LTS-5701AJF 0.56-inch Yellow-Orange 7-Segment LED Display Datasheet - Digit Height 14.22mm - Forward Voltage 2.6V - Power Dissipation 70mW - English Technical Document

1. Product Overview

The LTS-5701AJF is a high-performance, single-digit, seven-segment LED display module. Its primary function is to provide clear, bright numeric and limited alphanumeric character representation in electronic devices. The core technology is based on Aluminium Indium Gallium Phosphide (AlInGaP) semiconductor material, which is specifically engineered to emit light in the yellow-orange spectrum. This material system is known for its high efficiency and excellent brightness compared to older technologies like standard Gallium Phosphide (GaP). The device features a gray faceplate with white segment markings, which significantly enhances contrast and readability under various lighting conditions. It is designed as a common anode configuration, simplifying circuit design in many microcontroller-based applications where sourcing current is more straightforward.

1.1 Key Features and Advantages

The display offers several distinct advantages that make it suitable for a wide range of applications:

• Optimal Character Size: With a digit height of 0.56 inches (14.22 mm), it provides excellent visibility from a distance while maintaining a compact footprint.
• Superior Optical Performance: The use of AlInGaP chips delivers high brightness and high contrast. The continuous, uniform segments ensure a consistent and pleasing character appearance without dark spots or irregularities.
• Wide Viewing Angle: The design allows for clear visibility from a broad range of angles, which is critical for panel meters, instrumentation, and consumer electronics.
• Low Power Operation: It requires relatively low forward current to achieve good luminous intensity, making it energy-efficient and suitable for battery-powered devices.
• Enhanced Reliability: As a solid-state device, it offers high reliability, long operational life, and resistance to shock and vibration compared to mechanical or vacuum fluorescent displays.
• Quality Assurance: The devices are categorized (binned) for luminous intensity, ensuring consistency in brightness across production batches for uniform panel appearance.

2. In-Depth Technical Parameter Analysis

This section provides a detailed, objective interpretation of the electrical and optical parameters specified in the datasheet. Understanding these values is crucial for proper circuit design and ensuring long-term reliability.

2.1 Absolute Maximum Ratings

These ratings define the stress limits beyond which permanent damage to the device may occur. Operation under or at these limits is not guaranteed and should be avoided for reliable design.

• Power Dissipation per Segment (70 mW): This is the maximum amount of power that can be safely dissipated as heat by a single LED segment under continuous operation. Exceeding this limit risks overheating the semiconductor junction, leading to accelerated degradation or catastrophic failure.
• Peak Forward Current per Segment (60 mA, 1/10 duty cycle, 0.1ms pulse): This rating allows for brief pulses of higher current to achieve momentary peaks in brightness, for example in multiplexed displays or for highlighting. The strict duty cycle and pulse width limitations are critical; the average current must still comply with the continuous rating.
• Continuous Forward Current per Segment (25 mA): The recommended maximum current for steady-state, non-pulsed operation of a single segment. A linear derating factor of 0.33 mA/°C is specified above 25°C ambient temperature (Ta). This means if the ambient temperature rises to 50°C, the maximum allowable continuous current would be: 25 mA - ((50°C - 25°C) * 0.33 mA/°C) = 25 mA - 8.25 mA = 16.75 mA.
• Reverse Voltage per Segment (5 V): The maximum voltage that can be applied in the reverse-biased direction across an LED segment. Exceeding this can cause breakdown and damage the PN junction. Proper circuit design should include protection if reverse voltage transients are possible.
• Operating & Storage Temperature Range (-35°C to +85°C): Defines the environmental limits for reliable operation and non-operational storage.
• Solder Temperature (260°C for 3 seconds): Provides guidance for wave or reflow soldering processes, specifying the maximum temperature at a specific point for a limited time to prevent damage to the plastic package and internal wire bonds.

2.2 Electrical & Optical Characteristics (at Ta=25°C)

These are the typical performance parameters under specified test conditions. They are used for design calculations and performance expectations.

• Average Luminous Intensity (I_V): 320-900 μcd at I_F=1mA. This is the measure of perceived brightness by the human eye. The wide range (Min: 320, Typ: 900) indicates a binning process. Designers must use the minimum value for worst-case brightness calculations to ensure visibility under all conditions.
• Peak Emission Wavelength (λ_p): 611 nm (typical) at I_F=20mA. This is the wavelength at which the spectral output is strongest. It falls within the yellow-orange region of the visible spectrum.
• Dominant Wavelength (λ_d): 605 nm (typical) at I_F=20mA. This is the single wavelength perceived by the human eye that best matches the color of the emitted light. It is slightly lower than the peak wavelength, which is common for LEDs with broader spectra.
• Spectral Line Half-Width (Δλ): 17 nm (typical) at I_F=20mA. This parameter indicates the color purity. A value of 17 nm is moderately broad, resulting in a saturated but not monochromatic yellow-orange color.
• Forward Voltage per Segment (V_F): 2.05V (Min), 2.6V (Typ) at I_F=20mA. This is the voltage drop across the LED when operating. It is crucial for calculating the current-limiting resistor value: R = (V_supply - V_F) / I_F. Using the typical or maximum value ensures the current does not exceed the desired level.
• Reverse Current per Segment (I_R): 100 μA (Max) at V_R=5V. This is the small leakage current that flows when the LED is reverse-biased within its maximum rating.
• Luminous Intensity Matching Ratio (I_V-m): 2:1 (Max). This specifies the maximum allowable brightness variation between different segments of the same digit or between different digits in a multi-digit display. A ratio of 2:1 means the brightest segment should be no more than twice as bright as the dimmest, ensuring uniform appearance.

3. Binning System Explanation

The datasheet indicates that devices are "Categorized for Luminous Intensity." This refers to a binning or sorting process post-manufacturing.

• Luminous Intensity Binning: Due to natural variations in the semiconductor epitaxial growth and chip fabrication process, the light output of LEDs can vary. After production, devices are tested and sorted into different bins based on their measured luminous intensity at a standard test current (e.g., 1mA). The specified range of 320 to 900 μcd likely encompasses several bins. Manufacturers may offer specific bin codes for applications requiring tight brightness matching.
• Forward Voltage Sorting: While not explicitly mentioned as a binned parameter, the range given for V_F (2.05V to 2.6V) is typical. For very high-volume or sensitive designs, parts can also be sorted by forward voltage to ensure consistent power consumption and thermal characteristics across a display.

4. Performance Curve Analysis

While the provided datasheet excerpt mentions "Typical Electrical / Optical Characteristic Curves," the specific graphs are not included in the text. Based on standard LED behavior, these curves would typically illustrate the following relationships, which are vital for understanding device performance under non-standard conditions:

• Forward Current vs. Forward Voltage (I-V Curve): Shows the exponential relationship. The curve shifts with temperature; V_F decreases as junction temperature increases for a given current.
• Luminous Intensity vs. Forward Current: Generally shows a near-linear relationship at lower currents, with possible saturation or efficiency droop at very high currents. This graph is used to select the operating current for a desired brightness level.
• Luminous Intensity vs. Ambient Temperature: Demonstrates how light output decreases as the ambient (and thus junction) temperature rises. This is critical for designs operating in elevated temperature environments.
• Spectral Distribution: A plot of relative intensity versus wavelength, showing the peak at ~611 nm and the half-width of ~17 nm, defining the exact color characteristics.

5. Mechanical and Packaging Information

5.1 Package Dimensions and Pinout

The device is housed in a standard 10-pin, single-digit, seven-segment LED display package. The datasheet provides a detailed dimensional drawing (not reproduced here) with all critical measurements in millimeters. Key features include the overall height, width, and depth, the digit window size, the lead spacing (pitch), and the seating plane. Tolerances are typically ±0.25 mm unless otherwise noted. The pin connection is clearly defined:

1. Pin 1: Cathode E
2. Pin 2: Cathode D
3. Pin 3: Common Anode
4. Pin 4: Cathode C
5. Pin 5: Cathode D.P. (Decimal Point)
6. Pin 6: Cathode B
7. Pin 7: Cathode A
8. Pin 8: Common Anode
9. Pin 9: Cathode F
10. Pin 10: Cathode G

The internal circuit diagram shows that all segment LEDs (A-G and DP) have their anodes connected together internally to the two common anode pins (3 and 8), which are also internally connected. This common anode design means to illuminate a segment, its corresponding cathode pin must be driven low (connected to ground or a lower voltage) while the anode pins are held at a positive voltage through a current-limiting resistor.

6. Soldering and Assembly Guidelines

The absolute maximum ratings specify a soldering condition: 260°C for 3 seconds, measured 1/16 inch (approximately 1.59 mm) below the seating plane. This is a standard reference for wave soldering. For reflow soldering, a standard lead-free profile with a peak temperature not exceeding 260°C is appropriate. It is crucial to avoid excessive thermal stress, which can crack the epoxy package, damage the internal die attach, or break the fine wire bonds connecting the chip to the leads. Preheating is recommended to minimize thermal shock. After soldering, the device should be allowed to cool gradually. For storage, the specified range of -35°C to +85°C in a dry, non-condensing environment should be maintained to preserve solderability and prevent moisture absorption (which can cause "popcorning" during reflow).

7. Application Suggestions

7.1 Typical Application Scenarios

The LTS-5701AJF is ideal for applications requiring clear, reliable numeric readouts:

• Test and Measurement Equipment: Digital multimeters, frequency counters, power supplies, sensor readouts.
• Industrial Controls: Panel meters for temperature, pressure, flow, RPM, and process variable displays.
• Consumer Electronics: Clocks, timers, kitchen appliance displays, audio equipment level meters.
• Automotive Aftermarket: Gauges and displays for auxiliary systems (not primary instrumentation due to temperature and reliability certification requirements).
• Medical Devices: Simple parameter displays on non-critical monitoring equipment (subject to appropriate regulatory approvals).

7.2 Design Considerations and Circuit Implementation

• Current Limiting: A resistor must be connected in series with the common anode(s) or each cathode to limit the forward current to a safe value (e.g., 10-20 mA). The resistor value is calculated using the supply voltage (V_CC), the LED forward voltage (V_F), and the desired current (I_F): R = (V_CC - V_F) / I_F. Use the maximum V_F from the datasheet for a conservative design that ensures current never exceeds the target.
• Multiplexing: For multi-digit displays, a multiplexing technique is almost always used to minimize pin count on the driving microcontroller. This involves illuminating one digit at a time in rapid sequence. The persistence of vision makes the display appear continuously lit. When multiplexing, the peak current per segment can be higher (within the 60mA pulsed rating) to compensate for the reduced duty cycle and maintain average brightness. The design must ensure the average current and power dissipation per segment are within continuous limits.
• Microcontroller Drive: Common anode displays are easily driven by microcontroller port pins configured as open-drain or open-collector outputs sinking current to ground. Alternatively, dedicated LED driver ICs or transistor arrays (e.g., ULN2003) can be used for higher current capability or simpler logic.
• Viewing Angle and Mounting: Consider the intended user's viewing angle when designing the panel cutout and mounting depth to leverage the wide viewing angle of the display.

8. Technical Comparison and Differentiation

The primary differentiator of the LTS-5701AJF is its use of AlInGaP material for yellow-orange emission. Compared to older GaP yellow LEDs, AlInGaP offers significantly higher luminous efficiency, resulting in brighter displays at the same current or equivalent brightness at lower power. Compared to red GaAsP or AllnGaP LEDs, it provides a distinct color that can be easier to read in certain ambient light conditions and may be preferred for specific aesthetic or functional color-coding requirements. The 0.56-inch digit size places it in a common category for instrument panels, offering a good balance between size and readability.

9. Frequently Asked Questions (Based on Technical Parameters)

Q1: What resistor value should I use with a 5V supply to drive a segment at 15mA?
A1: Using the maximum V_F of 2.6V for a safe design: R = (5V - 2.6V) / 0.015A = 2.4V / 0.015A = 160 Ω. The nearest standard value of 150 Ω or 180 Ω would be suitable. Always verify actual brightness and current in the circuit.

Q2: Can I connect the two common anode pins together?
A2: Yes, pins 3 and 8 are internally connected. Connecting them together on the PCB is standard practice and helps distribute current, potentially improving brightness uniformity.

Q3: How do I display the number "7"?
A3: To display "7", you need to illuminate segments A, B, and C. Therefore, with a common anode configuration, apply a positive voltage (through a current-limiting resistor) to the common anode(s), and connect the cathode pins for A (pin 7), B (pin 6), and C (pin 4) to ground (low logic level).

Q4: Why does the maximum continuous current derate above 25°C?
A4: The power dissipation limit is fixed. As ambient temperature rises, the temperature difference between the LED junction and the ambient air (the thermal gradient) decreases, making it harder to dissipate heat. To prevent the junction temperature from exceeding its safe limit, the allowable power (and thus current for a given V_F) must be reduced.

10. Practical Design Example

Scenario: Designing a 4-digit voltmeter display.
A microcontroller with limited I/O pins is used. The four LTS-5701AJF displays are connected in a multiplexed configuration. The segment cathodes (A-G, DP) of all four digits are connected in parallel. Each digit's common anode pin is controlled by a separate NPN transistor driven by a microcontroller pin. The microcontroller uses a timer interrupt to cycle through the digits every 2-5 milliseconds. It calculates the segment data for the active digit and outputs it to a port connected to the common cathodes via current-limiting resistors. To maintain good brightness with a 1/4 duty cycle, the peak segment current during its active time might be set to 25-30 mA (well below the 60mA pulsed rating), resulting in an average current of ~6-7.5 mA per segment, which is safe and provides ample brightness. The design must include the derating calculation if the device is expected to operate in a hot environment.

11. Technology Principle Introduction

The LTS-5701AJF is based on a III-V semiconductor compound, Aluminium Indium Gallium Phosphide (Al_xIn_yGa_1-x-yP). The specific ratios of these elements determine the bandgap energy of the material, which directly dictates the wavelength (color) of the emitted light. In this case, the composition is engineered for a bandgap corresponding to yellow-orange photons (~605-611 nm). When a forward voltage is applied across the PN junction, electrons and holes are injected into the active region. They recombine radiatively, releasing energy in the form of light. The use of a non-transparent GaAs substrate helps absorb stray light, improving contrast. The gray face and white segments are made of molded epoxy with diffusing pigments, which helps spread the light evenly across each segment and enhances the contrast against the unlit background.

12. Technology Trends

While discrete seven-segment displays remain relevant for many applications, the general trend in display technology is towards integration and flexibility. This includes:
Integration: Multi-digit modules with built-in driver ICs (e.g., with SPI/I2C interface) are becoming more common, simplifying microcontroller interfacing.
Materials: While AlInGaP is efficient for red-orange-yellow, newer materials like InGaN (for blue/green/white) offer even higher efficiencies. Hybrid displays or full-color addressable LED matrices are gaining popularity for more complex information display.
Form Factors: There is a constant drive for thinner packages, higher brightness for sunlight readability, and lower power consumption for portable devices. However, the fundamental simplicity, robustness, and cost-effectiveness of standard seven-segment LEDs like the LTS-5701AJF ensure their continued use in a vast array of applications where simple numeric output is required.