LTS-3861JG LED Display Datasheet - 0.3-inch Digit Height - Green (AlInGaP) - 2.6V Forward Voltage - 70mW Power Dissipation - English Technical Document

1. Product Overview

The LTS-3861JG is a compact, single-digit, seven-segment alphanumeric display module designed for applications requiring clear, bright numeric indication with low power consumption. Its primary function is to provide a highly legible digital readout. The core technology utilizes Aluminum Indium Gallium Phosphide (AlInGaP) semiconductor material for the light-emitting diode (LED) chips. AlInGaP is renowned for its high efficiency and excellent luminous performance in the amber to green wavelength spectrum. This specific device emits a green light, offering a good balance of visibility and eye comfort. The display features a gray faceplate with white segment markings, which enhances contrast and readability when the segments are illuminated or unlit. It is categorized based on luminous intensity, allowing for binning and consistency in brightness across production batches. The device is constructed as a common anode configuration, simplifying circuit design for multiplexing applications.

2. Technical Parameters Deep Analysis

2.1 Photometric and Optical Characteristics

The optical performance is central to the display's functionality. The average luminous intensity (Iv) is specified with a typical value of 800 µcd at a forward current (IF) of 1 mA, with a minimum of 320 µcd. This parameter defines the perceived brightness. The dominant wavelength (λd) is 572 nm, placing the emission firmly in the green region of the visible spectrum. The peak emission wavelength (λp) is 571 nm, and the spectral line half-width (Δλ) is 15 nm, indicating a relatively pure color with minimal spectral spread. The luminous intensity matching ratio between segments is specified at a maximum of 2:1, ensuring uniform brightness across the digit for a consistent appearance.

2.2 Electrical and Thermal Characteristics

The electrical parameters define the operating boundaries and power requirements. The absolute maximum ratings are critical for reliable operation: the power dissipation per segment must not exceed 70 mW. The continuous forward current per segment is rated at 25 mA at 25°C, with a derating factor of 0.33 mA/°C for ambient temperatures above 25°C. A peak forward current of 60 mA is allowed under pulsed conditions (1/10 duty cycle, 0.1 ms pulse width). The forward voltage (VF) per segment has a typical value of 2.6 V at IF=20 mA, with a maximum of 2.6 V. The reverse voltage rating is 5 V, and the reverse current (IR) is a maximum of 100 µA at VR=5V. The device is rated for an operating and storage temperature range of -35°C to +85°C.

3. Binning System Explanation

The datasheet explicitly states that the device is \"categorized for luminous intensity.\" This implies a binning or sorting process post-manufacturing. LEDs naturally have variations in output due to microscopic differences in the semiconductor epitaxy. To ensure consistency for the end-user, manufacturers measure the luminous intensity of each unit and sort them into different bins or categories based on predefined intensity ranges (e.g., high-brightness bin, standard bin). This allows designers to select parts with guaranteed minimum brightness levels for their application, preventing noticeable brightness mismatches when multiple displays are used side-by-side. While the specific bin codes are not detailed in this document, the practice ensures predictable performance.

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 several key plots. The Forward Current vs. Forward Voltage (I-V) curve shows the nonlinear relationship, crucial for designing current-limiting circuitry. The Relative Luminous Intensity vs. Forward Current curve demonstrates how light output increases with current, often showing a region of linearity before efficiency droop. The Relative Luminous Intensity vs. Ambient Temperature curve is vital for understanding brightness reduction at high temperatures, informing thermal management decisions. The Spectral Power Distribution curve would visually confirm the dominant and peak wavelengths, showing the narrow emission band characteristic of AlInGaP LEDs.

5. Mechanical and Package Information

The LTS-3861JG is presented with a detailed package dimension drawing (referenced but not fully detailed in text). Key mechanical specifications include a digit height of 0.3 inches (7.62 mm). The overall package dimensions, lead spacing, and seating plane are defined in millimeters with a standard tolerance of ±0.25 mm unless otherwise noted. The physical construction houses the AlInGaP LED chips on a non-transparent Gallium Arsenide (GaAs) substrate within a plastic package. The gray face with white segments provides the non-illuminated appearance. The pin configuration is clearly defined for the 10-pin package.

6. Pin Connection and Internal Circuit

The device has a 10-pin configuration. Pins 1 and 6 are both connected to the COMMON ANODE. This dual-anode design helps in current distribution and can aid in PCB layout. The remaining pins are individual cathodes for each segment: Pin 2 (Cathode F), Pin 3 (Cathode G), Pin 4 (Cathode E), Pin 5 (Cathode D), Pin 7 (Cathode D.P. for the decimal point), Pin 8 (Cathode C), Pin 9 (Cathode B), and Pin 10 (Cathode A). The internal circuit diagram (referenced) would show these ten pins connected to the anodes and cathodes of the eight LEDs (seven segments plus one decimal point) arranged in a common anode matrix. Understanding this layout is essential for designing the correct driving circuitry, typically involving a microcontroller with segment drivers or a dedicated display driver IC.

7. Soldering and Assembly Guidelines

The absolute maximum ratings include a critical soldering specification: the device can withstand a maximum solder temperature of 260°C for a maximum duration of 3 seconds, measured at 1.6 mm (1/16 inch) below the seating plane. This is a standard reflow soldering profile constraint. Designers must ensure their PCB assembly process, whether wave or reflow soldering, adheres to this limit to prevent damage to the internal LED chips, wire bonds, or the plastic package. Prolonged exposure to high temperature can cause yellowing of the plastic, degradation of the epoxy, or failure of the semiconductor junctions. Proper handling to avoid electrostatic discharge (ESD) is also implied, although not explicitly stated, as LEDs are generally sensitive to voltage spikes.

8. Application Suggestions

8.1 Typical Application Scenarios

The LTS-3861JG is suited for a wide range of low-power, portable, and mains-powered devices requiring a single numeric digit display. Common applications include: instrument panels (voltmeters, ammeters, timers), household appliances (microwaves, ovens, coffee makers), consumer electronics (audio equipment, chargers), industrial controls (setpoint displays, counter units), and medical devices. Its low current requirement makes it ideal for battery-operated equipment.

8.2 Design Considerations

When integrating this display, several factors must be considered. Current Limiting: External current-limiting resistors are mandatory for each segment cathode (or a constant current driver) to set the forward current to a safe value (e.g., 10-20 mA for full brightness, 1-5 mA for lower power). The resistor value is calculated using R = (Supply Voltage - VF) / IF. Multiplexing: For multi-digit systems, this common anode display is easily multiplexed. A microcontroller would sequentially enable each digit's common anode via a transistor switch while outputting the segment pattern for that digit on the common cathode lines. Viewing Angle: The wide viewing angle is beneficial but consider the final mounting orientation. Thermal Management: While low power, ensure ambient temperature stays within spec, especially if enclosed.

9. Technical Comparison and Differentiation

The key differentiating advantages of the LTS-3861JG stem from its AlInGaP technology compared to older technologies like standard GaP (Gallium Phosphide) green LEDs. AlInGaP offers significantly higher luminous efficiency, resulting in greater brightness for the same drive current, or equivalent brightness at lower current, extending battery life. The color purity (narrow spectral width) is also superior. Compared to larger digit displays, the 0.3-inch size offers a compact footprint. The common anode design is more common and often easier to interface with standard microcontroller ports configured as current sinks. The categorization by luminous intensity provides an advantage over non-binned parts by guaranteeing brightness consistency.

10. Frequently Asked Questions (Based on Technical Parameters)

Q: What resistor value should I use for a 5V supply and 10 mA per segment?
A: Using the typical VF of 2.6V: R = (5V - 2.6V) / 0.01A = 240 Ohms. A 220 Ohm or 270 Ohm standard resistor would be suitable.

Q: Can I drive it directly from a microcontroller pin?
A: It is not recommended to source/sink the full segment current (up to 25 mA) directly from most MCU pins, which are often limited to 20 mA absolute max per pin and less for continuous operation. Use a transistor or dedicated driver IC (e.g., 74HC595 shift register with current-limiting resistors, or a constant current LED driver).

Q: Why are there two common anode pins (1 and 6)?
A> This aids in PCB layout by providing two connection points for the common anode, allowing for better power distribution and easier routing of traces, especially when the display is placed over other components.

Q: How does temperature affect brightness?
A> LED luminous intensity typically decreases as junction temperature increases. The derating of continuous current (0.33 mA/°C above 25°C) is one indicator. For precise brightness control over temperature, feedback or compensation may be needed.

11. Practical Design and Usage Case

Consider designing a simple digital timer using a microcontroller. The LTS-3861JG would display the seconds digit (0-9). The MCU's I/O ports would be configured: one pin to control a PNP transistor switching the common anode to Vcc, and 7 other pins (each with a 220-ohm series resistor) connected to cathodes A-G. The firmware would contain a look-up table converting numbers 0-9 to the corresponding 7-segment pattern (e.g., '0' = 0b00111111). It would enable the anode, output the pattern, wait for the multiplexing interval, then disable the anode. This approach minimizes pin usage. The low power consumption allows the timer to run for extended periods on a small battery. The high contrast and wide viewing angle ensure the time is readable from various positions.

12. Technology Principle Introduction

The LTS-3861JG is based on solid-state lighting technology. Each segment contains one or more AlInGaP LED chips. An LED is a semiconductor diode. When forward biased (positive voltage on anode relative to cathode), electrons from the n-type region and holes from the p-type region are injected into the active region where they recombine. In AlInGaP, this recombination releases energy in the form of photons (light) with a wavelength determined by the bandgap energy of the semiconductor material. The specific alloy composition of Aluminum, Indium, Gallium, and Phosphide is engineered to produce green light at around 572 nm. The non-transparent GaAs substrate absorbs any downward-emitted light, improving contrast. The light is then shaped and emitted through the epoxy lens of the package, forming the recognizable segment shape.

13. Technology Trends and Context

While AlInGaP was a significant advancement for red, orange, amber, and green LEDs, the landscape for green emitters has evolved. For very high-efficiency green light, Indium Gallium Nitride (InGaN) based LEDs are now dominant, especially in the pure green to blue spectrum. However, AlInGaP remains highly competitive in the amber-green region due to its excellent performance and stability. The trend in displays is towards higher density, full-color capability, and integration. Single-digit seven-segment displays like the LTS-3861JG represent a mature, cost-effective solution for applications where only numeric information is required. Their advantages are simplicity, robustness, low cost, and extreme ease of interfacing compared to more complex dot-matrix or graphic OLED/LCD modules. They continue to be widely used in applications where these attributes are paramount over graphical capability.