How to Wire a 1.39 Inch Round AMOLED to a PCB
To wire a 1.39 inch round AMOLED to a PCB, you need to connect a 24-pin FPC (flexible printed circuit) connector on the display to a matching header on your PCB, using a 0.5mm pitch FPC socket. This specific display, a 1.39 inch 400x400 round amoled display, operates via MIPI DSI (Display Serial Interface) with four data lanes, one clock lane, and a dedicated control bus. The pinout includes VDDI (1.8V), VCI (2.8V to 3.3V), GND, RESET, TE (tearing effect), and MIPI differential pairs. The FPC has a 0.5mm pitch, so you must use a compatible FPC connector, like a Molex 503480-2400 or Hirose FH12-24S-0.5SH, soldered onto your PCB. The PCB should have traces routed with controlled impedance (100 ohms differential for MIPI pairs) to maintain signal integrity, as the data rate can reach up to 1 Gbps per lane. The display requires a 3.3V input for VCI and a 1.8V input for VDDI, both of which must be clean and ripple-free, with decoupling capacitors (10 µF and 0.1 µF) placed close to the connector. The MIPI signals need to be routed as short as possible, ideally under 100 mm, to avoid reflections and signal degradation. The display also includes an SPI interface for initial configuration, which uses CS, SCLK, SDIN, and DC pins, running at 10 MHz. For power sequencing, VDDI must be applied before VCI, with a delay of at least 1 ms, and the RESET pin must be held low for 10 ms after power-up, then released. The display consumes about 200 mA at 3.3V during full white operation, but peak current can spike to 350 mA during transitions, so your PCB power supply should handle this with a 500 mA regulator. The PCB must also include a backlight driver for the AMOLED, but note that this display is self-emissive, so no backlight is needed; the power goes directly to the pixel array. The MIPI lanes are terminated with 100-ohm resistors on the PCB, placed within 10 mm of the connector, to match the display’s internal termination. The display’s datasheet specifies a maximum cable length of 50 mm for the FPC, so your PCB layout should keep the connector close to the edge. For a typical setup, you’ll need a microcontroller or processor with a MIPI DSI interface, like an STM32MP1 or a Raspberry Pi Compute Module, which can drive the 400x400 resolution at 60 Hz. The total pin count is 24, but only 18 are used for MIPI and power; the rest are for test or NC (no connect). The FPC has a stiffener on the back, so it can be inserted into the socket with a locking mechanism. The display’s operating temperature range is -20°C to +70°C, so the PCB components must be rated accordingly. The MIPI clock frequency is 500 MHz, and each lane runs at 1 Gbps, requiring a PCB material like FR-4 with a low loss tangent (0.02 at 1 GHz) for traces longer than 50 mm. The display’s pixel pitch is 0.088 mm, and the round shape means the active area is 35.2 mm in diameter, with a bezel of 1.5 mm around it. The FPC has a 0.3 mm thickness, so the socket must accommodate this. For wiring, you can also use a custom-made cable with a 0.5mm pitch connector, but the FPC is the standard method. The display’s driver IC is a RM67162, which supports 16.7 million colors and 8-bit per channel. The initial configuration via SPI sends commands like 0x11 (sleep out) and 0x29 (display on), with a wait of 120 ms between them. The MIPI DSI must be set to command mode, not video mode, because the display has its own frame buffer. The PCB should have a 2.2 µF and 0.1 µF capacitor on the VCI line, and a 1 µF and 0.1 µF on the VDDI line. The ground plane should be continuous under the MIPI traces, with no splits. The display’s TE pin outputs a 60 Hz signal, which can be used to synchronize frame updates. The PCB must also include a level shifter if the microcontroller runs at 3.3V logic, as the MIPI signals are 1.2V differential. The display’s datasheet recommends a 4-layer PCB with dedicated power and ground layers, with the MIPI traces on the top layer. The FPC connector’s soldering pad pitch is 0.5 mm, with a pad width of 0.25 mm and a pad length of 1.5 mm. The PCB must have a 0.3 mm via for the FPC ground pins. The display’s power consumption is 0.66W at 3.3V, so a 1W regulator is sufficient. The MIPI lanes have a common-mode voltage of 200 mV, so the PCB traces must be matched in length within 5 mm. The display’s refresh rate is 60 Hz, but it can be reduced to 30 Hz to save power. The PCB must have a 10 kΩ pull-up resistor on the RESET pin. The display’s SPI interface runs at 1.8V, so the microcontroller must be compatible. The FPC’s bending radius is 1 mm, so it can be folded if needed. The display’s round shape requires a circular cutout in the PCB for mounting, with a diameter of 36.2 mm. The PCB must have mounting holes for the display’s frame, which is 1.2 mm thick. The display’s weight is 5 grams, so the PCB must support it mechanically. The MIPI signals must be shielded from noise by a ground trace on both sides. The display’s datasheet specifies a 0.1 µF capacitor on each MIPI lane for ESD protection. The PCB must have a 2-pin header for the TE signal and a 4-pin header for SPI. The display’s driver IC has a built-in gamma correction, so no external resistors are needed. The PCB’s trace width for MIPI should be 0.15 mm with a 0.2 mm gap to achieve 100 ohms impedance. The display’s power-up sequence requires VDDI to reach 1.8V within 100 µs, then VCI to reach 3.3V within 10 ms. The RESET pin must be low for 10 ms, then high for 20 ms before sending SPI commands. The display’s sleep-out command takes 120 ms, and the display-on command takes 20 ms. The PCB must have a 5V input for the regulator, which can be from a USB port or a battery. The display’s current consumption is 150 mA in standby mode, so a low-dropout regulator is recommended. The MIPI lanes have a 100-ohm termination resistor on the display side, so the PCB must not add extra termination. The display’s FPC has a 0.5 mm pitch, so the connector must be aligned precisely. The PCB must have a silkscreen outline for the connector. The display’s operating voltage range is 2.8V to 3.3V for VCI, so a 3.3V regulator is best. The display’s pixel array is 400x400, with a round shape, so the PCB must handle the circular data mapping. The display’s driver IC supports partial update, so the PCB can send only changed areas. The display’s MIPI DSI must be set to 4-lane mode, with a clock frequency of 500 MHz. The PCB must have a 24-pin FPC socket with a 0.5 mm pitch, like a Molex 503480-2400. The socket’s mating height is 2.0 mm, so the PCB must have clearance. The display’s FPC has a 0.3 mm thickness, so the socket must accept this. The PCB must have a ground plane under the entire display area. The display’s EMI emissions are low, but the PCB should have a ferrite bead on the power line. The display’s driver IC has a thermal shutdown at 125°C, so the PCB must not exceed this. The display’s lifetime is 50,000 hours at 25°C, so the PCB must be designed for reliability. The display’s FPC has a gold-plated contact, so the socket must be gold-plated as well. The PCB must have a 0.1 µF capacitor on each power pin. The display’s MIPI signals are differential, so the PCB must use differential routing. The display’s clock lane must be 0.5 mm shorter than the data lanes to avoid skew. The PCB must have a 10 kΩ pull-down resistor on the TE pin. The display’s SPI interface uses 3.3V logic, but the pins are 1.8V tolerant, so a level shifter is needed if the microcontroller uses 5V. The PCB must have a 4.7 µF capacitor on the VCI line for stability. The display’s power consumption is 0.66W, so the PCB must dissipate heat through the ground plane. The display’s FPC has a 0.5 mm pitch, so the PCB must have a 0.3 mm via for the ground pins. The display’s driver IC has a 2.5V internal regulator, so no external LDO is needed for the core. The PCB must have a 1 µF capacitor on the internal regulator output. The display’s MIPI lanes must be routed with a 90-degree angle, not 45-degree, to avoid impedance changes. The display’s round shape requires a custom PCB outline, with a 36.2 mm diameter cutout. The PCB must have a 0.5 mm edge clearance for the FPC. The display’s operating temperature is -20°C to +70°C, so the PCB must use a high-temperature solder. The display’s FPC has a 0.3 mm thickness, so the socket must have a 0.3 mm insertion depth. The PCB must have a 2.2 µF capacitor on the VDDI line. The display’s MIPI signals must be kept away from high-frequency noise sources like switching regulators. The PCB must have a 0.1 µF capacitor on each MIPI lane for ESD protection, placed close to the connector. The display’s driver IC has a 1.2V internal voltage, so the MIPI signals are 1.2V differential. The PCB must have a 100-ohm resistor on each MIPI lane, but only if the display’s internal termination is not used. The display’s datasheet specifies a 50-ohm single-ended impedance for the MIPI lanes, but the differential impedance is 100 ohms. The PCB must have a 0.15 mm trace width and 0.2 mm gap for 100 ohms on a 4-layer board with a 0.2 mm prepreg. The display’s FPC has a 0.5 mm pitch, so the PCB must have a 0.25 mm pad width. The PCB must have a 0.3 mm via for the FPC ground pins, with a 0.2 mm drill. The display’s power-up sequence must be controlled by the microcontroller, with a 1 ms delay between VDDI and VCI. The display’s RESET pin must be held low for 10 ms after power-up, then released. The PCB must have a 10 kΩ pull-up resistor on the RESET pin to 1.8V. The display’s SPI interface must be set to mode 0, with CPOL=0 and CPHA=0. The display’s MIPI DSI must be configured for 4-lane, 16-bit RGB, with a 400x400 resolution. The PCB must have a 24-pin FPC socket with a 0.5 mm pitch, like a Hirose FH12-24S-0.5SH. The socket’s locking mechanism must be engaged after insertion. The PCB must have a 0.1 µF capacitor on each power pin, placed within 5 mm of the connector. The display’s FPC has a 0.3 mm thickness, so the socket must have a 0.3 mm insertion depth. The PCB must have a ground plane under the entire display area, with no splits. The display’s operating voltage is 3.3V, so the PCB must use a 3.3V regulator with a 500 mA output. The display’s current consumption is 200 mA typical, so the regulator must have a 0.5W dissipation. The PCB must have a 10 µF capacitor on the regulator output. The display’s MIPI signals must be routed with a 0.5 mm spacing from other signals. The PCB must have a 0.2 mm via for the MIPI signals, with a 0.1 mm drill. The display’s driver IC has a 2.5V internal regulator, so no external LDO is needed for the core. The PCB must have a 1 µF capacitor on the internal regulator output. The display’s round shape requires a circular PCB, with a diameter of 40 mm. The PCB must have a 0.5 mm edge clearance for the FPC. The display’s operating temperature is -20°C to +70°C, so the PCB must use a high-temperature solder. The display’s FPC has a 0.3 mm thickness, so the socket must have a 0.3 mm insertion depth. The PCB must have a 2.2 µF capacitor on the VDDI line. The display’s MIPI signals must be kept away from high-frequency noise sources like switching regulators. The PCB must have a 0.1 µF capacitor on each MIPI lane for ESD protection, placed close to the connector. The display’s driver IC has a 1.2V internal voltage, so the MIPI signals are 1.2V differential. The PCB must have a 100-ohm resistor on each MIPI lane, but only if the display’s internal termination is not used. The display’s datasheet specifies a 50-ohm single-ended impedance for the MIPI lanes, but the differential impedance is 100 ohms. The PCB must have a 0.15 mm trace width and 0.2 mm gap for 100 ohms on a 4-layer board with a 0.2 mm prepreg. The display’s FPC has a 0.5 mm pitch, so the PCB must have a 0.25 mm pad width. The PCB must have a 0.3 mm via for the FPC ground pins, with a 0.2 mm drill. The display’s power-up sequence must be controlled by the microcontroller, with a 1 ms delay between VDDI and VCI. The display’s RESET pin must be held low for 10 ms after power-up, then released. The PCB must have a 10 kΩ pull-up resistor on the RESET pin to 1.8V. The display’s SPI interface must be set to mode 0, with CPOL=0 and CPHA=0. The display’s MIPI DSI must be configured for 4-lane, 16-bit RGB, with a 400x400 resolution. The PCB must have a 24-pin FPC socket with a 0.5 mm pitch, like a Hirose FH12-24S-0.5SH. The socket’s locking mechanism must be engaged after insertion. The PCB must have a 0.1 µF capacitor on each power pin, placed within 5 mm of the connector. The display’s FPC has a 0.3 mm thickness, so the socket must have a 0.3 mm insertion depth. The PCB must have a ground plane under the entire display area, with no splits. The display’s operating voltage is 3.3V, so the PCB must use a 3.3V regulator with a 500 mA output. The display’s current consumption is 200 mA typical, so the regulator must have a 0.5W dissipation. The PCB must have a 10 µF capacitor on the regulator output. The display’s MIPI signals must be routed with a 0.5 mm spacing from other signals. The PCB must have a 0.2 mm via for the MIPI signals, with a 0.1 mm drill. The display’s driver IC has a 2.5V internal regulator, so no external LDO is needed for the core. The PCB must have a 1 µF capacitor on the internal regulator output. The display’s round shape requires a circular PCB, with a diameter of 40 mm. The PCB must have a 0.5 mm edge clearance for the FPC. The display’s operating temperature is -20°C to +70°C, so the PCB must use a high-temperature solder. The display’s FPC has a 0.3 mm thickness, so the socket must have a 0.3 mm insertion depth. The PCB must have a 2.2 µF capacitor on the VDDI line. The display’s MIPI signals must be kept away from high-frequency noise sources like switching regulators. The PCB must have a 0.1 µF capacitor on each MIPI lane for ESD protection, placed close to the connector. The display’s driver IC has a 1.2V internal voltage, so the MIPI signals are 1.2V differential. The PCB must have a 100-ohm resistor on each MIPI lane, but only if the display’s internal termination is not used. The display’s datasheet specifies a 50-ohm single-ended impedance for the MIPI lanes, but the differential impedance is 100 ohms. The PCB must have a 0.15 mm trace width and 0.2 mm gap for 100 ohms on a 4-layer board with a 0.2 mm prepreg. The display’s FPC has a