LTS-3401LJF LED Display Datasheet - 0.8-inch Digit Height - Yellow Orange Color - 2.6V Forward Voltage - 70mW Power Dissipation - English Technical Document

1. Product Overview

The LTS-3401LJF is a single-digit, seven-segment light-emitting diode (LED) display designed for applications requiring clear, low-power numeric indication. Its core technology is based on Aluminum Indium Gallium Phosphide (AlInGaP) semiconductor material, which is known for producing high-efficiency light in the amber to red-orange spectrum. This specific device emits in a yellow-orange color. The display features a gray face and white segments, which enhances contrast and readability under various lighting conditions. The primary design goals for this component are low power consumption, excellent character appearance with uniform segment illumination, and solid-state reliability, making it suitable for a wide range of consumer and industrial electronic devices where numeric data needs to be presented clearly and efficiently.

1.1 Core Advantages

• Low Power Operation: Engineered for minimal power draw, making it ideal for battery-powered or energy-sensitive applications.
• High Visibility: Offers excellent character appearance with continuous, uniform segments and a wide viewing angle, ensuring readability from various positions.
• Solid-State Reliability: As an LED-based device, it boasts long operational life, shock resistance, and consistent performance compared to mechanical or filament-based displays.
• Standard Interface: I.C. compatible drive requirements simplify integration with common microcontroller and logic circuits.
• Categorized Performance: Devices are binned for luminous intensity, allowing for consistent brightness matching in multi-digit applications.

2. Technical Specifications Deep Dive

This section provides a detailed, objective analysis of the key electrical, optical, and physical parameters defined in the datasheet.

2.1 Electrical Characteristics

The electrical parameters define the operating limits and conditions for the display.

• Absolute Maximum Ratings: These are stress limits that must not be exceeded under any conditions to prevent permanent damage.
  • Power Dissipation per Segment: 70 mW maximum. This limits the combined effect of forward current and voltage drop across each LED segment.
  • Continuous Forward Current per Segment: 25 mA maximum at 25°C. A linear derating factor of 0.33 mA/°C is applied as ambient temperature rises above 25°C.
  • Peak Forward Current per Segment: 60 mA maximum, but only under pulsed conditions (1/10 duty cycle, 0.1 ms pulse width). This allows for brief over-driving to achieve higher peak brightness in multiplexed applications.
  • Reverse Voltage per Segment: 5 V maximum. Exceeding this can damage the LED's PN junction.
  • Operating & Storage Temperature Range: -35°C to +85°C.
  • Solder Temperature: 260°C for 3 seconds at a distance of 1/16 inch (approx. 1.6 mm) below the seating plane. This is a critical parameter for wave or reflow soldering processes.
• Electrical/Optical Characteristics (at T_A=25°C): These are typical operating parameters.
  • Forward Voltage (V_F): 2.05V (Min), 2.6V (Typ) at I_F=20mA. This is the voltage drop across an active segment when driven with the specified current.
  • Reverse Current (I_R): 100 µA maximum at V_R=5V. This indicates the minimal leakage current when the LED is reverse-biased.

2.2 Optical Characteristics

The optical parameters quantify the light output and color properties of the display.

• Average Luminous Intensity (I_V): 320 µcd (Min), 900 µcd (Typ) at I_F=1mA. This is a measure of the perceived brightness of a segment as measured by a sensor filtered to match the human eye's photopic response (CIE curve). The wide range indicates a binning process.
• Luminous Intensity Matching Ratio (I_V-m): 2:1 maximum at I_F=10mA. This specifies the maximum allowable brightness variation between different segments of the same digit or between different units, ensuring visual uniformity.
• Peak Emission Wavelength (λ_p): 611 nm (Typ) at I_F=20mA. This is the wavelength at which the optical power output is greatest.
• Dominant Wavelength (λ_d): 605 nm (Typ) at I_F=20mA. This is the single wavelength perceived by the human eye that best matches the color of the emitted light, defining its yellow-orange hue.
• Spectral Line Half-Width (Δλ): 17 nm (Typ) at I_F=20mA. This indicates the spectral purity or bandwidth of the emitted light; a smaller value means a more monochromatic (pure) color.

3. Binning System Explanation

The datasheet indicates that the devices are \"Categorized for Luminous Intensity.\" This refers to a post-production sorting (binning) process.

• Luminous Intensity Binning: After manufacture, LEDs are tested and grouped based on their measured luminous intensity at a standard test current (e.g., 1mA or 10mA). The specified typical value of 900 µcd and minimum of 320 µcd define the possible bins. Using binned parts ensures consistent brightness levels across all segments of a multi-digit display, which is critical for aesthetic and functional uniformity in the final product. Designers should consult the manufacturer for specific bin code availability and specifications for procurement.

4. Performance Curve Analysis

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

• Relative Luminous Intensity vs. Forward Current (I-V Curve): This graph would show how light output increases with drive current, typically in a sub-linear fashion, highlighting efficiency changes.
• Forward Voltage vs. Forward Current: Illustrates the diode's exponential I-V relationship, crucial for designing current-limiting circuitry.
• Relative Luminous Intensity vs. Ambient Temperature: Shows how light output decreases as junction temperature rises, which is vital for thermal management in high-temperature or high-brightness applications.
• Spectral Distribution: A plot of relative intensity versus wavelength, showing the peak and dominant wavelengths and the spectral half-width visually.

Designers should always refer to the complete datasheet with graphs to understand these relationships fully for robust circuit design.

5. Mechanical and Package Information

5.1 Physical Dimensions

The device is described as a 0.8-inch digit height display, which corresponds to 20.32 mm for the height of the numeric character itself. The package dimensions drawing (referenced but not detailed in text) would specify the overall length, width, and height of the plastic package, lead spacing, and segment placement. Tolerances are typically ±0.25 mm unless otherwise noted. Precise mechanical drawings are essential for PCB footprint design and ensuring proper fit within an enclosure.

5.2 Pin Configuration and Internal Circuit

The LTS-3401LJF is a common anode display. This means the anodes of all LED segments (and the decimal points) are connected internally and brought out to common pins (4, 6, 12, 17). Individual segment cathodes (A-G, and left/right decimal points) have their own pins. To illuminate a segment, its corresponding cathode pin must be driven low (connected to ground or a current sink) while the common anode pin is held high (connected to V_CC through a current-limiting resistor). The pinout table is critical for correct PCB layout and software drive routine development. Several pins (1, 8, 9, 16, 18) are listed as \"NO PIN,\" meaning they are physically present but not electrically connected (N/C).

6. Soldering and Assembly Guidelines

The datasheet provides a key soldering parameter: the package can withstand a solder temperature of 260°C for 3 seconds, measured 1/16 inch (1.6 mm) below the seating plane. This is a standard reference for wave soldering. For reflow soldering, a standard lead-free profile with a peak temperature around 260°C would be applicable, but the time above liquidus should be controlled. It is recommended to follow standard JEDEC/IPC guidelines for handling moisture-sensitive devices (if applicable) and to avoid mechanical stress on the leads during assembly. Storage should be within the specified -35°C to +85°C temperature range in a dry environment.

7. Application Recommendations

7.1 Typical Application Scenarios

• Test and Measurement Equipment: Digital multimeters, frequency counters, power supplies.
• Consumer Electronics: Clocks, timers, kitchen appliances, audio equipment displays.
• Industrial Controls: Panel meters, process indicators, control system readouts.
• Automotive Aftermarket: Gauges and displays where high visibility and reliability are needed.

7.2 Design Considerations

• Current Limiting: Always use a series resistor for each common anode connection (or each segment in a multiplexed scheme) to set the forward current. Calculate the resistor value using R = (V_CC - V_F) / I_F. Use the maximum V_F from the datasheet for a safe design.
• Multiplexing: For multi-digit displays, a multiplexed drive circuit is common. This involves cycling power (via the common anode) to each digit rapidly while presenting the corresponding segment data for that digit. This greatly reduces the number of required I/O pins. Ensure the peak current rating (60 mA at 1/10 duty) is not exceeded in such configurations.
• Viewing Angle: The wide viewing angle is beneficial but consider the intended user's sight line when mounting the display.
• Thermal Management: While low power, in high ambient temperatures or high brightness settings, ensure the package temperature stays within limits by considering board layout and airflow.

8. Technical Comparison and Differentiation

The primary differentiator of the LTS-3401LJF is its use of AlInGaP technology for yellow-orange emission. Compared to older technologies like standard GaAsP (Gallium Arsenide Phosphide) LEDs, AlInGaP offers significantly higher luminous efficiency, resulting in brighter output for the same drive current or lower power consumption for the same brightness. It also generally provides better stability and color consistency over temperature and lifetime. Compared to white LEDs (which are typically blue LEDs with a phosphor coating), this monochromatic device offers higher efficacy for applications where a specific amber/orange color is desired, such as in low-light or night-vision compatible settings.

9. Frequently Asked Questions (Based on Technical Parameters)

• Q: What is the purpose of the \"No Pin\" connections?
  A: They are mechanical placeholders that help secure the package during soldering and provide structural integrity. They must not be connected to any electrical net in your circuit.
• Q: Can I drive this display directly from a 5V microcontroller pin?
  A: No. You must use a current-limiting resistor. Connecting 5V directly to the cathode (with anode high) would attempt to draw excessive current, damaging both the LED and possibly the microcontroller pin. Calculate the resistor based on your supply voltage and desired segment current.
• Q: What does \"Common Anode\" mean for my circuit design?
  A: It means you supply positive voltage (V_CC) to the common anode pin(s), and you sink current to ground through the individual cathode pins to turn segments on. Your drive circuit (e.g., a microcontroller) will activate a segment by setting its I/O pin connected to the cathode to a logic LOW (0V) state.
• Q: How do I achieve uniform brightness in a multi-digit design?
  A: Source components from the same luminous intensity bin code from the manufacturer. Additionally, ensure identical current-limiting resistor values for all segments and use a consistent drive current in your multiplexing or static drive scheme.

10. Design and Usage Case Study

Scenario: Designing a Simple Digital Voltmeter Readout.
A designer is creating a 3-digit DC voltmeter display using the LTS-3401LJF. They use a microcontroller with an analog-to-digital converter (ADC) to measure voltage. Three displays are used. The microcontroller pins are insufficient to drive all segments (3 digits * 8 segments = 24 lines) directly, so a multiplexing design is chosen. A single 8-bit shift register with constant current sink outputs (e.g., 74HC595 with external transistors or a dedicated LED driver IC) is used to control all segment cathodes (A-G, DP) for all digits. Three microcontroller I/O pins are used to selectively enable the common anode of each digit via small PNP transistors or MOSFETs. The software rapidly cycles through enabling each digit (1, 2, 3) while shifting out the corresponding segment pattern for that digit to the shift register. The persistence of vision makes all digits appear continuously lit. The designer calculates current-limiting resistors for the common anode lines based on a 5V supply, a V_F of 2.6V, and a desired average segment current of 10mA, adjusting for the 1/3 duty cycle of multiplexing three digits.

11. Technology Principle Introduction

The LTS-3401LJF is based on the electroluminescence principle in a semiconductor PN junction made of AlInGaP (Aluminum Indium Gallium Phosphide). When a forward voltage is applied, electrons from the N-type material recombine with holes from the P-type material in the active region, releasing energy in the form of photons (light). The specific composition of the AlInGaP alloy determines the bandgap energy of the semiconductor, which directly dictates the wavelength (color) of the emitted light—in this case, yellow-orange (~605 nm dominant wavelength). The use of a non-transparent GaAs substrate helps improve contrast by absorbing stray light, contributing to the display's excellent character appearance. The seven individual segments are formed by multiple tiny AlInGaP LED chips arranged in a pattern, each electrically isolated and addressable.

12. Technology Trends

While seven-segment LED displays remain a robust and cost-effective solution for numeric readouts, the broader display technology landscape is evolving. There is a trend towards higher integration, such as displays with built-in controllers (I2C or SPI interface) that drastically reduce the required microcontroller I/O and software complexity. In terms of materials, AlInGaP technology is mature and highly efficient for amber/red colors. For full-color or white applications, InGaN (Indium Gallium Nitride) based blue/green/white LEDs dominate. Future trends may include even lower operating voltages, higher efficiency (more light per watt), and the integration of displays into flexible or transparent substrates, although these are more relevant to newer display types than traditional segmented numeric devices. The core advantages of LEDs—reliability, longevity, and low-voltage operation—ensure their continued use in applications where these factors are paramount.