What are the dimensions of a 1.39 inch round AMOLED display?

By admin 2026-08-05

The actual dimensions of a 1.39 inch round AMOLED display are not just the screen diagonal; you need to look at the outer diameter, active area, and thickness to get the full picture. For a typical 1.39 inch round AMOLED panel, the outer diameter of the glass lens is usually around 35.5 mm to 36.0 mm, depending on the bezel width and the casing design. The active display area, where pixels actually light up, measures approximately 35.4 mm in diameter. The module thickness, including the glass, polarizer, and flexible printed circuit board, is typically between 1.2 mm and 1.5 mm, though some variants with touch sensors or reinforced glass can go up to 2.0 mm. The resolution is almost always 454x454 pixels, which gives a pixel density of about 326 pixels per inch, matching the "retina" standard for watch-sized screens. The aspect ratio is 1:1, which is standard for round displays. The connector interface is usually a 24-pin or 30-pin ZIF connector, with a MIPI DSI or SPI interface, and the display driver IC is often the RM69370 or similar, supporting 16.7 million colors. If you are looking for a specific model, check out this 1.39 inch 454x454 round amoled display for exact mechanical drawings and electrical specs.

The physical dimensions of the glass substrate are critical for mechanical integration. Most 1.39 inch round AMOLED displays come with a circular glass cover that has a diameter of 35.6 mm ± 0.1 mm. The active area diameter is 35.4 mm, leaving a 0.1 mm border for the black matrix or sealant. The glass thickness is typically 0.7 mm for the bottom glass and 0.5 mm for the top cover glass, but some modules use a single 1.0 mm thick glass to reduce cost. The flexible printed circuit board extends from the bottom edge of the glass, usually with a width of 8 mm to 10 mm and a length of 15 mm to 20 mm, depending on the connector placement. The FPC has a thickness of about 0.2 mm, and it is often bent at a 90-degree angle for compact assembly in smartwatches. The connector is a ZIF type, with a pitch of 0.3 mm or 0.5 mm, and the number of pins ranges from 24 to 30. The display module weight is around 5 grams to 8 grams, making it suitable for wearable devices.

Optical dimensions are just as important as physical ones. The display has a circular shape with a diameter of 35.4 mm for the active area, which corresponds to a total pixel count of 454x454. The pixel pitch is 0.078 mm, which is typical for high-density AMOLED panels. The color gamut covers 100% of the NTSC standard or 97% of the DCI-P3 color space, which is common for premium AMOLEDs. The brightness is typically 300 nits to 400 nits for normal operation, but can be boosted to 600 nits in high-brightness mode for outdoor visibility. The contrast ratio is 100,000:1, which is standard for AMOLED due to the self-emissive nature of the pixels. The viewing angle is 80 degrees in all directions, with minimal color shift. The refresh rate is 60 Hz, though some panels support 30 Hz for low-power static images. The response time is less than 1 ms, which is typical for AMOLED.

Electrical dimensions are often overlooked but are crucial for circuit design. The operating voltage for the display is 2.8V to 3.3V for the logic part, and 4.6V to 5.0V for the OLED panel power supply. The typical current consumption is 15 mA to 20 mA for a white image at 50% brightness, but can drop to 1 mA for a black image because AMOLED pixels are off when displaying black. The interface is either MIPI DSI (1-lane or 2-lane) or SPI (4-wire or 3-wire), with a maximum clock frequency of 60 MHz for MIPI and 32 MHz for SPI. The display driver IC supports 16.7 million colors, which is 24-bit color depth, and includes gamma correction, dithering, and partial update modes. The capacitive touch controller is often integrated into the same FPC, with a separate I2C interface for touch data, supporting up to 5-point multitouch.

Mechanical tolerances are important for assembly. The outer diameter of the glass lens has a tolerance of ±0.15 mm, and the active area diameter has a tolerance of ±0.1 mm. The thickness of the glass module has a tolerance of ±0.1 mm. The FPC length from the glass edge to the connector is usually 15 mm ± 1 mm, and the connector position is centered within ±0.2 mm. The display module is often supplied with a protective film on both sides, which adds 0.1 mm to the thickness. The module is designed to be mounted using a metal bezel or a plastic housing, with a recommended clearance of 0.3 mm around the glass edge. The operating temperature range is -20°C to +70°C, and the storage temperature range is -30°C to +80°C.

When comparing this 1.39 inch round AMOLED to other round displays, the dimensions are quite standard. For example, a 1.2 inch round AMOLED typically has a glass diameter of 30.5 mm and an active area of 30.2 mm, while a 1.4 inch round AMOLED has a glass diameter of 37.0 mm and an active area of 36.6 mm. The 1.39 inch size sits in the middle, making it popular for smartwatches like the Huawei Watch GT and some Amazfit models. The 454x454 resolution is higher than the 360x360 resolution found on older 1.2 inch displays, but lower than the 466x466 resolution on some 1.43 inch panels. The pixel density of 326 PPI is considered "retina" for a watch, meaning individual pixels are not visible at normal viewing distances. The color depth of 16.7 million colors is standard for 24-bit color, but some high-end AMOLEDs support 10-bit color for 1.07 billion colors, though this is rare in this size range.

Thermal management is another dimension to consider. The AMOLED panel generates heat during operation, especially at high brightness. The display module has a thermal resistance of about 10°C/W to 15°C/W, meaning that for every watt of power dissipated, the temperature rises by 10°C to 15°C. The typical power consumption at 300 nits brightness is about 0.5 watts, so the temperature rise is around 5°C to 7.5°C. The glass substrate acts as a heat spreader, but the FPC and connector are the main heat dissipation paths. The display driver IC is usually located on the FPC, and it can reach temperatures of up to 60°C during continuous operation. The touch controller also generates some heat, but it is negligible compared to the display driver. The module is designed to be used with a metal backplate or a heat sink in the watch housing to keep the temperature within safe limits.

Optical performance metrics are also part of the dimensional equation. The display has a typical luminance of 300 nits for the white point, but this can vary by ±10% across the panel. The color uniformity is within 0.02 CIE 1931 chromaticity coordinates, which is considered good for AMOLED. The gamma curve is set to 2.2, which is the standard for sRGB content. The display supports low-blue-light mode, which reduces the blue light emission by 30% to 50% by shifting the white point to a warmer color temperature. The flicker frequency is 60 Hz for the PWM dimming, but some panels use DC dimming at low brightness to reduce flicker. The viewing angle performance is excellent, with a contrast ratio of over 100:1 even at 80 degrees off-axis. The reflectivity of the display is about 5% to 8% due to the polarizer, which is standard for AMOLED panels used in outdoor applications.

Mechanical integration with a smartwatch housing requires precise dimensional matching. The display module is typically glued into the housing using a UV-curable adhesive, with a bonding gap of 0.1 mm to 0.2 mm. The housing has a recess that matches the outer diameter of the glass, usually with a tolerance of ±0.05 mm. The FPC is routed through a slot in the housing, and the connector is mated to a mainboard using a ZIF connector. The total height of the display module, including the glass, FPC, and connector, is about 2.5 mm to 3.0 mm, but this can vary depending on the thickness of the touch sensor and the cover glass. The display module is often shipped with a protective cover that must be removed before assembly. The module is sensitive to static electricity, so ESD protection is required during handling and assembly.

Reliability testing is based on dimensional and environmental standards. The display module is tested for thermal shock, with cycles from -40°C to +85°C for 100 cycles. It is tested for humidity, with 95% RH at 60°C for 240 hours. It is tested for vibration, with 10 Hz to 200 Hz at 1.5g for 30 minutes. It is tested for drop, with a 1.5 meter drop onto a concrete surface. The module is also tested for salt spray, UV exposure, and chemical resistance. The display is designed to meet the IP67 or IP68 standard for water and dust resistance, but this depends on the housing design. The module has a lifespan of 20,000 hours to 30,000 hours at 50% brightness, which is typical for AMOLED panels. The burn-in effect is minimal due to the pixel shifting and compensation algorithms in the driver IC.

Cost and supply chain dimensions are also relevant. The 1.39 inch round AMOLED display is manufactured by companies like BOE, Visionox, and Tianma. The cost per unit is typically $15 to $25 for small quantities, but can drop to $8 to $12 for bulk orders of 1000 units or more. The lead time is 4 to 6 weeks for standard orders, and 8 to 10 weeks for custom orders with specific touch sensors or cover glass. The display is often sold as a module with the touch sensor and FPC, but some suppliers sell the bare glass panel for OEM integration. The module is compatible with popular microcontrollers like the STM32, ESP32, and nRF52840, using the MIPI or SPI interface. The display driver IC is supported by libraries like LVGL, u8g2, and TFT_eSPI, making it easy to integrate into embedded projects.

If you are designing a smartwatch or a wearable device, the dimensions of the 1.39 inch round AMOLED display are critical for the mechanical layout. The outer diameter of 35.6 mm means the watch case must have an inner diameter of at least 36.0 mm to accommodate the display with a 0.2 mm gap. The thickness of 1.5 mm means the watch case must have a depth of at least 2.0 mm to allow for the FPC and connector. The FPC length of 15 mm means the mainboard must be placed within 15 mm of the display edge. The connector pitch of 0.3 mm means the mainboard must have a matching ZIF connector with a 0.3 mm pitch. The display resolution of 454x454 means the graphics buffer must be at least 454x454x3 bytes, which is about 620 KB for 24-bit color. The MIPI interface requires 4 to 6 GPIO pins, and the SPI interface requires 4 to 5 GPIO pins. The touch controller requires 2 I2C pins and one interrupt pin.

To summarize the key dimensional data, here is a table for quick reference:

This table is based on data from multiple datasheets and supplier specifications. The actual dimensions may vary slightly between manufacturers, so always check the mechanical drawing for the specific model. The 1.39 inch round AMOLED display is a mature product with a consistent form factor, making it a reliable choice for wearable devices. The dimensions are optimized for a balance between screen size and device compactness, and the 454x454 resolution provides sharp text and graphics. The display is available with different cover glass options, including mineral glass, sapphire glass, and Gorilla Glass, each with different thickness and scratch resistance. The touch sensor is usually a capacitive touch panel with a glass or film substrate, and it is integrated into the display module.

For engineers and designers, the dimensional data is essential for creating accurate 3D models and PCB layouts. The display module is typically modeled as a solid cylinder with a diameter of 35.6 mm and a height of 1.5 mm, with a rectangular FPC extending from the bottom. The FPC has a thickness of 0.2 mm and is often modeled as a flat ribbon. The connector is a small rectangular block with a width of 6 mm to 8 mm and a height of 1.5 mm. The touch sensor is a transparent layer on top of the display, with a thickness of 0.3 mm to 0.5 mm. The cover glass is a circular disc with a thickness of 0.5 mm to 1.0 mm, and it is often curved at the edges for a seamless look. The module is designed to be assembled using a press-fit or a glue bond, and the FPC is routed through a slot in the housing.

The display module is also available with different optical coatings, including anti-reflective coating, anti-fingerprint coating, and oleophobic coating. These coatings add a few microns to the thickness but do not affect the overall dimensions. The module is tested for optical performance using a spectroradiometer and a colorimeter, and the results are typically within the specifications. The display is also tested for electrical performance using a logic analyzer and an oscilloscope, and the timing diagrams are provided in the datasheet. The module is compatible with a wide range of microcontrollers and development boards, and the driver IC is supported by open-source libraries. The display is a popular choice for smartwatches, fitness trackers, and other wearable devices, and it is also used in some IoT devices and medical devices.

In terms of mechanical design, the 1.39 inch round AMOLED display requires a bezel that is at least 0.5 mm wide to cover the edge of the glass. The bezel can be made of metal, plastic, or ceramic, and it is usually anodized or painted to match the watch case. The display is glued into the bezel using a UV-curable adhesive, and the FPC is routed through a slot in the bezel. The bezel is then attached to the watch case using screws or a snap-fit. The watch case is usually made of stainless steel, aluminum, or plastic, and it is designed to protect the display from impact and water. The display module is also available with a metal frame that provides additional protection and heat dissipation. The frame is usually made of aluminum or stainless steel, and it is attached to the display using a heat-conductive adhesive.

The display module is also available with different cover glass options, including mineral glass, sapphire glass, and Gorilla Glass. Mineral glass is the most common and is used in mid-range smartwatches. Sapphire glass is more scratch-resistant but is more expensive and heavier. Gorilla Glass is a good compromise between scratch resistance and weight. The cover glass is usually curved at the edges to match the shape of the watch case, and it is coated with an anti-reflective coating to improve outdoor visibility. The cover glass is attached to the display using an optically clear adhesive, and the module is tested for optical clarity and adhesion strength. The display module is also available with a touch sensor that is integrated into the cover glass, which reduces the thickness and improves the touch sensitivity.

The display module is also available with different interface options, including MIPI DSI and SPI. MIPI DSI is a high-speed interface that is used in most modern smartwatches, and it supports higher resolutions and refresh rates. SPI is a slower interface that is used in low-power devices, and it is easier to implement with microcontrollers. The display driver IC is usually the RM69370 or the SH8601, and it supports both MIPI and SPI interfaces. The driver IC is also capable of partial update, which reduces power consumption when only a small part of the display is updated. The driver IC is also capable of gamma correction, which improves the color accuracy. The display module is also available with a built-in frame buffer, which reduces the load on the microcontroller.

The display module is also available with different touch sensor options, including capacitive touch and resistive touch. Capacitive touch is the most common and is used in most smartwatches. It supports multi-touch and is more responsive than