LTD-5435CKG-P LED Display Datasheet - 0.56-inch Digit Height - AlInGaP Green - 2.6V Forward Voltage - 25mA Continuous Current - English Technical Documentation

1. Product Overview

The LTD-5435CKG-P is a surface-mount device (SMD) featuring a dual-digit, seven-segment display configuration. Its primary application is in electronic devices requiring clear, bright numeric readouts, such as instrumentation panels, consumer electronics, industrial controls, and test equipment. The display utilizes Aluminium Indium Gallium Phosphide (AlInGaP) semiconductor technology for the LED chips, which are fabricated on a non-transparent Gallium Arsenide (GaAs) substrate. This technology is known for producing high-efficiency light emission in the red, orange, yellow, and green spectral regions. The device is constructed with a gray face and white segments, providing high contrast for optimal readability. It is specifically designed for reverse mount assembly processes.

1.1 Core Advantages

• High Brightness & Contrast: The AlInGaP technology and design yield excellent luminous intensity and character definition.
• Low Power Consumption: Designed for efficient operation with standard drive currents.
• Wide Viewing Angle: Ensures visibility from various positions.
• Solid-State Reliability: LED technology offers long operational life and resistance to shock and vibration.
• Categorized Output: Devices are binned for luminous intensity and hue (dominant wavelength) to ensure consistency in applications.
• RoHS Compliance: The package is lead-free, adhering to environmental regulations.

2. Technical Specifications Deep Dive

2.1 Absolute Maximum Ratings

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

• Power Dissipation per Segment: 70 mW
• Peak Forward Current per Segment: 60 mA (at 1 kHz, 10% duty cycle)
• Continuous Forward Current per Segment: 25 mA
• Forward Current Derating: 0.28 mA/°C above 25°C ambient temperature.
• Operating Temperature Range: -40°C to +105°C
• Storage Temperature Range: -40°C to +105°C

2.2 Electrical & Optical Characteristics

Measured at an ambient temperature (Ta) of 25°C, these are the typical performance parameters.

• Average Luminous Intensity per Segment (I_V): 14,000 µcd (Min), 26,000 µcd (Typ) at I_F = 10 mA.
• Peak Emission Wavelength (λ_p): 571 nm (Typ) at I_F = 20 mA.
• Spectral Line Half-Width (Δλ): 15 nm (Typ) at I_F = 20 mA.
• Dominant Wavelength (λ_d): 568 nm to 572 nm at I_F = 20 mA.
• Forward Voltage per Segment (V_F): 2.0 V (Min), 2.6 V (Typ) at I_F = 20 mA.
• Reverse Current per Segment (I_R): 100 µA (Max) at V_R = 5V. Note: This is a test condition; continuous reverse bias operation is not supported.
• Luminous Intensity Matching Ratio (I_V-m): 2:1 (Max) at I_F = 10 mA, ensuring segment brightness uniformity.
• Cross Talk: ≤ 2.5%, minimizing unwanted illumination of adjacent segments.

3. Binning System Explanation

To guarantee color and brightness consistency in production, the displays are categorized into bins.

3.1 Luminous Intensity Binning

Devices are sorted based on their average luminous intensity per segment at 10 mA.

• Grade P: 13,701 µcd to 21,820 µcd
• Grade Q: 21,821 µcd to 34,700 µcd
• Grade R: 34,701 µcd to 55,170 µcd
• The overall luminous intensity tolerance is ±15%.

3.2 Hue (Dominant Wavelength) Binning

Devices are also binned by their dominant wavelength at 20 mA to control the shade of green.

• Grade 5: 568.1 nm to 570.0 nm
• Grade 6: 570.1 nm to 572.0 nm
• The tolerance for each dominant wavelength bin is ±1 nm.

4. Performance Curve Analysis

The datasheet includes typical characteristic curves (not reproduced in text here but described). These curves graphically represent the relationship between key parameters, aiding in circuit design and performance prediction.

• Forward Current vs. Forward Voltage (I_F-V_F): Shows the non-linear relationship, critical for selecting current-limiting resistors or designing constant-current drivers.
• Luminous Intensity vs. Forward Current (I_V-I_F): Illustrates how light output increases with current, typically in a sub-linear fashion at higher currents due to heating effects.
• Luminous Intensity vs. Ambient Temperature (I_V-T_a): Demonstrates the decrease in light output as junction temperature rises, which is crucial for thermal management in the application.
• Spectral Distribution: A plot of relative intensity versus wavelength, showing the narrow emission peak characteristic of AlInGaP LEDs, centered around 571 nm.

5. Mechanical & Package Information

5.1 Package Dimensions

The device has a digit height of 0.56 inches (14.22 mm). Detailed dimensional drawings specify the overall package size, segment placement, and lead positions. All dimensions are in millimeters with a general tolerance of ±0.25 mm unless otherwise noted.

5.2 Solder Pad vs. Painting Diagram

This diagram is critical for PCB layout. It defines the solder pad area versus the painted (solder mask) area to ensure proper solder joint formation and prevent short circuits. Key notes include:

• Maximum plastic pin burr: 0.14 mm.
• Maximum PCB warping: 0.06 mm.
• Solder pad plating specification: Copper (Cu) min. 1200 µin, Nickel (Ni) min. 150 µin, Gold (Au) min. 4 µin.
• Painting (solder mask) thickness: 400 µin.

5.3 Pin Connection & Internal Circuit

The display has a multiplex common anode configuration. The internal circuit diagram shows two common anodes (one for each digit) and individual cathodes for each segment (A-G) and the colon/decimal points (L1, L2). The pinout is as follows:

• Pin 1: No Connection (NC)
• Pin 2: Cathode E
• Pin 3: Common Anode Digit 1
• Pin 4: Cathode D
• Pin 5: Cathode C
• Pin 6: Cathode L1, L2 (Colon)
• Pin 7: Common Anode Digit 2
• Pin 8: Cathode B
• Pin 9: Cathode A
• Pin 10: NC
• Pin 11: Cathode F
• Pin 12: Cathode G

6. Soldering & Assembly Guidelines

6.1 SMT Soldering Instructions

Proper soldering is essential for reliability.

• Reflow Soldering (Maximum 2 cycles):
  • Pre-heat: 120–150°C
  • Pre-heat Time: 120 seconds maximum
  • Peak Temperature: 260°C maximum
  • Time above liquidus: 5 seconds maximum
• Hand Soldering (Iron, Maximum 1 cycle):
  • Temperature: 300°C maximum
  • Time: 3 seconds maximum
• A cooling period to room temperature is required between the first and second reflow cycles if a second pass is necessary.

6.2 Recommended Soldering Pattern

A land pattern diagram is provided for PCB design, specifying the optimal copper pad dimensions (in mm) to ensure a reliable solder fillet and mechanical strength.

7. Packaging & Handling

7.1 Packing Formats

• Reel Dimensions: Specifications for the tape-and-reel packaging used for automated assembly.
• Carrier Dimensions: Details of the embossed carrier tape that holds the components.
• Direction of Pulling Out: Clearly indicated to prevent damage during feeder setup.

7.2 Moisture Sensitivity & Baking

The SMD display is moisture-sensitive (MSL). It is shipped in a sealed moisture-proof bag with a desiccant.

• Storage: Unopened bags should be stored at ≤30°C and ≤90% RH.
• Floor Life: Once the bag is opened, components must be used within a specified time (implied as 1 week under controlled conditions <30°C, <60% RH) or baked before reflow.
• Baking Conditions:
  • In Reel: 60°C for ≥48 hours.
  • In Bulk: 100°C for ≥4 hours or 125°C for ≥2 hours.
  • Baking should be performed only once to avoid thermal stress degradation.

8. Application Suggestions

8.1 Typical Application Scenarios

• Digital Multimeters & Test Equipment: For clear, bright numeric readouts.
• Industrial Control Panels: Displaying process variables like temperature, pressure, or count.
• Consumer Appliances: Microwave ovens, washing machines, or audio equipment displays.
• Automotive Aftermarket Displays: Where high brightness and wide viewing angle are beneficial.

8.2 Design Considerations

• Drive Circuit: Use constant current drivers or appropriate current-limiting resistors for each segment/anode combination, considering the multiplexed common anode design. The forward voltage and current ratings must be adhered to.
• Thermal Management: Ensure the PCB design allows for adequate heat dissipation, especially if operating near maximum current or in high ambient temperatures, as luminous intensity decreases with temperature.
• Viewing Angle: The wide viewing angle is an advantage, but the mounting height and bezel design should be considered to maximize readability for the end-user.
• ESD Protection: Implement standard ESD handling and protection practices during assembly, as LEDs are sensitive to electrostatic discharge.

9. Technical Comparison & Differentiation

Compared to other technologies like traditional GaP or newer InGaN-based green LEDs, the AlInGaP technology in the LTD-5435CKG-P offers specific advantages:

• vs. Older GaP Green LEDs: AlInGaP provides significantly higher luminous efficiency and brightness, better color purity (narrower spectrum), and improved reliability.
• vs. InGaN (Blue/Yellow Phosphor) Green LEDs: AlInGaP green LEDs typically have a higher efficacy in the pure green spectrum (around 570 nm) and do not suffer from phosphor degradation or color shift over time. They offer a distinct, saturated green color.
• Key Differentiator: The combination of high brightness (up to Grade R bin), excellent contrast (gray face/white segments), and the proven reliability of AlInGaP technology makes this display suitable for applications demanding long-life and consistent performance.

10. Frequently Asked Questions (Based on Technical Parameters)

10.1 What is the difference between peak wavelength and dominant wavelength?

Peak Wavelength (λ_p): The single wavelength where the spectral power distribution is maximum (571 nm Typ). Dominant Wavelength (λ_d): The single wavelength of monochromatic light that matches the perceived color of the LED. It is the parameter used for hue binning (568-572 nm).

10.2 Can I drive this display with a 5V supply?

Yes, but not directly. The typical forward voltage is 2.6V at 20 mA. You must use a current-limiting resistor in series with each segment/anode path. The resistor value is calculated as R = (V_supply - V_F) / I_F. For a 5V supply and 20 mA target: R = (5V - 2.6V) / 0.02A = 120 Ω. Always verify power dissipation in the resistor.

10.3 Why is there a limit on the number of reflow cycles?

Multiple reflow cycles subject the component to repeated thermal stress, which can potentially damage the internal wire bonds, degrade the LED chip, or delaminate the package materials. The limit of two cycles is a reliability precaution.

10.4 What does \"categorized for luminous intensity\" mean for my design?

It means you can select a specific bin (P, Q, R) when ordering. For a product where brightness uniformity across all units is critical, you would specify a tighter bin (e.g., only Grade Q). This may affect cost and availability but ensures consistent visual performance.

11. Design-in Case Study

Scenario: Designing a new benchtop power supply unit requiring a bright, reliable voltage/current display.

Selection Rationale: The LTD-5435CKG-P was chosen for its 0.56\" digit height (easily readable at a distance), high brightness (Grade R bin specified for sunlight readability), and AlInGaP reliability for continuous operation. The common anode configuration simplified the multiplexing driver circuit design using a single microcontroller.

Implementation: A constant current driver IC was used to supply 15 mA per segment (derated from the 25 mA max for longevity and thermal management). The PCB layout followed the recommended solder pad pattern precisely. Components were stored in a dry cabinet after the moisture-proof bag was opened and used within 3 days to avoid the need for baking.

12. Technology Principle Introduction

The LED chips in this display are based on Aluminium Indium Gallium Phosphide (AlInGaP) semiconductor material. By varying the ratios of Al, In, Ga, and P, the bandgap of the semiconductor can be engineered to emit light at specific wavelengths in the red to green region of the spectrum. In this case, the composition is tuned for green emission around 571 nm. The electrons and holes recombine in the active region of the semiconductor junction, releasing energy in the form of photons (light). The non-transparent GaAs substrate absorbs some light, but the chip design and package reflector are optimized to direct light out through the top of the segment, achieving high efficiency and brightness.

13. Technology Trends

While AlInGaP remains the dominant high-efficiency technology for red, orange, amber, and pure green LEDs, the broader LED industry sees ongoing trends:

• Miniaturization: Continued reduction in package size for higher-density displays.
• Increased Efficiency: Ongoing material and epitaxial growth improvements yield more lumens per watt.
• Direct Green InGaN: Research into efficient direct green emission from Indium Gallium Nitride (InGaN) materials continues, which could eventually offer an alternative for some applications.
• Integration: Trends towards displays with integrated driver circuitry (\"smart displays\") to simplify system design, though the LTD-5435CKG-P remains a standard, driver-less component.

The LTD-5435CKG-P represents a mature, reliable, and high-performance solution within its specific niche of medium-sized, high-brightness numeric displays.