LTS-4301JD LED Display Datasheet - 0.4-inch Digit Height - Hyper Red 650nm - 2.6V Forward Voltage - 70mW Power Dissipation - English Technical Document

1. Product Overview

The LTS-4301JD is a compact, high-performance single-digit numeric display module designed for applications requiring clear, bright numerical readouts. Its core function is to visually represent the digits 0 through 9 using a standard seven-segment configuration, augmented by a right-hand decimal point. The device is engineered for integration into a wide array of electronic equipment where space, power efficiency, and readability are critical factors.

The display utilizes advanced AlInGaP (Aluminum Indium Gallium Phosphide) semiconductor technology for its light-emitting elements. This material system is specifically chosen for its efficiency in producing high-brightness red light. The chips are fabricated on a non-transparent GaAs (Gallium Arsenide) substrate, which enhances contrast by preventing internal light scattering and improving the definition of the unlit segments. The package features a gray faceplate with white segment markings, providing an excellent off-state appearance and high contrast when the segments are illuminated.

The primary target markets for this component include industrial instrumentation, consumer appliances, test and measurement equipment, point-of-sale systems, and automotive dashboard displays. Its categorized luminous intensity ensures consistent brightness levels across production batches, which is vital for applications requiring uniform visual performance.

2. Technical Parameters Deep Objective Interpretation

2.1 Photometric and Optical Characteristics

The optical performance is defined under standard test conditions at an ambient temperature (Ta) of 25°C. The key parameter, Average Luminous Intensity (Iv), has a typical value of 650 µcd (microcandelas) when driven at a forward current (IF) of 1 mA. The minimum specified value is 200 µcd, ensuring a baseline level of brightness. Luminous intensity is measured using a sensor and filter combination calibrated to the CIE (Commission Internationale de l'Eclairage) standard photopic eye-response curve, guaranteeing that the reported values correspond to human visual perception.

The device emits light in the hyper-red spectrum. The Peak Emission Wavelength (λp) is typically 650 nanometers (nm). The Dominant Wavelength (λd), which is more closely related to the perceived color, is specified at 639 nm. The Spectral Line Half-Width (Δλ) is 20 nm, indicating the spectral purity and the narrow range of wavelengths emitted, which results in a saturated red color. A Luminous Intensity Matching Ratio of 2:1 maximum is specified, meaning the brightness difference between any two segments under identical drive conditions will not exceed this ratio, ensuring uniform appearance of the formed digit.

2.2 Electrical Parameters

The electrical characteristics define the operating boundaries and typical performance. The Forward Voltage per segment (VF) ranges from 2.1V to 2.6V at a test current of 20 mA. Designers must ensure the driving circuit can provide sufficient voltage to overcome this. The Absolute Maximum Ratings set strict limits: the Continuous Forward Current per segment must not exceed 25 mA, with a linear derating factor of 0.33 mA/°C above 25°C. This derating is crucial for thermal management; as the ambient temperature rises, the maximum allowable current must be reduced to prevent overheating and permanent damage.

A Peak Forward Current of 90 mA is permitted under pulsed conditions (1/10 duty cycle, 0.1 ms pulse width), which can be used for multiplexing schemes or short-term brightness enhancement. The maximum Reverse Voltage (VR) per segment is 5V; exceeding this can damage the LED's PN junction. The Reverse Current (IR) is specified at a maximum of 100 µA when 5V is applied in reverse bias, indicating the junction's leakage characteristic.

2.3 Thermal and Reliability Parameters

The device is rated for an Operating Temperature Range of -35°C to +85°C. This wide range makes it suitable for environments subject to significant temperature variations. The Storage Temperature Range is identical (-35°C to +85°C). The Power Dissipation per segment is limited to 70 mW. Managing this dissipation through proper current limiting and, if necessary, heatsinking is essential for long-term reliability. The datasheet also specifies a soldering temperature profile: the device can withstand 260°C for 3 seconds at a point 1/16 inch (approximately 1.6 mm) below the seating plane, which guides the reflow soldering process.

3. Binning System Explanation

The datasheet indicates that the devices are \"Categorized for Luminous Intensity.\" This implies a binning or sorting process post-manufacturing. While specific bin code details are not provided in this excerpt, typical categorization for such displays involves grouping units based on measured luminous intensity at a standard test current (e.g., 1 mA). This ensures that customers receive products with consistent brightness levels. Designers sourcing these components should confirm the specific binning structure from the manufacturer to ensure the selected intensity category meets their application's requirements for uniformity, especially when multiple displays are used side-by-side.

4. Performance Curve Analysis

The datasheet references \"Typical Electrical / Optical Characteristic Curves\" on the final page. Although the specific graphs are not detailed in the provided text, such curves typically included in full datasheets are critical for design. These would normally illustrate:

• Relative Luminous Intensity vs. Forward Current (I-V Curve): This graph shows how light output increases with drive current. It is typically non-linear, with efficiency often dropping at very high currents.
• Forward Voltage vs. Forward Current: This curve helps in designing the current-limiting circuitry by showing the dynamic resistance of the LED.
• Relative Luminous Intensity vs. Ambient Temperature: This shows the derating of light output as temperature increases, which is vital for applications operating in non-ambient conditions.
• Spectral Distribution: A plot of relative intensity versus wavelength, visually confirming the peak and dominant wavelength specifications and the spectral half-width.

Engineers should use these curves to optimize drive conditions for a balance of brightness, efficiency, and longevity, rather than operating solely at absolute maximum ratings.

5. Mechanical and Packaging Information

The device is presented with a detailed package dimension drawing. All dimensions are provided in millimeters, with a general tolerance of ±0.25 mm (0.01 inch) unless otherwise specified. The display has a digit height of 0.4 inches (10.0 mm). The mechanical drawing would define the overall length, width, and height of the package, the segment and decimal point placement, the lead (pin) spacing and dimensions, and any keying or orientation features. This information is essential for creating the PCB footprint, ensuring proper fit within the product enclosure, and aligning the display correctly on the board.

6. Pin Connection and Internal Circuit

The LTS-4301JD is a Common Cathode device. The pin connection diagram is explicitly provided:

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

The presence of two common cathode pins (3 and 8) is typical, serving to reduce current density in the package and improve reliability. The internal circuit diagram shows that all segment anodes (A-G and DP) are electrically isolated from each other, while their cathodes are connected together internally to the two common cathode pins. This configuration requires the driving circuit to source current to the individual segment anodes and sink the combined current through the common cathode connection(s).

7. Soldering and Assembly Guidelines

The key assembly guideline provided is the soldering temperature limit: the component can withstand 260°C for 3 seconds at a point 1.6 mm below the seating plane. This is a standard IPC reflow profile reference. For assembly:

• Use a recommended reflow profile for lead-free soldering (as indicated by the 260°C peak temperature).
• Ensure the PCB pad design matches the package dimensions to avoid tombstoning or misalignment.
• Avoid mechanical stress on the leads during handling. The plastic lens should not be touched directly with contaminated tools.
• Follow standard ESD (Electrostatic Discharge) precautions during handling and assembly to protect the semiconductor junctions.
• Adhere to the specified storage temperature range (-35°C to +85°C) and humidity conditions prior to use.

8. Application Suggestions

8.1 Typical Application Scenarios

This display is ideal for any device requiring a single, highly legible numeric readout. Common applications include: digital thermometers/hygrometers, timer and counter displays, voltage/current meter readouts, appliance control panels (e.g., ovens, microwaves), basic calculator displays, and status code indicators on network or industrial equipment.

8.2 Design Considerations

• Current Limiting: Always use a series current-limiting resistor for each segment anode. The resistor value is calculated as R = (Vsupply - VF) / IF, where VF is the forward voltage (use max value for safety) and IF is the desired operating current (not exceeding the continuous rating).
• Multiplexing: For multi-digit applications using several such displays, a multiplexed drive scheme is standard. This involves sequentially energizing one digit's common cathode at a time while presenting the segment data for that digit. The peak current rating allows for higher pulsed currents in this mode, but the duty cycle and average current must be managed to stay within the continuous power dissipation limits.
• Microcontroller Interface: The display is easily driven by a microcontroller's GPIO pins, often through a driver IC or transistor array to handle the higher current requirements, especially for the common cathode.
• Viewing Angle: The datasheet claims a wide viewing angle. For optimal placement, consider the primary sight lines of the end-user relative to the installed display.

9. Technical Comparison and Differentiation

Compared to older technologies like GaAsP (Gallium Arsenide Phosphide) red LEDs, the AlInGaP technology in the LTS-4301JD offers significantly higher luminous efficiency, resulting in greater brightness for the same input current or equivalent brightness at lower power. The use of a non-transparent substrate improves contrast compared to devices on transparent substrates, as it prevents unwanted emission from the chip sides. The gray face with white segments offers a professional, high-contrast appearance even when unpowered, which is superior to all-black or clear-face displays in many ambient lighting conditions. Its 0.4-inch digit height fills a specific niche between smaller, less readable displays and larger, more power-hungry ones.

10. Frequently Asked Questions Based on Technical Parameters

Q: Can I drive this display directly from a 5V microcontroller pin?
A: No. You must use a current-limiting resistor in series with each segment. For a 5V supply and a desired current of 20 mA, using the maximum VF of 2.6V, the resistor value would be (5V - 2.6V) / 0.020A = 120 Ohms. Always verify the microcontroller's pin current sourcing capability.

Q: What does \"common cathode\" mean for my circuit design?
A: It means all the cathodes (negative sides) of the LED segments are connected together inside the package. To light a segment, you apply a positive voltage (through a resistor) to its specific anode pin and connect the common cathode pin(s) to ground (0V).

Q: The maximum continuous current is 25 mA, but the test condition for VF uses 20 mA. Which should I use?
A: 20 mA is a standard test condition and a safe, typical operating point that provides good brightness while maintaining longevity. You can operate up to 25 mA if higher brightness is needed, but you must strictly adhere to the ambient temperature and derating rules. Operating at or near the maximum rating may reduce operational lifespan.

Q: Why are there two common cathode pins?
A> For mechanical symmetry and to distribute the total cathode current (which is the sum of currents from all lit segments) across two pins. This reduces current density per pin, improves reliability, and can make PCB layout easier.

11. Practical Design and Usage Case

Case: Designing a Simple Digital Voltmeter Readout.
A designer is creating a 0-5V DC voltmeter. An analog-to-digital converter (ADC) with a 3-digit output is connected to a microcontroller. The microcontroller's firmware converts the digital reading to a 3-digit number (e.g., 4.23V). To display this, three LTS-4301JD units are used. The design employs time-division multiplexing. The microcontroller uses a port to drive the segment anodes (A-G, DP) for all three displays in parallel. Three NPN transistors (or a dedicated driver IC) are used to sink current through the common cathode of each digit, one at a time, in rapid sequence (e.g., at 100 Hz per digit). The firmware synchronizes the segment data with the active digit cathode. Current-limiting resistors are placed on each of the eight segment lines. The high brightness and contrast ensure the reading is clear even in well-lit environments. The categorized luminous intensity ensures all three digits appear equally bright.

12. Principle Introduction

A seven-segment display is a form of electronic display device composed of seven light-emitting diodes (LEDs) arranged in a rectangular figure-eight pattern. Each LED is called a segment because it forms part of a digit when illuminated. By selectively turning on specific combinations of these seven segments, the display can represent the ten decimal digits (0-9) and some hexadecimal letters (A, b, C, d, E, F). An additional LED for a decimal point (DP) is often included. The LTS-4301JD implements this principle using AlInGaP semiconductor material. When a forward bias voltage exceeding the diode's junction potential is applied across a segment's anode and cathode, electrons and holes recombine in the active region of the semiconductor, releasing energy in the form of photons (light) at a wavelength determined by the material's bandgap—in this case, approximately 650 nm (red). The non-transparent substrate absorbs stray photons, enhancing contrast.

13. Development Trends

The evolution of seven-segment displays follows broader trends in optoelectronics. While the basic seven-segment form factor remains enduringly useful for numeric readouts, the underlying technology continues to advance. There is a constant drive towards higher luminous efficacy (more light output per watt of electrical input), which improves energy efficiency and allows for lower power operation or increased brightness. Wider color gamuts and the development of more efficient green and blue LEDs based on materials like InGaN (Indium Gallium Nitride) have enabled full-color, multi-digit dot-matrix displays to become more common, though seven-segment remains dominant for pure numeric applications due to its simplicity and cost-effectiveness. Integration is another trend, with driver electronics, microcontrollers, and sometimes even sensors being combined into \"smart display\" modules. However, discrete components like the LTS-4301JD maintain a strong position in designs requiring flexibility, specific performance characteristics, or cost optimization at higher volumes.