LTD-4608JR LED Display Datasheet - 0.4-inch Digit Height - AlInGaP Super Red - 2.6V Forward Voltage - English Technical Document

1. Product Overview

The LTD-4608JR is a dual-digit, seven-segment alphanumeric LED display module. It is designed for applications requiring clear, bright numeric readouts such as instrumentation panels, consumer electronics, industrial controls, and test equipment. The device utilizes advanced AlInGaP (Aluminum Indium Gallium Phosphide) semiconductor technology for its light-emitting chips, which are mounted on a non-transparent GaAs substrate. This construction contributes to its performance characteristics. The display features a gray faceplate with white segment markings, providing high contrast for optimal legibility under various lighting conditions.

1.1 Core Features and Advantages

• Digit Size: Features a 0.4-inch (10.0 mm) character height, offering a good balance between size and readability.
• Segment Quality: Provides continuous, uniform light emission across each segment for a consistent visual appearance.
• Power Efficiency: Engineered for low power requirement, making it suitable for battery-powered or energy-conscious devices.
• Optical Performance: Delivers high brightness and high contrast, ensuring visibility in both dim and brightly lit environments.
• Viewing Angle: Offers 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.
• Binning: The luminous intensity is categorized (binned), allowing for selection of units with matched brightness levels in multi-display applications.
• Environmental Compliance: The package is lead-free and complies with the RoHS (Restriction of Hazardous Substances) directive.

1.2 Device Configuration

The part number LTD-4608JR specifies a device with AlInGaP Super Red LED chips arranged in a duplex (dual-digit), common anode configuration. It includes a right-hand decimal point. The common anode design simplifies multiplexing driving circuits, where the anodes of each digit are controlled separately while the cathodes (segment pins) are shared.

2. Technical Parameters: In-Depth Objective Interpretation

2.1 Absolute Maximum Ratings

These ratings define the limits beyond which permanent damage to the device may occur. Operation should always be maintained within these boundaries.

• Power Dissipation per Segment: 70 mW maximum. Exceeding this can lead to overheating and accelerated degradation.
• Peak Forward Current per Segment: 90 mA under pulsed conditions (1/10 duty cycle, 0.1ms pulse width). This is for short-duration testing, not continuous operation.
• Continuous Forward Current per Segment: 25 mA at 25°C. This rating derates linearly at 0.28 mA/°C as ambient temperature (Ta) increases above 25°C. For example, at 85°C, the maximum allowable 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. The device is rated for industrial temperature ranges.
• Soldering Temperature: The leads can be soldered at 260°C for 5 seconds, measured 1/16 inch (approx. 1.6 mm) below the seating plane.

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

These parameters define the normal operating performance of the display.

• Average Luminous Intensity (Iv): Ranges from 320 to 850 microcandelas (µcd) at a forward current (IF) of 1 mA. This wide range indicates the binning process, where devices are sorted by brightness.
• Peak Emission Wavelength (λp): 639 nm, which falls within the red region of the visible spectrum.
• Forward Voltage per Segment (VF): Typically 2.6V with a maximum of 2.6V at IF=20 mA. The minimum is 2.0V. Circuit design must account for this range to ensure consistent current drive.
• Reverse Current (IR): Maximum 100 µA at a reverse voltage (VR) of 5V. This parameter is for test purposes only; the device is not designed for continuous reverse bias operation.
• Luminous Intensity Matching Ratio: 2:1 maximum for segments within the same "similar light area." This means the brightest segment should not be more than twice as bright as the dimmest segment within a defined group, ensuring uniformity.
• Cross Talk: Specified as ≤2.5%. This refers to unwanted light leakage from an energized segment to an adjacent non-energized segment.

3. Binning System Explanation

The LTD-4608JR employs a categorization system for luminous intensity. This is a standard practice in LED manufacturing to group devices with similar light output. The marking on the module includes a "Z" code which represents the bin code. Designers can specify a particular bin code when ordering to ensure consistent brightness across all displays in a product, which is critical for applications where multiple displays are used side-by-side.

4. Performance Curve Analysis

The datasheet references typical curves which are essential for understanding device behavior under non-standard conditions. While the specific graphs are not provided in the text, standard curves for such devices typically include:

• Relative Luminous Intensity vs. Forward Current (I-V Curve): Shows how light output increases with drive current, usually in a non-linear relationship. Operating above the recommended current leads to diminishing returns in brightness and increased heat.
• Relative Luminous Intensity vs. Ambient Temperature: Demonstrates the thermal derating of light output. As temperature increases, luminous efficiency generally decreases.
• Forward Voltage vs. Forward Current: Illustrates the diode's V-I characteristic, crucial for designing the current-limiting circuitry.
• Spectral Distribution: A plot of relative intensity versus wavelength, showing the narrow bandwidth typical of AlInGaP LEDs, centered around the dominant wavelength of 631 nm.

5. Mechanical & Package Information

5.1 Package Dimensions

The display has a standard dual-in-line package footprint. Key dimensional notes include:

• All dimensions are in millimeters with a general tolerance of ±0.20 mm.
• Pin tip shift tolerance is ±0.4 mm.
• Limits are defined for foreign material, ink contamination, bending of the reflector, and bubbles within the segment area to ensure cosmetic and optical quality.
• A PCB hole diameter of 1.30 mm is recommended for best fit.

5.2 Pin Connection and Polarity

The device has 10 pins in a single row. The internal circuit diagram shows a common anode configuration for two digits. The pinout is as follows:

1. Pin 1: Cathode C
2. Pin 2: Cathode D.P. (Decimal Point)
3. Pin 3: Cathode E
4. Pin 4: Common Anode (Digit 2)
5. Pin 5: Cathode D
6. Pin 6: Cathode F
7. Pin 7: Cathode G
8. Pin 8: Cathode B
9. Pin 9: Common Anode (Digit 1)
10. Pin 10: Cathode A

This arrangement is optimal for multiplexed driving, where Digit 1 and Digit 2 anodes are turned on alternately at a high frequency while the appropriate segment cathodes are energized to form the desired number.

6. Soldering & Assembly Guidelines

6.1 Automated Soldering

For wave or reflow soldering, the condition is 260°C for 5 seconds, measured 1.6 mm (1/16 inch) below the seating plane of the package. The temperature of the display body itself must not exceed the maximum storage temperature of 105°C during the process.

6.2 Manual Soldering

When hand-soldering, a soldering iron tip temperature of 350°C ±30°C is specified. The soldering time should not exceed 5 seconds per pin, again measured from 1.6 mm below the seating plane. Using a heatsink on the lead between the iron tip and the package body is a good practice to prevent excessive heat transfer.

7. Application Recommendations

7.1 Typical Application Scenarios

The LTD-4608JR is suited for ordinary electronic equipment including, but not limited to:

• Digital multimeters and oscilloscopes
• Audio equipment displays (amplifiers, receivers)
• Industrial timer and counter panels
• Consumer appliances (microwaves, washing machines)
• Point-of-sale terminals and basic information displays

7.2 Critical Design Considerations

• Drive Method: Constant current driving is strongly recommended over constant voltage driving. This ensures consistent luminous intensity regardless of variations in the forward voltage (VF) from segment to segment or unit to unit. A simple series resistor can provide a basic form of current limiting, but dedicated LED driver ICs offer better stability and multiplexing control.
• Circuit Protection: The driving circuit must incorporate protection against reverse voltages and voltage transients that can occur during power-up or shutdown. A simple diode in series or a transient voltage suppressor (TVS) can be used depending on the application.
• Thermal Management: Do not exceed the absolute maximum ratings for current and power dissipation. Ensure adequate ventilation in the end product to keep the ambient temperature around the display within specified limits. The linear derating of continuous current with temperature must be factored into the design for high-temperature environments.
• Multiplexing: When multiplexing the two digits, the refresh rate must be high enough to avoid visible flicker (typically >60 Hz). The peak current during the multiplexed pulse can be higher than the DC continuous current rating, but the average current over time must remain within the continuous rating, considering the duty cycle.

8. Reliability Testing

The device undergoes a comprehensive suite of reliability tests based on military (MIL-STD), Japanese industrial (JIS), and internal standards. These tests validate its robustness and longevity:

• Operating Life Test (RTOL): 1000 hours of continuous operation at maximum rated conditions.
• Environmental Stress Tests: Includes high-temperature/high-humidity storage, high-temperature storage, low-temperature storage, temperature cycling, and thermal shock tests.
• Mechanical & Process Tests: Solder resistance (260°C for 10s) and solderability (245°C for 5s) tests ensure the leads can withstand standard assembly processes.

9. Cautions and Usage Limitations

The datasheet includes important cautions that define the intended use and liability:

• The display is designed for "ordinary" electronic equipment. Applications requiring exceptional reliability, especially where failure could jeopardize life or health (aviation, medical devices, critical safety systems), require prior consultation and likely a different grade of component.
• The manufacturer is not responsible for damage resulting from operation outside the absolute maximum ratings or failure to follow the provided instructions.
• Strict adherence to the electrical and thermal limits is emphasized as the primary means of ensuring product lifetime and performance.

10. Technical Comparison and Differentiation

Compared to older technologies like GaAsP (Gallium Arsenide Phosphide) red LEDs, the AlInGaP technology used in the LTD-4608JR offers significant advantages:

• Higher Efficiency & Brightness: AlInGaP provides superior luminous efficiency, resulting in higher brightness for the same drive current.
• Better Temperature Stability: The light output of AlInGaP LEDs is generally less sensitive to temperature changes than older technologies.
• Color Purity: The spectral line half-width (Δλ) of 20 nm indicates a relatively pure red color compared to broader-spectrum sources.
• The common anode configuration with a right-hand decimal point is a specific feature that may differentiate it from other dual-digit displays which might have common cathode or left-hand decimal configurations.

11. Frequently Asked Questions (Based on Technical Parameters)

Q: Can I drive this display with a 5V supply and a resistor?
A: Yes, but careful calculation is needed. With a typical VF of 2.6V at 20 mA, a series resistor value of (5V - 2.6V) / 0.02A = 120 Ohms would be required. You must ensure the 5V supply is stable and account for the minimum VF (2.0V) which would result in a higher current. A constant current driver is more reliable.

Q: What does the luminous intensity matching ratio of 2:1 mean for my design?
A: It means that within a single display, the brightness difference between segments should not exceed a factor of two. For most applications, this is acceptable. If perfect uniformity is critical, you may need to select units from a tighter bin or implement individual segment calibration in software/hardware.

Q: How do I interpret the date code "YYWW" on the marking?
A: "YYWW" typically stands for a two-digit year followed by a two-digit week of manufacture. For example, "2415" would indicate the device was manufactured in the 15th week of 2024.

12. Practical Design and Usage Case

Scenario: Designing a simple two-digit counter.
A microcontroller (e.g., an Arduino, PIC, or ARM Cortex-M) would be used. Two I/O pins would be configured as outputs to drive the common anodes (Pins 4 and 9) via small NPN transistors or MOSFETs. Seven other I/O pins (or a shift register like 74HC595 to save pins) would drive the segment cathodes (Pins 1, 3, 5, 6, 7, 8, 10) through current-limiting resistors or a constant current sink array. The decimal point (Pin 2) can be ignored or used. The firmware would implement multiplexing: turn on the transistor for Digit 1, set the segment pattern for the first digit's value, wait a short time (e.g., 5ms), turn off Digit 1, turn on the transistor for Digit 2, set the segment pattern for the second digit, wait, and repeat. The current for each segment during its ON time must be calculated based on the duty cycle (50% for two digits) to ensure the average current does not exceed the continuous rating.

13. Operating Principle Introduction

A seven-segment LED display is an assembly of multiple Light Emitting Diodes (LEDs). Each segment (labeled A through G) and the decimal point is a separate LED or a group of LED chips. In a common anode configuration like the LTD-4608JR, the anodes of all LEDs for a given digit are connected together to a common pin. The cathode of each individual segment LED is brought out to a separate pin. To illuminate a segment, its cathode pin is connected to a lower voltage (ground or a current sink) while the common anode pin is connected to a higher voltage (Vcc), completing the circuit and allowing current to flow through that specific LED. By controlling which cathode pins are active relative to the active anode pin, different numerals and some letters can be formed.

14. Technology Trends

While discrete seven-segment LED displays remain relevant for specific applications, the broader trend in display technology is moving towards integrated solutions:

• Integrated Driver Displays: Modules that include the LED array, multiplexing circuitry, and sometimes a simple serial interface (I2C, SPI) on a single PCB, simplifying design for the end engineer.
• Shift to OLED and LCD: For applications requiring more complex graphics or alphanumerics, organic LED (OLED) and liquid crystal display (LCD) modules are becoming more cost-competitive and offer greater flexibility.
• Miniaturization & Efficiency: Ongoing development in LED chip technology continues to improve luminous efficacy (lumens per watt), allowing for brighter displays at lower power or smaller chip sizes for higher resolution within the same footprint. However, the fundamental AlInGaP technology for red/orange/yellow remains a high-performance standard.

The LTD-4608JR represents a mature, reliable, and well-understood technology ideal for applications where simple, bright, low-cost numeric readouts are required.