LTC-5623JD LED Display Datasheet - 0.56-inch Digit Height - Hyper Red Color - 2.6V Forward Voltage - English Technical Document

1. Product Overview

The LTC-5623JD is a quadruple-digit, seven-segment light-emitting diode (LED) display module. Its primary function is to provide a clear, bright numeric readout for various electronic devices and instrumentation. The core application is in scenarios requiring the display of numerical data, such as in test equipment, industrial controls, consumer appliances, and panel meters.

The device's key positioning lies in its balance of character size, brightness, and reliability. It utilizes AlInGaP (Aluminum Indium Gallium Phosphide) semiconductor technology for its LED chips, specifically in a Hyper Red color. This technology offers advantages in efficiency and luminous intensity compared to older technologies like standard GaAsP. The display features a gray face with white segment markings, enhancing contrast and readability under various lighting conditions.

Its core advantages, as listed in the datasheet, include a continuous uniform segment appearance, low power requirement, excellent character appearance, high brightness and contrast, a wide viewing angle, and solid-state reliability. The device is also categorized for luminous intensity and is offered in a lead-free package compliant with RoHS directives.

2. Technical Specifications and Objective Interpretation

2.1 Absolute Maximum Ratings

These parameters define the limits beyond which permanent damage to the device may occur. They are not conditions for normal operation.

• Power Dissipation per Segment: 70 mW. This is the maximum allowable power loss as heat for a single segment (e.g., segment 'A'). Exceeding this can overheat the semiconductor junction.
• Peak Forward Current per Segment: 90 mA. This is allowed only under pulsed conditions (1/10 duty cycle, 0.1ms pulse width). It is useful for multiplexing schemes where higher instantaneous current is used to achieve perceived brightness.
• Continuous Forward Current per Segment: 25 mA at 25°C. This current derates linearly by 0.28 mA/°C as ambient temperature (Ta) increases above 25°C. For example, at 85°C, the maximum continuous current would be approximately: 25 mA - ((85°C - 25°C) * 0.28 mA/°C) = 8.2 mA.
• Operating & Storage Temperature Range: -35°C to +105°C. The device can function and be stored within this full range.
• Solder Temperature: Maximum 260°C for a maximum of 3 seconds, measured 1.6mm (1/16 inch) below the seating plane. This is critical for wave or reflow soldering processes to prevent thermal damage to the plastic package and internal wire bonds.

2.2 Electrical & Optical Characteristics

These are the typical performance parameters measured at an ambient temperature (Ta) of 25°C.

• Average Luminous Intensity (Iv): 320 μcd (min), 700 μcd (typ) at a forward current (IF) of 1 mA. This quantifies the light output. The device is binned/categorized based on this parameter.
• Peak Emission Wavelength (λp): 650 nm (typ) at IF=20mA. This is the wavelength at which the spectral output is strongest.
• Spectral Line Half-Width (Δλ): 20 nm (typ) at IF=20mA. This indicates the spectral purity; a smaller value means a more monochromatic light.
• Dominant Wavelength (λd): 639 nm (typ) at IF=20mA. This is the single wavelength perceived by the human eye, defining the 'Hyper Red' color.
• Forward Voltage per Segment (Vf): 2.1V (min), 2.6V (typ) at IF=20mA. This is the voltage drop across an illuminated segment. It is crucial for designing current-limiting circuitry.
• Reverse Current per Segment (Ir): 100 μA (max) at a reverse voltage (Vr) of 5V. This parameter is for test purposes only; the device is not intended for continuous reverse bias operation.
• Luminous Intensity Matching Ratio (Iv-m): 2:1 (max). This specifies the maximum allowable ratio between the brightest and dimmest segment within a device, ensuring uniform appearance.

3. Binning and Categorization System

The datasheet states the device is \"Categorized for Luminous Intensity.\" This implies that units are sorted (binned) based on measured light output at a standard test current (typically 1mA or 20mA). While specific bin codes are not provided in this excerpt, common practice involves alphanumeric codes (e.g., B1, B2, C1) representing ranges of luminous intensity. This allows designers to select displays with consistent brightness levels for their application. The tight 2:1 intensity matching ratio further ensures visual consistency across all segments of a single digit and between digits.

4. Performance Curve Analysis

The datasheet references \"Typical Electrical / Optical Characteristic Curves\" on the final page. Although the specific graphs are not provided in the text, we can infer their standard content based on LED technology:

• Forward Current vs. Forward Voltage (I-V Curve): This graph would show the exponential relationship typical of a diode. The curve allows designers to determine the necessary driving voltage for a desired operating current, which is essential for designing stable constant-current drivers.
• Luminous Intensity vs. Forward Current (I-L Curve): This shows how light output increases with current. It is generally linear over a range but will saturate at very high currents due to thermal and efficiency droop.
• Luminous Intensity vs. Ambient Temperature: This curve demonstrates how light output decreases as the junction temperature rises. Understanding this derating is critical for applications operating in elevated temperature environments.
• Spectral Distribution: A plot of relative intensity versus wavelength, showing the peak at ~650nm and the ~20nm half-width, confirming the Hyper Red color specification.

5. Mechanical and Packaging Information

5.1 Package Dimensions

The device has a 0.56-inch (14.2 mm) digit height. The dimensional drawing (not fully detailed in text) would provide critical measurements for PCB footprint design: overall length, width, and height; digit-to-digit spacing; segment dimensions; and pin length, diameter, and spacing. The notes specify all dimensions are in millimeters with a general tolerance of ±0.25 mm. A critical note is the pin tip shift tolerance of ±0.4 mm, which advises designing motherboard pin holes with a diameter (ψ) of 1.0 mm to accommodate this potential misalignment during insertion.

5.2 Pin Connection and Polarity

The LTC-5623JD uses a common anode configuration. This means the anodes of the LEDs for each digit are connected together internally and brought out to separate pins (Digits 1-4), while the cathodes for each segment type (A-G, DP) are shared across all digits and brought out to individual pins. The pinout is as follows: Pin 1: Cathode E, Pin 2: Cathode D, Pin 3: Cathode DP, Pin 4: Cathode C, Pin 5: Cathode G, Pin 6: Common Anode Digit 4, Pin 7: Cathode B, Pin 8: Common Anode Digit 3, Pin 9: Common Anode Digit 2, Pin 10: Cathode F, Pin 11: Cathode A, Pin 12: Common Anode Digit 1. The internal circuit diagram would show this multiplexing arrangement clearly.

6. Soldering and Assembly Guidelines

The key guideline provided is the soldering temperature limit: a maximum of 260°C for a maximum of 3 seconds, measured 1.6mm below the seating plane. This is a standard profile for lead-free reflow soldering. Designers must ensure their PCB assembly process adheres to this limit to prevent package cracking, lens deformation, or damage to the internal die and wire bonds. For wave soldering, contact time should be minimized. Proper handling to avoid electrostatic discharge (ESD) is also recommended, although not explicitly stated, as LEDs are semiconductor devices.

7. Application Suggestions and Design Considerations

7.1 Typical Application Circuits

For a common anode display, the driving circuit typically involves connecting the common anode pins to a positive voltage supply (Vcc) through digit-select transistors (e.g., PNP or P-channel MOSFETs). The segment cathode pins are connected to ground through current-limiting resistors and segment-driver transistors or a dedicated LED driver IC. A multiplexing technique is used: one digit is illuminated at a time by enabling its anode, while the appropriate cathodes for that digit's desired number are enabled. This cycle repeats rapidly across all four digits, creating the illusion of all digits being lit simultaneously. This method reduces the number of required driver pins from 32 (4 digits * 8 segments) to 12 (4 anodes + 8 cathodes).

7.2 Design Calculations

Current-Limiting Resistor Calculation: Assuming a 5V supply (Vcc), a typical segment forward voltage (Vf) of 2.6V, and a desired segment current (Iseg) of 10 mA for normal brightness. The resistor value R = (Vcc - Vf) / Iseg = (5 - 2.6) / 0.01 = 240 Ω. The power rating of the resistor should be at least I²R = (0.01)² * 240 = 0.024 W, so a standard 1/8W or 1/10W resistor is sufficient.

Peak Current in Multiplexing: To achieve an average segment current of 10 mA with a 1/4 duty cycle (for four digits), the peak current during its active time slot would need to be 40 mA. This is within the absolute maximum peak current rating of 90 mA but must be checked against the continuous current derating if the display operates in a hot environment.

7.3 Viewing Angle and Readability

The wide viewing angle specification ensures the display remains readable when viewed from the side. The gray face and white segments enhance contrast, making the numerals stand out clearly against the background, which is beneficial in both dim and brightly lit environments.

8. Technical Comparison and Differentiation

The LTC-5623JD differentiates itself through several factors. The use of AlInGaP Hyper Red technology generally offers higher luminous efficiency and better temperature stability compared to older red LED technologies like GaAsP, resulting in brighter and more consistent output. The 0.56-inch digit height places it in a specific size category, larger than 0.3-inch displays for better visibility at a distance, but potentially smaller than 1-inch displays used in larger panels. The quadruple-digit, common anode configuration with right-hand decimal is a standard but essential feature set for many numeric display applications. Its wide operating temperature range (-35°C to +105°C) makes it suitable for industrial and automotive environments where temperature extremes are common, providing an advantage over displays with narrower ranges.

9. Frequently Asked Questions (Based on Technical Parameters)

Q: Can I drive this display directly from a microcontroller pin?
A: No. A typical MCU pin can only source/sink 20-25mA, which is the total for the pin. Since this display uses multiplexing, a single segment might require 10-40mA, and the common anode for a whole digit would need the sum of currents for all lit segments (e.g., 8 segments * 10mA = 80mA). Therefore, external transistors or a dedicated driver IC are mandatory.

Q: Why is there a difference between Peak Wavelength (650nm) and Dominant Wavelength (639nm)?
A> Peak wavelength is the physical peak of the emitted light spectrum. Dominant wavelength is calculated based on the human eye's photopic response curve (CIE). The eye is more sensitive to certain wavelengths, so the \"perceived\" color (dominant) can be at a different wavelength than the physical peak.

Q: The storage temperature is up to 105°C. Can I solder it at 260°C?
A> Yes, but with critical timing. The storage rating is for long-term, non-operating conditions. The soldering rating (260°C for 3s) is a short-term, extreme thermal process that the package is designed to withstand if the profile is strictly followed. Exceeding the time or temperature can cause damage.

10. Design and Usage Case Study

Scenario: Designing a Digital Voltmeter Readout. A designer is creating a 4-digit DC voltmeter with a 0-20V range. They select the LTC-5623JD for its clear readability. The analog-to-digital converter (ADC) and microcontroller process the input voltage. The MCU's firmware calculates the digits to display (e.g., 12.34) and controls the display via a multiplexing routine. The common anode pins are connected to the MCU via PNP transistors to switch the 5V supply to each digit sequentially. The segment cathode pins are connected to the MCU through a 74HC595 shift register or a dedicated LED driver like the MAX7219, which also provides the constant-current sinks. Current-limiting resistors are placed in series with the segment lines. The firmware ensures the refresh rate is above 60 Hz to avoid visible flicker. The wide operating temperature range allows the voltmeter to be used in a workshop garage where temperatures can vary significantly.

11. Operating Principle

The device operates on the principle of electroluminescence in a semiconductor p-n junction. When a forward voltage exceeding the diode's threshold (approximately 2.1-2.6V for this AlInGaP material) is applied across a segment (anode positive relative to cathode), electrons and holes 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 AlInGaP alloy determines the bandgap energy, which in turn dictates the wavelength (color) of the emitted light, in this case, Hyper Red (~639-650 nm). The plastic package serves to encapsulate and protect the fragile semiconductor die, shape the light output for optimal viewing, and provide the mechanical interface (pins) for circuit board mounting.

12. Technology Trends

While seven-segment displays remain a staple for numeric readouts, the broader landscape is evolving. There is a trend towards higher integration, where the driver electronics are embedded within the display module itself, simplifying the host system design. The use of AlInGaP for red/orange/amber is well-established, but for full-color capability, displays may combine different LED technologies (e.g., InGaN for blue/green) or move towards dot-matrix OLED or micro-LED panels that offer greater flexibility in displaying characters and graphics. However, for applications requiring very high brightness, wide temperature range, long lifetime, and simplicity, discrete LED seven-segment displays like the LTC-5623JD continue to be a robust and cost-effective solution. Developments in packaging may lead to even smaller form factors or surface-mount versions for automated assembly.