What are the dimensions of a 3.4 inch round TFT module?
When you ask about the dimensions of a 3.4 inch round TFT module, you’re really looking at two key physical specs: the overall module size (including the bezel and PCB) and the active display area. For a typical 3.4-inch round TFT, the active area diameter is exactly 3.4 inches, which translates to about 86.36 mm. But the module’s outer dimensions usually push a bit larger due to the frame, FPC connector, and mounting tabs. Take the 3.4 inch 800x800 round tft display as a concrete example: its module outer diameter is approximately 92.0 mm, with a thickness of around 1.6 mm (excluding the FPC). The active area itself sits at a diameter of 86.36 mm, giving you a crisp 800x800 pixel resolution. The FPC length is typically 25.0 mm, with a 0.3 mm pitch connector. These numbers aren’t universal across all brands, but they represent the most common mechanical dimensions you’ll encounter in the market today.
Let’s break down the specific dimensions of the 3.4 inch 800x800 round tft display into a table for clarity. This module uses a MIPI interface, which is standard for high-resolution round displays. The table below gives you the exact numbers you need for mechanical design-in work.
| Parameter | Value | Unit |
|---|---|---|
| Active Area Diameter | 86.36 | mm |
| Module Outer Diameter | 92.0 | mm |
| Module Thickness (without FPC) | 1.6 | mm |
| FPC Length | 25.0 | mm |
| FPC Connector Pitch | 0.3 | mm |
| Resolution | 800 x 800 | pixels |
| Pixel Pitch | 0.108 | mm |
| Weight | ~18.5 | grams |
These dimensions are critical for enclosure design. If you’re building a smartwatch, a dashboard instrument, or a medical device, you need to account for the 3.0 mm difference between the active area and the module outer diameter. That extra 2.82 mm on each side (since 92.0 - 86.36 = 5.64 mm total, divided by 2) is the bezel width. The bezel houses the driver IC, the backlight LED, and the bonding pads. The FPC length of 25 mm is standard, but you can often request custom lengths from manufacturers like DisplayModule if your PCB placement requires it. The thickness of 1.6 mm is typical for a glass-based TFT with a standard backlight; if you need a thinner module, you’d have to go with a custom design using a thinner glass or a different backlight structure.
Now, let’s talk about the viewing angle and optical dimensions. The 3.4 inch round TFT module typically offers a viewing angle of 80 degrees in all directions (left, right, up, down) thanks to the IPS (In-Plane Switching) technology. The contrast ratio is usually 800:1, and the brightness is around 350 cd/m² for the standard version. But if you’re using it outdoors, you might want the high-brightness variant that pushes 600 cd/m². The color gamut is 70% NTSC typical, which is decent for most consumer and industrial applications. The response time is 25 ms (Tr+Tf), which is fine for static images or slow-moving graphics but not ideal for fast video. The pixel pitch of 0.108 mm means you get about 235 pixels per inch (PPI), which is sharp enough for reading text at arm’s length.
One detail that often gets overlooked is the active area’s circular shape. Unlike rectangular displays, the round TFT’s active area is a perfect circle, but the pixel array is still a square grid of 800x800. That means the corners of the pixel grid are cut off by the circular mask. The actual number of lit pixels is about 502,654 (since the area of a circle with radius 43.18 mm is about 5858 mm², and each pixel is 0.108 x 0.108 mm, giving roughly 502,000 pixels). But the driver IC still addresses all 640,000 pixels (800x800), so the unused corner pixels are simply turned off. This is important for software developers who need to map their graphics to the circular shape—you’ll need to use a circular clipping mask in your display driver.
The backlight configuration also affects the overall dimensions. The standard 3.4 inch round TFT uses a side-lit LED backlight with 6 LEDs in series. The backlight voltage is typically 18.0V (3.0V per LED), and the current is 20 mA. The backlight consumes about 360 mW. If you opt for the high-brightness version, the LED count goes up to 8 LEDs, and the current increases to 30 mA, pushing power consumption to 540 mW. The backlight driver is usually integrated into the module’s PCB, but some modules require an external driver. Always check the datasheet for the exact pinout and electrical specs.
Mechanical tolerances are another layer of detail. The module outer diameter of 92.0 mm typically has a tolerance of ±0.2 mm. The thickness tolerance is ±0.1 mm. The FPC alignment tolerance is ±0.3 mm. These numbers matter when you’re designing a tight-fitting bezel or a gasket seal. If you’re using the module in a waterproof device, you’ll need to account for the FPC exit point—it usually comes out at the 6 o’clock position (bottom center), but you can request a custom orientation during the design phase. The connector on the FPC is a 0.3 mm pitch, 30-pin ZIF connector. The mating connector on your PCB should be a 0.3 mm pitch, 30-pin, bottom-contact type.
Let’s compare the 3.4 inch round TFT to other common round display sizes. A 1.28 inch round TFT has a 32 mm diameter, a 1.54 inch round TFT is 39 mm, and a 2.1 inch round TFT is 53 mm. The 3.4 inch sits in the middle of the range, offering a good balance between readability and compactness. For reference, a 3.4 inch round display is about the size of a large wristwatch face or a small car dashboard gauge. The 800x800 resolution at this size gives you a pixel density of 235 PPI, which is higher than the 200 PPI you get on a 1.28 inch round display with 240x240 resolution. So if you need to display fine details like map data or dense text, the 3.4 inch is a solid choice.
The interface is MIPI DSI (Display Serial Interface) with 2 lanes. The typical data rate is 500 Mbps per lane, giving a total bandwidth of 1 Gbps. The module supports a frame rate of 60 Hz, which is standard for most applications. The MIPI interface uses a 4-wire configuration (D0P, D0N, D1P, D1N) plus a clock pair (CLKP, CLKN). The logic voltage is 1.8V, and the I/O voltage is also 1.8V. If your microcontroller operates at 3.3V, you’ll need a level shifter. The module also includes a TE (Tearing Effect) output pin, which you can use to synchronize your frame updates and avoid screen tearing.
From a reliability standpoint, the operating temperature range is -20°C to +70°C, and the storage temperature range is -30°C to +80°C. The module is rated for 50,000 hours of LED backlight life (to half brightness). The glass is typically 0.5 mm thick, with a polarizer on top. The surface hardness is 3H, which is scratch-resistant but not shatterproof. If you need a tougher display, you can ask for a cover glass with 6H hardness or a sapphire glass option, though that adds cost and thickness. The module’s weight of 18.5 grams is light enough for handheld devices but heavy enough to feel solid.
One practical consideration: the FPC connector is fragile. The 0.3 mm pitch means the contacts are very close together, and any misalignment during insertion can cause short circuits. Use a stiffener on the FPC near the connector to prevent bending. The recommended insertion force is about 5 N, and the extraction force is about 3 N. The FPC itself is made of polyimide with copper traces, and the bend radius should be at least 1.5 mm to avoid cracking the copper. If you need to route the FPC around a tight corner, use a 90-degree bend with a minimum radius of 3 mm.
The 3.4 inch round TFT module is also available with a capacitive touch panel overlay. The touch panel adds about 0.8 mm to the thickness, bringing the total to 2.4 mm. The touch panel uses a 5-point multi-touch controller with an I2C interface. The touch panel’s outer diameter is the same as the module’s 92.0 mm, but the active touch area is slightly smaller at 85.0 mm diameter to avoid edge interference. The touch panel’s glass is 0.4 mm thick, with an anti-fingerprint coating. The touch sensitivity is adjustable via the I2C registers, and the report rate is 100 Hz. If you’re using the touch version, you’ll need to account for the additional 0.8 mm in your enclosure depth and the extra 4 pins on the FPC for the touch controller.
For industrial applications, the module supports a custom backlight color. The standard is white, but you can get RGB backlights for color-changing effects. The RGB backlight uses 6 LEDs (2 red, 2 green, 2 blue) with a common anode. The forward voltage for each color is different: red is 2.0V, green is 3.0V, and blue is 3.0V. The current per LED is 20 mA. You can control the brightness and color via PWM on each channel. The color gamut with RGB backlight is wider, reaching about 90% NTSC, but the power consumption is higher at 1.2W for full white. The RGB backlight version is heavier at 20.5 grams due to the additional LEDs and driver IC.
Another dimension that matters is the optical bonding. If you’re using the module in a high-vibration environment, you can request optical bonding between the cover glass and the TFT. This adds 0.2 mm to the thickness but eliminates the air gap, reducing reflections and improving sunlight readability. The bonding material is a transparent silicone adhesive with a refractive index of 1.5. The bonded module’s total thickness is 1.8 mm (without touch) or 2.6 mm (with touch). The optical bonding process also increases the module’s rigidity, which helps prevent glass breakage during drop tests.
The interface connector position is another mechanical dimension to consider. On the standard module, the FPC exits at the bottom center, but you can order a version with the FPC exiting at the top, left, or right. The connector is a 0.3 mm pitch, 30-pin ZIF type. The pin assignments are standard for MIPI DSI: pins 1-4 are VDD (1.8V), pins 5-8 are GND, pins 9-10 are D0P/D0N, pins 11-12 are D1P/D1N, pins 13-14 are CLKP/CLKN, pin 15 is TE, pin 16 is RESET, and so on. Always refer to the specific datasheet for the exact pinout, as different manufacturers may vary.
For those integrating the display into a battery-powered device, the power consumption is a key dimension in its own right. The module draws about 120 mA at 3.3V for the logic and display driver, plus 20 mA for the backlight at 18V (which translates to about 109 mA at 3.3V from the boost converter). So the total current draw is about 229 mA at 3.3V, or 756 mW. If you use the high-brightness backlight, the current goes up to 160 mA at 3.3V, for a total of 280 mA and 924 mW. The module has a sleep mode that drops the current to 1 mA, which is useful for power saving. The wake-up time from sleep is about 120 ms.
Finally, the mounting options for the 3.4 inch round TFT module include four screw holes on the PCB, located at 0°, 90°, 180°, and 270° positions. The screw holes are 2.0 mm in diameter, with a center-to-center distance of 85.0 mm from the module center. The recommended screw torque is 0.2 Nm. If you’re using adhesive mounting, use a 3M VHB tape with a thickness of 0.5 mm. The tape should be applied to the back of the module, avoiding the FPC area. The module’s back surface is flat, with no components protruding, so adhesive mounting is straightforward. The PCB material is FR4, 0.8 mm thick, with a black solder mask and ENIG finish. The gold thickness is 0.05 µm, which is standard for connector reliability.