LTS-10304JD LED Display Datasheet - 1.0-inch Digit Height - Hyper Red 650nm - 24mA Forward Current - English Technical Document

1. Product Overview

The LTS-10304JD is a single-digit, seven-segment LED display designed for applications requiring clear numeric readouts with low power consumption. Its primary function is to provide a highly visible, reliable numeric indicator. The core advantage of this device lies in its use of AlInGaP (Aluminium Indium Gallium Phosphide) HYPER RED LED chips, which offer high brightness and efficiency. This technology, grown on a GaAs substrate, is known for superior performance in the red spectrum. The display features a black face with white segments, creating a high-contrast appearance that enhances readability. It is categorized for luminous intensity and is offered in a lead-free package compliant with RoHS directives, making it suitable for modern electronic designs with environmental considerations.

2. In-Depth Technical Parameter Analysis

2.1 Photometric and Optical Characteristics

The optical performance is central to this display's functionality. At a standard test current of 1mA per segment, the average luminous intensity (Iv) ranges from a minimum of 410 µcd to a typical value of 2200 µcd. This high brightness is achievable at very low drive currents, a key feature. The dominant wavelength (λd) is typically 639 nm, with a peak emission wavelength (λp) of 650 nm, placing it firmly in the hyper-red region of the visible spectrum. The spectral line half-width (Δλ) is 20 nm, indicating a relatively pure color emission. Luminous intensity matching between segments is specified at a ratio of 2:1 maximum, ensuring uniform appearance across the digit when driven under identical conditions.

2.2 Electrical and Thermal Ratings

The electrical parameters define the operating limits and conditions. The absolute maximum continuous forward current per segment is 24 mA at 25°C, with a derating factor of 0.28 mA/°C as temperature increases. A peak forward current of 90 mA is permissible under pulsed conditions (1/10 duty cycle, 0.1ms pulse width). The forward voltage (Vf) per segment typically ranges from 4.2V to a maximum of 5.2V at a drive current of 20mA. The maximum reverse voltage rating is 10V. Power dissipation per segment is rated at 134 mW. The device is rated for an operating and storage temperature range of -35°C to +105°C, indicating robustness for various environments. Soldering must be performed at a maximum temperature of 260°C for no more than 3 seconds at a distance of 1.6mm below the seating plane.

3. Mechanical and Packaging Information

3.1 Physical Dimensions and Drawing

The device has a digit height of 1.0 inch (25.4 mm). The package dimensions are provided in the datasheet with all measurements in millimeters. Standard tolerances are ±0.25 mm unless otherwise specified. A specific note indicates a pin tip shift tolerance of +0.4 mm, which is important for PCB layout and assembly planning. The drawing typically shows the overall length, width, and height of the package, the digit segment dimensions, and the precise spacing and diameter of the 14 pins.

3.2 Pin Configuration and Polarity Identification

The LTS-10304JD is a common cathode display. It features 14 pins, not all of which are active. The pin connection is as follows: Pin 1 (Anode E), Pin 2 (Anode D), Pin 3 (No Pin), Pin 4 (Common Cathode), Pin 5 (Anode C), Pin 6 (Anode D.P. - Decimal Point), Pin 7 (No Pin), Pin 8 (Anode B), Pin 9 (Anode A), Pin 10 (No Pin), Pin 11 (Common Cathode), Pin 12 (Anode F), Pin 13 (No Pin), Pin 14 (Anode G). The presence of two common cathode pins (4 and 11) allows for flexible circuit design. The decimal point is located on the right-hand side of the digit.

3.3 Internal Circuit Diagram

The internal circuit diagram shows the electrical connection of the seven segments (A through G) and the decimal point (DP). All segment anodes are isolated from each other, while their cathodes are connected together to the common cathode pins. This configuration is standard for a common-cathode, multiplexable display, where individual segments are lit by applying a positive voltage to their respective anode pins while sinking current through the common cathode.

4. Performance Curve Analysis

The datasheet references typical electrical and optical characteristic curves. While the specific graphs are not detailed in the provided text, standard curves for such a device would typically include: Relative Luminous Intensity vs. Forward Current (I-V Curve): This graph would show how light output increases with drive current, demonstrating the high efficiency at low currents (e.g., 1mA). Forward Voltage vs. Forward Current: Illustrating the diode's IV characteristic, important for designing current-limiting circuitry. Relative Luminous Intensity vs. Ambient Temperature: Showing how light output decreases as the junction temperature rises, which is critical for understanding thermal management needs. Spectral Distribution: A plot of relative intensity versus wavelength, centering around 650 nm with the specified 20 nm half-width.

5. Soldering and Assembly Guidelines

Assembly must adhere to the specified thermal limits to prevent damage. The maximum allowable solder temperature is 260°C, and the component should be subjected to this temperature for a maximum of 3 seconds. This measurement is taken 1.6mm (1/16 inch) below the seating plane of the package. These parameters are compatible with standard lead-free reflow soldering profiles. It is crucial to ensure the PCB pad design matches the recommended footprint to achieve reliable solder joints without causing mechanical stress on the LED package pins.

6. Application Suggestions and Design Considerations

6.1 Typical Application Scenarios

This display is ideal for battery-powered or low-power electronic devices where clear numeric indication is required. Common applications include portable instrumentation, consumer electronics (clocks, timers, scales), industrial control panels, medical devices, and automotive dashboard displays (for secondary functions). Its low-current operation extends battery life significantly.

6.2 Circuit Design and Driving Methods

To utilize the low-current capability, designers can use simple current-limiting resistors or constant-current drivers. For multiplexing multiple digits (though this is a single-digit unit, the principle applies to multi-digit systems using similar displays), a common-cathode configuration is easily driven by sinking current through a transistor or dedicated driver IC on the cathode side while sequentially enabling the segment anodes. The typical forward voltage of 4.2-5.2V at 20mA means the display often requires a supply voltage higher than 5V for direct driving with resistors; a boost converter or dedicated LED driver may be necessary in 3.3V or 5V systems to achieve full brightness. At the recommended low current of 1mA per segment, the voltage drop will be lower, potentially allowing operation from a 5V rail.

6.3 Thermal and Optical Design Notes

While the device has a wide operating temperature range, maintaining a lower junction temperature will preserve luminous output and long-term reliability. Adequate spacing on the PCB and, if necessary, thermal vias can help. The high contrast ratio (black face, white segments) is optimized for direct viewing. For best readability in bright ambient light, ensure the display is not overpowered by external light sources; a recessed bezel or filter can be beneficial.

7. Technical Comparison and Differentiation

The primary differentiation of the LTS-10304JD lies in its AlInGaP Hyper Red technology combined with low-current operation. Compared to older GaAsP or standard red GaP LEDs, AlInGaP offers significantly higher luminous efficiency, resulting in brighter output at the same current or equivalent brightness at much lower current. Compared to other low-current displays, its specification for operation down to 1mA per segment with matched intensity is a key advantage for ultra-low-power designs. The lead-free, RoHS-compliant construction aligns it with modern manufacturing standards, unlike some legacy components.

8. Frequently Asked Questions (Based on Technical Parameters)

Q: Can I drive this display directly from a 5V microcontroller pin?
A: Not directly for full brightness. At 20mA, the forward voltage (4.2-5.2V) is very close to or exceeds 5V, leaving little voltage drop for a current-limiting resistor. You would need a driver circuit. However, at 1mA, the forward voltage is lower, making it more feasible, though a driver IC is still recommended for control and multiplexing.

Q: What is the purpose of the two common cathode pins?
A> They are internally connected. Providing two pins helps distribute current, reduces current density in a single pin/PCB trace, and offers layout flexibility. You can use one or both, but connecting both is generally good practice.

Q: How is the luminous intensity \"categorized\"?
A: The datasheet indicates the parts are categorized (binned) for luminous intensity. This means during manufacturing, units are tested and sorted into different intensity groups. The datasheet provides the min/typ range (410-2200 µcd @1mA). For precise matching in critical applications, consult the manufacturer for specific binning codes.

Q: What does \"segments are matched\" mean?
A> It means the electrical and optical characteristics (like forward voltage and luminous intensity) are closely matched from one segment to another within the same device. This ensures uniform brightness when all segments are driven with the same current, which is not always guaranteed in lower-grade displays.

9. Practical Design and Usage Case

Consider designing a low-power environmental data logger that displays temperature on a 4-digit readout. Using four LTS-10304JD displays, a designer would create a multiplexing circuit. A low-power microcontroller would sequentially activate each digit's common cathode via a small NPN transistor while outputting the segment pattern for that digit on a set of I/O pins (possibly through a shift register or port expander to save pins). By setting the segment drive current to 2-3mA (well below the maximum), excellent readability is achieved while minimizing total system power consumption. The high contrast ratio ensures the display is readable in both indoor and shaded outdoor conditions. The wide temperature range of the display matches the logger's operational spec.

10. Operating Principle Introduction

A seven-segment LED display is an assembly of multiple light-emitting diodes arranged in a figure-eight pattern. Each of the seven bars (segments A-G) and the decimal point (DP) is an individual LED. In a common cathode configuration like the LTS-10304JD, the cathodes of all these internal LEDs are connected together to one or more common pins. To illuminate a specific segment, a positive voltage must be applied to its dedicated anode pin while the common cathode is connected to ground (or a lower voltage), completing the circuit and allowing current to flow. By controlling which combination of segments is lit, the numerals 0-9 and some letters can be formed. The AlInGaP material system emits light when electrons and holes recombine in the active region under forward bias, with the specific alloy composition determining the red color wavelength.

11. Technology Trends and Context

The development of AlInGaP LED technology in the 1990s was a major breakthrough for high-brightness red, orange, and yellow LEDs. It largely replaced the less efficient GaAsP and GaP technologies in applications requiring high visibility. The trend in display components continues toward higher efficiency (more light per watt), lower operating voltages, and integration. While discrete seven-segment displays remain vital for many applications, there is a parallel trend toward integrated dot-matrix displays and OLEDs for more complex graphics. However, for simple, high-reliability, low-power, and high-brightness numeric readouts, AlInGaP-based seven-segment displays like the LTS-10304JD continue to be a preferred and cost-effective solution, especially in industrial and automotive contexts where robustness and long lifetime are paramount.