LTP-22801JF 17-Segment Alphanumeric LED Display Datasheet - 2.24-inch Digit Height - AlInGaP Yellow Orange - 5.2V Forward Voltage - English Technical Documentation

1. Product Overview

The LTP-22801JF is a high-performance, single-digit alphanumeric display module designed for applications requiring clear, bright, and reliable character presentation. Its primary function is to display alphanumeric characters (letters A-Z, numbers 0-9, and some symbols) using a 17-segment configuration, offering greater flexibility than traditional 7-segment displays.

The core advantage of this device lies in its use of Aluminium Indium Gallium Phosphide (AlInGaP) semiconductor material for the LED chips, specifically in a Yellow Orange color. AlInGaP technology is renowned for its high luminous efficiency and excellent performance in the amber to red color spectrum. The display features a black face with white segments, which provides a high contrast ratio for optimal readability even in various ambient lighting conditions. The device is categorized for luminous intensity, ensuring consistent brightness levels across production batches.

The target market includes industrial control panels, test and measurement equipment, medical devices, instrumentation, and any embedded system where a single, highly legible digit is required for status indication, data readout, or user interface feedback.

2. Technical Specifications Deep Dive

2.1 Photometric and Optical Characteristics

The optical performance is central to the display's functionality. At a standard test current of 20mA per segment and an ambient temperature of 25\u00b0C, the device offers a typical average luminous intensity of 41.6 millicandelas (mcd). When driven at a higher current of 40mA, this value increases to a typical 72.8 mcd, demonstrating good linearity in light output with current.

The color characteristics are defined by specific wavelengths. The peak emission wavelength (\u03bbp) is typically 611 nanometers (nm), placing it firmly in the yellow-orange region of the visible spectrum. The dominant wavelength (\u03bbd), which more closely correlates with perceived color, is typically 605 nm. The spectral line half-width (\u0394\u03bb) is 17 nm, indicating a relatively pure, saturated color with minimal spectral spread. Luminous intensity matching between segments is specified with a ratio of 2:1 maximum, ensuring uniform appearance across the character.

2.2 Electrical Parameters

The electrical characteristics define the operating boundaries and conditions for the display. The absolute maximum ratings provide the limits beyond which permanent damage may occur. The maximum continuous forward current per segment is 24 mA, with a linear derating factor of 0.31 mA/\u00b0C above 25\u00b0C. For pulsed operation at a 1/10 duty cycle and 1.0ms pulse width, the peak forward current can reach 60 mA per segment. The maximum power dissipation per segment is 134 mW under continuous operation.

Under typical operating conditions (IF=20mA), the forward voltage (VF) per segment ranges from a minimum of 4.1V to a maximum of 5.2V, with a typical value expected within this range. This relatively higher forward voltage is characteristic of AlInGaP LEDs. The maximum reverse voltage (VR) that can be applied per segment is 10V, with a reverse current (IR) of 100 \u00b5A maximum under that condition.

2.3 Thermal and Environmental Specifications

The device is rated for an operating temperature range of -35\u00b0C to +85\u00b0C, making it suitable for a wide variety of environments, from industrial cold storage to equipment near heat sources. The storage temperature range is identical. A critical parameter for assembly is the solder temperature rating: the device can withstand a maximum soldering temperature of 260\u00b0C for a maximum duration of 3 seconds, measured at a point 1.6mm (1/16 inch) below the seating plane of the package. This information is vital for defining reflow soldering profiles during PCB assembly.

3. Mechanical and Packaging Information

3.1 Physical Dimensions and Outline

The display has a digit height of 2.24 inches (57.0 mm), which classifies it as a large-format display for clear viewing at a distance. The package dimensions are provided in a detailed drawing. All critical dimensions are specified in millimeters, with standard tolerances of \u00b10.25 mm unless otherwise noted. Engineers must refer to this drawing for accurate PCB footprint design, ensuring proper clearance and alignment.

3.2 Pin Configuration and Circuit Diagram

The LTP-22801JF is a common anode device. It features 19 pins in a single-row configuration. The internal circuit diagram reveals that the 17 segments (A1, A2, B, C, D1, D2, E, F, G1, G2, H, I, J, K, L, M) and the decimal point (DP) are individual LEDs. The common anode pins (pin 1 and pin 11) are internally connected, providing two points for connecting the positive supply voltage, which can aid in current distribution and PCB layout. Each segment cathode has its own dedicated pin (pins 2-10, 12-19). This configuration allows for individual multiplexing control of each segment.

4. Application Guidelines and Design Considerations

4.1 Driving the Display

As a common anode display, the anodes (pins 1 & 11) should be connected to the positive supply voltage through a current-limiting scheme. Each cathode pin must be driven individually, typically by a microcontroller port pin or a dedicated driver IC (like a shift register or segment driver). The driver must be capable of sinking the required segment current when activated (cathode pulled low). The forward voltage (4.1V-5.2V) must be considered when selecting the logic voltage levels and driver ICs; 5V systems are commonly used.

Current Limiting: External current-limiting resistors are mandatory for each segment or, more commonly, for each common anode node if multiplexing. The resistor value (R) can be calculated using Ohm's Law: 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). Using the maximum VF ensures brightness consistency even with device variation.

4.2 Multiplexing Considerations

For multi-digit applications or to reduce microcontroller pin count, this single-digit display can be integrated into a multiplexed array. In a multiplexed setup, the common anodes of multiple digits are connected together (digit 1 anode, digit 2 anode, etc.), and the corresponding segment cathodes are also connected together (all 'A' segments, all 'B' segments, etc.). Digits are illuminated one at a time in rapid succession. When multiplexing, the peak pulsed current rating (60mA at 1/10 duty) becomes relevant. The average current must not exceed the continuous rating, so the pulse current can be higher. For example, driving at 40mA with a 1/4 duty cycle gives an average current of 10mA.

4.3 Thermal Management and PCB Layout

While individual segment power dissipation is low, the total power for a fully lit digit (all 17 segments + DP at 20mA and ~4.5V) can approach 1.5W. Adequate PCB copper area and possibly thermal vias under the package may be necessary to dissipate heat, especially in high ambient temperatures or when driven at higher currents. Ensuring a good solder joint on all pins is also crucial for thermal conduction away from the LED chips.

5. Performance Analysis and Curves

The datasheet references typical electrical and optical characteristic curves, which are essential for understanding device behavior under non-standard conditions. While the specific graphs are not detailed in the provided text, standard curves for such devices typically include:

• Relative Luminous Intensity vs. Forward Current (I-V Curve): This graph shows how light output increases with current. It is generally linear at lower currents but may saturate at higher currents due to thermal effects.
• Forward Voltage vs. Forward Current: Shows the exponential relationship, confirming the VF range specified in the table.
• Relative Luminous Intensity vs. Ambient Temperature: For AlInGaP LEDs, luminous intensity typically decreases as junction temperature increases. This curve is critical for applications operating across the full temperature range.
• Spectral Distribution: A plot of intensity vs. wavelength, showing the peak at ~611nm and the half-width.

Designers should use these curves to predict performance in their specific application, accounting for effects of temperature and drive current variations.

6. Comparison and Technology Context

6.1 AlInGaP vs. Other LED Technologies

The use of AlInGaP on a non-transparent GaAs substrate is a key differentiator. Compared to older GaAsP or GaP technologies, AlInGaP offers significantly higher luminous efficiency and better temperature stability in the amber-red range. Compared to phosphor-converted white LEDs used in some displays, AlInGaP provides a pure, saturated color without the complexity and efficiency loss of phosphor conversion, resulting in higher contrast and potentially longer lifetime.

6.2 17-Segment vs. 7-Segment and Dot-Matrix

A 17-segment display (sometimes called a "starburst" display) sits between a 7-segment display and a full dot-matrix display. It can display a much wider range of alphanumeric characters more legibly than a 7-segment display (e.g., distinguishing 'S' from '5', displaying 'M', 'W', 'K' properly) while requiring far fewer control lines and being simpler to drive than a high-resolution dot-matrix panel. The LTP-22801JF is an optimal solution when the application requires a limited set of clear, distinct characters on a single, large digit.

7. Frequently Asked Questions (FAQ)

Q: Can I drive this display directly from a 3.3V microcontroller?
A: No, not directly. The typical forward voltage (4.1V-5.2V) is higher than 3.3V. You would need a supply voltage of at least 5V for the LED side. The control signals from the 3.3V microcontroller to the cathode drivers would need to be level-shifted if the drivers require 5V logic-high inputs, or you must use drivers compatible with 3.3V logic.

Q: Why are there two common anode pins?
A> The two internally connected anode pins (1 and 11) allow for flexibility in PCB routing and help distribute the total anode current, which can be significant when all segments are lit. Connecting both to the supply is recommended.

Q: What is the purpose of the luminous intensity matching ratio?
A> This ratio (2:1 max) guarantees that the dimmest segment in a device will be no less than half as bright as the brightest segment under the same conditions. This ensures visual uniformity across the character, preventing some segments from appearing noticeably dimmer than others.

Q: How do I create characters?
A> You need a character map or font table in your microcontroller code. This is a lookup table that defines, for each alphanumeric character you want to display, which combination of the 17 segments (and DP) need to be turned ON (cathode driven low) when the common anode is high.

8. Practical Application Example

Scenario: A Digital Timer Display. A single LTP-22801JF can be used to show the seconds digit on a large countdown timer. The microcontroller would cycle through displaying numbers 9 down to 0. The design would involve: 1) Providing a stable 5V supply. 2) Placing a single current-limiting resistor on the common anode line (pins 1 & 11). 3) Connecting each of the 18 cathode pins (17 segments + DP) to an individual pin of a microcontroller or, more efficiently, to the outputs of two 8-bit serial-in/parallel-out shift registers to save I/O pins. 4) Programming the microcontroller with the segment patterns for digits 0-9 and potentially a colon or other symbol using the DP. The high brightness and large digit size ensure the time is visible from a distance.