LTS-3401TBE 0.8-Inch Blue LED Display Datasheet - Digit Height 20.32mm - Forward Voltage 3.8V - Power 70mW - English Technical Document

1. Product Overview

The LTS-3401TBE is a solid-state, seven-segment alphanumeric display module designed for applications requiring clear, bright numeric readouts. Its primary function is to visually represent digits (0-9) and some letters using individually addressable LED segments. The device utilizes blue LED chips based on InGaN (Indium Gallium Nitride) epitaxy on a sapphire substrate. The display features a light gray face and white segment color, which provides high contrast for excellent readability. It is categorized as a common anode type display, meaning the anodes of all segments are connected internally to common pins, requiring a current-sinking driver configuration.

1.1 Core Advantages and Target Market

This display is engineered for low-power operation, making it suitable for battery-powered or energy-conscious devices. Key advantages include its low current requirement, with segments capable of being driven effectively at currents as low as 1mA, and excellent luminous intensity matching between segments for uniform appearance. The high brightness and wide viewing angle ensure visibility from various perspectives. Its solid-state construction offers high reliability and long operational life compared to other display technologies. The primary target markets include portable instrumentation, consumer electronics, industrial control panels, test equipment, and any device requiring a compact, reliable numeric display.

2. Technical Parameter Deep Dive

2.1 Photometric and Optical Characteristics

The optical performance is central to the display's functionality. Under a standard test condition of a 10mA forward current (I_F) per segment, the average luminous intensity (I_V) ranges from a minimum of 6.4 millicandelas (mcd) to a typical value of 10 mcd. This intensity is measured using a sensor filtered to match the CIE photopic eye-response curve, ensuring the value correlates with human perception. The dominant wavelength (λ_d) is specified at 470 nanometers (nm), placing the emission in the blue region of the visible spectrum. The peak emission wavelength (λ_p) is typically 468 nm, and the spectral line half-width (Δλ) is 25 nm, indicating a relatively pure blue color. The luminous intensity matching ratio between segments is 2:1 maximum, ensuring acceptable uniformity across the digit.

2.2 Electrical Parameters

The electrical characteristics define the drive requirements and limits. The absolute maximum continuous forward current per segment is 20 mA at 25°C, derating linearly by 0.25 mA/°C as ambient temperature increases. The peak forward current, for pulsed operation at a 1/10 duty cycle and 0.1ms pulse width, can reach 100 mA. The forward voltage (V_F) per segment, measured at I_F=20mA, has a maximum value of 3.8 volts, with a typical value of 3.3 volts. This parameter is crucial for designing the current-limiting circuitry. The maximum power dissipation per segment is 70 mW. The reverse current (I_R) is limited to a maximum of 100 µA at a reverse voltage (V_R) of 5V, though the device is not intended for continuous reverse bias operation.

2.3 Thermal and Environmental Ratings

The device is rated for an operating temperature range of -35°C to +85°C, with an identical storage temperature range. This wide range makes it suitable for various environmental conditions. A critical handling specification is the solder temperature limit: the device can withstand a maximum of 260°C for up to 3 seconds, measured 1.6mm (1/16 inch) below the seating plane, which is essential information for PCB assembly using reflow soldering processes.

3. Mechanical and Packaging Information

3.1 Dimensions and Tolerances

The display has a digit height of 0.8 inches (20.32 mm). All package dimensions are provided in millimeters. General tolerances are ±0.25 mm unless otherwise specified. Key mechanical notes include a pin tip shift tolerance of ±0.4 mm, limits on foreign material and ink contamination on the segment surface, and a limit on bending of the reflector (≤1% of its length). The recommended PCB hole diameter for the pins is 1.0 mm to ensure a proper fit.

3.2 Pinout and Connection Diagram

The device has 18 pins in a dual-in-line package (DIP) configuration. The internal circuit diagram confirms a common anode architecture. The pin connection is as follows: Pins 4, 6, 12, and 17 are Common Anode connections. The segment cathodes are distributed across other pins: A (Pin 2), B (Pin 15), C (Pin 13), D (Pin 11), E (Pin 5), F (Pin 3), and G (Pin 14). Additionally, there are cathodes for the left decimal point (L.D.P, Pin 7) and right decimal point (R.D.P, Pin 10). Pins 1, 8, 9, 16, and 18 are noted as having no connection (NO PIN). This pinout is essential for designing the PCB layout and driver circuit.

4. Performance Curve Analysis

The datasheet references typical electrical and optical characteristic curves, which are standard for LED components. While the specific graphs are not detailed in the provided text, these curves typically include the relationship between forward current (I_F) and forward voltage (V_F), which is non-linear and crucial for driver design. Another common curve shows luminous intensity versus forward current, demonstrating how brightness increases with current. A third typical curve illustrates the shift in dominant wavelength or forward voltage relative to the junction temperature. Analyzing these curves allows designers to optimize performance, understand efficiency, and predict behavior under different operating conditions, such as temperature variations or dimming schemes.

5. Soldering and Assembly Guidelines

5.1 Reflow Soldering Parameters

As noted in the absolute maximum ratings, the device can withstand a peak soldering temperature of 260°C for a maximum duration of 3 seconds. This aligns with typical lead-free reflow soldering profiles. Designers must ensure the thermal profile used during PCB assembly does not exceed this limit to prevent damage to the internal LED chips, wire bonds, or the plastic package.

5.2 Electrostatic Discharge (ESD) Precautions

LEDs are sensitive to electrostatic discharge. To prevent ESD damage during handling and assembly, the following measures are strongly recommended: Personnel should use conductive wrist straps or anti-static gloves. All equipment, workbenches, and storage racks must be properly grounded. An ionizer (ion blower) should be used to neutralize static charges that may accumulate on the plastic package surface due to friction during handling or storage. These precautions are vital for maintaining high yield and reliability in manufacturing.

5.3 Storage Conditions

The device should be stored within its specified temperature range of -35°C to +85°C. It is advisable to store components in moisture-barrier bags with desiccant if they are sensitive to moisture absorption, though this specific requirement is not called out in the provided datasheet. Proper handling to avoid mechanical stress on the pins or the display face is also important.

6. Application Suggestions

6.1 Typical Application Scenarios

The LTS-3401TBE is ideal for any application requiring a compact, low-power numeric display. Common uses include digital multimeters, frequency counters, clock displays, weighing scales, medical monitoring equipment, automotive dashboard readouts (for non-critical information), and industrial process indicators. Its blue color offers good visibility and can be chosen for aesthetic or functional differentiation from traditional red or green displays.

6.2 Design Considerations and Circuitry

When designing a driver circuit, the common anode configuration must be considered. This typically involves connecting the common anode pins to a positive supply voltage (V_CC) through a possible current-limiting resistor for the common line. Each segment cathode is then connected to a driver IC capable of sinking the required segment current. The current for each segment must be limited based on the desired brightness and the maximum ratings. Using the typical forward voltage of 3.3V-3.8V, the current-limiting resistor value can be calculated as R = (V_CC - V_F) / I_F. For multiplexing multiple digits, the peak current must be managed to stay within the pulsed current rating while maintaining average brightness. Designers should also account for the 2.5% maximum crosstalk specification, which defines the unintended illumination of a non-selected segment.

7. Technical Comparison and Differentiation

Compared to older incandescent or vacuum fluorescent displays (VFDs), this LED display offers significantly lower power consumption, longer lifetime, and higher reliability due to its solid-state nature. Within the LED display segment, its key differentiators are its specific low-current optimization (down to 1mA per segment), which is lower than many standard displays, and its categorization for luminous intensity, providing better brightness consistency. The blue color, achieved with InGaN technology, typically offers higher efficiency and different aesthetic options compared to older red GaAsP LEDs. The inclusion of both left and right decimal points adds flexibility for different numerical formatting needs.

8. Frequently Asked Questions (Based on Technical Parameters)

Q: What is the difference between common anode and common cathode?
A: In a common anode display, all LED segment anodes are connected together to a common pin (or pins), which is connected to the positive supply. Segments are turned ON by applying a LOW (ground) signal to their respective cathode pins. In a common cathode display, the cathodes are common and connected to ground, and segments are turned ON by applying a HIGH signal to their anodes. The LTS-3401TBE is a common anode type.

Q: Can I drive this display with a 5V microcontroller?
A: Yes, but you must use current-limiting resistors. Since the forward voltage is about 3.3-3.8V, a resistor is needed to drop the remaining voltage (e.g., 5V - 3.5V = 1.5V) and limit the current to the desired value (e.g., 10mA would require a 150Ω resistor). The driver pins of the microcontroller must be able to sink the required segment current.

Q: What does "categorized for luminous intensity" mean?
A: It means the displays are tested and binned (grouped) based on their measured luminous output. This ensures more consistent brightness between different units of the same model, leading to a more uniform appearance if multiple displays are used in a single product.

Q: How do I connect the four common anode pins?
A: All common anode pins (4, 6, 12, 17) should be connected together to the same positive voltage supply line, typically through a single current-limiting resistor if driving all segments of a single digit simultaneously. This ensures all segments have the same reference voltage.

9. Practical Design and Usage Example

Consider designing a simple digital voltmeter display. The microcontroller's analog-to-digital converter reads a voltage, processes it, and needs to display a 3-digit value (e.g., 5.12V). Three LTS-3401TBE displays would be used. The common anode pins of all three digits would be connected to three separate microcontroller I/O pins configured as digital outputs for multiplexing control. All corresponding segment cathodes (all 'A' segments, all 'B' segments, etc.) across the three digits would be connected together and then to eight microcontroller I/O pins (seven segments + one decimal point) via appropriate current-limiting resistors, likely using a transistor array or dedicated display driver IC to handle the current sink. The microcontroller rapidly cycles (multiplexes) through each digit, turning on one common anode at a time while setting the cathode pattern for that specific digit. The persistence of vision makes all digits appear continuously lit. The right decimal point on the middle digit would be illuminated to show the decimal place. The low current capability allows this multiplexing scheme to work efficiently without excessive power draw.

10. Operating Principle Introduction

A seven-segment LED display is an assembly of light-emitting diodes arranged in a figure-eight pattern. Each of the seven segments (labeled A through G) is an individual LED. By selectively powering different combinations of these segments, the patterns for numerals 0-9 and some letters can be formed. In the LTS-3401TBE, these LEDs are fabricated from InGaN semiconductor material deposited on a sapphire substrate. When a forward voltage exceeding the diode's threshold is applied, electrons and holes recombine in the active region, releasing energy in the form of photons (light). The specific composition of the InGaN layers determines the wavelength (color) of the emitted light, in this case, blue. The common anode design simplifies the driving circuitry in many applications where the power supply is positive relative to the control logic ground.

11. Technology Trends and Context

Seven-segment LED displays represent a mature and reliable display technology. While dot-matrix and graphic OLED/LCD displays offer more flexibility for showing arbitrary characters and graphics, seven-segment displays remain highly relevant due to their simplicity, low cost, high brightness, excellent readability in various lighting conditions (including direct sunlight), and extremely low power consumption in static or low-multiplexing scenarios. The trend in this segment is towards higher efficiency LEDs (more lumens per watt), allowing for even lower drive currents or higher brightness, and towards surface-mount device (SMD) packages for automated assembly, though through-hole DIP packages like this one are still widely used for prototyping, repair, and certain industrial applications. The move to lead-free and RoHS-compliant packaging, as seen with this device, is now a standard industry requirement.