LTC-4627KD-11 LED Display Datasheet - 0.4-inch Digit Height - Hyper Red (650nm) - 2.6V Forward Voltage - English Technical Document

1. Product Overview

The LTC-4627KD-11 is a high-performance, triple-digit, seven-segment LED display module designed for applications requiring clear, bright numeric readouts. With a digit height of 0.4 inches (10.0 mm), it offers excellent visibility. The device utilizes advanced AS-AlInGaP (Aluminum Indium Gallium Phosphide) Hyper Red LED chips, which are epitaxially grown on a GaAs substrate. This technology is known for its high efficiency and bright output. The display features a gray faceplate with white segment markings, providing high contrast for optimal character appearance under various lighting conditions. Its primary design goals are low power consumption, solid-state reliability, and a wide viewing angle, making it suitable for industrial instrumentation, consumer electronics, and test equipment.

1.1 Core Advantages & Target Market

The display boasts several key advantages that differentiate it in the market. Its continuous uniform segments ensure a cohesive and professional-looking numeric display without gaps or irregularities. The high brightness and high contrast ratio guarantee readability even in brightly lit environments. The wide viewing angle is crucial for applications where the display may be viewed from off-axis positions. Furthermore, the device is categorized for luminous intensity, meaning units are binned and sorted based on their light output, allowing for consistent brightness across multiple displays in a single product. The lead-free package ensures compliance with environmental regulations like RoHS. The target markets include panel meters, process control equipment, medical devices, automotive diagnostic tools, and any application requiring a reliable, multiplexed numeric display.

2. Technical Parameter Deep Dive

This section provides a detailed, objective analysis of the device's key technical parameters as defined in the datasheet.

2.1 Photometric & Optical Characteristics

The optical performance is central to this display's function. The primary color is Hyper Red, characterized by a peak emission wavelength (λp) of 650 nanometers and a dominant wavelength (λd) of 639 nanometers, measured at a forward current (IF) of 20mA. The spectral line half-width (Δλ) is 20 nm, indicating a relatively pure red color. The most critical parameter is the average luminous intensity (Iv). At a low current of 1mA, the typical intensity is 200 μcd (microcandelas). At the standard operating current of 10mA, the intensity rises significantly to a typical value of 750 μcd, with a maximum specified up to 9750 μcd, showcasing the high-brightness capability of the AlInGaP technology. The luminous intensity matching ratio between segments is specified at a maximum of 2:1 under similar lighting conditions (IF=1mA), ensuring uniform brightness across all segments of a digit.

2.2 Electrical Parameters

The electrical characteristics define the operating boundaries and power requirements. The forward voltage per segment (VF) is typically 2.6V, with a maximum of 2.6V when driven at 20mA. This relatively low voltage contributes to lower overall power dissipation. The absolute maximum ratings set hard limits: the continuous forward current per segment is 25 mA, and the power dissipation per segment must not exceed 70 mW. For pulsed operation, a peak forward current of 90 mA is allowed under specific conditions (1kHz frequency, 18% duty cycle). The device can withstand a reverse voltage (VR) of up to 5V per segment, with a reverse current (IR) of less than 100 μA at that voltage. The operating and storage temperature range is quite wide, from -35°C to +105°C, indicating robustness for harsh environments.

2.3 Thermal Characteristics & Soldering

Thermal management is implied through derating guidelines. The continuous forward current rating derates linearly from 25°C at a rate of 0.28 mA/°C. This means the safe operating current decreases as the ambient temperature increases. For assembly, the datasheet specifies a soldering temperature profile: the device can be subjected to a temperature of 260°C for 3 seconds, measured 1/16 inch (approximately 1.6 mm) below the seating plane of the package. This is a critical parameter for wave or reflow soldering processes to prevent damage to the LED chips or the plastic package.

3. Binning System Explanation

The datasheet explicitly states that the device is "Categorized for Luminous Intensity." This refers to a binning or sorting process performed during manufacturing. Due to inherent minor variations in the semiconductor epitaxial growth and chip fabrication, individual LEDs can have slightly different optical outputs even when driven identically. To ensure consistency in end products, manufacturers test and sort LEDs into different "bins" based on specific parameters. For the LTC-4627KD-11, the primary binning criterion is luminous intensity (Iv). Units are grouped so that displays within the same order or production batch have closely matched brightness levels, maintaining a uniform appearance. The 2:1 maximum intensity matching ratio specification is a direct result of this binning process. While not detailed in this specific datasheet, other common binning parameters for LEDs can include forward voltage (VF) and dominant wavelength (λd) to ensure color and electrical consistency.

4. Performance Curve Analysis

While the provided datasheet excerpt references "Typical Electrical / Optical Characteristic Curves" on the final page, the specific graphs are not included in the text. Based on standard LED behavior and the parameters given, we can infer the likely trends these curves would show. A typical Forward Current vs. Forward Voltage (I-V) curve would show an exponential relationship, with the voltage rising to around 2.1-2.6V in the 10-20mA operating region. A Luminous Intensity vs. Forward Current (L-I) curve would show a near-linear increase in light output with current in the normal operating range, beginning to saturate at very high currents. A spectrum distribution curve would show a single peak centered around 650 nm with the specified 20 nm half-width. Temperature characteristics would show a decrease in luminous intensity and a slight decrease in forward voltage as the junction temperature increases.

5. Mechanical & Packaging Information

5.1 Physical Dimensions & Outline

The device comes in a standard LED display package. The key dimension is the digit height of 10.0 mm (0.4 inches). The package dimensions drawing (referenced but not detailed in the text) would typically show the overall length, width, and height of the module, the spacing between digits, the segment size, and the lead (pin) spacing and length. Tolerances for all linear dimensions are specified as ±0.25 mm (0.01 inches) unless otherwise noted, which is standard for this type of component.

5.2 Pinout & Connection Diagram

The pin connection is clearly defined for this 16-pin device. It is a multiplexed, common-cathode configuration. The internal circuit diagram shows that each of the four digits (Digit 1, 2, 3, 4) has its own common cathode pin (pins 1, 2, 6, 8 respectively). The segments (A, B, C, D, E, F, G, DP) and colon segments (L1, L2, L3) are anode-connected. Specifically, segment anodes are grouped: A & L1 share a cathode (pin 14), B & L2 share a cathode (pin 16), C & L3 share a cathode (pin 13), while D, E, F, G, and DP have individual cathode pins (3, 5, 11, 15, 7). This arrangement is optimized for multiplexing, where digits are illuminated one at a time in rapid succession.

6. Soldering & Assembly Guidelines

The primary assembly instruction provided is the soldering temperature limit: 260°C for 3 seconds at a point 1.6 mm below the package body. This is a critical guideline for preventing thermal damage. For reflow soldering, a profile with a peak temperature not exceeding 260°C and a time above liquidus (e.g., 217°C) carefully controlled should be used. Manual soldering with an iron should be performed quickly and with appropriate heat sinking if possible. Prolonged exposure to high temperature can yellow the plastic lens, degrade the epoxy, or damage the wire bonds inside the package. The storage temperature range (-35°C to +105°C) should also be observed before and after assembly. The device should be kept in its original moisture-barrier bag until use if it is sensitive to moisture.

7. Packaging & Ordering Information

The part number is LTC-4627KD-11. The "LTC" prefix likely identifies it as a Lite-On display product. "4627" is the series or base model number. "KD" may indicate specific characteristics like color (Hyper Red) and package type. "-11" is likely a revision or variant code. The device is lead-free, complying with RoHS directives. Standard packaging for such displays is often in anti-static tubes or trays to protect the pins and lens during handling and shipping. The exact quantity per tube/tray and the master carton size are not specified in this excerpt but would be available in separate packaging specifications.

8. Application Suggestions

8.1 Typical Application Circuits

The LTC-4627KD-11 is designed for multiplexed operation. A typical driver circuit involves a microcontroller or a dedicated display driver IC (like the MAX7219 or TM1637). The microcontroller would have several output pins connected to the segment cathodes (A-G, DP) and several other pins connected to the digit common cathode pins (Digit 1-4). The software would implement a multiplexing routine: it sets the pattern for Digit 1 on the segment lines, enables (sinks current to) the Digit 1 common cathode for a short period (e.g., 2-5 ms), then disables it, sets the pattern for Digit 2, enables the Digit 2 cathode, and so on, cycling through all four digits rapidly. The human eye perceives this as a continuously lit 3-digit display (plus colon). Current-limiting resistors are mandatory in series with each segment cathode line to set the desired forward current (e.g., 10mA).

8.2 Design Considerations

Current Limiting: Always use external current-limiting resistors. The value can be calculated using R = (Vcc - Vf) / If, where Vcc is the supply voltage (e.g., 5V), Vf is the forward voltage (~2.6V), and If is the desired forward current (e.g., 0.01A). This gives R = (5 - 2.6)/0.01 = 240 Ohms. A standard 220 or 270 Ohm resistor would be suitable.
Multiplexing Frequency: The refresh rate should be high enough to avoid visible flicker, typically above 60 Hz per digit. With 4 digits, the complete cycle should be >240 Hz. A digit scan rate of 1-2 kHz is common.
Driver Current Capability: Ensure the microcontroller or driver IC can sink the total peak current for one digit. When Digit 1 is on, all 7 segments plus the decimal point could be lit, requiring the common cathode pin to sink 8 * 10mA = 80mA. This often exceeds a microcontroller pin's rating, necessitating the use of external transistors (e.g., PNP or N-channel MOSFETs) to switch the common cathodes.
Viewing Angle: Position the display considering its wide viewing angle to maximize readability for the end-user.

9. Technical Comparison & Differentiation

Compared to older technologies like standard GaP red LEDs or even early AlGaAs LEDs, the AlInGaP technology in the LTC-4627KD-11 offers significantly higher luminous efficiency. This means it produces more light (higher μcd/mA) for the same electrical input, leading to lower power consumption for a given brightness or higher brightness at standard currents. The gray face/white segment design provides better contrast than all-red or all-green displays, especially under ambient light. The categorization (binning) for intensity is a key differentiator from unbinned, lower-cost displays, ensuring professional-grade consistency. Its -35°C to +105°C operating range is wider than many consumer-grade displays, making it suitable for industrial and automotive applications where temperature extremes are encountered.

10. Frequently Asked Questions (Based on Technical Parameters)

Q: What is the purpose of the "No Connection" and "No Pin" designations on the pinout?
A: "No Connection" (NC) pins are physically present but are not electrically connected to any internal component. They provide mechanical stability in the socket or PCB. "No Pin" means the pin position is physically absent from the package; the hole in the PCB should be plated but not connected to any trace.

Q: Can I drive this display with a constant current (non-multiplexed) circuit?
A: Technically yes, but it is highly inefficient and not recommended. You would need 4 (digits) * 8 (segments max) = 32 individual driver channels, vastly increasing circuit complexity and cost. Multiplexing is the intended and optimal method.

Q: The max luminous intensity is 9750 μcd at 10mA. Does this mean my display will be that bright?
A: No. 9750 μcd is the maximum rating from the datasheet. The typical value is 750 μcd. Due to the binning process, you will receive displays that fall within a specific intensity range, but they are unlikely to be at the absolute maximum. Design for the typical or minimum value to ensure your product works with any unit within spec.

Q: What does "Hyper Red" mean compared to standard red?
A: Hyper Red typically refers to AlInGaP LEDs with a dominant wavelength around 630-660 nm. They appear as a deeper, more saturated red compared to the orange-red of standard GaAsP LEDs (~620 nm) and are significantly brighter and more efficient.

11. Practical Design & Usage Case

Case: Designing a 3-Digit Voltmeter Readout. A designer is creating a benchtop power supply unit that requires a 3-digit voltage display (0.0V to 30.0V). The LTC-4627KD-11 is selected for its brightness, readability, and industrial temperature rating. The design uses a microcontroller with an ADC to measure the output voltage. The microcontroller's firmware handles the conversion to BCD (Binary-Coded Decimal) format for the display. Since the microcontroller's I/O pins cannot sink 80mA, small SMD N-channel MOSFETs are used to switch the common cathode pins for each digit. The segment lines are connected directly to the microcontroller via 220 Ohm current-limiting resistors. The multiplexing routine runs at 500 Hz per digit (2 ms on-time), resulting in a flicker-free display. The gray face provides excellent contrast against the black bezel of the instrument panel. The wide viewing angle allows the user to read the voltage accurately from various positions around the workbench.

12. Technical Principle Introduction

The core technology is the AS-AlInGaP LED chip. AlInGaP is a III-V semiconductor compound. By precisely controlling the ratios of Aluminum, Indium, Gallium, and Phosphorus during the epitaxial growth process on a Gallium Arsenide (GaAs) substrate, engineers can tune the bandgap of the material. The bandgap energy determines the wavelength (color) of light emitted when electrons recombine with holes across the junction. AlInGaP is particularly efficient at producing red, orange, and yellow light. The "Hyper Red" designation indicates a specific composition yielding deep red light around 650 nm. The chip is then wire-bonded and encapsulated in an epoxy lens within the plastic display package. The seven-segment format is created by placing multiple tiny LED chips (or a single chip with multiple junctions) in the pattern of a digit, with their anodes or cathodes connected appropriately to form the segments.

13. Technology Trends & Development

While discrete seven-segment LED displays remain vital for many applications, the overall trend in display technology is towards integration and higher density. This includes the development of dot-matrix LED displays and OLEDs that can show alphanumeric characters and graphics. However, for dedicated numeric readouts, seven-segment displays offer unbeatable cost-effectiveness, simplicity, and extreme readability. The evolution within this segment focuses on improving efficiency (lumens per watt), allowing for lower power consumption and reduced heat generation. There is also a trend towards miniaturization while maintaining or increasing brightness, and towards offering a wider variety of colors and package styles (surface-mount vs. through-hole). The move to lead-free, RoHS-compliant packaging, as seen with the LTC-4627KD-11, is now a standard requirement driven by global environmental regulations. Future developments may include integrated driver circuitry within the display package to further simplify system design.