LTS-5325CTB-P LED Display Datasheet - 0.56-inch Digit Height - Blue Color - 3.8V Forward Voltage - 70mW Power Dissipation - English Technical Document

1. Product Overview

The LTS-5325CTB-P is a surface-mount device (SMD) designed as a single-digit, alphanumeric display. Its primary function is to provide clear, bright numeric or limited alphanumeric indication in electronic equipment. The core technology is based on InGaN (Indium Gallium Nitride) blue LED chips grown on a sapphire substrate, which is known for producing efficient and bright blue light. The device features a gray face for high contrast and white segments for light diffusion, resulting in excellent character appearance.

1.1 Key Features and Advantages

• Digit Size: Features a large 0.56-inch (14.22 mm) digit height, ensuring excellent visibility from a distance.
• Segment Quality: Offers continuous, uniform segments for a consistent and professional visual output without gaps or irregularities.
• Power Efficiency: Designed with low power requirement, making it suitable for battery-powered or energy-conscious applications.
• Optical Performance: Delivers high brightness and high contrast ratio, ensuring readability even in well-lit environments.
• Viewing Angle: Provides a wide viewing angle, allowing the display to be read clearly from various positions.
• Reliability: Benefits from solid-state reliability with no moving parts, leading to long operational life and resistance to shock and vibration.
• Quality Control: Devices are categorized (binned) for luminous intensity, ensuring consistent brightness levels within a specified range for a given order.
• Environmental Compliance: The package is lead-free and manufactured in accordance with RoHS (Restriction of Hazardous Substances) directives.

1.2 Device Configuration

This is a common cathode display. The specific part number LTS-5325CTB-P denotes a blue (B) display with a right-hand decimal point (DP). The common cathode configuration simplifies circuit design when using microcontroller or driver ICs that sink current.

2. Technical Parameters: In-Depth Objective Interpretation

This section provides a detailed, objective analysis of the device's operational limits and performance characteristics under defined conditions.

2.1 Absolute Maximum Ratings

These are stress limits that must not be exceeded under any conditions, as doing so may cause permanent damage to the device. Operation should always be maintained within the recommended operating conditions detailed later.

• Power Dissipation per Segment: 70 mW maximum. This is the total electrical power (current * voltage) that can be safely converted into light and heat within one segment.
• Peak Forward Current per Segment: 30 mA maximum, but only under pulsed conditions (1/10 duty cycle, 0.1 ms pulse width). This rating is for brief, high-current pulses, not continuous operation.
• Continuous Forward Current per Segment: 25 mA maximum at 25°C. This current derates linearly by 0.28 mA for every 1°C increase in ambient temperature (Ta) above 25°C. For example, at 85°C, the maximum continuous current would be approximately: 25 mA - [0.28 mA/°C * (85°C - 25°C)] = 25 mA - 16.8 mA = 8.2 mA.
• Operating & Storage Temperature Range: -35°C to +105°C. The device can be stored or operated within this full range.
• Soldering Temperature: Withstands iron soldering at 260°C for 3 seconds, with the iron tip positioned at least 1/16 inch (≈1.6 mm) below the seating plane of the package.

2.2 Electrical & Optical Characteristics

These parameters define the typical performance of the device when operated within its recommended conditions (Ta=25°C).

• Average Luminous Intensity (I_V): Ranges from 8600 µcd (minimum) to 28500 µcd (typical) when driven at a forward current (I_F) of 10 mA. This wide range indicates the device is binned; specific intensity grades would be specified in ordering information.
• Forward Voltage per Chip (V_F): Typically 3.8V, with a maximum of 3.8V, at I_F=5 mA. This is the voltage drop across the LED when it is illuminated. Designers must ensure the driving circuit can provide this voltage.
• Peak Emission Wavelength (λ_p): 468 nm. This is the wavelength at which the emitted light intensity is highest, squarely in the blue region of the visible spectrum.
• Dominant Wavelength (λ_d): 470 nm. This is the single wavelength perceived by the human eye to represent the color of the light, very close to the peak wavelength.
• Spectral Line Half-Width (Δλ): 25 nm. This indicates the spectral purity; a smaller value means a more monochromatic (pure color) light. 25 nm is typical for a standard blue LED.
• Reverse Current (I_R): Maximum 100 µA at a reverse voltage (V_R) of 5V. This parameter is for test purposes only; the device is not designed to operate under reverse bias.
• Luminous Intensity Matching Ratio: Maximum 2:1 for segments within the same "similar light area." This means the brightest segment should be no more than twice as bright as the dimmest segment in a matched group, ensuring uniformity.
• Cross Talk: Specified as ≤ 2.5%. This refers to unwanted light leakage or electrical interference between adjacent segments.

2.3 Electrostatic Discharge (ESD) Protection

LEDs are highly sensitive to electrostatic discharge. The datasheet strongly advises implementing ESD control measures during handling and assembly to prevent latent or catastrophic damage:

• Personnel should use grounded wrist straps or anti-static gloves.
• All workstations, equipment, and storage facilities must be properly grounded.
• An ionizer (ion blower) is recommended to neutralize static charges that may accumulate on the plastic package surface due to friction during handling, especially for non-diffused (N/D) types.

3. Binning System Explanation

The datasheet explicitly states that the devices are "categorized for luminous intensity." This implies a binning system is in place, although specific bin codes are not detailed in this excerpt. Typically, such a system involves:

• Luminous Intensity Binning: LEDs from a production batch are tested and sorted into different groups (bins) based on their measured light output at a standard test current (e.g., 10 mA). This ensures customers receive LEDs with consistent brightness within a predefined range (e.g., 8600-12000 µcd, 12000-18000 µcd, etc.). The wide MIN to TYP range (8600 to 28500 µcd) in the characteristics table supports this practice.
• Forward Voltage Binning: While not explicitly mentioned here, it is common practice to also bin LEDs based on forward voltage (V_F) to ensure uniform current distribution when multiple LEDs are connected in parallel.
• Wavelength Binning: For color-critical applications, LEDs may also be binned by dominant or peak wavelength to ensure color consistency. The tight specification (λ_d = 470 nm) suggests a controlled process, but binning may still occur for premium grades.

4. Performance Curve Analysis

The datasheet includes a section for "Typical Electrical / Optical Characteristics Curves." While the specific curves are not provided in the text, these typically include the following, which are critical for design:

• Relative Luminous Intensity vs. Forward Current (I-V Curve): Shows how light output increases with driving current. It is typically non-linear, saturating at higher currents.
• Forward Voltage vs. Forward Current: Illustrates the relationship between voltage and current, crucial for designing current-limiting circuits or constant-current drivers.
• Relative Luminous Intensity vs. Ambient Temperature: Demonstrates how light output decreases as the junction temperature of the LED rises. This is vital for thermal management in the application.
• Spectral Power Distribution: A graph showing the intensity of light emitted at each wavelength, confirming the blue color and spectral width.

Designers should consult these curves to optimize drive current for desired brightness, understand voltage requirements, and plan for thermal effects.

5. Mechanical and Package Information

5.1 Package Dimensions

The device conforms to a specific SMD footprint. Key dimensional notes include:

• All dimensions are in millimeters, with a general tolerance of ±0.25 mm unless specified otherwise.
• Quality criteria for the segment area: foreign material ≤ 10 mils, ink contamination ≤ 20 mils, bubbles ≤ 10 mils.
• Reflector bending must be ≤ 1% of its length.
• Burr on plastic pins must not exceed 0.14 mm.

Engineers must use the provided dimensional drawing (not fully detailed in text) to create the correct PCB land pattern.

5.2 Pin Configuration and Polarity

The device has a 10-pin configuration. Pin 1 is marked in the diagram. The pinout is as follows:

• Pin 1: Anode for segment E
• Pin 2: Anode for segment D
• Pin 3: Common Cathode 1
• Pin 4: Anode for segment C
• Pin 5: Anode for Decimal Point (DP)
• Pin 6: Anode for segment B
• Pin 7: Anode for segment A
• Pin 8: Common Cathode 2
• Pin 9: Anode for segment F
• Pin 10: Anode for segment G

The internal circuit diagram shows that all segment anodes are independent, while the cathodes for all segments are connected internally to two pins (3 and 8), which must be connected together on the PCB to form the common cathode.

5.3 Recommended Soldering Pad Pattern

A recommended PCB land pattern is provided to ensure reliable solder joint formation and proper alignment during reflow soldering. This pattern accounts for the package dimensions and solder paste volume requirements.

6. Soldering and Assembly Guidelines

6.1 SMT Soldering Instructions

Critical instructions for surface-mount assembly:

• Reflow Soldering (Primary Method):
  • Pre-heat: 120–150°C.
  • Pre-heat Time: Maximum 120 seconds.
  • Peak Temperature: Maximum 260°C.
  • Time Above Liquidus: Maximum 5 seconds.
• Soldering Iron (For Repair/Rework Only):
  • Iron Temperature: Maximum 300°C.
  • Contact Time: Maximum 3 seconds per joint.
• Crucial Restriction: The device can withstand a maximum of two reflow process cycles. After the first reflow, the board must be allowed to cool completely to room temperature before undergoing a second reflow process (e.g., for double-sided assembly).

6.2 Moisture Sensitivity and Storage

The SMD display is shipped in moisture-proof packaging. To prevent "popcorning" (package cracking due to rapid vapor expansion during reflow), the following storage conditions are mandated:

• Storage: Unopened bags should be stored at ≤ 30°C and ≤ 60% Relative Humidity.
• Exposure Time: Once the sealed bag is opened, moisture absorption begins. The components have a limited "floor life" at ambient conditions.
• Baking: If components have been exposed to ambient humidity beyond their safe limit, they must be baked before reflow to remove moisture. Baking should be performed only once to avoid thermal stress.
  • Components on reel: 60°C for ≥ 48 hours.
  • Loose components (in bulk): 100°C for ≥ 4 hours or 125°C for ≥ 2 hours.

7. Packaging and Ordering Information

7.1 Packaging Specifications

The device is supplied on tape-and-reel for automated pick-and-place assembly.

• Carrier Tape: Made of black conductive polystyrene alloy. Dimensions conform to EIA-481-D standards.
• Tape Dimensions: Includes specific pocket dimensions to hold the component securely. Camber (warp) is controlled within 1 mm over 250 mm length.
• Reel Information:
  • Standard packing length per 22-inch reel: 44.5 meters.
  • Component count per 13-inch reel: 700 pieces.
  • Minimum order quantity for remainder/reel ends: 200 pieces.
• Leader and Trailer Tape: The reel includes a leader (minimum 400 mm) and trailer (minimum 40 mm) for machine feeding.

8. Application Suggestions and Design Considerations

8.1 Typical Application Scenarios

• Test and Measurement Equipment: Digital multimeters, oscilloscopes, power supplies, where clear numeric readout is needed.
• Consumer Electronics: Audio amplifiers, home appliance displays (microwaves, ovens), fitness equipment.
• Industrial Controls: Panel meters, process indicators, timer displays.
• Automotive Aftermarket: Gauges and displays where high brightness is required.

8.2 Design Considerations

• Current Driving: Always use a constant current driver or a current-limiting resistor in series with each segment anode. Calculate the resistor value based on the supply voltage (V_cc), the typical LED forward voltage (V_F ~ 3.8V), and the desired forward current (I_F, e.g., 10-20 mA for good brightness while staying within limits). Example: R = (V_cc - V_F) / I_F.
• Thermal Management: Although power dissipation is low per segment, ensure adequate PCB copper area or thermal vias if multiple segments are illuminated simultaneously for extended periods, especially in high ambient temperatures. Remember the current derating rule.
• Microcontroller Interface: For common cathode displays, the microcontroller pins typically sink current (act as ground switches). Use GPIO pins configured as open-drain/low output or dedicated LED driver ICs with sufficient current sink capability. Ensure the total current sourced from the power supply is within its ratings.
• ESD Protection in Circuit: In the final application, consider adding transient voltage suppression (TVS) diodes or other protection on lines connected to the display, especially if they are exposed to user interfaces or external connectors.

9. Technical Comparison and Differentiation

While a direct comparison with other models is not in the datasheet, the LTS-5325CTB-P's key differentiators based on its specifications are:

• vs. Smaller Displays (e.g., 0.3-inch): Offers superior visibility at a distance due to its larger 0.56-inch digit height.
• vs. Through-Hole LED Displays: The SMD package enables automated assembly, reduces PCB space, and allows for lower-profile end products.
• vs. Standard Brightness LEDs: The high typical luminous intensity (up to 28500 µcd at 10mA) makes it suitable for applications requiring high brightness.
• vs. Non-Binned LEDs: The categorization for luminous intensity provides designers with more predictable and uniform brightness across all segments and multiple units, which is critical for professional-looking equipment.

10. Frequently Asked Questions (Based on Technical Parameters)

1. Q: What is the difference between peak wavelength (468 nm) and dominant wavelength (470 nm)?
   A: Peak wavelength is where the physical light output is strongest. Dominant wavelength is the single wavelength the human eye perceives as the color. They are often close, as here, but can differ for some colors. Both confirm a blue LED.
2. Q: Can I drive this display with a 5V supply and a resistor?
   A: Yes. With a 5V supply (V_cc) and a typical V_F of 3.8V, you need a current-limiting resistor. For I_F=10 mA: R = (5V - 3.8V) / 0.01A = 120 Ω. Use the next standard value, e.g., 120 Ω or 150 Ω. Always verify actual brightness and power dissipation.
3. Q: Why are there two common cathode pins (3 and 8)?
   A> This is for current handling and PCB layout flexibility. The total cathode current is the sum of currents from all illuminated segments. Having two pins splits this current, reducing current density per pin and improving reliability. Both pins MUST be connected to ground on your PCB.
4. Q: The maximum reflow cycles is two. What if I need to rework a board a third time?
   A> It is strongly discouraged. A third reflow exposes the plastic package and internal bonds to excessive thermal stress, significantly increasing the risk of failure. For rework, use a soldering iron with extreme care (max 300°C for 3 sec) only on the specific joint needing repair, avoiding heating the entire component.
5. Q: How do I interpret the luminous intensity matching ratio of 2:1?
   A> This means that within a single display unit, the brightest segment should not be more than twice as bright as the dimmest segment when driven under identical conditions. This ensures visual uniformity of the displayed character.

11. Practical Design and Usage Case

Case: Designing a Simple Digital Voltmeter Readout

A designer is creating a 0-30V DC voltmeter using a microcontroller with an ADC. The LTS-5325CTB-P is chosen for its readability.

1. Circuit Design: The microcontroller's I/O pins are connected to the segment anodes (A-G, DP) via 150 Ω current-limiting resistors (calculated for a 5V system). The two common cathode pins are connected together to a single NPN transistor (e.g., 2N3904) acting as a low-side switch, controlled by a microcontroller pin. This allows multiplexing if needed, though for a single digit, it can be constantly on.
2. Software: The microcontroller reads the ADC value, converts it to a voltage, and then maps that value to the correct 7-segment pattern (0-9). The segment data is sent to the corresponding I/O pins.
3. PCB Layout: The recommended soldering pattern from the datasheet is used for the footprint. Thermal reliefs are added to the pad connections to facilitate soldering. The ground connection for the common cathode is robust.
4. Assembly: The board is assembled using a standard lead-free reflow profile, ensuring the peak temperature does not exceed 260°C. The component is only subjected to one reflow cycle.
5. Result: The final product displays a clear, bright, and uniform blue voltage reading.

12. Operating Principle Introduction

The LTS-5325CTB-P operates on the principle of electroluminescence in a semiconductor p-n junction. The active material is InGaN (Indium Gallium Nitride). When a forward voltage exceeding the diode's turn-on voltage (approximately 3.3-3.8V) is applied, electrons from the n-type region and holes from the p-type region are injected into the active region. When these charge carriers recombine, they release energy in the form of photons (light). The specific composition of the InGaN alloy determines the bandgap energy, which in turn defines the wavelength (color) of the emitted light—in this case, blue (~470 nm). The sapphire substrate provides a crystalline template for growing the high-quality InGaN layers. The gray face and white segment material act as a diffuser and contrast enhancer, shaping the light into recognizable numeric segments.

13. Technology Trends and Context

This device represents a mature and widely adopted technology. The use of InGaN on sapphire for blue LEDs is a standard industrial process. Trends in display technology that provide context for this component include:

• Miniaturization: While 0.56-inch is a common size, there is a trend towards even smaller high-brightness SMD digits for ultra-compact devices.
• Increased Efficiency: Ongoing materials science improves the luminous efficacy (lumens per watt) of InGaN LEDs, allowing for higher brightness at lower currents or reduced thermal load.
• Integration: A trend exists towards integrating the LED display with its driver IC and microcontroller into more complete "smart display" modules, simplifying end-product design.
• Color Options & RGB: While this is a monochrome blue display, the underlying InGaN technology is also the foundation for producing green and, when combined with phosphors, white LEDs. Full-color RGB displays using tiny SMD LEDs are also becoming more common for more complex graphics.
• Alternative Technologies: For certain applications, OLED (Organic LED) displays offer advantages in thinness and viewing angle but may have different lifetime and brightness characteristics compared to inorganic LEDs like this one.

The LTS-5325CTB-P remains a robust, reliable, and cost-effective solution for applications requiring a simple, bright, and durable numeric display where SMD assembly is preferred.