LTD-2701JD LED Digital Tube Datasheet - 0.28 Inch Character Height - Super Bright Red - 2.6V Forward Voltage - Technical Documentation

1. Product Overview

LTD-2701JD is a dual-digit seven-segment light-emitting diode (LED) digital display module. Its primary function is to provide clear, easily readable numerical displays for various electronic devices and instruments. Its core technology utilizes AlInGaP (aluminum indium gallium phosphide) semiconductor material, which emits ultra-bright red light, offering high brightness and excellent color purity. The device features a gray panel with white segment design, enhancing contrast and readability under various lighting conditions. It is designed as a common cathode type, a standard configuration that simplifies multiplexing drive circuits in multi-digit display applications.

1.1 Main Features and Core Advantages

• Character Height:0.28 inches (7.0 mm), balanced size, ensuring good visibility without occupying excessive space.
• Segment Uniformity:Continuous and uniform segment codes ensure consistent character appearance between two digits.
• Energy Efficiency:Low power consumption, suitable for battery-powered applications or those emphasizing energy efficiency.
• Optical Performance:High brightness and high contrast deliver excellent character readability.
• Viewing Angle:Wide viewing angle allows for clear reading from different positions.
• Reliability:The solid-state structure ensures a long service life and provides resistance to shock and vibration.
• Grading:Devices are binned according to luminous intensity to facilitate brightness matching in multi-display setups.
• Environmental Compliance:Lead-free package, compliant with the RoHS (Restriction of Hazardous Substances) directive.

1.2 Target Market and Applications

This display is suitable for general electronic devices. Typical application areas include but are not limited to:

• Test and measurement instruments (multimeters, power supplies).
• Consumer appliances (microwave ovens, ovens, washing machines).
• Industrial control panels and timers.
• Communication equipment status display.
• Automotive aftermarket accessories (e.g., voltage monitor).
• Point of sale terminals and basic digital readout displays.

A cikin hankali, don aikace-aikacen da ke buƙatar ingantacciyar aminci, inda gazawar za ta iya haifar da barazana ga rayuwa ko lafiya (kamar jiragen sama, kiwon lafiya ko tsarin aminci mai mahimmanci), ana buƙatar tuntuba.

2. Technical Specifications and Objective Interpretation

2.1 Absolute Maximum Ratings

These ratings define the stress limits that may cause permanent damage to the device. Operation at or beyond these limits is not guaranteed.

• Power dissipation per segment:Maximum 70 mW. Exceeding this value may cause the LED chip to overheat and accelerate aging.
• Peak forward current per segment:Under pulse conditions (1/10 duty cycle, 0.1 ms pulse width) is 90 mA. This rating applies to short pulses, not continuous operation.
• Continuous forward current per segment:25 mA at 25°C. This current must be linearly derated by 0.33 mA/°C when the ambient temperature (Ta) exceeds 25°C to prevent thermal runaway.
• Operating and storage temperature range:-35°C to +85°C. The device can withstand these extreme temperatures, but its optical performance will vary with temperature.
• Welding Conditions:260°C for 3 seconds, measurement point is 1/16 inch (approximately 1.6 mm) below the mounting plane. This guides wave soldering or reflow soldering processes.

2.2 Electrical and Optical Characteristics

These are typical performance parameters measured under specified test conditions at Ta=25°C.

• Average luminous intensity (I_V):At I_F200-600 µcd at =1mA. This wide range indicates the effect of the binning process; designers should consider the minimum value for visibility calculations.
• Peak emission wavelength (λ_p):650 nm. This is the wavelength at which the emitted optical power is greatest.
• Dominant wavelength (λ_d):639 nm. This is the single wavelength that matches the perceived color of the light to the human eye, with a tolerance of ±1 nm.
• Spectral line half-width (Δλ):20 nm. This defines the spectral purity; the narrower the width, the closer the color is to monochromatic.
• Forward voltage per chip (V_F):At I_F=20mA, it is 2.1V (minimum), 2.6V (typical), with a tolerance of ±0.1V. This is crucial for driving circuit design, especially when multiplexing multiple digits, to ensure current consistency.
• Reverse current (I_R):At V_R=5V, maximum 100 µA. The datasheet explicitly warns that reverse voltage is for test purposes only, and continuous reverse bias operation must be avoided.
• Luminous intensity matching ratio:At I_FWhen =10mA, the maximum ratio of similar luminous areas is 2:1. This specifies the maximum allowable brightness difference between segments within the same display.
• Crosstalk:≤ 2.5%. This refers to unwanted luminescence in non-driven segments caused by electrical leakage or optical coupling.

2.3 Binning System Description

Takardar ƙayyadaddun bayanai ta bayyana cewa samfurin "an raba shi da ƙarfin haske". Wannan yana nufin tsarin rarrabawa, wanda LED ke rarrabuwa bisa ga fitowar haske (a cikin µcd) da aka auna a daidaitaccen gwajin na yanzu (mai yuwuwa 1mA ko 10mA). Ana ba da shawarar sosai cewa a yi amfani da nuni daga rukunin ƙarfi ɗaya a cikin kayan haɗin gwiwa ɗaya, don guje wa bambance-bambancen haske (rashin daidaiton launi) a tsakanin raka'a maƙwabta. Mai zane ya kamata ya ƙayyade rukunin da ake buƙata, ko kuma ya yi aiki tare da mai kayan don tabbatar da daidaito a aikace-aikacen nuni da yawa.

3. Mechanical and Packaging Information

3.1 Package Dimensions

This display conforms to the standard through-hole DIP (Dual In-line Package) format. Key dimensional specifications include:

• All dimensions are in millimeters (mm).
• Unless otherwise specified, the standard tolerance is ±0.25 millimeters.
• The pin tip offset tolerance is ±0.4 millimeters, which is important for PCB hole alignment.
• Allowed defects on the display panel: Foreign matter on the segment ≤10 mils, ink contamination ≤20 mils, bubbles within the segment ≤10 mils.
• Reflector bending is limited to ≤1% of its length.

3.2 Pin Connection and Polarity Identification

The device has 10 pins arranged in a single row. The pin definitions are as follows:

• Pin 1: E Segment Anode
• Pin 2: Segment D anode
• Pin 3: Segment C anode
• Pin 4: Segment G (middle segment) anode
• Pin 5: Decimal point (DP) anode
• Pin 6: Digit 2 (right digit) common cathode
• Pin 7: Segment A Anode
• Pin 8: Segment B Anode
• Pin 9: Digit 1 (Left Digit) Common Cathode
• Pin 10: Segment F anode

The description "right decimal point" confirms that the decimal point is associated with the right digit. Common cathode configuration means all LED cathodes for one digit are internally connected. To illuminate a segment, a positive voltage must be applied to its corresponding anode pin while pulling the common cathode pin of the corresponding digit low to ground.

3.3 Internal Circuit Diagram

The internal circuit diagram shows two independent sets of seven-segment LEDs (plus a decimal point LED), each set sharing a common cathode connection (pins 6 and 9). This structure is the basis for multiplexing: by enabling one cathode (digit) sequentially and presenting the pattern for that digit on the anode lines, multiple digits can be controlled with fewer I/O pins.

4. Performance Curve Analysis

The datasheet references "Typical Electrical/Optical Characteristic Curves." While the provided text does not detail specific graphs, typical curves for such devices include:

• I-V (Current-Voltage) Curve:Shows the exponential relationship between forward voltage (V_F) and forward current (I_F). This curve varies with temperature.
• Luminous intensity vs. forward current:It shows that within a certain range, the light output has an approximately linear relationship with the current, but it saturates at higher currents and decays more rapidly due to heat.
• Luminous Intensity vs. Ambient Temperature:It demonstrates the decrease in light output as the junction temperature increases, emphasizing the necessity of thermal management and current derating.
• Spectral Distribution:A graph showing the relationship between relative intensity and wavelength, with a peak at approximately 650nm and a half-width of about 20nm.

These curves are crucial for designing drivers that provide stable brightness across the expected operating temperature range.

5. Welding, Assembly and Storage Guide

5.1 Welding and Assembly

• Follow the specified soldering profile (3 seconds at 260°C).
• Avoid applying abnormal force to the main body of the display using inappropriate tools or methods.
• If a decorative film is applied, avoid direct contact with the front panel/cover, as external force may cause it to shift.

5.2 Storage Conditions

Proper storage is crucial to prevent pin oxidation.

• Standard LED Display (Through-Hole):In original packaging. Temperature: 5°C to 30°C. Humidity: below 60% RH. Long-term storage outside these conditions may require re-plating of oxidized pins. If the moisture barrier bag is opened for more than 6 months, it is recommended to bake at 60°C for 48 hours before use and complete assembly within one week.
• SMD LED display (refer to instructions):在密封袋中：5-30°C，<60% RH。一旦打开：相同条件，但必须在168小时（7天，MSL 3级）内使用。

6. Application Design Considerations and Precautions

6.1 Drive Circuit Design

• Constant Current Drive:An ba yi amince da shi da ƙarfi a yi amfani da tuƙi na yau da kullun maimakon tuƙi na ƙarfi don tabbatar da cewa ko da V_FTsakanin sassan lambobi da yadda suke canzawa tare da zafin jiki, ƙarfin haske ya kasance daidai.
• Iyakokin yanzu:Dole ne kewayen ya iyakance yanzu a cikin ƙimar ƙididdiga ta ci gaba (25mA a 25°C, yana buƙatar rage daraja). Wuce wannan ƙimar zai haifar da tsufa cikin sauri.
• Voltage Range:The driver must accommodate the full V_Frange (approximately 2.0V to 2.7V per segment) to deliver the intended current.
• Reverse Voltage Protection:The circuit should prevent reverse voltage or transient voltage during power cycling to avoid metal migration and increased leakage current.
• Thermal Management:Consider the maximum ambient temperature (T_a) to select a safe operating current. At high T_a environments.

Heat dissipation may be required in the environment.

• 6.2 Environmental and Operational Precautions
• Avoid rapid changes in ambient temperature in humid environments to prevent condensation from forming on the display.

When using two or more displays in the same assembly, displays from the same luminous intensity bin should be selected to ensure uniform brightness.

7. Technical Comparison and Differentiation

• Compared to older GaAsP or GaP LED technologies, the AlInGaP (aluminum indium gallium phosphide) used in the LTD-2701JD offers significant advantages:Higher Efficiency and Brightness:
• AlInGaP provides excellent luminous efficiency, producing higher brightness at the same drive current.Better color purity:
• Ultra-bright red emission (dominant wavelength 639-650nm) is more saturated and visually sharper than standard red LEDs.Improved temperature stability:
• Although all LEDs experience efficiency degradation due to heat, AlInGaP typically maintains better performance retention compared to older materials.

A common-cathode design with independent digital cathodes is a standard yet effective multiplexing method, distinct from common-anode types or displays with internally integrated multiplexing controllers.

8. Frequently Asked Questions (Based on Technical Specifications)
Q: Can I drive this display directly from a 5V microcontroller pin?_FA: No. Connecting 5V directly to the anode without a current-limiting resistor may damage the LED due to excessive current. You must use a series resistor, or preferably a constant current driver. The resistor value depends on your supply voltage, the LED's V_F.

and the desired I
Tambaya: Me ya sa ake ba da shawarar tuƙin mai ɗaukar kaya na yau da kullun?_FAmsa: Hasken LED galibi aikin ƙarfin lantarki ne, ba ƙarfin lantarki ba. Ƙarfin lantarki na gaba (V

) na iya bambanta dangane da guntu kuma yana raguwa yayin da zafin jiki ya ƙaru. Maɓuɓɓugar ƙarfin lantarki ta yau da kullun tana daidaita ƙarfin lantarki ta atomatik don kiyaye ƙarfin lantarki da aka saita, tana rama waɗannan canje-canje, don tabbatar da kwanciyar hankali na haske.
Q: For peak current rating, what does "1/10 duty cycle, 0.1ms pulse width" mean?

A: This means you can drive the LED with a short pulse of up to 90mA, but the pulse width must not exceed 0.1 milliseconds, and the long-term average current must not exceed the value equivalent to a 1/10 duty cycle (e.g., 0.1ms on, 0.9ms off). This is not suitable for continuous illumination.
Q: How to control two digits independently?

答：使用多路复用。在一个周期内：1）将阳极引脚（1,2,3,4,5,7,8,10）设置为数字1的图案。2）将阴极引脚9（数字1）拉低（接地），同时保持阴极引脚6（数字2）为高电平（断开）。3）点亮短时间（例如，5ms）。4）关闭数字1。5）将阳极设置为数字2的图案。6）将阴极引脚6拉低，引脚9拉高。7）点亮。快速重复此周期（>60Hz）以产生两个数字持续点亮的错觉。

9. Practical Design and Use Cases

1. Case: Design a simple digital voltmeter reading (0-99V).Component Selection:
2. LTD-2701JD was chosen for its dual-digit display capability, good brightness, and through-hole package suitable for prototyping.Driving Circuit:
3. A yi amfani da microcontroller (misali ATmega328P). I/O pins ɗinsa ba su iya ba da/ɗaukar isasshen kwarara a lokaci guda ga dukkan sassan lambobi. Saboda haka, an yi amfani da transistors NPN guda biyu (misali 2N3904) don ɗaukar kwararar cathode na lambobi 1 da 2, don aiwatar da tsarin multiplexing. An haɗa anodes na sassan lambobi zuwa microcontroller ta hanyar resistors masu iyakance kwarara (misali, don wutar lantarki na 5V, ana amfani da 150Ω, da niyyar kusan 20mA kowane sashi: R = (5V - 2.6V) / 0.02A ≈ 120Ω, amma don aminci ana amfani da 150Ω).Software:
4. Firmware yana karanta ƙarfin lantarki ta ADC, yana canza shi zuwa lambobin BCD guda biyu, kuma yana amfani da katsewar timer don multiplexing a mitar 100Hz don kunna na'urar nuni.Notices:

Tolerancin ƙarfin lantarki na gaba yana nufin haske na iya ɗan bambanta tsakanin sassan. Amfani da direban kwarara mai tsayi (kamar LED driver IC na musamman) maimakon resistor zai iya haɓaka daidaito. Bi shawarar ajiya, yin odar ƙananan adadi don guje wa ajiyar dogon lokaci.

10. Brief Introduction to Working Principle

A light-emitting diode (LED) is a semiconductor p-n junction diode. When a forward voltage exceeding the junction's built-in potential is applied, electrons from the n-region and holes from the p-region are injected into the junction region. When these carriers recombine in the active region, energy is released in the form of photons (light). The specific wavelength (color) of the emitted light is determined by the bandgap energy of the semiconductor material. The bandgap of AlInGaP corresponds to red light. In a seven-segment display, multiple independent LED chips are mounted and connected to form the standard segments (A-G and DP). A common cathode configuration internally connects the cathodes of all LEDs belonging to one digit.

11. Technical Trends

• The LED display industry continues to evolve. While through-hole displays like the LTD-2701JD remain relevant for prototyping, repair, and certain applications, broader trends include:Miniaturization and SMD Dominance:
• Surface Mount Device (SMD) packages are becoming the standard for automated assembly, offering smaller size and lower profile height.Integrated Controllers:
• Monitors with built-in driver ICs (such as MAX7219-compatible modules) simplify microcontroller interfaces by internally handling multiplexing and decoding.Higher Efficiency Materials:
• The continuous development of materials like InGaN for blue/green light and improved AlInGaP and phosphor-converted white LEDs pushes efficiency (lumens per watt) to higher levels.Flexible and Novel Form Factors:

The development of flexible substrates and micro-LEDs enables new display shapes and ultra-high densities.