LTS-4301JR LED Display Datasheet - 0.4-inch Digit Height - Super Red Color - 2.6V Forward Voltage - 70mW Power Dissipation - English Technical Document

1. Product Overview

The LTS-4301JR is a single-digit, seven-segment alphanumeric LED display module. It is designed to provide clear, high-contrast numeric readouts in a compact form factor. The device utilizes advanced AlInGaP (Aluminum Indium Gallium Phosphide) semiconductor technology for its light-emitting chips, which are fabricated on a transparent GaAs substrate. This combination results in the characteristic \"super red\" emission. The display features a gray faceplate with white segment markings, enhancing contrast and readability under various lighting conditions. Its primary application is in electronic equipment where a simple, reliable, and bright numeric indicator is required, such as in instrumentation, consumer electronics, and industrial control panels.

1.1 Core Features and Advantages

• 0.4-inch (10.0 mm) Digit Height: Offers a balance between size and visibility, suitable for panel-mounted applications where space is a consideration.
• Continuous Uniform Segments: Provides a consistent and unbroken luminous appearance across each segment, improving aesthetic quality and legibility.
• Low Power Requirement: Designed for energy efficiency, making it suitable for battery-powered or low-power devices.
• High Brightness & High Contrast: The AlInGaP super red chips deliver intense luminous output, while the gray face/white segment design maximizes contrast for easy viewing.
• Wide Viewing Angle: Ensures the display remains readable from a broad range of perspectives, not just head-on.
• Categorized for Luminous Intensity: Units are binned according to their light output, allowing for consistent brightness matching in multi-digit applications.
• Lead-Free Package (RoHS Compliant): Manufactured in accordance with environmental regulations restricting hazardous substances.
• Solid-State Reliability: LEDs offer long operational life, shock resistance, and fast switching times compared to other display technologies.

1.2 Device Identification

The part number LTS-4301JR specifically denotes a common cathode configuration with a right-hand decimal point. The \"JR\" suffix is critical for identifying the decimal point placement. It is an AlInGaP super red emission type display.

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 under these conditions is not guaranteed.

• Power Dissipation per Segment: 70 mW. This is the maximum allowable power loss as heat for a single segment. Exceeding this can lead to overheating and accelerated degradation.
• Peak Forward Current per Segment: 90 mA (at 1/10 duty cycle, 0.1ms pulse width). This rating is for pulsed operation only, not for continuous DC driving.
• Continuous Forward Current per Segment: 25 mA at 25°C. This current derates linearly at a rate of 0.33 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) * 0.33 mA/°C) = ~5.2 mA.
• Operating & Storage Temperature Range: -35°C to +85°C. The device is rated for industrial temperature ranges.
• Solder Condition: Wave or reflow soldering should be performed with the solder point at least 1/16 inch (≈1.6 mm) below the seating plane of the display body. The recommended peak temperature is 260°C for a maximum of 3 seconds to prevent thermal damage to the plastic package and internal bonds.

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

These are the typical performance parameters under specified test conditions.

• Average Luminous Intensity (I_V): 200-520 µcd at I_F=1mA. This wide range indicates the device is binned. The luminous intensity is measured using a sensor filtered to match the photopic (human eye) response curve (CIE). A tolerance of ±15% applies.
• Peak Emission Wavelength (λ_p): 639 nm (typical) at I_F=20mA. This is the wavelength at which the emitted optical power is greatest.
• Dominant Wavelength (λ_d): 631 nm (typical) at I_F=20mA. This is the wavelength perceived by the human eye, defining the \"super red\" color. Tolerance is ±1 nm.
• Spectral Line Half-Width (Δλ): 20 nm (typical) at I_F=20mA. This specifies the spectral purity or bandwidth of the emitted light.
• Forward Voltage per Chip (V_F): 2.0V (Min), 2.6V (Typ), with a tolerance of ±0.1V at I_F=20mA. Circuit design must account for this range to ensure proper current regulation.
• Reverse Current (I_R): 100 µA (Max) at V_R=5V. This parameter is for test purposes only; continuous reverse bias operation is prohibited.
• Luminous Intensity Matching Ratio: 2:1 (Max). In a multi-digit setup, the brightest segment should not be more than twice as bright as the dimmest segment within a similar light area, ensuring uniformity.
• Cross Talk: ≤ 2.5%. This refers to unwanted light emission from a segment that is meant to be off, caused by electrical leakage or optical coupling.

3. Binning System Explanation

The LTS-4301JR employs a binning system primarily for Luminous Intensity. As indicated by the typical I_V range of 200-520 µcd, displays are sorted into different bins based on their measured light output at a standard test current (1mA). This allows designers to select displays from the same intensity bin when assembling multi-digit units, preventing noticeable brightness differences between digits. The datasheet advises choosing displays from the same bin to \"avoid hue uneven problems,\" which in this context refers to brightness uniformity rather than color shift, as the dominant wavelength is tightly controlled (±1 nm).

4. Performance Curve Analysis

The datasheet references typical characteristic curves which would normally include:

• Relative Luminous Intensity vs. Forward Current (I-V Curve): Shows how light output increases with drive current, typically in a sub-linear relationship. Operating above the recommended continuous current leads to efficiency drop (droop) and reduced lifetime.
• Forward Voltage vs. Forward Current: Illustrates the diode's I-V characteristic, crucial for designing the current-limiting circuitry.
• Relative Luminous Intensity vs. Ambient Temperature: Demonstrates the thermal quenching effect, where light output decreases as junction temperature rises. This underscores the importance of thermal management and current derating.
• Spectral Distribution: A graph showing the relative power emitted across wavelengths, centered around 631-639 nm with a ~20 nm bandwidth.

These curves are essential for understanding the device's behavior under non-standard conditions and for optimizing the drive circuit for performance and longevity.

5. Mechanical and Package Information

5.1 Package Dimensions

The display conforms to a standard 10-pin, single-digit DIP (Dual In-line Package) outline. Key dimensional notes include:

• All linear dimensions are in millimeters (mm).
• General tolerance is ±0.25 mm unless otherwise specified.
• Pin tip shift tolerance is ±0.4 mm.
• Defect allowances on the display face: foreign material ≤ 10 mils (0.254 mm), ink contamination ≤ 20 mils (0.508 mm), bubbles in segments ≤ 10 mils.
• Reflector bending must be ≤ 1% of its length.
• The recommended PCB hole diameter for the pins is 0.9 mm to ensure a proper fit.

5.2 Pin Connection and Polarity

The LTS-4301JR is a common cathode device. It has two common cathode pins (Pin 3 and Pin 8), which must be connected to ground (or the low-side driver). The anodes for segments A-G and the decimal point (D.P.) are on separate pins (Pins 1, 2, 4, 5, 6, 7, 9, 10). Pin 6 is specifically for the right-hand decimal point anode. A pin is marked as \"No Connection\" (N/C). The internal circuit diagram shows each segment LED and the decimal point LED with their anodes connected to individual pins and their cathodes tied together to the common pins.

6. Soldering and Assembly Guidelines

6.1 Soldering Process

The absolute maximum rating specifies a soldering condition of 260°C for 3 seconds, measured 1/16\" below the seating plane. This is compatible with standard wave soldering and many reflow profiles. Care must be taken to avoid excessive heat transfer to the plastic body, which can cause deformation or internal damage.

6.2 Storage Conditions

To prevent pin oxidation and moisture absorption (MSL concerns), the following storage conditions are recommended for the LED display in its original packaging:

• Temperature: 5°C to 30°C.
• Relative Humidity: Below 60% RH.

If the moisture barrier bag is opened or the product is stored outside these conditions for more than 6 months, a bake-out at 60°C for 48 hours is recommended prior to assembly, which should be completed within one week after baking.

7. Application Suggestions and Design Considerations

7.1 Typical Application Scenarios

This display is intended for \"ordinary electronic equipment\" such as office equipment, communication devices, and household appliances. It is suitable for any application requiring a single, bright, and reliable numeric readout: digital multimeters, clocks, timers, panel meters, appliance controls, and test equipment.

7.2 Critical Design Notes (Cautions)

• Drive Circuit Design: Constant current driving is strongly recommended over constant voltage to ensure consistent brightness and protect the LEDs. The circuit must be designed to accommodate the full V_F range (2.0V to 2.6V).
• Current Limiting: The safe operating current must be selected based on the maximum ambient temperature, applying the derating factor of 0.33 mA/°C above 25°C.
• Protection: The circuit must include protection against reverse voltages and transient voltage spikes during power cycling to prevent damage.
• Thermal Management: Avoid operating at currents or ambient temperatures higher than rated, as this causes severe light output degradation and premature failure.
• Mechanical Handling: Do not apply abnormal force to the display body during assembly. If a decorative film or filter is applied with pressure-sensitive adhesive, avoid letting it press directly against the display face, as shifting may occur.
• Multi-Digit Assemblies: Always use displays from the same luminous intensity bin to ensure uniform appearance.
• Environmental: Avoid rapid temperature changes in humid environments to prevent condensation on the display.

8. Technical Comparison and Differentiation

The LTS-4301JR's primary differentiators are its use of AlInGaP technology and its specific super red color. Compared to older GaAsP or GaP LED technologies, AlInGaP offers significantly higher luminous efficiency, resulting in greater brightness for the same drive current. The \"super red\" (631-639 nm) is a distinct, saturated red color. The gray face/white segment design provides a high contrast ratio even when the LED is off, improving overall aesthetics. Its categorization for luminous intensity is a key feature for professional applications requiring consistency.

9. Frequently Asked Questions (Based on Technical Parameters)

Q: Can I drive this display with a 5V supply and a simple resistor?
A: Yes, but careful calculation is needed. Using the maximum V_F of 2.6V and a desired I_F of 20mA, the series resistor value would be R = (5V - 2.6V) / 0.02A = 120 Ω. However, you must check power dissipation in the resistor and ensure the current does not exceed the derated limit for your operating temperature.

Q: Why is constant current drive recommended?
A: LED brightness is a function of current, not voltage. The forward voltage (V_F) has a tolerance and varies with temperature. A constant current source ensures the desired luminous intensity is maintained regardless of these variations, leading to consistent performance and longer life.

Q: What does \"common cathode\" mean for my microcontroller interface?
A: For a common cathode display, the common pins are connected to ground. The microcontroller pins (or driver IC) should source current to the individual segment anode pins to turn them on. This typically requires active-high signals from the driver.

Q: The peak current is 90mA, can I use that for brighter display?
A: No. The 90mA rating is strictly for very short pulses (0.1ms width) at a low duty cycle (1/10 or 10%). Using this current continuously will destroy the LED. Always design for the continuous forward current rating (25mA at 25°C, derated with temperature).

10. Practical Design and Usage Case

Case: Designing a Single-Digit Voltmeter Readout.
A designer is creating a simple 0-9V voltmeter with a single-digit display for coarse indication. They select the LTS-4301JR for its brightness and clarity. The circuit uses a microcontroller with an ADC to measure voltage. The microcontroller's I/O pins cannot source enough current, so a dedicated LED driver IC (e.g., a 7-segment decoder/driver with constant current outputs) is used. The designer sets the driver's constant current to 15 mA per segment, providing ample brightness while staying well within the 25mA rating at room temperature, allowing headroom for warmer environments. The common cathode pins are connected to the driver's ground. The designer specifies LTS-4301JR units from the same intensity bin (e.g., 400-450 µcd) to the purchasing department to ensure uniform brightness. A current-limiting resistor is not needed as the driver IC provides regulation. The PCB layout places the holes for the display pins at the recommended 0.9 mm diameter.

11. Operating Principle Introduction

The LTS-4301JR is based on the electroluminescence principle of a semiconductor P-N junction. When a forward bias voltage exceeding the diode's turn-on voltage (≈2.0-2.6V) is applied, electrons from the n-type AlInGaP region recombine with holes from the p-type region in the active layer. This recombination event releases energy in the form of photons (light). The specific composition of the AlInGaP alloy determines the bandgap energy, which directly corresponds to the wavelength (color) of the emitted light—in this case, red light around 631-639 nm. The transparent GaAs substrate allows more of this generated light to escape, enhancing external efficiency. Each segment of the '7' shape contains one or more of these tiny LED chips connected in parallel.

12. Technology Trends and Context

AlInGaP LED technology represents a significant advancement over earlier red LED materials like GaAsP. It provides superior luminous efficacy, meaning more light output per electrical watt input, and better temperature stability. The trend in display components is towards higher efficiency, lower power consumption, and greater integration. While discrete 7-segment displays like the LTS-4301JR remain vital for specific applications requiring simplicity, robustness, and direct visibility, many new designs are migrating towards integrated dot-matrix LED displays or OLEDs for graphical flexibility. However, for dedicated numeric readouts where cost, brightness, and reliability are paramount, single-digit AlInGaP displays continue to be a preferred and technologically mature solution.