LTC-5723JD LED Display Datasheet - 0.56-inch Digit Height - AlInGaP Red - Multiplex Common Cathode - English Technical Document

1. Product Overview

The LTC-5723JD is a high-performance, quadruple-digit, seven-segment display module designed for applications requiring clear, bright numeric readouts. Its primary function is to visually represent numerical data across four distinct digits, each composed of seven individually addressable segments plus a decimal point. The core technology behind this display is the use of Aluminium Indium Gallium Phosphide (AlInGaP) light-emitting diode chips, which are renowned for their high efficiency and excellent luminous output in the red spectrum. These chips are fabricated on a non-transparent Gallium Arsenide (GaAs) substrate, contributing to the device's overall contrast and performance. The display features a gray faceplate with white segment markings, enhancing readability by providing a high-contrast background for the illuminated red segments. This combination is particularly effective in various lighting conditions, ensuring the displayed information is easily discernible.

The device is engineered for multiplexed operation, utilizing a common cathode configuration for each digit. This design significantly reduces the number of required input/output pins from a driving microcontroller or circuit, making it a space-efficient and cost-effective solution for multi-digit displays. By sequentially activating each digit at a high frequency, all four digits appear to be continuously illuminated to the human eye, a technique standard in multiplexed LED displays. The LTC-5723JD is categorized for luminous intensity, meaning units are binned and sold according to specific brightness ranges, allowing designers to select parts that meet precise application requirements for uniformity or minimum brightness thresholds.

1.1 Key Features and Advantages

The display offers several distinct advantages that make it suitable for a wide range of industrial, commercial, and instrumentation applications.

• Optical Performance: It delivers high brightness and high contrast, ensuring excellent character appearance and legibility even in brightly lit environments. The wide viewing angle allows the display to be read clearly from various positions, not just directly head-on.
• Electrical Efficiency: The device has a low power requirement per segment, contributing to lower overall system power consumption. The use of high-efficiency AlInGaP technology is central to achieving this performance.
• Design and Reliability: It features continuous uniform segments, which provide a clean, professional aesthetic without visible breaks in the illuminated bars. As a solid-state device, it offers superior reliability and longevity compared to mechanical or vacuum-based displays, with no moving parts or filaments to wear out.
• Physical Characteristics: With a digit height of 0.56 inches (14.2 mm), it provides a large, easily readable numeric display suitable for panel meters, test equipment, and other devices where data must be monitored from a distance.

2. Technical Specifications and Objective Interpretation

This section provides a detailed, objective analysis of the electrical, optical, and physical parameters specified in the datasheet. Understanding these specifications is crucial for proper circuit design and ensuring reliable operation within the device's limits.

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 in normal use.

• 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 any condition.
• Peak Forward Current per Segment: 90 mA. This current is allowed only under pulsed conditions with a 1/10 duty cycle and a 0.1 ms pulse width. It is used for achieving very high instantaneous brightness, for example in multiplexed schemes.
• Continuous Forward Current per Segment: 25 mA at 25°C. This rating decreases linearly above 25°C at a rate of 0.28 mA/°C. For reliable long-term operation, the continuous current must be derated as ambient temperature increases to prevent overheating.
• Reverse Voltage per Segment: 5 V. Applying a reverse voltage greater than this value can break down the LED junction.
• Operating and Storage Temperature Range: -35°C to +85°C. The device is rated for industrial temperature ranges.
• Solder Temperature: Maximum 260°C for a maximum of 3 seconds, measured 1.6mm below the seating plane. This is critical for wave or reflow soldering processes to prevent thermal damage to the LED chips or package.

2.2 Electrical and Optical Characteristics

These parameters are typically measured at an ambient temperature (Ta) of 25°C and define the normal operating performance of the device.

• Average Luminous Intensity (I_V): 340 μcd (Min), 700 μcd (Typ) at a forward current (I_F) of 1 mA. This is a measure of the perceived brightness of a segment. The wide range indicates the device is available in different brightness bins.
• Peak Emission Wavelength (λ_p): 650 nm (Typ) at I_F=20 mA. This is the wavelength at which the optical output power is greatest, placing it in the bright red portion of the visible spectrum.
• Spectral Line Half-Width (Δλ): 20 nm (Typ) at I_F=20 mA. This indicates the spectral purity; a smaller value means a more monochromatic (pure color) output.
• Dominant Wavelength (λ_d): 639 nm (Typ) at I_F=20 mA. This is the single wavelength that best represents the perceived color of the light.
• Forward Voltage (V_F): 2.1V (Typ), 2.6V (Max) at I_F=20 mA. This is the voltage drop across the LED when operating. It is crucial for designing the current-limiting circuitry.
• Reverse Current (I_R): 100 μA (Max) at a reverse voltage (V_R) of 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) at I_F=1 mA. This specifies the maximum allowable brightness variation between different segments of the same device, ensuring visual uniformity.

Note on Measurement: Luminous intensity is measured using a sensor and filter combination that approximates the CIE photopic eye-response curve, ensuring the values correspond to human brightness perception.

3. Binning System Explanation

The datasheet indicates the device is \"categorized for luminous intensity.\" This refers to a common practice in LED manufacturing known as binning.

• Luminous Intensity Binning: Due to inherent variations in the semiconductor manufacturing process, LEDs from the same production batch can have slightly different brightness outputs. Manufacturers test and sort (bin) these LEDs into groups based on their measured luminous intensity at a standard test current (e.g., 1 mA). The LTC-5723JD is available with a minimum intensity of 340 μcd and a typical of 700 μcd. Specific order codes or suffixes likely correspond to different brightness bins (e.g., a standard bin and a high-brightness bin). Designers can specify the required bin to ensure consistency across multiple displays in a product or to meet a minimum brightness requirement.
• Wavelength/Color Binning: While not explicitly detailed in the provided excerpt, AlInGaP LEDs may also be binned for dominant or peak wavelength to ensure a consistent shade of red across all segments and devices. The tight typical values for λ_p (650 nm) and λ_d (639 nm) suggest good inherent color consistency.

4. Performance Curve Analysis

The datasheet references \"Typical Electrical/Optical Characteristic Curves.\" While the specific graphs are not provided in the text, standard curves for such devices typically include:

• Forward Current vs. Forward Voltage (I_F-V_F Curve): This non-linear curve shows how much voltage is required to achieve a given forward current. It is essential for designing the driver circuit, especially for constant-current drivers.
• Luminous Intensity vs. Forward Current (I_V-I_F Curve): This curve shows how brightness increases with current. It is generally linear over a range but will saturate at very high currents. It helps determine the operating current needed to achieve a desired brightness level.
• Luminous Intensity vs. Ambient Temperature (I_V-T_a Curve): This shows how brightness decreases as the ambient (or junction) temperature rises. This derating is critical for applications operating in high-temperature environments.
• Relative Intensity vs. Wavelength (Spectrum): A plot showing the distribution of light output across different wavelengths, centered around the peak emission wavelength. It defines the color characteristics of the LED.

5. Mechanical and Packaging Information

5.1 Package Dimensions

The mechanical drawing provides critical dimensions for PCB footprint design and panel cutouts. All dimensions are in millimeters with a standard tolerance of ±0.25 mm unless otherwise specified. Key features include the overall length, width, and height of the package, the spacing between digits, the size and position of the mounting pins, and the location of the decimal point relative to the digits. Designers must adhere to these dimensions to ensure proper physical fit and alignment on the final product assembly.

5.2 Pin Connection and Internal Circuit Diagram

The device has a 12-pin configuration. The internal circuit diagram reveals a multiplexed common-cathode architecture.

• Pinout:
  1: Anode E
  2: Anode D
  3: Anode DP (Decimal Point)
  4: Anode C
  5: Anode G
  6: Common Cathode (Digit 4)
  7: Anode B
  8: Common Cathode (Digit 3)
  9: Common Cathode (Digit 2)
  10: Anode F
  11: Anode A
  12: Common Cathode (Digit 1)
• Circuit Architecture: All similar segment anodes (e.g., all \"A\" segments from digits 1-4) are connected internally to a single pin. Each digit has its own dedicated common cathode pin. To illuminate a specific segment on a specific digit, the corresponding anode pin must be driven high (or connected to a current source), and the corresponding digit's cathode pin must be driven low (connected to ground). This structure minimizes the required drive lines from 32 (4 digits * 8 segments) to just 12 (7 segment anodes + 1 DP anode + 4 digit cathodes).

6. Soldering and Assembly Guidelines

Adherence to the specified soldering profile is mandatory to prevent damage.

• Reflow Soldering Parameters: The maximum allowable temperature at the lead/solder joint is 260°C, and this temperature must not be sustained for more than 3 seconds. The profile should be designed to stay within this window. Preheating is necessary to minimize thermal shock.
• Hand Soldering: If hand soldering is necessary, a temperature-controlled iron should be used. Contact time per pin should be minimized, ideally to less than 3 seconds, using a low thermal mass tip.
• Cleaning: Use only cleaning agents compatible with the display's plastic face and epoxy materials. Harsh solvents should be avoided.
• Storage Conditions: The device should be stored in its original moisture-barrier bag in an environment within the storage temperature range (-35°C to +85°C) and at low humidity. If the bag has been opened, devices should be used within a specified time frame or baked before soldering if they have absorbed moisture.

7. Application Suggestions

7.1 Typical Application Scenarios

• Test and Measurement Equipment: Digital multimeters, oscilloscopes, power supplies, and frequency counters.
• Industrial Controls and Instrumentation: Panel meters for temperature, pressure, flow, and level monitoring; process timers; counter displays.
• Consumer and Commercial Electronics: Point-of-sale systems, weighing scales, clock radios, and appliance displays.
• Automotive Aftermarket: Gauges and diagnostic tools (where environmental specifications are met).

7.2 Design Considerations and Driver Circuitry

• Multiplexing Driver: A microcontroller or dedicated display driver IC (e.g., MAX7219, TM1637) is almost always required. The firmware or hardware must cycle through the four digits rapidly (typically >100 Hz) to avoid visible flicker.
• Current Limiting: Each anode or cathode line must have appropriate current-limiting resistors or be driven by a constant-current source. The resistor value is calculated using R = (V_supply - V_F) / I_F. For a 5V supply and a target I_F of 10 mA with a typical V_F of 2.1V, R = (5 - 2.1) / 0.01 = 290 Ω. A 270 Ω or 330 Ω resistor would be suitable.
• Power Dissipation: Calculate the total power for the worst-case scenario (all segments of one digit on). With 8 segments at 10 mA each and V_F=2.1V, power per digit is 8 * 0.01 * 2.1 = 0.168W. Ensure the driver circuit can handle this.
• Viewing Angle and Mounting: Position the display behind the panel cutout so the bezel does not obstruct the wide viewing angle. Ensure even back support to avoid stress on the pins.

8. Technical Comparison and Differentiation

Compared to other display technologies and LED types:

• vs. LCD: LEDs are emissive (produce their own light), offering superior brightness, wider viewing angles, and better performance in low-temperature environments. They do not require a backlight. However, they typically consume more power than reflective LCDs and have a fixed color.
• vs. Other LED Colors (GaAsP, GaP): AlInGaP technology, as used in the LTC-5723JD, offers significantly higher luminous efficiency and better temperature stability than older red LED materials like GaAsP, resulting in brighter displays with more consistent color over temperature.
• vs. Single-Digit or Smaller Displays: The integration of four digits in one package saves PCB space, reduces assembly time, and improves alignment accuracy compared to using four separate single-digit displays.
• vs. Common Anode Displays: The choice between common cathode and common anode is often dictated by the driver IC or microcontroller circuit. Common cathode is frequently used with microcontrollers that source current well but sink less, as they can source current to the anodes and use NPN transistors or N-channel MOSFETs to sink the higher cathode currents.

9. Frequently Asked Questions (Based on Technical Parameters)

• Q: Can I drive this display with a 3.3V microcontroller?
  A: Yes, but you must check the forward voltage. At a lower drive current (e.g., 5 mA), V_F may be around 2.0V, leaving 1.3V for the current-limiting resistor, which is sufficient. You may need to reduce the target current to maintain brightness or use a driver IC that can boost the voltage to the segments.
• Q: Why is the peak current (90 mA) so much higher than the continuous current (25 mA)?
  A: LEDs can handle very short, high-current pulses without overheating because the thermal mass of the chip prevents a rapid temperature rise. This is exploited in multiplexing, where each digit is only on for 25% of the time (1/4 duty cycle). A peak current of 40-50 mA at 25% duty cycle can make the display appear much brighter than running at 25 mA continuously.
• Q: What does \"luminous intensity matching ratio 2:1\" mean in practice?
  A: It means that within a single device, the dimmest segment will be no less than half as bright as the brightest segment under the same test conditions. This ensures visual uniformity across the display. For critical applications, specifying a tighter bin (e.g., 1.5:1) may be necessary.
• Q: How do I calculate the refresh rate for multiplexing?
  A: The entire cycle of illuminating all four digits must complete at a rate high enough to avoid flicker, typically >60-100 Hz. Therefore, the period for each digit is 1/(Refresh Rate * Number of Digits). For a 100 Hz refresh and 4 digits, each digit is on for 1/400s = 2.5 ms. The microcontroller timer must switch digits every 2.5 ms.

10. Design and Usage Case Study

Scenario: Designing a Simple 4-Digit Voltmeter.
A designer is creating a 0-30V DC voltmeter. The analog voltage is read by a microcontroller's ADC. The microcontroller must drive the LTC-5723JD display.

1. Hardware Design: The microcontroller's I/O pins are connected to the 8 anode lines (A-G, DP) via 330Ω current-limiting resistors. Four other I/O pins are connected to the bases of four NPN transistors (e.g., 2N3904). The collectors of these transistors connect to the four cathode pins (Digits 1-4), and the emitters connect to ground. A base resistor (e.g., 4.7kΩ) is used for each transistor.
2. Firmware Logic: The firmware converts the ADC reading to four separate digits. It enters a timer interrupt routine running at 400 Hz. In each interrupt, it turns off all digit transistors. It then sets the anode lines (via a port or shift register) to the segment pattern for the next digit in sequence. Finally, it turns on the transistor for that specific digit. This cycles continuously.
3. Brightness Control: Display brightness can be adjusted in two ways: 1) By changing the value of the current-limiting resistors (lower resistance = higher current = brighter), staying within the maximum ratings. 2) By using Pulse-Width Modulation (PWM) on the digit enable lines within the multiplexing routine, effectively changing the duty cycle for all digits simultaneously.

11. Operating Principle

The fundamental operating principle is based on electroluminescence in a semiconductor p-n junction. When a forward voltage exceeding the diode's turn-on voltage (approximately 2.1V for this AlInGaP material) is applied, electrons from the n-type region and holes from the p-type region are injected into the active region where they recombine. In a direct bandgap semiconductor like AlInGaP, this recombination releases energy in the form of photons (light). The specific composition of the Al_xIn_yGa_1-x-yP alloy determines the bandgap energy and thus the wavelength (color) of the emitted light, which is in the red spectrum for this device. The non-transparent GaAs substrate absorbs any downward-emitted light, improving contrast by preventing internal reflections that could light up non-activated segments.

12. Technology Trends

While the AlInGaP technology represented in this datasheet is mature and highly reliable, the broader field of display technology continues to evolve. Trends include the development of even higher efficiency materials, such as those based on Gallium Nitride (GaN) for blue and green, which are now dominant. For multi-digit numeric displays, there is a trend towards fully integrated modules with built-in controllers, I2C or SPI interfaces, and sometimes even embedded fonts and special characters, simplifying design. Furthermore, dot-matrix OLED and micro-LED displays offer potential for greater flexibility in showing alphanumeric and graphic information in similar form factors. However, for applications requiring simple, bright, rugged, and cost-effective numeric readouts, dedicated seven-segment LED displays like the LTC-5723JD remain a highly viable and popular solution due to their proven performance, simplicity, and excellent readability.