LTP-15801KD 16-Segment Alphanumeric LED Display Datasheet - 1.5-inch Digit Height - Hyper Red (650nm) - 2.6V Forward Voltage - English Technical Documentation

1. Product Overview

The LTP-15801KD is a single-digit, 16-segment alphanumeric light-emitting diode (LED) display module. Its primary function is to provide clear, high-visibility numeric and limited alphabetic character output for electronic devices and instrumentation. The core technology utilizes AlInGaP (Aluminum Indium Gallium Phosphide) semiconductor material to produce a Hyper Red emission, which is known for its high efficiency and luminous intensity. The device features a black face with white segment markings, enhancing contrast and readability under various lighting conditions. It is categorized based on its luminous intensity, allowing for consistency in brightness across production batches for applications where uniform appearance is critical.

2. Technical Parameters Deep Objective Interpretation

2.1 Photometric and Optical Characteristics

The optical performance is defined at a standard test condition of an ambient temperature (Ta) of 25°C and a forward current (IF) of 20mA per segment. The key parameter, Average Luminous Intensity (Iv), has a typical value of 27.3 millicandelas (mcd). This value represents the perceived brightness of the lit segments. The device emits light at a Peak Emission Wavelength (λp) of 650 nanometers (nm), which falls within the deep red portion of the visible spectrum. The Dominant Wavelength (λd) is specified at 639 nm. The Spectral Line Half-Width (Δλ) is 20 nm, indicating the spectral purity or the narrowness of the emitted light band. A Luminous Intensity Matching Ratio of 2:1 (maximum) is specified, meaning the brightness difference between the brightest and dimmest segment within a single unit should not exceed this ratio, ensuring visual uniformity.

2.2 Electrical Parameters

The electrical characteristics define the operating limits and conditions for reliable use. The Absolute Maximum Ratings set the boundaries: a maximum Power Dissipation of 70 mW per segment, a Peak Forward Current of 90 mA under pulsed conditions (1/10 duty cycle), and a maximum Continuous Forward Current of 25 mA per segment at 25°C, derating linearly at 0.33 mA/°C above that temperature. The maximum Reverse Voltage (VR) per segment is 5V. Under normal operating conditions (IF=20mA), the typical Forward Voltage (VF) per segment is 2.6V, with a maximum of 5.2V. The Reverse Current (IR) is a maximum of 100 µA at VR=5V. These parameters are crucial for designing the current-limiting circuitry and ensuring the LED is not subjected to conditions that could cause premature failure.

2.3 Thermal and Environmental Specifications

The device is rated for an Operating Temperature Range of -35°C to +85°C and an identical Storage Temperature Range. This wide range makes it suitable for use in both consumer and industrial environments. A critical handling specification is the maximum Solder Temperature of 260°C for a maximum duration of 3 seconds, measured at a point 1.6mm (1/16 inch) below the seating plane of the component. Adherence to this reflow soldering profile is essential to prevent thermal damage to the LED chips, internal bonds, and the plastic package.

3. Binning System Explanation

The datasheet indicates that the device is "Categorized for Luminous Intensity." This refers to a production binning process where manufactured units are sorted (binned) based on their measured luminous output at a standard test current. While the specific bin codes are not detailed in this document, such a system ensures that designers can source displays with consistent brightness levels. This is particularly important in multi-digit displays or products where multiple units are used side-by-side, as it prevents noticeable variations in intensity between individual digits or devices.

4. Performance Curve Analysis

The datasheet references "Typical Electrical / Optical Characteristic Curves" which are standard for LED components. Although the specific graphs are not reproduced in the provided text, these curves typically illustrate the relationship between forward current (IF) and forward voltage (VF), the relationship between luminous intensity (Iv) and forward current (IF), and the variation of luminous intensity with ambient temperature. These curves are invaluable for designers. The VF-IF curve helps in selecting the appropriate drive voltage and series resistor. The Iv-IF curve shows how brightness increases with current, but also highlights the point of diminishing returns and increased heat. The Iv-Ta curve demonstrates the negative temperature coefficient of LEDs, where light output decreases as the junction temperature rises, informing thermal management decisions.

5. Mechanical and Package Information

5.1 Dimensions and Outline

The package is a through-hole type (DIP) display. All critical dimensions are provided in millimeters, with a general tolerance of ±0.25 mm unless otherwise specified. The key feature is the 1.5-inch (38 mm) digit height, which defines the physical size of the displayed character. The drawing details the segment layout (A1, A2, B, C, D1, D2, E, F, G1, G2, H, I, J, K, L, M) and the overall footprint of the device on a printed circuit board (PCB).

5.2 Pinout and Polarity Identification

The device has a 17-pin configuration. Pin 1 is identified as the COMMON ANODE. This is a critical polarity identifier; all other pins (2 through 17) are CATHODES for individual segments or the decimal point. The internal circuit diagram confirms a common anode configuration, meaning all LED segment anodes are connected internally to the common pin (Pin 1). To illuminate a segment, the common anode pin must be connected to a positive voltage (through a current-limiting resistor), and the corresponding cathode pin must be pulled to ground (logic low). The pin connection table explicitly maps each cathode pin number to its corresponding segment (e.g., Pin 2 = G1, Pin 3 = E, etc.). A right-hand decimal point is also integrated into the package.

6. Soldering and Assembly Guidelines

The primary assembly instruction concerns the soldering process. As noted in the Absolute Maximum Ratings, the component can withstand a maximum solder (reflow) temperature of 260°C for no more than 3 seconds. This is a standard profile for wave or reflow soldering processes using lead-free solder. It is imperative to control the time and temperature during assembly to prevent the plastic housing from warping, discoloring, or cracking, and to protect the internal wire bonds and semiconductor dies from thermal stress. Manual soldering with an iron should also be performed quickly and with controlled heat to avoid localized overheating.

7. Packaging and Ordering Information

The specific part number is LTP-15801KD. The "LTP" prefix likely denotes the product family (LED display), "15801" may indicate the 1.5-inch size and 16-segment type, and "KD" could be a suffix denoting the color (Hyper Red) and perhaps the common anode configuration. The datasheet does not provide details on bulk packaging (e.g., tubes, trays, or reels) or minimum order quantities. For production, one would need to consult the manufacturer's or distributor's packaging specifications.

8. Application Suggestions

8.1 Typical Application Scenarios

This display is suited for applications requiring a single, highly visible digit or character. Common uses include: panel meters for voltage, current, or temperature readouts; digital clocks or timers; industrial control panels; test and measurement equipment; and consumer appliances like microwave ovens or audio amplifiers where a single parameter is displayed.

8.2 Design Considerations

Drive Circuitry: A common anode display requires a current-sinking driver. Each segment cathode must be connected to a driver capable of sinking the required current (e.g., 20mA) when active. The common anode is typically connected to the positive supply via a current-limiting resistor. Alternatively, a constant current driver IC can be used for better brightness uniformity and stability over temperature.
Multiplexing: While this is a single-digit display, the principle applies if multiple digits are used. The segments of all digits can be connected in parallel, and each digit's common anode is driven sequentially at a high frequency. This reduces the number of required driver pins significantly.
Current Limiting: An external resistor in series with the common anode is mandatory to set the forward current. The resistor value is calculated as R = (Vcc - VF) / IF, where Vcc is the supply voltage, VF is the forward voltage of the LED (use max value for safety), and IF is the desired forward current (e.g., 20mA).
Viewing Angle: The datasheet claims a "Wide Viewing Angle," which is beneficial for applications where the display may be viewed from off-axis positions.

9. Technical Comparison

The key differentiator of the LTP-15801KD is its use of AlInGaP (Aluminum Indium Gallium Phosphide) technology for the Hyper Red emission. Compared to older technologies like standard GaAsP (Gallium Arsenide Phosphide) red LEDs, AlInGaP LEDs offer significantly higher luminous efficiency, meaning they produce more light (higher mcd) for the same amount of electrical current. They also generally have better temperature stability and longer operational lifetime. The 16-segment design, as opposed to a simpler 7-segment display, allows for the representation of a fuller alphanumeric character set (A-Z, 0-9, and some symbols), increasing its versatility over purely numeric displays.

10. Frequently Asked Questions (Based on Technical Parameters)

Q: What is the difference between Peak Wavelength (650nm) and Dominant Wavelength (639nm)?
A: Peak Wavelength is the wavelength at which the emission spectrum has its maximum intensity. Dominant Wavelength is the single wavelength of monochromatic light that would produce the same perceived color as the LED's actual broad-spectrum output. For red LEDs, the dominant wavelength is often slightly shorter than the peak wavelength.

Q: Why is the maximum continuous current 25mA but the peak pulsed current 90mA?
A: Continuous current is limited by the device's ability to dissipate heat. At 25mA, the power dissipation (VF * IF) is within the 70mW limit. Pulsed current (90mA at 1/10 duty cycle) allows for a higher instantaneous brightness (as luminous intensity is roughly proportional to current) because the average power over time is lower, preventing overheating. The LED junction has time to cool between pulses.

Q: How do I connect this display to a microcontroller?
A: You cannot connect the 17 pins directly to a standard MCU due to pin count and current limitations. You must use external driver circuitry. A common approach is to use a dedicated LED driver IC with constant current sinks (like the MAX7219 or similar) or a bank of transistor arrays (like the ULN2003) controlled by the MCU's GPIO pins. The driver handles the current sinking for the cathodes, while the common anode is powered through a resistor.

11. Practical Use Case

Designing a Single-Digit DC Voltmeter: A practical application is building a 0-9.9V voltmeter. The LTP-15801KD can display the tens digit (0-9). It would be driven by a microcontroller (e.g., an Arduino or PIC). The MCU reads an analog voltage via its ADC, scales it, and determines which segments to illuminate to form the correct digit. The 16-segments allow for clear rendering of numbers. The driver circuit, as described above, interfaces the MCU's low-current digital outputs to the LED's higher current requirements. The Hyper Red color provides excellent visibility. Care must be taken in the PCB layout to place current-limiting resistors close to the display and to ensure clean power supply lines to avoid noise affecting the analog reading.

12. Principle of Operation Introduction

An LED is a semiconductor diode. When a forward voltage exceeding its characteristic forward voltage (VF) is applied across the anode and cathode, electrons from the n-type semiconductor material recombine with holes from the p-type material in the active region (the junction). This recombination releases energy in the form of photons (light). The specific wavelength (color) of the emitted light is determined by the energy bandgap of the semiconductor material. AlInGaP has a bandgap that corresponds to red/orange/yellow light. In this 16-segment display, multiple individual AlInGaP LED chips are mounted within the package, each forming one segment of the character. They are electrically connected in a common anode configuration for simplified driving.

13. Technology Trends

While through-hole displays like the LTP-15801KD remain relevant for prototyping, hobbyist projects, and certain industrial applications, the broader trend in display technology is towards surface-mount device (SMD) packages. SMD LEDs offer smaller footprints, lower profile, and are better suited for automated pick-and-place assembly, reducing manufacturing costs. For alphanumeric displays, dot-matrix panels (using many smaller LEDs in a grid) have become more prevalent as they offer greater flexibility in displaying graphics and a wider character set. Furthermore, organic LED (OLED) displays are now common in consumer electronics, offering superior contrast, viewing angles, and thinness, though they differ significantly in technology and application from discrete LED segment displays. The AlInGaP material system itself represents an advancement over older LED materials, offering higher efficiency and reliability.