasheet references "Typical Electrical / Optical Characteristics Curves" which are essential for understanding device behavior beyond single-point specifications. These typically include:

• I-V (Current-Voltage) Curve: Shows the relationship between forward voltage and forward current. It is non-linear, with a threshold voltage (around 1.8-2.0V for AlInGaP) below which very little current flows. The curve helps in designing appropriate current-limiting circuitry.
• Luminous Intensity vs. Forward Current (I_V vs. I_F): Displays how light output increases with drive current. It is generally linear at lower currents but may saturate at higher currents due to thermal and efficiency droop.
• Luminous Intensity vs. Ambient Temperature: Shows how light output decreases as the junction temperature rises. This is critical for designing systems that operate over a wide temperature range.
• Spectral Distribution: A graph of relative intensity vs. wavelength, showing the peak at 571nm and the 15nm half-width.

These curves allow engineers to optimize drive conditions for specific brightness, efficiency, and lifetime targets.

5. Mechanical and Packaging Information

5.1 Package Dimensions

The display conforms to a standard through-hole DIP (Dual In-line Package) style. Key dimensional notes include:

• All dimensions are in millimeters, with general tolerances of ±0.25 mm unless specified otherwise.
• Pin tip shift tolerance is ±0.4 mm.
• Quality control limits are set for foreign material (≤10 mil), ink contamination (≤20 mil), and bubbles within the segment (≤10 mil).
• Reflector bending is limited to ≤1% of its length.

The precise dimensional drawing (not fully detailed in the text) would define the overall height, width, depth, digit size, segment dimensions, and the precise spacing and diameter of the 10 pins.

5.2 Pin Connection and Polarity Identification

The device has a 10-pin configuration (Pin 1 is marked as "No Connection"). The internal circuit diagram and pinout table show a common anode design with two common anode pins (3 and 8). The segment cathodes are assigned to specific pins: E(1), D(2), C(4), DP(5), B(6), A(7), F(9), G(10). Correct identification of pin 1 (often indicated by a notch, bevel, or dot on the package) is essential for proper orientation during PCB assembly.

6. Soldering, Assembly, and Storage Guidelines

6.1 Soldering and Assembly

The maximum solder condition is specified. For hand soldering, a temperature-controlled iron should be used to avoid exceeding the 260°C limit at the lead. The note cautions against using unsuitable tools or methods that apply abnormal force to the display body. Furthermore, if a decorative film is applied to the display surface, it should not be pressed tightly against a front panel, as external force may cause it to shift.

6.2 Storage Conditions

Proper storage is vital to prevent pin oxidation and moisture absorption.

• For LED Displays (Through-Hole): Store in original packaging at 5°C to 30°C and below 60% RH. If stored outside a moisture barrier bag or if the bag has been open for >6 months, baking at 60°C for 48 hours is recommended before use, with assembly to be completed within one week.
• General Principle: Avoid long-term inventory. Consume stock promptly. Non-compliant storage may necessitate re-plating of oxidized pins before use.

7. Application Suggestions and Design Considerations

7.1 Target Applications and Cautions

This display is intended for ordinary electronic equipment: office equipment, communication devices, and household appliances. It is explicitly stated that consultation is required for applications demanding exceptional reliability where failure could jeopardize life or health (e.g., aviation, medical systems). Designers must adhere to absolute maximum ratings.

7.2 Critical Design Considerations

• Drive Method: Constant current driving is strongly recommended over constant voltage to ensure consistent luminous intensity and longevity, as LED brightness is a function of current, not voltage.
• Current Limiting: The driver circuit must be designed to accommodate the full range of forward voltage (2.1V to 2.6V) to deliver the intended current to all devices.
• Thermal Management: The safe operating current must be derated based on the maximum ambient temperature. Excess current or high temperature leads to severe light degradation or premature failure.
• Reverse Bias Protection: The circuit must protect against reverse voltages and voltage spikes during power cycling to prevent metal migration and increased leakage current.
• Environmental Protection: Avoid rapid temperature changes in humid environments to prevent condensation on the display.
• Consistency in Multi-Display Setups: Always use displays from the same intensity bin to avoid uneven brightness (hue) across a multi-digit readout.

8. Technical Comparison and Differentiation

Compared to older technologies like incandescent or vacuum fluorescent displays (VFDs), the LTS-546AJG offers superior solid-state reliability, lower power consumption, and higher shock/vibration resistance. Within the LED segment display market, its use of AlInGaP technology for green light offers higher efficiency and potentially brighter output than older GaP (Gallium Phosphide) green LEDs. The common anode configuration is one of two standard types (the other being common cathode), and the choice between them depends primarily on the driver IC or microcontroller output configuration (sourcing vs. sinking current).

9. Frequently Asked Questions (Based on Technical Parameters)

1. Q: What is the difference between peak wavelength and dominant wavelength? A: Peak wavelength is the single wavelength at the highest point of the emission spectrum. Dominant wavelength is the single wavelength of monochromatic light that would match the perceived color of the LED. They are often close but not identical, especially for broader spectra.
2. Q: Why is constant current drive recommended? A: An LED's light output is directly proportional to forward current. A constant current source compensates for variations in forward voltage (V_F) between devices and over temperature, ensuring stable and uniform brightness.
3. Q: Can I drive this display directly from a 5V microcontroller pin? A: No. You must use a current-limiting resistor or a dedicated driver circuit. Connecting it directly would likely exceed the maximum continuous current, destroying the LED. The resistor value is calculated as R = (V_supply - V_F) / I_F.
4. Q: What does "categorized for luminous intensity" mean for my design? A: It means you should specify to your supplier that you need units from the same bin code, especially if using multiple displays in one product, to ensure all digits have matched brightness.

10. Practical Application Example

Scenario: Designing a simple digital voltmeter display. A microcontroller's analog-to-digital converter reads a voltage. The firmware converts this value to a decimal number. To display it on the LTS-546AJG, the microcontroller would use a driver IC (like a 74HC595 shift register with current-limiting resistors or a dedicated LED driver like the MAX7219). The common anode pins would be connected to a positive supply (e.g., 5V through a transistor if multiplexing). The microcontroller would sequentially set the appropriate segment cathode pins to ground (low) to form the desired digit. The driver circuit would be designed to provide a constant 15-20 mA per segment, well within the 25 mA continuous rating, with resistors calculated based on the worst-case V_F of 2.6V. For a multi-digit meter, displays from the same intensity bin would be used.

11. Operating Principle

The LTS-546AJG operates on the principle of electroluminescence in a semiconductor p-n junction. When a forward voltage exceeding the diode's threshold is applied (anode positive relative to cathode), electrons from the n-type AlInGaP/GaAs material recombine with holes from the p-type material. This recombination event releases energy in the form of photons (light). The specific composition of the AlInGaP alloy determines the bandgap energy, which in turn defines the wavelength (color) of the emitted light—in this case, green at around 572 nm. Each of the seven segments (plus the decimal point) contains one or more of these microscopic LED chips. The common anode configuration internally connects all the anodes, requiring external control of the individual cathodes.

12. Technology Trends

While seven-segment displays remain a staple for numeric readouts, the broader LED display technology field is evolving. Trends include: Miniaturization and Integration: Development of smaller pitch and chip-on-board (COB) displays. Advanced Materials: Ongoing research into more efficient materials like Gallium Nitride (GaN) for broader color gamuts and higher efficiencies, though AlInGaP remains dominant for high-efficiency red-amber-yellow-green. Smart Displays: Integration of driver ICs, memory, and communication interfaces (I2C, SPI) directly into the display module, simplifying system design. Flexible and Unconventional Form Factors: Development of bendable or curved segment displays for novel product designs. The LTS-546AJG represents a mature, reliable, and optimized solution for its specific application niche, balancing performance, cost, and availability.