LTC-561JG LED Display Datasheet - 0.56-inch Digit Height - AlInGaP Green - 2.6V Forward Voltage - English Technical Document

1. Product Overview

The LTC-561JG is a high-performance, low-power, triple-digit seven-segment display module. Its primary application is in devices requiring clear, bright numeric readouts such as test equipment, industrial control panels, instrumentation, and consumer electronics. The core advantage of this device lies in its use of advanced AlInGaP (Aluminum Indium Gallium Phosphide) semiconductor technology for the LED chips, which provides superior luminous efficiency and color purity compared to traditional materials.

The display features a digit height of 0.56 inches (14.2 mm), offering excellent readability. It is designed as a multiplex common anode configuration, which simplifies driving circuitry when interfacing with microcontrollers or display drivers. A key design goal was achieving excellent performance at very low drive currents, making it suitable for battery-powered or energy-sensitive applications. The segments are continuous and uniform, and the device is categorized for luminous intensity to ensure consistency in production batches.

2. Technical Specifications Deep Dive

2.1 Photometric and Optical Characteristics

The optical performance is central to this display's functionality. At a standard test current of 1mA per segment, the average luminous intensity (Iv) has a typical value of 577 µcd, with a minimum specified value of 200 µcd. This ensures the display is sufficiently bright for most indoor lighting conditions. The light emission is characterized by a peak wavelength (λp) of 571 nm and a dominant wavelength (λd) of 572 nm, placing it firmly in the pure green region of the visible spectrum. The spectral line half-width (Δλ) is 15 nm, indicating a relatively narrow and well-defined color output.

2.2 Electrical Characteristics

Electrical parameters define the operating boundaries and power requirements. The absolute maximum ratings provide the limits for safe operation: a maximum power dissipation of 70 mW per segment, a peak forward current of 60 mA (under pulsed conditions with a 1/10 duty cycle), and a continuous forward current of 25 mA at 25°C, derating linearly by 0.33 mA/°C above that temperature. The maximum reverse voltage per segment is 5V.

Under typical operating conditions (Ta=25°C), the forward voltage (Vf) per segment is 2.6V at a drive current of 20mA. A key feature highlighted in the datasheet is the device's excellent low-current characteristics; it is tested and selected to perform well with a driving current as low as 1mA per segment, which significantly reduces overall system power consumption. The reverse current (Ir) is specified at a maximum of 100 µA at the full 5V reverse bias.

2.3 Thermal and Environmental Specifications

The device is rated for an operating temperature range of -35°C to +105°C and an identical storage temperature range. This wide range makes it suitable for use in harsh environments, from industrial freezers to equipment near heat sources. The datasheet also provides specific soldering guidance: the component can be subjected to wave or reflow soldering with the temperature at 1/16 inch (approximately 1.6 mm) below the seating plane not exceeding 260°C for 3 seconds. This information is critical for PCB assembly to prevent thermal damage to the LED chips or the plastic package.

3. Binning and Matching System

The LTC-561JG is categorized for luminous intensity. This means units are tested and sorted into bins based on their measured light output at a standard test condition (typically 1mA). This binning process ensures that designers receive displays with consistent brightness levels, which is vital for multi-digit displays or products where multiple units are used side-by-side. The datasheet specifies a luminous intensity matching ratio (for similar lit area) of 2:1 maximum. This ratio defines the allowable variation in brightness between the segments of a single device, ensuring visual uniformity across the displayed number.

4. Performance Curve Analysis

While the specific graphs are not detailed in the provided text, typical curves for such a device would include:

• Forward Current vs. Forward Voltage (I-V Curve): This curve shows the nonlinear relationship between the current through the LED and the voltage across it. It is essential for designing the current-limiting circuitry.
• Luminous Intensity vs. Forward Current: This graph shows how the brightness increases with drive current. It is typically sub-linear, meaning efficiency decreases at very high currents.
• Luminous Intensity vs. Ambient Temperature: This curve demonstrates the thermal derating of light output. As temperature increases, luminous efficiency generally decreases.
• Spectral Distribution: A plot of relative intensity versus wavelength, showing the narrow peak around 571-572 nm.

These curves allow engineers to optimize the drive conditions for a specific application, balancing brightness, power consumption, and device longevity.

5. Mechanical and Package Information

5.1 Physical Dimensions

The package is a standard through-hole type. All critical dimensions are provided in millimeters. Tolerances for most dimensions are ±0.25 mm, ensuring compatibility with standard PCB layouts and sockets. A specific note mentions a pin tip shift tolerance of +0.4 mm, which is important for automated insertion equipment.

5.2 Pinout and Internal Circuit

The device has a 12-pin configuration. The internal circuit diagram shows it is a multiplexed common anode display. The three digits share their segment cathodes, and each digit has its own common anode pin (pins 12, 9, and 8 for Digit 1, 2, and 3 respectively). This allows the microcontroller to illuminate one digit at a time by turning on its anode and sinking current through the appropriate segment cathode pins. The pin connections are: 1:E, 2:D, 3:DP (Decimal Point), 4:C, 5:G, 6:NC (No Connection), 7:B, 8:Anode Digit 3, 9:Anode Digit 2, 10:F, 11:A, 12:Anode Digit 1.

6. Soldering and Assembly Guidelines

As mentioned in the thermal specifications, the maximum allowable soldering temperature is 260°C for 3 seconds, measured 1.6mm below the seating plane. It is crucial to adhere to this to prevent the plastic package from warping or the internal wire bonds from failing. For reflow soldering, a profile with a peak temperature below 260°C and limited time above liquidus is recommended. For manual soldering, a temperature-controlled iron should be used with minimal contact time. The device should be stored in its original moisture-barrier bag until use to prevent moisture absorption, which can cause \"popcorning\" during reflow.

7. Application Suggestions

7.1 Typical Application Circuits

The multiplexed common anode design requires a driver circuit. This typically involves using a microcontroller with sufficient I/O pins or a dedicated LED display driver IC (like the MAX7219 or TM1637). The driver will sequentially enable each digit's anode (via a transistor switch) while outputting the pattern for the segments that should be lit on that digit. A current-limiting resistor is required in series with each segment cathode line (or built into the driver IC). The value of this resistor is calculated based on the desired segment current and the forward voltage of the LED. For example, with a 5V supply and a desired current of 5mA: R = (Vcc - Vf) / I = (5V - 2.6V) / 0.005A = 480Ω (a 470Ω standard resistor would be used).

7.2 Design Considerations

• Refresh Rate: When multiplexing, the refresh rate must be high enough (typically >60 Hz) to avoid visible flicker.
• Current Limiting: Always use current-limiting resistors. Driving the LEDs directly from a microcontroller pin can damage both the LED and the microcontroller.
• Power Sequencing: Avoid applying reverse voltage or exceeding the absolute maximum ratings.
• Viewing Angle: The wide viewing angle is beneficial, but the mounting position should still be considered relative to the user's typical line of sight.

8. Technical Comparison and Advantages

The primary differentiator of the LTC-561JG is its use of AlInGaP technology for green emission. Compared to older technologies like GaP (Gallium Phosphide), AlInGaP offers significantly higher luminous efficiency, resulting in brighter displays for the same current, or equivalent brightness at lower power. The \"low power requirement\" and ability to operate down to 1mA per segment are direct results of this material advantage. Furthermore, the \"gray face and white segments\" construction enhances contrast ratio, making the lit green segments stand out more clearly against the background, especially in high-ambient-light conditions.

9. Frequently Asked Questions (Based on Technical Parameters)

Q: What is the minimum current needed to see a visible display?
A: The device is characterized down to 1mA per segment, which will produce a visible output (minimum 200 µcd). For very low-power applications, currents in the 1-2mA range are usable.

Q: Can I drive this display with a 3.3V microcontroller?
A: Yes. The typical forward voltage is 2.6V. With a 3.3V supply, there is 0.7V across the current-limiting resistor, which is sufficient for stable current regulation at low to moderate currents (e.g., 5-10mA).

Q: Why is there a \"No Connection\" pin (Pin 6)?
A> This is common in display packages to maintain a standard pin count and footprint across different product variants (e.g., with or without decimal points, different colors). It provides mechanical stability but should not be connected electrically.

Q: How do I achieve uniform brightness across all three digits?
A> In multiplexed operation, ensure the on-time (duty cycle) is equal for each digit. Also, use the luminous intensity binning information; specifying a tight bin from your supplier helps.

10. Design and Usage Case Study

Scenario: Portable Multimeter Display
A designer is creating a handheld digital multimeter. Key requirements are: battery operation (9V), clear outdoor/indoor readability, and low power consumption for extended battery life. The LTC-561JG is an ideal candidate. The designer chooses to drive each segment at 2mA. Using a multiplexing driver IC powered from the 9V battery (stepped down to 5V for logic), the average current draw for a fully lit \"888\" display can be calculated. With 3 digits * 7 segments = 21 segments lit, but due to multiplexing, only one digit is on at a time. The peak current per digit is 7 segments * 2mA = 14mA. With a 1/3 duty cycle, the average current is ~4.7mA. Adding quiescent current for the driver, the total is well under 10mA, allowing for hundreds of hours of operation on a standard 9V battery. The high brightness and contrast ensure readability in various lighting conditions.

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 turn-on voltage (approximately 2.05V for this AlInGaP device) is applied, electrons from the n-type region and holes from the p-type region recombine in the active region. In AlInGaP, this recombination releases energy primarily in the form of photons in the green wavelength range (around 572 nm). Each of the seven segments (A through G) and the decimal point (DP) contains one or more of these LED chips. In the common anode configuration, all the anodes of the LEDs for a particular digit are connected together internally. To light a segment, its cathode is connected to a lower voltage (ground through a resistor) while its digit's common anode is connected to a positive supply voltage.

12. Technology Trends

While seven-segment displays remain ubiquitous for numeric readouts, the underlying LED technology continues to evolve. AlInGaP represents a mature and highly efficient material system for red, orange, amber, and green LEDs. Current trends in display technology include a shift towards all-silicon-based micro-LEDs and further miniaturization. However, for through-hole, medium-sized digit displays, AlInGaP offers an excellent balance of performance, reliability, and cost. The trend towards lower power consumption in all electronic devices aligns perfectly with this display's capability to operate at very low currents. Furthermore, the RoHS compliance (lead-free package) mentioned in the datasheet reflects the industry-wide move towards environmentally friendly manufacturing processes.