LTD-6740KD-06J LED Display Datasheet - 0.56-inch Digit Height - AlInGaP Hyper Red - 2.6V Forward Voltage - 70mW Power - English Technical Document

1. Product Overview

The LTD-6740KD-06J is a dual-digit, seven-segment light-emitting diode (LED) display module. Its primary function is to provide a clear, legible numeric readout in various electronic devices. The core technology utilizes AlInGaP (Aluminum Indium Gallium Phosphide) semiconductor material to produce Hyper Red light emission. This material system, grown on a non-transparent GaAs substrate, is known for its high efficiency and brightness in the red spectral region. The device features a gray-colored faceplate with white segment markings, offering a high-contrast appearance ideal for user interfaces.

1.1 Key Features and Advantages

The display is designed with several user-centric and performance-oriented features:

• Digit Height: 0.56 inches (14.22 mm), providing excellent visibility.
• Segment Uniformity: Continuous and uniform light emission across each segment ensures consistent character appearance.
• Power Efficiency: Low power requirement, making it suitable for battery-powered or energy-conscious applications.
• Optical Performance: High brightness and high contrast ratio enhance readability under various ambient lighting conditions.
• Viewing Angle: Wide viewing angle allows the display to be read from off-axis positions.
• Reliability: Solid-state construction offers long operational life and resistance to shock and vibration.
• Binning: Devices are categorized (binned) for luminous intensity, allowing for consistent brightness matching in multi-digit applications.
• Environmental Compliance: The package is lead-free, complying with RoHS (Restriction of Hazardous Substances) directives.

1.2 Target Applications and Market

This display is intended for use in ordinary electronic equipment. Typical application areas include office automation equipment (e.g., calculators, desk clocks), communication devices, instrumentation panels, household appliances, and consumer electronics where clear numeric indication is required. It is designed for applications where high reliability is expected under standard operating conditions.

2. Technical Specifications and Objective Interpretation

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

2.1 Absolute Maximum Ratings

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

• Power Dissipation per Segment: 70 mW maximum. This limit is crucial for thermal management.
• Peak Forward Current per Segment: 90 mA, but only under pulsed conditions (1/10 duty cycle, 0.1ms pulse width). This rating is for brief, high-current pulses, not continuous operation.
• Continuous Forward Current per Segment: Derated linearly from 25 mA at 25°C at a rate of 0.28 mA/°C. This means the allowable continuous current decreases as ambient temperature (Ta) increases to prevent overheating.
• Reverse Voltage per Segment: 5 V maximum. Exceeding this can cause junction breakdown.
• Operating & Storage Temperature Range: -35°C to +105°C. The device is rated for industrial temperature ranges.
• Soldering Temperature: 260°C for 5 seconds, measured 1/16 inch (approx. 1.6 mm) below the seating plane.

2.2 Electrical & Optical Characteristics

These are typical operating parameters measured at Ta=25°C, defining the device's performance under normal conditions.

• Average Luminous Intensity (Iv): 320 ucd (min), 700 ucd (typ) at a forward current (IF) of 1 mA. This is the key measure of brightness.
• Peak Emission Wavelength (λp): 650 nm (typ) at IF=20mA, placing it in the Hyper Red region of the spectrum.
• Dominant Wavelength (λd): 639 nm (typ). This is the wavelength perceived by the human eye.
• Forward Voltage per Chip (VF): 2.1V (min), 2.6V (typ) at IF=20mA. This parameter is essential for designing the current-limiting circuitry.
• Reverse Current per Segment (IR): 100 µA (max) at VR=5V. This is a leakage current specification.
• Luminous Intensity Matching Ratio: 2:1 (max) for segments within the same light area. This ensures visual consistency between segments.
• Cross Talk: ≤ 2.50%. This specifies the amount of unintended light leakage between adjacent segments.

3. Binning System Explanation

The datasheet indicates that devices are \"categorized for luminous intensity.\" This refers to a binning process where manufactured LEDs are sorted based on measured light output (Iv) at a standard test current (1mA). Devices falling within specific intensity ranges are grouped into bins. This allows designers to select parts from the same bin to ensure uniform brightness across all digits and segments in an assembly, avoiding a patchy or uneven display appearance. The specific bin code is marked on the module as \"Z\".

4. Performance Curve Analysis

While the provided PDF excerpt mentions \"Typical Electrical / Optical Characteristics Curves,\" the specific graphs are not included in the text. Typically, such curves for an LED display would include:

• Relative Luminous Intensity vs. Forward Current (I-V Curve): Shows how light output increases with current, usually in a non-linear relationship. It helps determine the operating point for desired brightness.
• Forward Voltage vs. Forward Current: Illustrates the diode's I-V characteristic, crucial for driver design.
• Relative Luminous Intensity vs. Ambient Temperature: Demonstrates how light output decreases as junction temperature rises, highlighting the importance of thermal management.
• Spectral Distribution: A plot of relative intensity versus wavelength, showing the narrow bandwidth characteristic of AlInGaP LEDs centered around 650 nm.

5. Mechanical and Package Information

5.1 Package Dimensions

The display has a standard dual-digit seven-segment through-hole package. Key dimensional notes include:

• All dimensions are in millimeters with a general tolerance of ±0.25 mm unless specified otherwise.
• Pin length is specified (subject to revisions noted in the document). The recommended PCB hole diameter is 1.30 mm.
• Tolerances are provided for pin tip shift, foreign materials, bubbles in the segment, bending of the reflector, and surface ink contamination to define visual and mechanical quality.

5.2 Pin Connection and Circuit Diagram

The device has an 18-pin configuration. It is a common cathode type, meaning the cathodes (negative terminals) of all LEDs for each digit are connected together internally. The internal circuit diagram shows two independent sets of seven segments plus a decimal point, one set for each digit. The pinout table clearly defines the function of each pin (e.g., Pin 1: Anode E for Digit 1, Pin 14: Common Cathode for Digit 1). Correct interpretation of this table is essential for proper PCB layout and multiplexing driver circuit design.

5.3 Polarity and Marking

The module is marked with the Part Number (LTD-6740KD-06J), a Date Code in YYWW format, the Manufacturing Country, and the Bin Code (Z). Proper orientation during assembly is critical and can be determined from the pin-1 identifier on the package drawing.

6. Soldering and Assembly Guidelines

6.1 Soldering Profile

The datasheet provides specific soldering conditions to prevent thermal damage:

• Automatic Soldering: 260°C for 5 seconds, measured 1.6 mm (1/16 inch) below the seating plane.
• Manual Soldering: 350°C ±30°C for a maximum of 5 seconds.

Adhering to these time and temperature limits is crucial. Excessive heat or prolonged exposure can damage the plastic package, internal wire bonds, or the LED semiconductor material itself.

6.2 Storage and Handling

While not explicitly detailed beyond the storage temperature range (-35°C to +105°C), standard ESD (Electrostatic Discharge) precautions should be observed when handling these devices. They should be stored in a dry, anti-static environment.

7. Packaging and Ordering Information

The packing specification is hierarchical:

• Units per Tube: 20 displays are packed in one tube.
• Tubes per Inner Carton: 30 tubes, resulting in 600 units per inner carton.
• Tubes per Outer Carton: 120 tubes, resulting in 2400 units per outer carton.

The primary part number for ordering is LTD-6740KD-06J. The suffix \"-06J\" likely denotes specific options such as right-hand decimal point placement, color (gray face/white segment), and possibly the intensity bin.

8. Application Suggestions

8.1 Typical Application Circuits

As a common cathode display, it is typically driven using a multiplexing technique. A microcontroller or dedicated driver IC sequentially activates each digit's common cathode (sinking current) while providing the appropriate segment anode data (sourcing current) for that digit. This method reduces the number of required I/O pins compared to static driving. External current-limiting resistors are mandatory for each segment anode (or a regulated current source) to set the forward current (IF) to the desired value, typically between 5-20 mA depending on the required brightness and power budget.

8.2 Design Considerations

• Current Limiting: Always use series resistors. Calculate resistor value as R = (Vcc - VF) / IF, where VF is taken from the datasheet (e.g., 2.6V typ).
• Multiplexing Frequency: Use a refresh rate high enough to avoid visible flicker, typically above 60 Hz per digit.
• Peak Current in Multiplexing: When multiplexed with a duty cycle (DC), the instantaneous segment current can be higher than the average. Ensure the peak current does not exceed the Absolute Maximum Rating for Peak Forward Current (90 mA under specified conditions).
• Thermal Management: Ensure the PCB and overall design allow for heat dissipation, especially if operating near maximum ratings or in high ambient temperatures.

9. Technical Comparison and Differentiation

The key differentiators of the LTD-6740KD-06J are its use of AlInGaP Hyper Red technology and its specific mechanical/optical specifications. Compared to older GaAsP or GaP red LEDs, AlInGaP offers significantly higher luminous efficiency and brightness. Compared to other colors or technologies, the 650 nm Hyper Red wavelength provides a distinct, saturated red color. The 0.56-inch digit height, gray face/white segment combination, and common cathode configuration position it for specific readability and interface design requirements.

10. Frequently Asked Questions (Based on Technical Parameters)

Q1: What is the difference between Peak Wavelength (650 nm) and Dominant Wavelength (639 nm)?
A1: Peak wavelength is the point of maximum power output in the spectrum. Dominant wavelength is the single wavelength that would produce the same color perception as the LED's output. For a monochromatic source like this red LED, they are close but not identical due to the shape of the human eye's sensitivity curve.

Q2: Can I drive this display with a 5V supply?
A2: Yes, but you must use a current-limiting resistor. For example, to achieve a typical IF of 20 mA with a VF of 2.6V using a 5V supply: R = (5V - 2.6V) / 0.02A = 120 Ohms. A standard 120Ω resistor would be suitable.

Q3: What does \"Luminous Intensity Matching Ratio ≤ 2:1\" mean?
A3: It means the brightest segment in a device will be no more than twice as bright as the dimmest segment within the same defined \"light area.\" This ensures visual uniformity.

Q4: Why is there a derating curve for continuous forward current?
A4: As temperature increases, the LED's ability to dissipate heat decreases. To prevent the junction temperature from exceeding safe limits, the maximum allowed continuous current must be reduced. The derating factor of 0.28 mA/°C provides the guideline for this reduction.

11. Practical Design and Usage Case

Case: Designing a Simple Digital Voltmeter Readout
A designer is building a 2-digit DC voltmeter using a microcontroller with an ADC. The LTD-6740KD-06J is selected for its readability. The microcontroller will run a multiplexing routine. Two of its I/O pins are configured as open-drain outputs to sink current for the common cathodes (Digits 1 & 2). Eight other I/O pins (7 segments + 1 decimal point) are configured to source current through 150Ω resistors to the segment anodes. The software scans each digit at a 100 Hz rate, converting the measured voltage to BCD format and looking up the corresponding 7-segment pattern from a table to output to the anodes. The gray face provides good contrast in the well-lit lab environment.

12. Operating Principle

An LED is a semiconductor diode. When a forward voltage exceeding its bandgap energy is applied across the p-n junction, electrons and holes recombine in the active region (the AlInGaP layer in this case). This recombination releases energy in the form of photons (light). The specific wavelength of the light (color) is determined by the bandgap energy of the semiconductor material. AlInGaP has a bandgap corresponding to red/orange light. In a seven-segment display, multiple individual LED chips are mounted in the pattern of the segments and electrically interconnected according to the pinout diagram.

13. Technology Trends

While traditional through-hole seven-segment displays like this one remain relevant for many applications, the broader trend in display technology is towards surface-mount device (SMD) packages for automated assembly, higher density, and lower profile. There is also a trend towards integration, where the driver circuitry is combined with the display module. Furthermore, for numeric readouts, dot-matrix or fully integrated alphanumeric displays offer greater flexibility. However, the simplicity, robustness, high brightness, and excellent readability of discrete seven-segment LEDs ensure their continued use in instrumentation, industrial controls, and applications where a classic, highly legible numeric display is preferred.