LTD-5721AKF LED Digital Tube Datasheet - 0.56 Inch Character Height - AlInGaP Yellow Orange - 2.6V Forward Voltage - Simplified Chinese Technical Document

1. Product Overview

LTD-5721AKF, net, parlak ve güvenilir sayısal okuma gerektiren uygulamalar için tasarlanmış yüksek performanslı, çift haneli bir LED dijital gösterge modülüdür. Temel işlevi, kompakt ve verimli bir paketleme içinde görsel sayısal veri sağlamaktır. Cihazın temel avantajı, LED çiplerinin üretiminde, sarı-turuncu spektrum aralığında yüksek verimlilikle ışık yayma özelliğiyle bilinen gelişmiş AlInGaP (alüminyum indiyum galyum fosfor) yarı iletken teknolojisinin kullanılmasıdır. Bu teknoloji, opak GaAs alt tabaka üzerindeki özel çip yapısıyla birleşerek, bu göstergenin temel performans özelliklerini oluşturur.

This device is classified as a common anode type, which is the standard configuration for simplifying the driving circuit of multi-segment displays. Each digit is equipped with a right-side decimal point, providing flexibility for displaying decimals. The physical design employs a combination of a gray panel and white segment codes, meticulously engineered to maximize contrast and improve character readability under various lighting conditions. The 0.56-inch character height (14.22 mm) makes it suitable for applications requiring information to be read from a medium distance without the need for oversized components.

2. In-depth Technical Parameter Analysis

2.1 Absolute Maximum Ratings

Absolute maximum ratings define the stress limits that may cause permanent damage to the device. It is not recommended to operate the display continuously near or at these limits, as doing so may shorten its service life.

• Power consumption per segment:70 mW. This is the maximum power that a single LED segment can safely dissipate as heat without causing damage.
• Peak forward current per segment:60 mA. This current rating applies to pulse conditions (1 kHz frequency, 10% duty cycle), allowing for higher instantaneous brightness in multiplexed driving schemes.
• Continuous forward current per segment:25 mA at 25°C. This is the maximum recommended DC current for continuous operation of a single segment. A derating factor of 0.28 mA/°C is specified, meaning the maximum allowable continuous current decreases when the ambient temperature (Ta) exceeds 25°C to prevent overheating.
• Reverse voltage per segment:5 V. Applying a reverse voltage exceeding this value may break down the PN junction of the LED.
• Operating and Storage Temperature Range:-35°C to +105°C. This device is rated for industrial-grade temperature tolerance.
• Soldering Conditions:Wave soldering temperature is 260°C, maximum 3 seconds, provided the body temperature of the device does not exceed the maximum rated temperature. This is critical for assembly to prevent thermal damage to the plastic package and internal connections.

2.2 Electrical and Optical Characteristics

These parameters are measured under standard test conditions (Ta = 25°C) and define the typical performance of the device.

• Average luminous intensity (I_V):At I_F= 20 mA, it is 43.75 mcd (minimum), 70 mcd (typical). This is a measure of the light output power perceived by the human eye. The test condition was revised from 1 mA to 20 mA, indicating the standard operating current for brightness specifications.
• Peak emission wavelength (λ_p):611 nm (typical value). This is the wavelength at which the spectral power distribution of the emitted light reaches its maximum.
• Spectral line half-width (Δλ):17 nm (typical value). This parameter indicates the spectral purity or bandwidth of the emitted light, measured as the full width at half maximum (FWHM) of the emission peak.
• Dominant wavelength (λ_d):605 nm (typical value). This is the single wavelength that best represents the perceived color of light, calculated based on the emission spectrum and the CIE color matching functions.
• Forward voltage per segment (V_F):At I_F= 20 mA, 2.05 V (min), 2.6 V (typical). This is the voltage drop across an LED segment when operating. Designers must ensure the drive circuit can supply this voltage.
• Reverse current per segment (I_R):at V_RAt = 5 V, it is 100 μA (maximum). This is the tiny leakage current that flows when the specified reverse voltage is applied.
• Luminous intensity matching ratio:For similar luminous areas, the maximum is 2:1. This parameter specifies the maximum allowable ratio between the brightest and darkest segments within the device under the same driving conditions, ensuring visual uniformity.

Measurement description:The luminous intensity value is measured using a combination of a sensor and a filter designed to approximate the CIE photopic luminosity function, which models the spectral sensitivity of the standard human eye under normal (photopic) lighting conditions.

3. Binning System Description

The datasheet explicitly states that the device is "binned by luminous intensity." This indicates that a binning or sorting process exists after production. Due to inherent variations in semiconductor epitaxial growth and chip manufacturing processes, LED parameters (such as luminous intensity and forward voltage) can vary between different batches or even within the same batch.

The binning process involves testing each unit and sorting them into different groups (bins) based on specific measurement parameters. For LTD-5721AKF, the primary binning criteria areAverage Luminous Intensity. Units are grouped based on their measured light output at a standard test current (20mA). This ensures customers receive displays with consistent brightness levels. While not explicitly detailed in this brief datasheet, such displays typically also bin for forward voltage (V_F) to ensure electrical consistency and may bin for dominant wavelength (λ_d) are binned to maintain color consistency, despite its narrow half-width indicating good intrinsic color purity.

4. Performance Curve Analysis

The datasheet references "Typical Electrical/Optical Characteristic Curves" on page 5. Although no specific graphs are provided in the text, we can infer their standard content and significance based on the listed parameters.

Typical curves for such devices include:

• Forward Current vs. Forward Voltage (I-V Curve):This graph shows the nonlinear relationship between the current flowing through an LED and the voltage across it. This is crucial for designing current-limiting circuits. The curve will show a turn-on voltage (approximately 2V), after which the current increases rapidly with a small increase in voltage.
• Luminous Intensity vs. Forward Current (I-L Curve):This graph illustrates how light output increases with drive current. It is typically linear within a certain range but saturates at very high currents due to thermal effects and efficiency droop. This curve validates the 20mA test point for intensity specifications.
• Luminous Intensity vs. Ambient Temperature:This curve shows the derating of light output as the LED junction temperature rises. It is known that the efficiency of AlInGaP LEDs is temperature-dependent, and output typically decreases with increasing temperature. This provides a basis for thermal management design.
• Spectral Distribution:A plot of relative intensity versus wavelength, showing a peak at ~611 nm and a FWHM of ~17 nm, confirming monochromatic yellow-orange emission.

5. Mechanical and Packaging Information

5.1 Package Dimensions

The device utilizes a standard LED display package. The dimension drawing provides critical dimensions for PCB (Printed Circuit Board) pad design and mechanical integration. Key notes in the drawing include:

• All linear dimensions are specified in millimeters (mm).
• The default tolerance for dimensions is ±0.25 mm, unless otherwise specified.
• The specific tolerance for pin tip offset is ±0.4 mm, which is crucial for ensuring proper alignment of pins with PCB holes during automatic insertion.

5.2 Pin Connections and Internal Circuitry

The device adopts a dual in-line package with a total of 18 pins. The internal circuit diagram and pin connection table are crucial for correct electrical interfacing.

• Circuit Type:Common anode. This means the anode terminals of all LED segments for each digit are internally connected together. To illuminate a segment, its corresponding cathode pin must be driven low (connected to ground or a current sink), while the common anode for that digit is driven high (connected to the positive supply through a current-limiting resistor).
• Pinout:A detailed table maps each pin number to its function: the cathode for a specific segment (A-G, DP) of Digit 1 or Digit 2, or the common anode for each digit. For example, Pin 1 is the cathode for segment 'E' of Digit 1, and Pin 14 is the common anode for Digit 1. This precise mapping is crucial for creating the correct driving sequence in the microcontroller or driver IC software.

6. Soldering and Assembly Guide

Proper handling during assembly is crucial for reliability. The specification provides specific soldering parameters.

• Wave soldering:The recommended condition is 260°C for a maximum of 3 seconds. The note "1/16 inch below the mounting plane" may refer to the depth to which the leads should be immersed in the solder wave.
• Key Conditions:The most important precaution is that "the temperature of the device [must] not exceed the maximum rated temperature (during assembly)." This means that throughout the entire soldering process (including preheating and post-heating stages), the temperature of the LED display package itself must never exceed the maximum storage temperature of 105°C. Failure to comply may lead to internal delamination, lens cracking, or degradation of LED chip performance.
• General Operations:Standard ESD (Electrostatic Discharge) precautions should be observed as LED chips are sensitive to static electricity.

7. Application Recommendations

7.1 Typical Application Scenarios

The LTD-5721AKF is suitable for various industrial, commercial, and instrumentation applications requiring compact, bright, and reliable digital displays. Examples include:

• Kayan aikin gwaji da aunawa:Mitocin dijital masu yawa, ƙididdiga na mitar, hanyoyin wutar lantarki, na'urori masu karanta ma'aunin firikwensin.
• Sarrafa masana'antu:Panel instruments for displaying temperature, pressure, speed, or count on machinery.
• Consumer Appliances:High-end kitchen appliances, audio equipment tuners, older model digital clocks or timers.
• Automotive Aftermarket:Instrument and Display Module (though environmental specifications should be verified against specific automotive requirements).

7.2 Design Considerations

• Current Limiting:LED is a current-driven device. A series current-limiting resistor must be used for each common anode connection (or for each segment in more advanced constant-current drive designs) to set the operating current to 20 mA or lower according to derating guidelines. The resistor value is calculated using R = (V_{Power Supply}- V_F- V_{Driver saturation voltage drop}) / I_F.
• Multiplexed driver:对于双位数显示器，复用是标准的驱动技术。数字一个接一个地快速连续点亮（例如，频率>100 Hz）。这需要顺序控制共阳极引脚（数字）和阴极引脚（段）。这种方法减少了所需的驱动引脚数量和总功耗。
• Viewing Angle:The datasheet claims a "wide viewing angle," which is typical for LED displays with diffuser lenses or surfaces. This should be considered when placing the display in the final product.
• Thermal Management:Although this device can operate at temperatures up to 105°C, its luminous efficacy decreases as temperature rises. To achieve optimal brightness and service life, it is recommended to provide adequate ventilation or heat dissipation in the design, especially when operating near the maximum current or under high ambient temperatures.

8. Technical Comparison and Differentiation

Compared to other digital LED displays (especially older technologies), the key differentiating factors of the LTD-5721AKF include:

• AlInGaP technology versus traditional GaAsP or GaP:Compared to older semiconductor materials, AlInGaP LEDs offer significantly higher luminous efficiency and brightness in red, orange, and yellow colors. This results in better visibility and/or lower power consumption at the same perceived brightness.
• Gray panel / white segment:The specific color combination of panel and segments is designed to achieve high contrast. The grey panel absorbs more ambient light than a black panel, reducing reflections, while the white segment area helps to uniformly diffuse the emitted yellow-orange light, improving character appearance.
• Lead-Free Package (RoHS Compliant):The device construction complies with the Restriction of Hazardous Substances (RoHS) directive, suitable for products sold in markets with stringent environmental regulations. This is a key compliance differentiator.
• Solid State Reliability:Like all LEDs, it surpasses mechanical displays (such as flip-disc displays) or vacuum fluorescent displays (VFD) in terms of shock/vibration resistance, instant start-up capability, and long service life.

9. Frequently Asked Questions (Based on Technical Parameters)

Q1: What is the purpose of the "Luminous Intensity Matching Ratio" being 2:1?
A1: This ratio ensures visual consistency. It guarantees that within a single display unit, when driven under identical electrical conditions, the brightness of any one segment will not exceed twice that of any other segment. This prevents the digits from appearing uneven or "patchy."

Q2: Can I drive this display with a 5V power supply?
A2: Yes, a 5V supply is very common. However, you must connect a current-limiting resistor in series with each common anode. Using a typical V_FIt is 2.6V, target I_Fis 20 mA, the resistance value is approximately (5V - 2.6V) / 0.02A = 120 ohms. A standard 120Ω or 150Ω resistor is suitable, and can be adjusted based on the actual V_Fand the required brightness.

Q3: What does "common anode" mean for my circuit design?
A3: In a common anode configuration, you apply positive voltage to the common pin of the digit you want to activate. Then, you sink current to ground through the cathode pins of the segments you wish to illuminate on that digit. Your driving circuit (microcontroller or driver IC) must be configured to source current to the anode and sink current from the cathodes.

Q4: Why is the peak wavelength (611nm) different from the dominant wavelength (605nm)?
A4: This is normal for LEDs. The peak wavelength is the literal highest point on the emission spectrum curve. The dominant wavelength is calculated based on the entire spectrum and the human eye's color response; it is the single wavelength of pure light that appears to have the same color. This difference accounts for the shape and asymmetry of the LED's actual emission spectrum.

10. Design Use Case Studies

Scenario: Design a simple digital voltmeter reading display.
A designer is creating a 0-20V DC voltmeter. The analog-to-digital converter (ADC) outputs a binary-coded decimal (BCD) value. This BCD data needs to be converted into 7-segment format and displayed on two digits (e.g., 19.99V).

Implementation:
1. Use a microcontroller with sufficient I/O pins (or a dedicated BCD to 7-segment decoder/driver IC).
2. Connect the microcontroller's I/O pins to the LTD-5721AKF's segment cathodes (A-G, DP).
3. Connect two additional pins of the microcontroller to the two common anodes (Digit 1 and Digit 2).
4. In software, write a multiplexing routine. It first calculates which segments to light for Digit 1 (tens place), enables (sets high) the anode pin for Digit 1, and sets the corresponding segment cathode pins low. After a brief delay (e.g., 5ms), it disables Digit 1, calculates the segments for Digit 2 (ones place), enables the anode for Digit 2, and sets its segment pins low. This cycle repeats rapidly.
5. Place current-limiting resistors (e.g., 150Ω) on the common anode lines between the microcontroller pins and the display. The resistor value is chosen based on the supply voltage (e.g., 5V) and the desired segment current (~20mA).
6. Grey panel/white segment design ensures the display's workbench is easily readable under bright lighting conditions.

11. Introduction to Technical Principles

The core light-emitting component is the AlInGaP LED chip. AlInGaP is a III-V compound semiconductor. By precisely controlling the ratios of aluminum (Al), indium (In), gallium (Ga), and phosphorus (P) during the crystal growth process (typically via Metal-Organic Chemical Vapor Deposition - MOCVD), engineers can adjust the material's bandgap. The bandgap energy directly determines the wavelength (color) of photons emitted when electrons recombine with holes in the junction region.

In the LTD-5721AKF, its composition is adjusted to emit in the yellow-orange region (~605-611 nm). The chip is fabricated on a non-transparent gallium arsenide (GaAs) substrate. The display's "grey panel" is part of the plastic encapsulation molding, which includes a diffuser to evenly spread light from the small chip across the larger segment area. The internal circuitry uses wire bonding to connect the anodes and cathodes of multiple LED chips (one per segment per digit) to the appropriate package pins, forming the common anode matrix described in the pinout arrangement.

12. Technology Trends

While discrete LED numeric displays like LTD-5721AKF remain relevant in specific applications, the broader trends in display technology have shifted. For new designs, designers typically consider:

• Integrated Dot Matrix LED Displays:These displays offer alphanumeric and symbolic capabilities, not just numeric, providing greater flexibility within similar package sizes.
• OLED (Organic LED) Displays:They offer superior contrast, wider viewing angles, and a thinner form factor, although historically their lifespan and cost profile have differed in industrial applications.
• TFT-LCD module:They provide complete graphics capabilities, color, and the ability to display complex information, although they require more complex driving electronics and backlighting.
• LED display internal trends:The efficiency (lumens per watt) of all LED colors continues to improve, developing more robust and temperature-resistant packaging, and integrating drive electronics directly into the display module to simplify system design.

The enduring value of devices like the LTD-5721AKF lies in their simplicity, robustness, high brightness, low cost for purely digital applications, and ease of interfacing with microcontrollers, ensuring their place in the electronic ecosystem for dedicated readout functions.