LTS-5325CKR-P LED Display Datasheet - 0.56-inch Digit Height - Super Red - 2.6V Forward Voltage - 70mW Power Dissipation - English Technical Document

1. Product Overview

The LTS-5325CKR-P is a surface-mount device (SMD) designed as a single-digit numeric display. Its primary function is to provide clear, high-visibility numeric readouts in various electronic applications. The core technology utilizes AlInGaP (Aluminum Indium Gallium Phosphide) epitaxial layers grown on a GaAs substrate to produce a Super Red emission. This material system is known for its high efficiency and excellent brightness at relatively low drive currents. The device features a gray face with white segments, which enhances contrast and improves readability under different lighting conditions. It is categorized for luminous intensity, ensuring consistency in brightness levels across production batches, and is constructed with lead-free materials in compliance with RoHS directives.

1.1 Key Features and Advantages

The display offers several distinct advantages for integration into modern electronic designs:

• 0.56-Inch Digit Height (14.22 mm): Provides a character size suitable for applications requiring clear visibility from a moderate distance.
• Continuous Uniform Segments: Ensures a consistent and unbroken appearance of illuminated characters, contributing to a professional look.
• Low Power Requirement: The AlInGaP technology enables high luminous efficiency, allowing for bright output while minimizing power consumption.
• High Brightness & High Contrast: The combination of bright Super Red emission against a gray face offers superior contrast ratios, improving legibility.
• Wide Viewing Angle: The SMD package and optical design provide a broad viewing angle, making the display effective from various perspectives.
• Solid-State Reliability: As an LED-based device, it offers long operational life, shock resistance, and vibration tolerance compared to mechanical displays.
• Categorized Luminous Intensity: Parts are binned for intensity, allowing designers to select components for consistent brightness in their applications.

2. Technical Specifications Deep Dive

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

2.1 Absolute Maximum Ratings

These ratings define the stress limits beyond which permanent damage to the device may occur. Operation outside these limits is not advised.

• Power Dissipation per Segment: 70 mW. This is the maximum power that can be safely dissipated by a single LED segment.
• Peak Forward Current per Segment: 90 mA. This is permissible only under pulsed conditions (1/10 duty cycle, 0.1ms pulse width) to prevent overheating.
• Continuous Forward Current per Segment: 25 mA at 25°C. This current derates linearly at a rate of 0.28 mA/°C as ambient temperature (Ta) increases above 25°C. For example, at 85°C, the maximum continuous current would be approximately: 25 mA - ((85°C - 25°C) * 0.28 mA/°C) = 8.2 mA.
• Operating & Storage Temperature Range: -35°C to +105°C. This wide range makes the device suitable for industrial and automotive environments.
• Soldering Temperature: Withstands 260°C for 3 seconds at 1/16 inch (approx. 1.6mm) below the seating plane.

2.2 Electrical & Optical Characteristics (Ta=25°C)

These are the typical performance parameters under specified test conditions.

• Average Luminous Intensity (I_V): Ranges from 501 µcd (min) to 18000 µcd (typ) depending on drive current. At a standard test current of 1mA, the typical intensity is 1700 µcd. At 10mA, it reaches 18000 µcd, demonstrating high efficiency.
• Peak Emission Wavelength (λ_p): 639 nm (typical). This defines the wavelength at which the spectral output is strongest, placing it in the red-orange region of the visible spectrum.
• Dominant Wavelength (λ_d): 631 nm (typical). This is the single-wavelength perception of the color by the human eye, slightly shorter than the peak wavelength.
• Spectral Line Half-Width (Δλ): 20 nm (typical). This indicates the spectral purity; a narrower width means a more monochromatic color.
• Forward Voltage per Chip (V_F): 2.0V (min), 2.6V (typ) at I_F=20mA. This parameter is crucial for designing the driving circuitry and calculating power dissipation.
• Reverse Current (I_R): 100 µA (max) at V_R=5V. The datasheet explicitly notes that reverse voltage is for test purposes only and the device should not be operated under continuous reverse bias.
• Luminous Intensity Matching Ratio: 2:1 (max). This specifies the maximum allowable ratio between the brightest and dimmest segment within a single device, ensuring uniform appearance.
• Cross Talk: ≤ 2.5%. This refers to unwanted illumination of a non-selected segment due to electrical leakage or optical coupling.

2.3 Binning System Explanation

The datasheet states the device is \"categorized for luminous intensity.\" This implies a binning process where manufactured units are sorted based on their measured light output at a standard test current (likely 1mA or 10mA). Designers can specify a bin code to ensure all displays in an assembly have matched brightness, preventing uneven illumination. The specific bin code ranges and labels are not detailed in this excerpt but would typically be part of the ordering information.

3. Performance Curve Analysis

While the specific graphs are not reproduced in text, the datasheet includes typical curves. Based on standard LED behavior and the provided parameters, these curves would typically illustrate:

• Forward Current vs. Forward Voltage (I-V Curve): Would show the exponential relationship, with the knee voltage around 2.0-2.6V. The curve helps in selecting current-limiting resistor values.
• Luminous Intensity vs. Forward Current: Would demonstrate that light output increases with current but may begin to saturate at higher currents due to thermal effects and efficiency droop.
• Luminous Intensity vs. Ambient Temperature: Would show the output decreasing as temperature rises, a key consideration for high-temperature applications.
• Spectral Distribution: Would plot relative intensity against wavelength, showing a peak around 639nm with a ~20nm half-width.

4. Mechanical & Package Information

4.1 Package Dimensions

The device is housed in an SMD package. Key dimensional notes include: all dimensions are in millimeters with a general tolerance of ±0.25mm. Specific quality controls are noted, such as limits on foreign material (≤10 mil), ink contamination (≤20 mils), bubbles in segments (≤10 mil), bending (≤1% of reflector length), and plastic pin burr (max 0.14mm).

4.2 Pin Connection and Circuit Diagram

The display has a common cathode configuration with two common cathode pins (Pin 3 and Pin 8). This configuration is often preferred in multiplexed driving schemes. The pinout is as follows: Pin 1 (Anode E), Pin 2 (Anode D), Pin 3 (Common Cathode), Pin 4 (Anode C), Pin 5 (Anode DP - Decimal Point), Pin 6 (Anode B), Pin 7 (Anode A), Pin 8 (Common Cathode), Pin 9 (Anode F), Pin 10 (Anode G). The internal circuit diagram shows the ten individual LED segments (a, b, c, d, e, f, g, and the right-hand decimal point DP) with their anodes connected to the respective pins and their cathodes tied together to the common cathode pins.

4.3 Recommended Soldering Pattern

A land pattern (footprint) is provided for PCB design. Adhering to this pattern is essential for reliable solder joint formation, proper alignment, and thermal management during reflow.

5. Soldering & Assembly Guidelines

5.1 SMT Soldering Instructions

Critical instructions are provided to prevent damage during assembly:

• Reflow Soldering (Maximum 2 times): A pre-heat stage of 120-150°C for a maximum of 120 seconds is recommended. The peak temperature during reflow must not exceed 260°C. A cooling process to normal temperature is mandatory between the first and second soldering process if a second reflow is necessary.
• Hand Soldering (Iron): If required, the soldering iron tip temperature should not exceed 300°C, and contact time should be limited to 3 seconds maximum.
• Importance of Limits: Exceeding the temperature, time, or number of reflow cycles can damage the plastic package, degrade the LED epoxy, or cause internal wire bond failure.

5.2 Moisture Sensitivity and Storage

The device is shipped in moisture-proof packaging. It must be stored at ≤30°C and ≤60% Relative Humidity (RH). Once the sealed bag is opened, the components begin to absorb moisture from the atmosphere. If they are not used immediately and are exposed to ambient conditions beyond the specified limits, they must be baked before reflow to prevent \"popcorning\" or delamination caused by rapid vapor expansion during soldering. Baking conditions are specified: 60°C for ≥48 hours when in reel, or 100°C for ≥4 hours / 125°C for ≥2 hours when in bulk. Baking should be performed only once.

6. Packaging & Ordering Information

6.1 Packing Specifications

The device is supplied on embossed carrier tape and reels, compatible with automated pick-and-place equipment. Key packing details include:

• Carrier Tape: Made of black conductive polystyrene alloy. Dimensions comply with EIA-481-D standards. Camber is within 1mm over 250mm. Thickness is 0.30±0.05mm.
• Reel Information: A 22-inch reel contains 44.5 meters of tape. A 13-inch reel contains 700 pieces of the component.
• Minimum Order Quantity (MOQ): The minimum packing quantity for remainder/reel ends is 200 pieces.
• Leader/Trailer Tape: The reel includes a leader (minimum 400mm) and trailer (minimum 40mm) for machine feeding.

7. Application Suggestions & Design Considerations

7.1 Typical Application Scenarios

The LTS-5325CKR-P is well-suited for applications requiring a compact, reliable, and bright numeric display. Examples include:

• Industrial control panels and instrumentation (e.g., timers, counters, temperature displays).
• Consumer appliances (e.g., microwave ovens, washing machines, air conditioner controls).
• Automotive aftermarket accessories (e.g., voltage monitors, RPM gauges).
• Medical device readouts.
• Test and measurement equipment.

7.2 Design Considerations

• Driving Circuitry: Use constant current drivers or appropriate current-limiting resistors for each segment anode. The common cathode configuration simplifies multiplexing. Calculate resistor values based on the supply voltage (V_CC), the typical forward voltage (V_F ~2.6V), and the desired segment current (I_F). For example, with a 5V supply: R = (V_CC - V_F) / I_F = (5V - 2.6V) / 0.01A = 240Ω for a 10mA drive.
• Thermal Management: Observe the current derating curve. In high ambient temperature environments, reduce the drive current accordingly to stay within the power dissipation limits and ensure long-term reliability.
• PCB Layout: Follow the recommended soldering pattern. Ensure adequate trace width for the segment current. Consider the placement relative to other heat-generating components.
• Optical Integration: The gray face/white segment design offers good contrast. For additional diffusion or color filtering, ensure any overlay material has high transmission at the dominant wavelength (~631nm).

8. Technical Comparison & Differentiation

Compared to older technologies like standard GaP red LEDs, the AlInGaP-based LTS-5325CKR-P offers significantly higher luminous efficiency, resulting in brighter output at the same current or equivalent brightness at lower power. Compared to some white-light LED backlit LCDs, this direct LED segment display offers wider viewing angles, higher contrast, and better performance in bright ambient light. Its SMD package provides greater mechanical robustness and easier automated assembly than through-hole LED displays.

9. Frequently Asked Questions (FAQ)

Q1: What is the difference between peak wavelength (639nm) and dominant wavelength (631nm)?
A1: Peak wavelength is the physical point of maximum spectral emission. Dominant wavelength is the perceptual \"color\" as seen by the human eye, calculated from the full spectrum. They often differ slightly.

Q2: Can I drive this display with a 3.3V microcontroller GPIO pin directly?
A2: Not directly. The GPIO pin must source current through a current-limiting resistor. With a 3.3V supply and a V_F of 2.6V, the voltage drop across the resistor is only 0.7V. To achieve a 10mA current, you would need a 70Ω resistor (R = 0.7V / 0.01A). However, ensure the microcontroller pin can safely source 10mA continuously.

Q3: Why is the reverse current specification important if I should not apply reverse voltage?
A3: It is a quality and leakage test parameter. A high reverse current can indicate a defect in the LED chip junction. The specification assures the integrity of the device.

Q4: How do I interpret the \"2:1\" luminous intensity matching ratio?
A4: It means that within a single device, the measured intensity of the brightest segment should not be more than twice the intensity of the dimmest segment when tested under identical conditions (I_F=1mA). This ensures visual uniformity.

10. Practical Use Case Example

Scenario: Designing a simple digital timer display.
The timer needs to show minutes and seconds (four digits). Four LTS-5325CKR-P displays would be used. A microcontroller with sufficient I/O pins would be employed in a multiplexed driving scheme. All segment anodes for the same segment letter (e.g., all \"A\" segments) across the four digits would be connected together and driven by a single microcontroller pin via a current-limiting resistor. Each digit's common cathode would be connected to a separate microcontroller pin acting as a digit select switch. The microcontroller would rapidly cycle through illuminating one digit at a time (e.g., for 2.5ms each in a 10ms total cycle), relying on persistence of vision to make all digits appear lit simultaneously. This method drastically reduces the number of required driver pins from 40 (4 digits * 10 pins) to 14 (7 segment anodes + 1 DP + 4 common cathodes + 2 unused). The design must ensure the peak current per segment during its brief on-time does not exceed the absolute maximum rating, while the average current provides the desired brightness.

11. Operating Principle

The device operates on the principle of electroluminescence in a semiconductor p-n junction. When a forward voltage exceeding the junction's built-in potential is applied, electrons from the n-type AlInGaP layer recombine with holes from the p-type layer. 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, Super Red. The light is emitted from the active region, shaped by the package's reflector cup and epoxy lens to form the visible segments.

12. Technology Trends

AlInGaP technology represents a mature and highly efficient solution for red, orange, and yellow LEDs. Current trends in display technology include the development of even higher efficiency materials, such as those based on gallium nitride (GaN) for broader spectrum coverage, and the integration of micro-LEDs for ultra-high-resolution direct-view displays. For single-digit and small alphanumeric displays, the trend continues towards miniaturization, higher brightness, lower power consumption, and improved compatibility with lead-free, high-temperature reflow processes required for RoHS compliance and modern SMT assembly lines. The use of advanced plastics and encapsulation materials also improves long-term reliability and resistance to environmental factors like humidity and UV exposure.