LTC-2723JD LED Display Datasheet - 0.28-inch Digit Height - AlInGaP Red - 2.6V Forward Voltage - 70mW Power Dissipation - English Technical Document

1. Product Overview

The LTC-2723JD is a quadruple-digit, seven-segment alphanumeric LED display module. Its primary function is to provide clear, bright numeric and limited alphanumeric readouts in various electronic devices. The core technology utilizes AlInGaP (Aluminum Indium Gallium Phosphide) LED chips, which are known for their high efficiency and brightness in the red spectrum. The device features a gray face with white segments, offering high contrast for excellent character appearance and wide viewing angles. It is categorized for luminous intensity and is offered in a lead-free package compliant with RoHS directives, making it suitable for modern electronic applications with environmental considerations.

1.1 Key Features and Advantages

• Digit Height: 0.28 inches (7.0 mm), providing a balanced size for good visibility without excessive space consumption.
• Segment Design: Continuous uniform segments ensure consistent illumination and a professional aesthetic.
• Power Efficiency: Low power requirement due to the high-efficiency AlInGaP technology.
• Optical Performance: High brightness and high contrast ratio enhance readability under various lighting conditions.
• Viewing Angle: Wide viewing angle allows the display to be read from different positions.
• Reliability: Solid-state construction offers long operational life and robustness against vibration.
• Binning: Categorized (binned) for luminous intensity, ensuring consistency in brightness across production batches.
• Environmental Compliance: Lead-free package in accordance with RoHS regulations.

1.2 Device Identification

The part number LTC-2723JD specifically denotes an AlInGaP High-Efficiency Red, multiplex common cathode display with a right-hand decimal point. This naming convention helps in precise identification and ordering.

2. Mechanical and Package Information

The display comes in a standard through-hole package. Detailed dimensional drawings are provided in the datasheet, with all primary dimensions specified in millimeters. Key tolerances are typically ±0.20 mm unless otherwise noted. Specific attention is given to assembly-related tolerances: pin tip shift is ±0.4mm, and recommendations are made for the best PCB hole diameter (1.30mm). The module is marked with the part number (LTC-2723JD), a date code in YYWW format, the manufacturing country, and a bin code for luminous intensity grading.

3. Electrical Configuration and Pinout

3.1 Internal Circuit and Pin Connection

The LTC-2723JD employs a multiplexed common cathode configuration. This means the cathodes of the LEDs for each digit are connected together internally, while the anodes for corresponding segments across digits are connected. This design minimizes the number of required driver pins. The pin connection table is as follows:

• Pin 1: Common Cathode (Digit 1)
• Pin 2: Anode C, L3
• Pin 3: Anode D.P. (Decimal Point)
• Pin 4: No Connection
• Pin 5: Anode E
• Pin 6: Anode D
• Pin 7: Anode G
• Pin 8: Common Cathode (Digit 4)
• Pin 9: No Connection
• Pin 10: No Pin
• Pin 11: Common Cathode (Digit 3)
• Pin 12: Common Cathode L1, L2, L3 (for separate LEDs)
• Pin 13: Anode A, L1
• Pin 14: Common Cathode (Digit 2)
• Pin 15: Anode B, L2
• Pin 16: Anode F

An internal circuit diagram visually represents these connections, showing the common cathode groups for the four digits and the shared anode lines for the seven segments (A-G) and the decimal point.

4. Absolute Maximum Ratings and Electrical/Optical Characteristics

4.1 Absolute Maximum Ratings (Ta=25°C)

These ratings define the limits beyond which permanent damage to the device may occur. They should never be exceeded during operation.

• Power Dissipation per Segment: 70 mW
• Peak Forward Current per Segment: 100 mA (at 1/10 duty cycle, 0.1ms pulse width)
• Continuous Forward Current per Segment: 25 mA (derated linearly from 25°C at 0.33 mA/°C)
• Operating Temperature Range: -35°C to +85°C
• Storage Temperature Range: -35°C to +85°C
• Solder Condition: 1/16 inch (1.6mm) below seating plane for 5 seconds at 260°C.

4.2 Electrical and Optical Characteristics (Ta=25°C)

These are the typical operating parameters under specified test conditions.

• Average Luminous Intensity (I_V): 200 - 600 μcd (Min - Max) at I_F = 1mA.
• Peak Emission Wavelength (λ_p): 656 nm (Typical) at I_F = 20mA.
• Spectral Line Half-Width (Δλ): 22 nm (Typical) at I_F = 20mA.
• Dominant Wavelength (λ_d): 640 nm (Typical) at I_F = 20mA.
• Forward Voltage per Segment (V_F): 2.1 - 2.6 V (Typical) at I_F = 20mA.
• Reverse Current per Segment (I_R): 10 μA (Maximum) at V_R = 5V. Note: This is a test condition; continuous reverse bias operation is not allowed.
• Luminous Intensity Matching Ratio: 2:1 (Maximum) for segments within a similar light area at I_F = 1mA.
• Cross Talk: ≤ 2.5%.

Luminous intensity is measured using a sensor and filter approximating the CIE photopic eye-response curve.

5. Performance Curves and Characteristics Analysis

The datasheet includes typical characteristic curves, which are essential for design engineers. These curves graphically represent the relationship between key parameters, providing deeper insight than tabular data alone. While the specific curves are not detailed in the provided text, they typically include:

• Forward Current vs. Forward Voltage (I-V Curve): Shows the nonlinear relationship, critical for designing current-limiting circuits.
• Luminous Intensity vs. Forward Current: Demonstrates how light output increases with current, helping to optimize for brightness and efficiency.
• Relative Luminous Intensity vs. Ambient Temperature: Illustrates the decrease in light output as temperature rises, which is vital for applications in non-climate-controlled environments.
• Spectral Distribution: A graph of relative intensity versus wavelength, confirming the dominant and peak wavelengths and the spectral purity (half-width).

Analyzing these curves allows designers to select appropriate drive currents, understand thermal effects, and predict performance under real-world operating conditions.

6. Reliability Testing and Qualification

The LTC-2723JD undergoes a comprehensive suite of reliability tests based on recognized industry standards (MIL-STD, JIS). These tests validate the device's robustness and longevity.

• Operating Life Test (RTOL): 1000 hours at room temperature under maximum rated conditions to assess long-term performance.
• High Temperature/Humidity Storage (THS): 500 hours at 65°C and 90-95% RH to test moisture resistance.
• High Temperature Storage (HTS): 1000 hours at 105°C to evaluate stability under thermal stress.
• Low Temperature Storage (LTS): 1000 hours at -35°C.
• Temperature Cycling (TC): 30 cycles between -35°C and 105°C to test for failures induced by thermal expansion/contraction.
• Thermal Shock (TS): 30 cycles of rapid transition between -35°C and 105°C, a more severe thermal test.
• Solder Resistance (SR): Tests the leads' ability to withstand soldering heat (260°C for 10 seconds).
• Solderability (SA): Verifies that the leads can be properly wetted with solder (245°C for 5 seconds).

These tests ensure the display can withstand the rigors of assembly processes and harsh operating environments.

7. Soldering and Assembly Guidelines

7.1 Automated Soldering

For wave or reflow soldering, the recommended condition is to immerse the leads to a depth of 1/16 inch (1.6mm) below the seating plane for a maximum of 5 seconds at a solder temperature of 260°C. The body temperature of the display must not exceed the maximum storage temperature during this process.

7.2 Manual Soldering

When hand-soldering, the iron tip should contact the lead (1/16 inch below the seating plane) for no more than 5 seconds. The recommended soldering iron temperature is 350°C ±30°C. Precise control of time and temperature is crucial to prevent thermal damage to the LED chips or the plastic package.

8. Critical Application Cautions and Design Considerations

Intended Use: This display is designed for ordinary electronic equipment (office, communication, household). It is not certified for safety-critical applications (aviation, medical life-support, etc.) without prior consultation and specific qualification.

Parameter Adherence: The driving circuit must be designed to ensure operation within the Absolute Maximum Ratings and recommended operating conditions. Exceeding current or temperature limits will accelerate light output degradation and can cause premature failure.

Drive Circuit Design:

• Constant Current Drive: Highly recommended over constant voltage drive. LEDs are current-driven devices; their forward voltage has a tolerance and varies with temperature. A constant current source ensures stable, predictable brightness and protects the LED from thermal runaway.
• Reverse Voltage Protection: The driving circuit must incorporate protection (e.g., series diodes or integrated circuit features) to prevent the application of reverse voltage or transient voltage spikes to the LED segments during power-up, power-down, or in multiplexing circuits. The maximum reverse voltage is only 5V for testing; continuous reverse bias is prohibited.
• Multiplexing Considerations: As a common cathode multiplexed display, it requires a driver circuit that sequentially energizes each digit's cathode while applying voltage to the anodes of the segments that should be lit for that digit. The peak current rating (100mA at low duty cycle) is relevant for multiplexed drive schemes where instantaneous current is higher to achieve the required average brightness.

Thermal Management: Although power dissipation is low per segment, the collective heat from four digits in a small package must be considered. Adequate ventilation and avoiding placement near other heat sources are advised to maintain junction temperature within safe limits.

9. Technical Comparison and Application Scenarios

9.1 Differentiation from Other Technologies

Compared to older GaAsP or GaP LED technologies, AlInGaP offers significantly higher luminous efficiency, resulting in brighter displays at lower currents. The gray face/white segment design provides superior contrast compared to diffused or tinted packages. The 0.28-inch digit size positions it between smaller indicators and larger panel-mounted displays, offering a good balance of readability and compactness.

9.2 Typical Application Scenarios

• Test and Measurement Equipment: Digital multimeters, oscilloscopes, power supplies.
• Industrial Controls: Panel meters, timer displays, process indicators.
• Consumer Electronics: Audio equipment (amplifiers, receivers), appliance displays.
• Automotive Aftermarket: Gauges and diagnostic tools (not for primary vehicle safety systems).

9.3 Design Example: Microcontroller Interface

A typical design involves a microcontroller with sufficient I/O pins or using external shift registers/driver ICs (like the MAX7219 or TM1637) specifically designed for multiplexed LED displays. The driver IC manages the multiplexing timing, current limiting, and often includes brightness control via PWM, greatly simplifying the software and hardware design for the system engineer.

10. Frequently Asked Questions (FAQs)

Q1: What is the purpose of the luminous intensity bin code?
A1: The bin code indicates the measured brightness range of the specific unit. This allows designers to select displays with matched brightness for multi-unit panels, ensuring a uniform appearance.

Q2: Can I drive this display with a 5V microcontroller pin directly?
A2: No. The forward voltage is around 2.6V, but LEDs require current limiting. Connecting directly to a 5V pin would cause excessive current and destroy the segment. A series current-limiting resistor or a dedicated constant-current driver is mandatory.

Q3: Why is constant current drive recommended?
A3: An LED's light output is proportional to current, not voltage. Its forward voltage (Vf) varies from unit to unit and decreases with rising temperature. A constant voltage source with a resistor provides approximate current regulation, but a true constant current source provides precise brightness control and inherent protection against thermal runaway.

Q4: What does \"multiplex common cathode\" mean for my circuit?
A4: It means you control the display by turning on one digit at a time, in rapid succession (multiplexing). You set the pattern of segments (anodes) to be lit, then enable the cathode for digit 1, then disable it, set the pattern for digit 2, enable its cathode, and so on. This cycles continuously, reducing the required driver pins from 29 (4x7 segments + 4 cathodes + DP) to just 12 anode lines + 4 cathode lines (plus the common cathode for separate LEDs).

11. Operational Principles and Technology Trends

11.1 Basic Operating Principle

An LED is a semiconductor diode. When a forward voltage exceeding its bandgap is applied, electrons and holes recombine in the active region (the AlInGaP layer), releasing energy in the form of photons (light). The specific composition of the AlInGaP alloy determines the bandgap energy and thus the color of the emitted light, which in this case is in the red spectrum (~640-656 nm). The seven-segment layout is a standardized pattern where illuminating different combinations of the segments (labeled A through G) forms the numerals 0-9 and some letters.

11.2 Industry Trends

The trend in display technology continues towards higher efficiency, lower power consumption, and greater integration. While discrete seven-segment displays like the LTC-2723JD remain vital for cost-effective, medium-size numeric readouts, there is a parallel growth in areas like:
Organic LED (OLED) Displays: Offering superior contrast, flexibility, and thinness for high-end applications.
Integrated Driver Displays: Modules that include the controller/driver IC on-board, simplifying interface design.
Surface-Mount Device (SMD) Packages: For automated assembly, though through-hole parts like this one are still preferred for prototyping, repair, and applications requiring robust mechanical connections.

The AlInGaP material system itself represents a mature and highly optimized technology for red, orange, and yellow LEDs, balancing performance, reliability, and cost effectively.