LTS-3403LJS LED Display Datasheet - 0.8-inch Digit Height - AlInGaP Yellow - 2.6V Forward Voltage - 70mW Power Dissipation - English Technical Document

1. Product Overview

The LTS-3403LJS is a single-digit, seven-segment alphanumeric display module designed for applications requiring clear, low-power numeric indication. Its primary function is to provide a highly legible digital readout. The core advantage of this device lies in its utilization of Aluminum Indium Gallium Phosphide (AlInGaP) semiconductor technology for the LED chips, which are fabricated on a non-transparent Gallium Arsenide (GaAs) substrate. This specific material combination is engineered to produce a distinct yellow emission. The display features a gray faceplate with white segment markings, enhancing contrast and readability under various lighting conditions. It is categorized as a common cathode type display, which is a standard configuration for simplifying multiplexing in multi-digit applications. The target market for this component includes industrial control panels, test and measurement equipment, consumer appliances, automotive dashboards (for non-critical indicators), and any embedded system requiring a reliable, single-digit numeric display.

2. Technical Specifications Deep Dive

2.1 Photometric and Optical Characteristics

The optical performance is central to the display's functionality. The key parameter, Average Luminous Intensity (Iv), is specified with a minimum of 320 \u00b5cd, a typical value of 900 \u00b5cd, and no stated maximum, when driven at a forward current (IF) of 1mA. This indicates a bright output suitable for indoor use. The light output is characterized by a Peak Emission Wavelength (\u03bbp) of 588 nm and a Dominant Wavelength (\u03bbd) of 587 nm at IF=20mA, firmly placing its emission in the yellow region of the visible spectrum. The Spectral Line Half-Width (\u0394\u03bb) is 15 nm, denoting a relatively pure color with minimal spectral spread. Luminous intensity matching between segments is guaranteed to be within a 2:1 ratio, ensuring uniform brightness across the digit, which is critical for aesthetic and legibility purposes. All photometric measurements are aligned with the CIE (Commission Internationale de l'Eclairage) standard photopic eye-response curve.

2.2 Electrical Parameters

The electrical specifications define the operating boundaries and conditions for reliable use. The Absolute Maximum Ratings set the hard limits: a Power Dissipation of 70 mW per segment, a Peak Forward Current of 60 mA per segment (under pulsed conditions: 1/10 duty cycle, 0.1ms pulse width), and a Continuous Forward Current of 25 mA per segment at 25\u00b0C, derating linearly at 0.33 mA/\u00b0C. The maximum Reverse Voltage per segment is 5 V. Under standard operating conditions (Ta=25\u00b0C), the Forward Voltage (VF) per segment ranges from 2.05V (min) to 2.6V (max) at a test current of 10mA. The Reverse Current (IR) is a maximum of 100 \u00b5A at the full reverse voltage of 5V, indicating good diode characteristics.

2.3 Thermal and Environmental Specifications

The device is rated for an Operating Temperature Range of -35\u00b0C to +85\u00b0C, with an identical Storage Temperature Range. This wide range makes it suitable for applications in non-climate-controlled environments. A critical assembly parameter is the Solder Temperature rating: the device can withstand 260\u00b0C for 3 seconds at a point 1/16 inch (approximately 1.59 mm) below the seating plane. This is a standard rating for wave or reflow soldering processes, but care must be taken to not exceed this thermal profile.

3. Binning and Categorization System

The datasheet explicitly states that the devices are \"Categorized for Luminous Intensity.\" This implies a binning process where units are sorted and labeled based on their measured light output at a standard test condition (likely IF=1mA). This allows designers to select parts with consistent brightness for a given application or across a production run, ensuring visual uniformity in multi-digit displays. While not detailed in this specific document, typical binning for such displays may involve sorting into intensity ranges (e.g., Iv > 500 \u00b5cd, Iv > 700 \u00b5cd). The tight 2:1 luminous intensity matching ratio is another form of performance categorization within a single device.

4. Performance Curve Analysis

While the provided datasheet excerpt references \"Typical Electrical / Optical Characteristic Curves,\" the specific graphs are not included in the text. Typically, such curves for an LED display would include: Forward Current vs. Forward Voltage (I-V Curve): This graph shows the exponential relationship, helping designers select appropriate current-limiting resistors. The knee voltage is around the typical VF of 2.6V. Luminous Intensity vs. Forward Current (L-I Curve): This shows how light output increases with current, up to the maximum rated limits. It is generally linear in the normal operating range. Luminous Intensity vs. Ambient Temperature: This curve would show the decrease in light output as junction temperature rises, important for high-temperature or high-current applications. Relative Spectral Power Distribution: A plot showing the intensity of emitted light across wavelengths, centered around 587-588 nm with the stated 15 nm half-width.

5. Mechanical and Package Information

The LTS-3403LJS comes in a standard dual-in-line package (DIP) format suitable for through-hole mounting on a printed circuit board (PCB) or insertion into a socket. The package dimensions are provided in millimeters with a general tolerance of \u00b10.25 mm. Key mechanical features include the 0.8-inch (20.32 mm) digit height, which defines the physical size of the displayed character. The gray face and white segments are part of the package molding. The pin arrangement is designed for compatibility with standard PCB layouts and sockets.

6. Pin Connection and Internal Circuit

The device has a 17-pin configuration, though not all pins are active. The pinout is as follows: Pin 2: Anode for segment A, Pin 3: Anode for segment F, Pins 4, 6, 12, 17: Common Cathode (all connected internally), Pin 5: Anode for segment E, Pin 7: Anode for Left Decimal Point (L.D.P), Pin 10: Anode for Right Decimal Point (R.D.P), Pin 11: Anode for segment D, Pin 13: Anode for segment C, Pin 14: Anode for segment G, Pin 15: Anode for segment B. Pins 1, 8, 9, and 16 are listed as \"NO PIN\" (not connected). The internal circuit diagram shows a common cathode configuration, where all LED segment cathodes are tied together internally to the common cathode pins. Each segment anode is individually accessible. The two decimal points (left and right) are also separate LEDs with their own anodes.

7. Soldering and Assembly Guidelines

The primary guideline provided is the absolute maximum solder temperature profile: 260\u00b0C for 3 seconds, measured 1.59 mm (1/16\") below the seating plane. This is critical for wave soldering processes. For manual soldering, a temperature-controlled iron should be used, and contact time per pin should be minimized to prevent heat damage to the internal die and plastic package. The device should be stored in the specified temperature range (-35\u00b0C to +85\u00b0C) in a dry environment to prevent moisture absorption, which can cause \"popcorning\" during reflow if not properly baked before use.

8. Application Suggestions

8.1 Typical Application Scenarios

This display is ideal for applications requiring a single, highly visible numeric digit. Examples include: Instrumentation: Panel meters, frequency counters, timers. Consumer Electronics: Microwave oven clock display, thermostat readout, bathroom scale. Industrial ControlsAutomotive Aftermarket: Auxiliary gauges (voltage, temperature). Educational Kits: For teaching digital electronics and microcontroller interfacing.

8.2 Design Considerations

Current Limiting: Each segment anode must be driven through a current-limiting resistor. The resistor value (R) is calculated using R = (Vcc - VF) / IF, where Vcc is the supply voltage, VF is the forward voltage (use max value for reliability), and IF is the desired forward current (not to exceed 25 mA DC). For a 5V supply and IF=10mA, R = (5 - 2.6) / 0.01 = 240 Ohms. Driver Circuitry: Being common cathode, the cathodes are typically connected to ground (or a switching transistor for multiplexing), and the anodes are driven high to illuminate a segment. Microcontrollers or dedicated display driver ICs (like 74HC595 shift registers or MAX7219) are commonly used. Multiplexing: For multi-digit displays, multiple LTS-3403LJS units can be multiplexed by sequentially enabling the common cathode of each digit while presenting the segment data for that digit. This reduces the required I/O pins. Viewing Angle: The wide viewing angle is beneficial for applications where the display may be viewed from off-axis positions.

9. Technical Comparison and Differentiation

The LTS-3403LJS differentiates itself primarily through its use of AlInGaP Yellow LED technology. Compared to older technologies like standard GaP (which produces a less efficient, more greenish-yellow) or filtered light, AlInGaP offers higher luminous efficiency and a more saturated, pure yellow color. The gray face with white segments provides excellent contrast when the LEDs are off, making the digit outline always visible, unlike all-black faces. Its low power consumption (enabled by efficient LEDs and low VF) makes it suitable for battery-powered devices. The categorization for luminous intensity is a key quality differentiator, ensuring brightness consistency, which is not always guaranteed with lower-cost displays.

10. Frequently Asked Questions (FAQ)

Q: What is the difference between common cathode and common anode?
A: In a common cathode display, all LED cathodes are connected together. To light a segment, its anode is driven high (to Vcc) while the common cathode is connected low (to ground). In common anode, the opposite is true. The LTS-3403LJS is common cathode.

Q: Can I drive this display directly from a microcontroller pin?
A: Yes, but with important caveats. A microcontroller pin can source/sink only a limited current (often 20-25mA). You must use a current-limiting resistor for each segment you drive. Furthermore, if driving multiple segments simultaneously from one port, ensure the total current does not exceed the microcontroller's total port or chip current limit. Using a driver IC is often safer.

Q: What does \"I.C. Compatible\" mean?
A: It means the electrical characteristics (forward voltage, current requirements) of the display are within the output voltage and current sourcing/sinking capabilities of standard integrated circuit (IC) outputs, such as those from TTL or CMOS logic families or microcontrollers, especially when used with appropriate current-limiting resistors.

Q: How do I calculate the resistor value for a segment?
A: Use Ohm's Law: R = (Supply Voltage - LED Forward Voltage) / Desired LED Current. Always use the maximum VF from the datasheet (2.6V) for a conservative design that ensures the current is never exceeded even with part-to-part variation.

11. Practical Design and Usage Example

Case Study: Building a Single-Digit Counter with an Arduino. The goal is to create a counter that increments from 0 to 9. Components: Arduino Uno, LTS-3403LJS, eight 220\u03a9 resistors (one for segments A-G and the decimal point), a breadboard, and jumper wires. Wiring: Connect the common cathode pins (4,6,12,17) of the display to Arduino GND. Connect each segment anode (pins 2,3,5,7,10,11,13,14,15) to an individual Arduino digital pin (e.g., 2 through 10) via a 220\u03a9 current-limiting resistor. Software: In the Arduino sketch, define an array that maps digits (0-9) to the combination of segments that need to be lit (a \"segment map\"). In the loop, cycle through the digits 0-9, use the segment map to set the correct Arduino pins HIGH to illuminate the corresponding segments, wait for a second, then clear the display and move to the next digit. This example demonstrates direct drive, current limiting, and the use of a common cathode.

12. Technology Principle Introduction

The LTS-3403LJS is based on Light Emitting Diode (LED) technology. An LED is a semiconductor p-n junction diode. When forward biased (positive voltage applied to the p-side relative to the n-side), electrons from the n-region and holes from the p-region are injected into the junction region. When these charge carriers recombine, they release energy. In a standard silicon diode, this energy is released as heat. In a direct bandgap semiconductor like AlInGaP, a significant portion of this energy is released as photons (light). The specific wavelength (color) of the emitted light is determined by the bandgap energy of the semiconductor material. AlInGaP alloys are engineered to have a bandgap corresponding to light emission in the red, orange, amber, and yellow regions of the spectrum. The \"non-transparent GaAs substrate\" mentioned in the datasheet is the base wafer on which the AlInGaP layers are grown. Its non-transparent nature helps reflect light upward, improving the overall light extraction efficiency from the top of the chip.

13. Technology Trends and Context

While this specific datasheet is from 2001, the underlying AlInGaP technology represented a significant advancement at the time for producing high-brightness yellow, orange, and red LEDs. It largely replaced older, less efficient technologies like GaAsP and GaP for these colors. In the broader display technology landscape, discrete seven-segment LED displays like the LTS-3403LJS have been largely supplanted in new designs by more integrated solutions. These include: Dot-Matrix LED Displays and OLED Displays, which offer full alphanumeric and graphic capabilities. Integrated Display Modules with built-in controllers (I2C, SPI) that simplify interfacing. LCDs for ultra-low power applications. However, discrete seven-segment LEDs remain relevant in niches where their specific advantages are paramount: extreme simplicity, very high brightness and contrast, wide viewing angles, robustness, low cost for single-digit needs, and the distinctive \"retro\" aesthetic that is sometimes desired. They are also fundamental educational tools for learning digital electronics.