LTC-4627JD LED Display Datasheet - 0.4-inch Digit Height - Hyper Red Color - 2.6V Forward Voltage - 70mW Power Dissipation - English Technical Document

1. Product Overview

The LTC-4627JD is a quadruple-digit, seven-segment LED display designed for applications requiring clear numeric readouts. Each digit features a height of 0.4 inches (10.0 mm), providing good visibility. The device utilizes AlInGaP (Aluminum Indium Gallium Phosphide) semiconductor technology to produce a Hyper Red emission. The display has a gray face with white segment markings, enhancing contrast and readability. It is constructed as a multiplex common anode type, which is a standard configuration for multi-digit displays to minimize the number of required driver pins.

1.1 Key Features

• 0.4 inch (10.0 mm) digit height.
• Continuous uniform segments for consistent character appearance.
• Low power requirement, suitable for battery-powered devices.
• Excellent character appearance with high brightness and high contrast.
• Wide viewing angle for visibility from various positions.
• Solid-state reliability with no moving parts.
• Luminous intensity is categorized (binned) for consistent performance across units.
• Lead-free package compliant with RoHS (Restriction of Hazardous Substances) directives.

1.2 Device Identification

The part number LTC-4627JD specifically denotes a Hyper Red, multiplex common anode display with a right-hand decimal point configuration.

2. Technical Parameters Deep Dive

2.1 Absolute Maximum Ratings

These ratings define the limits beyond which permanent damage to the device may occur. Operation should always be maintained within these limits.

• Power Dissipation per Segment: 70 mW maximum.
• Peak Forward Current per Segment: 90 mA maximum, under pulsed conditions (1/10 duty cycle, 0.1ms pulse width).
• Continuous Forward Current per Segment: 25 mA maximum at 25°C. This rating derates linearly at 0.33 mA/°C as ambient temperature increases above 25°C.
• Operating Temperature Range: -35°C to +85°C.
• Storage Temperature Range: -35°C to +85°C.
• Solder Temperature: Maximum 260°C for a maximum of 3 seconds, measured 1.6mm (1/16 inch) below the seating plane of the component.

2.2 Electrical & Optical Characteristics

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

• Average Luminous Intensity (I_V): 200 µcd (min), 650 µcd (typ) at a forward current (I_F) of 1 mA. Intensity is measured using a filter that approximates the human eye's photopic response (CIE curve).
• Peak Emission Wavelength (λ_p): 650 nm (typ) at I_F=20mA.
• Spectral Line Half-Width (Δλ): 20 nm (typ) at I_F=20mA, indicating the spectral purity of the red light.
• Dominant Wavelength (λ_d): 639 nm (typ) at I_F=20mA, defining the perceived color.
• Forward Voltage per Segment (V_F): 2.1V (min), 2.6V (typ) at I_F=20mA. Designers must account for this range to ensure proper current drive.
• Reverse Current per Segment (I_R): 100 µA (max) at a reverse voltage (V_R) of 5V. Note: The device is not intended for continuous operation under reverse bias.
• Luminous Intensity Matching Ratio (I_V-m): 2:1 (max) at I_F=1mA. This specifies the maximum allowable variation in brightness between segments within a display.

3. Binning System Explanation

The datasheet indicates that the luminous intensity is categorized. This means displays are sorted (binned) based on their measured light output at a standard test current. Using displays from the same intensity bin within a single application is strongly recommended to avoid noticeable brightness differences (hue unevenness) between adjacent digits or units. While not explicitly detailed for wavelength or forward voltage in this document, such binning is common practice in LED manufacturing to ensure color and electrical consistency.

4. Performance Curve Analysis

The datasheet references typical electrical/optical characteristic curves. These graphical representations are crucial for design:

• I-V (Current-Voltage) Curve: Shows the relationship between forward voltage and forward current, essential for designing the current-limiting circuitry.
• Luminous Intensity vs. Forward Current: Illustrates how light output increases with drive current, helping to select an operating point for desired brightness and efficiency.
• Luminous Intensity vs. Ambient Temperature: Demonstrates how light output decreases as temperature rises, which is critical for thermal management in high-temperature environments.
• Spectral Distribution: A plot of relative intensity versus wavelength, confirming the dominant and peak wavelengths and the spectral width.

5. Mechanical & Package Information

5.1 Package Dimensions

The display comes in a standard dual in-line package (DIP). All dimensions are provided in millimeters with a general tolerance of ±0.25 mm unless otherwise specified. The detailed mechanical drawing shows the overall length, width, height, pin spacing, and digit spacing.

5.2 Pin Connection & Polarity

The device has a 16-pin configuration. The internal circuit diagram reveals it is a multiplexed common anode display. This means the anodes of the LEDs for each digit are connected together internally, while the cathodes for each segment type (A-G, DP) are connected across digits. The pinout is as follows:

• Pin 1: Common Anode for Digit 1
• Pin 2: Common Anode for Digit 2
• Pin 3: Cathode for Segment D
• Pin 4: Common Anode for Segments L1, L2, L3 (likely colon or other markers)
• Pin 5: Cathode for Segment E
• Pin 6: Common Anode for Digit 3
• Pin 7: Cathode for Decimal Point (DP)
• Pin 8: Common Anode for Digit 4
• Pin 9: No Connection
• Pin 10: No Pin
• Pin 11: Cathode for Segment F
• Pin 12: No Pin
• Pin 13: Cathode for Segments C and L3
• Pin 14: Cathode for Segments A and L1
• Pin 15: Cathode for Segment G
• Pin 16: Cathode for Segments B and L2

6. Soldering & Assembly Guidelines

6.1 Soldering Parameters

The maximum soldering temperature is 260°C for a maximum duration of 3 seconds. This is typically for wave soldering or hand soldering, measured at a point 1.6mm below the body of the display. For reflow soldering, a standard lead-free profile with a peak temperature not exceeding 260°C should be used.

6.2 Storage Conditions

Proper storage is essential to prevent pin oxidation.

• For DIP Displays (LTC-4627JD): Store in original packaging at 5°C to 30°C with humidity below 60% RH. If the moisture barrier bag is opened for more than 6 months, it is recommended to bake the components at 60°C for 48 hours before use, with assembly completed within one week after baking.
• General Caution: Avoid rapid temperature changes in humid environments to prevent condensation on the display. Do not apply abnormal mechanical force during assembly.

7. Application Recommendations

7.1 Typical Application Scenarios

This display is suitable for ordinary electronic equipment requiring numeric readouts, such as:

• Test and measurement instruments (multimeters, counters).
• Industrial control panels and timers.
• Consumer appliances (microwaves, scales, audio equipment).
• Point-of-sale terminals and basic information displays.

Important Note: The datasheet explicitly states it is for ordinary equipment. Applications requiring exceptional reliability (aviation, medical, transportation safety) require prior consultation.

7.2 Design Considerations

• Drive Circuit: Constant current driving is recommended for consistent brightness and longevity. The circuit must be designed to accommodate the full range of forward voltage (2.1V to 2.6V).
• Current Limiting: The operating current must be chosen based on the maximum ambient temperature, considering the current derating of 0.33 mA/°C above 25°C.
• Protection: The driving circuit should include protection against reverse voltages and voltage transients during power cycling to prevent damage.
• Multiplexing: As a common anode multiplexed display, a microcontroller or dedicated driver IC must sequentially activate each digit's common anode while supplying the correct segment cathode pattern for that digit. The refresh rate must be high enough to avoid flicker (typically >60 Hz).
• Mechanical Integration: If a front panel or film is used, ensure it does not apply pressure that could shift printed overlays or damage the display body.

8. Technical Comparison & Differentiation

The LTC-4627JD's key differentiators are its use of AlInGaP technology for Hyper Red emission and its specific mechanical/electrical format. Compared to older GaAsP or GaP red LEDs, AlInGaP offers higher efficiency, better brightness, and more stable wavelength over temperature. The 0.4-inch digit height fills a niche between smaller (0.3-inch) and larger (0.5-inch or 0.56-inch) displays. The multiplexed common anode design is industry-standard for multi-digit displays, balancing pin count and driver complexity.

9. Frequently Asked Questions (FAQ)

9.1 What is the purpose of the "Luminous Intensity Matching Ratio"?

This ratio (2:1 max) ensures that within a single display unit, no segment is more than twice as bright as another when driven under the same conditions. This guarantees uniform appearance of the formed characters.

9.2 Why is constant current drive recommended over constant voltage?

LED brightness is primarily a function of current. The forward voltage (V_F) has a tolerance range (2.1V-2.6V). A constant voltage source with a simple resistor would result in different currents (and thus different brightness levels) for displays with different V_F. A constant current source ensures identical current, and therefore consistent brightness, regardless of V_F variations.

9.3 Can I drive this display with a 5V microcontroller directly?

No. The maximum continuous forward current per segment is 25mA, and a microcontroller GPIO pin connected directly would attempt to source/sink much higher current if the segment's V_F is ~2.6V, potentially damaging the microcontroller. You must use external transistors (for the common anodes) and current-limiting resistors or a dedicated LED driver IC.

9.4 What does "Right Hand Decimal" mean in the part description?

It indicates the position of the decimal point LED. In this case, the decimal point is located to the right of the digit. Some displays may offer left-hand or center decimal points.

10. Practical Design Case Study

Scenario: Designing a 4-digit voltmeter display using the LTC-4627JD, powered by a 5V system with a microcontroller.

1. Driver Selection: Choose a dedicated multiplexing LED driver IC (e.g., MAX7219, TM1637) or implement multiplexing in software using the microcontroller's GPIOs.
2. Current Setting: For good brightness and longevity, select a segment current of 10-15 mA. Check that this is within the derated limit for your maximum expected ambient temperature.
3. Circuit Design: If using a driver IC, follow its datasheet. If using discrete transistors, use PNP or P-channel MOSFETs to switch the common anode pins (connected to 5V) and NPN or N-channel MOSFETs/resistors on the cathode side, controlled by the microcontroller. Calculate current-limiting resistors: R = (V_CC - V_F - V_CE(sat)) / I_F. Use the maximum V_F (2.6V) for a worst-case (brightest) calculation.
4. Software: Implement a timer interrupt to refresh the display. The routine should turn off all digits, set the segment pattern for the next digit, turn on that digit's common anode, and then wait for the multiplexing time slice.
5. Thermal & Mechanical: Ensure adequate ventilation. Design the front panel with a clear aperture slightly larger than the display's viewing area to avoid pressure on the face.

11. Operating Principle

The LTC-4627JD is based on AlInGaP semiconductor technology. When a forward voltage exceeding the diode's junction potential is applied, electrons and holes recombine in the active region, releasing energy in the form of photons. The specific composition of the AlInGaP layers determines the bandgap energy, which corresponds to the red wavelength of light emitted (~639-650 nm). Each of the seven segments (A through G) and the decimal point (DP) is a separate LED or a group of LED chips. In a multiplexed common anode configuration, one side (anode) of all LEDs in a single digit is connected, allowing that entire digit to be enabled by applying a positive voltage to that common node. The other sides (cathodes) of each segment type are connected across all digits, allowing control of which segments light up in the enabled digit.

12. Technology Trends

While traditional seven-segment LED displays like the LTC-4627JD remain vital for specific applications due to their simplicity, high brightness, and wide viewing angle, the broader display market is evolving. There is a trend towards higher integration, such as displays with built-in controllers (I2C or SPI interface) that simplify the host microcontroller's task. Dot matrix and graphic OLED/LCD displays are becoming more cost-competitive for applications requiring alphanumeric or graphical output. However, for pure numeric displays in harsh environments (wide temperature, high brightness required), LED seven-segment technology, particularly with efficient materials like AlInGaP, continues to offer a robust and reliable solution. Future developments may focus on even higher efficiency, lower power consumption, and possibly integrated smart features while maintaining the classic form factor for backward compatibility.