Description
Product Core Architecture of Wide Temperature Round LCD
Product Introduction
The TFT-H034A04ZJIGCKN40 is a high-performance, active-matrix Round LCD with a nominal display size of 3.4 inches. This module features a fully symmetrical resolution of 800 (RGB) × 800, providing an ultra-high pixel density that delivers a delicate, grain-free visual experience for close-proximity viewing. Its active area is a perfect circle, with a diameter of 87.60mm × 87.60mm.
The screen offers full viewing angles and is equipped with a Parallel 24-bit RGB interface (for the TFT) and an IIC interface (for the CTP). The capacitive touchscreen driver IC is the GT911. The product supports two configurations: without a touch panel or with a capacitive touch panel.
In terms of physical structure, the base version has a thickness of just 2.20 mm (outline dimensions: 94.90(H) × 96.95(V) × 2.20(D) mm), making it easy to embed into various thin or compact enclosures. The module operates stably over a wide temperature range of -30°C to +80°C and can withstand extreme storage conditions from -40°C to +90°C. This meets the rigorous stability requirements for industrial and demanding commercial environments, effectively avoiding catastrophic failures such as no display, line defects, or display abnormalities.
Special Version Description: With Capacitive Touch Panel and Glass Cover
For products requiring high-frequency HMI, water and dust resistance, or operation in environments prone to physical impact, the advanced derivative version with a capacitive touch panel and integrated glass cover is strongly recommended. Due to significant changes in the hardware stack-up, special attention must be paid to the following expanded dimensions and performance specifications when integrating:
- Substantially Increased External Physical Dimensions: The total outer diameter of the outer tempered protective glass cover expands to 130.00 mm. This makes the outer glass significantly larger than the internal 94.90 mm TFT display substrate, greatly facilitating seamless, flat, and flush opening mounting for the product enclosure.
- Increased Total Module Thickness: With the addition of optically clear adhesive (OCA), the capacitive sensor array, and the protective glass, the core stack-up thickness of the module increases from 2.20 mm to 3.95 mm (tolerance ±0.3 mm). The product’s enclosure design must reserve this additional thickness.
- Multi-Touch and Scratch Resistance: This touch variant is centrally controlled by the integrated GT911 capacitive touch driver IC, perfectly supporting advanced gesture interaction with up to 5-point simultaneous touch. The cover glass surface is hardened, achieving a pencil hardness standard of 6H, providing excellent scratch resistance, fingerprint resistance, and wear resistance.
Pin Configuration and Hardware Interface of Round LCD
TFT Main Display Interface Pin Definition
The display connects to the host controller (e.g., MCU/Linux motherboard) via a 40-pin flexible printed circuit interface. The detailed functions and electrical assignments for each pin are provided in the accompanying diagram.
Capacitive Touch Panel Auxiliary Interface Pin Definition
For versions with the optional touch function, the module features an additional, independent 6-pin touch control FPC.
Backlight Drive Specifications and Optical Performance of Round LCD
This Round LCD module integrates a light-emitting architecture composed of multiple high-brightness LEDs connected in series. The backlight must be driven by a constant current source; using a traditional constant voltage source is strictly prohibited.
- Operating Current and Voltage: The standard drive current for the backlight is 80mA. Under this constant current, the typical forward voltage drop (Vf) of the backlight string is 18.0V (tolerance ±1.5V).
- Display Luminance Output:Base Version (No TP)， Delivers a very high typical brightness of up to 1100 cd/m², offering excellent visibility under strong ambient light.With CTP Version， Due to physical light absorption and reflection from the touch layer and glass cover, the typical surface brightness is adjusted to 1000 cd/m², still significantly outperforming conventional indoor displays.
Core Product Application Scenarios of Round LCD
With its unique perfect circular visual structure and ultra-high brightness physical characteristics, this high-resolution Round LCD effectively solves interaction pain points in various cutting-edge hardware products:
- Smart Home Ecosystems and Core Control Panels: Embedded smart wall thermostat control knobs, smart security circular control terminals, and circular interactive knobs for high-end audio systems.
- High-End Smart Home Appliance Dials: Color displays for premium kitchen ovens and food processors, central circular program selection and control display assemblies for high-end washing machines and dryers.
- Industrial Instrumentation and Medical Monitoring Equipment: Digital diagnostic circular panels for pressure and flow, lightweight knobs and monitoring screens for laboratory centrifuges or specific testing equipment.
Optimized Technical FAQ of Round LCD
Q1: Why choose a native Round LCD? What are its technical advantages over covering a standard square screen with a circular bezel?
A1: A native Round LCD achieves a circular pixel arrangement and effective pixel display area at the physical hardware level. This allows product engineers to maximize space utilization within a compact, circular enclosure. Using a traditional square screen with a circular bezel not only wastes significant physical space in the corners but also forces the driver IC to continuously allocate frame buffer memory and render for these masked, inactive pixel areas. Choosing a native Round LCD allows the host’s graphics framework (such as LVGL) to better adapt to the circular coordinate system, optimize frame buffer memory usage, and effectively save power consumed by backlighting and driving.
Q2: The datasheet emphasizes using an 80mA constant current test for the backlight. What happens if a constant voltage power supply is connected directly?
A2: LEDs are current-sensitive semiconductor devices. Their forward voltage drop (Vf) exhibits a negative dynamic drift as the ambient temperature rises. If a developer connects a fixed constant voltage supply directly to the LEDA and LEDK pins, and the internal temperature of the display increases during operation, the LED’s forward voltage drop will decrease. Under a constant voltage supply, this will cause the current through the backlight array to surge sharply, ultimately leading to thermal runaway. This results in severe localized heating of the screen, uneven backlight brightness, or premature LED burnout and damage. Using a fixed 80mA constant current driver locks the drive current regardless of ambient temperature, ensuring stable output power and fully guaranteeing the normal 30,000-hour design life of the screen.
If you have custom requirements, please contact us.
