LTP-3862JF LED Display Datasheet - 0.3-inch Digit Height - AlInGaP Yellow Orange - 2.6V Forward Voltage - 70mW Power Dissipation - English Technical Document

1. Product Overview

The LTP-3862JF is a dual-digit, 17-segment alphanumeric light-emitting diode (LED) display module. Its primary function is to provide clear, high-visibility numeric and limited alphabetic character output in electronic devices. The core technology is based on Aluminium Indium Gallium Phosphide (AlInGaP) semiconductor material, specifically engineered to emit light in the yellow-orange wavelength spectrum. This device is categorized as a multiplex common anode display, meaning the anodes of each digit are connected together internally to simplify driving circuitry when using time-division multiplexing techniques.

The display features a black face with white segment outlines, which significantly enhances contrast and readability by minimizing reflected ambient light from the non-illuminated areas. The 0.3-inch (7.62 mm) digit height strikes a balance between being large enough for clear viewing at a moderate distance and compact enough for integration into space-constrained panels and instruments.

2. In-Depth Technical Parameter Analysis

2.1 Photometric and Optical Characteristics

The optical performance is defined under standard test conditions at an ambient temperature (T_A) of 25°C. The key parameter, Average Luminous Intensity (I_V), is specified with a minimum of 320 µcd, a typical value of 800 µcd, and no stated maximum, when driven at a forward current (I_F) of 1 mA. This indicates a bright output suitable for indoor and many well-lit environments. The luminous intensity matching ratio between segments is specified at a maximum of 2:1, ensuring uniform brightness across the display for a consistent appearance.

The spectral characteristics are centered in the yellow-orange region. The Peak Emission Wavelength (λ_p) is typically 611 nm, while the Dominant Wavelength (λ_d) is typically 605 nm, measured at I_F=20mA. The Spectral Line Half-Width (Δλ) is typically 17 nm, describing the narrow bandwidth of the emitted light, which is characteristic of AlInGaP technology and contributes to a saturated, pure color.

2.2 Electrical and Thermal Parameters

The Absolute Maximum Ratings define the operational limits beyond which permanent damage may occur. The Continuous Forward Current per segment is rated at 25 mA, with a derating factor of 0.33 mA/°C above 25°C. This derating is crucial for thermal management, as exceeding the maximum junction temperature can degrade performance and lifespan. The Peak Forward Current per segment, for pulsed operation (1/10 duty cycle, 0.1ms pulse width), is higher at 60 mA, allowing for brief overdrive to achieve higher peak brightness in multiplexed applications.

The Power Dissipation per segment is limited to 70 mW. The Forward Voltage per segment (V_F) ranges from 2.0V (min) to 2.6V (max) at I_F=20mA. Designers must account for this voltage drop when calculating series current-limiting resistor values. The Reverse Voltage rating is a modest 5V, highlighting the need for proper circuit design to avoid accidental reverse bias. The Reverse Current (I_R) is specified at a maximum of 100 µA at V_R=5V.

3. Mechanical and Packaging Information

The device conforms to a standard dual-digit 17-segment LED package footprint. The provided dimensional drawing specifies the exact physical layout, including overall length, width, and height, as well as the precise spacing and diameter of the 20 pins. All dimensions are provided in millimeters with a general tolerance of ±0.25 mm unless otherwise noted. The pinout is arranged in a single row along the bottom edge of the package. The seating plane and recommended solder pad geometry are also typically indicated to guide PCB layout for reliable mechanical attachment and soldering.

3.1 Pin Connection and Internal Circuit

The display has 20 pins. The internal circuit diagram reveals a multiplex common anode configuration. Pin 4 is the Common Anode for Digit 1, and Pin 10 is the Common Anode for Digit 2. All other pins (1-3, 5-9, 11-13, 15-20) are connected to the cathodes of specific segments (labeled A through U, DP, and others as per the segment naming convention). Pin 14 is noted as \"No Connection\" (N/C). This pinout is essential for designing the correct driver circuitry, which must sequentially power the common anode of each digit while sinking current through the appropriate segment cathode pins to form the desired character.

4. Performance Curve Analysis

Typical performance curves graphically illustrate the relationship between key parameters under varying conditions. While specific curves are referenced, they generally include:

• Forward Current vs. Forward Voltage (I-V Curve): This non-linear curve shows how V_F increases with I_F. It is critical for determining the operating point and the value of the current-limiting resistor required to achieve a desired brightness level without exceeding the maximum current rating.
• Luminous Intensity vs. Forward Current: This curve demonstrates the relative light output as a function of drive current. It is typically sub-linear, meaning efficiency (lumens per watt) may decrease at very high currents.
• Luminous Intensity vs. Ambient Temperature: This curve shows the derating of light output as the junction temperature rises. For AlInGaP LEDs, luminous intensity generally decreases with increasing temperature, which must be factored into designs for high-temperature environments.
• Spectral Distribution: A plot of relative intensity versus wavelength, showing the characteristic peak near 611 nm and the narrow half-width.

5. Soldering and Assembly Guidelines

The datasheet specifies critical soldering parameters to prevent thermal damage to the LED chips and the epoxy package. The maximum allowable solder temperature is defined as 260°C measured 1/16 inch (approximately 1.6 mm) below the seating plane of the component. The exposure time at this temperature must not exceed 3 seconds. These parameters are aligned with typical infrared or convection reflow soldering profiles. It is imperative to follow these guidelines to avoid compromising the internal wire bonds, degrading the epoxy material, or inducing thermal stress that could lead to premature failure. Proper storage conditions are also implied, typically in a dry, anti-static environment to prevent moisture absorption and electrostatic discharge damage.

6. Application Suggestions and Design Considerations

6.1 Typical Application Scenarios

This display is well-suited for applications requiring compact, low-power numeric readouts. Common uses include:

• Test and measurement equipment (multimeters, frequency counters).
• Consumer electronics (audio amplifiers, clock radios, appliance displays).
• Industrial control panels (process indicators, timer displays).
• Automotive aftermarket devices (voltage monitors, simple gauges).

The yellow-orange color offers excellent visibility and lower eye strain in varied lighting conditions compared to some other colors.

6.2 Design and Driving Circuit Considerations

Designing with the LTP-3862JF requires attention to several key areas:

1. Current Limiting: External resistors are mandatory for each segment cathode or digit anode (depending on driver topology) to set the operating current. The resistor value (R) is calculated using Ohm's Law: R = (V_SUPPLY - V_F - V_{DRIVER_SAT}) / I_F. Use the maximum V_F from the datasheet for a conservative design.
2. Multiplexing Drivers: To control 34 segments (17 per digit x 2) with only 20 pins, a multiplexed drive scheme is used. This requires a microcontroller or dedicated display driver IC capable of sourcing/sinking sufficient current and providing the correct multiplexing timing. The driver must cycle between activating Digit 1 and Digit 2 at a frequency high enough to avoid visible flicker (typically >60 Hz).
3. Thermal Management: Ensure the average power dissipation per segment, especially when driven at higher currents or in high ambient temperatures, does not exceed the 70 mW rating. Adequate PCB copper area or ventilation may be necessary.
4. Viewing Angle: The wide viewing angle is beneficial, but the mounting position on the front panel should be considered to align the optimal viewing cone with the user's typical line of sight.

7. Technical Comparison and Differentiation

The LTP-3862JF's primary differentiators stem from its AlInGaP material system and specific package design.

• vs. Traditional GaAsP or GaP LEDs: AlInGaP technology offers significantly higher luminous efficiency and better temperature stability, resulting in brighter, more consistent output. The yellow-orange color from AlInGaP is also more saturated and pure compared to older technologies.
• vs. Standard Red LEDs: The yellow-orange emission provides superior visual acuity and readability in many environments and may be preferred for certain aesthetic or functional requirements.
• vs. Larger or Smaller Displays: The 0.3-inch digit height positions it between smaller, more dense displays and larger, longer-range viewing displays. It is a common size for bench-top and portable instrumentation.
• vs. Common Cathode Configurations: The common anode configuration is often preferred when interfacing with microcontroller ports configured as current sinks (active-low drivers), which is a common setup.

8. Frequently Asked Questions (Based on Technical Parameters)

Q: Can I drive this display with a constant DC current without multiplexing?
A: Yes, but it is inefficient in terms of pin usage. You would need to connect all segment cathodes for both digits independently, requiring many more I/O lines. Multiplexing is the standard and recommended method.

Q: What is the purpose of the \"Luminous Intensity Matching Ratio\" specification?
A: It guarantees that the brightness difference between the dimmest and brightest segment on the same display will not exceed a 2:1 ratio. This ensures visual uniformity, preventing some segments from appearing noticeably darker than others.

Q: The Peak Forward Current is 60mA, but Continuous is only 25mA. Can I use 60mA continuously?
A: Absolutely not. The 60mA rating is for very short pulses (0.1ms) at a low duty cycle (10%). Exceeding the continuous current rating will cause excessive heating, leading to rapid luminous degradation and potential catastrophic failure.

Q: How do I calculate the required current-limiting resistor for a multiplexed design?
A: In a multiplexed design with a 1/2 duty cycle (for two digits), to achieve an effective average current of I_{F_avg}, you would typically set the peak current during the active time slot to 2 * I_{F_avg}. Then calculate the resistor using the peak current and the supply voltage. For example, for a target average of 10mA per segment, use a peak of 20mA in the calculation: R = (V_CC - V_F) / 0.020A.

9. Practical Design and Usage Case

Case: Designing a Simple Two-Digit Voltmeter Readout.
A microcontroller with an analog-to-digital converter (ADC) measures a voltage (0-99V scaled to 0-5V). The firmware converts the digital value to two decimal digits. Using a multiplexing routine, the microcontroller:

1. Activates the common anode for Digit 1 (sets the pin high or connects to V_CC via a transistor).
2. Sets the appropriate pattern on the segment cathode lines (sinking current to ground) to display the \"tens\" digit.
3. Holds this state for a short period (e.g., 5ms).
4. Deactivates Digit 1 and activates the common anode for Digit 2.
5. Sets the segment pattern for the \"ones\" digit (and optionally the decimal point, Pin 5).
6. Holds for 5ms, then repeats the cycle. The 10ms total period results in a 100 Hz refresh rate, eliminating flicker.

Current-limiting resistors are placed in series with each segment cathode line. The power supply must be regulated to ensure consistent brightness.

10. Operating Principle Introduction

The LTP-3862JF operates on the principle of electroluminescence in a semiconductor p-n junction. The active material is AlInGaP. When a forward voltage exceeding the junction's built-in potential (approximately 2.0-2.6V) is applied, electrons from the n-type region and holes from the p-type region are injected across the junction. These charge carriers recombine in the active region, releasing energy in the form of photons. The specific bandgap energy of the AlInGaP alloy determines the wavelength (color) of the emitted light, which in this case is in the yellow-orange range (605-611 nm). Each segment of the display contains one or more of these tiny LED chips. The black face absorbs stray light, while the white segment outlines help diffuse the emitted light evenly across the segment area.

11. Technology Trends and Context

While newer display technologies like organic LEDs (OLEDs) and high-resolution dot-matrix LCDs are prevalent in consumer electronics, discrete LED segment displays like the LTP-3862JF remain highly relevant in specific industrial, automotive, and instrumentation niches. Their advantages include extreme reliability, wide operating temperature range, high brightness, low cost for simple numeric readouts, and ease of interface. The trend within this segment is towards higher efficiency materials (like improved AlInGaP and InGaN for other colors), lower operating voltages, and potentially integrated driver circuitry within the package. The fundamental design and multiplexing principles, however, remain stable and widely understood, ensuring the longevity of such components in engineering design libraries.