What are the pinouts of a 5 inch 1080x1080 round TFT?
The pinouts of a 5 inch 1080x1080 round TFT display, specifically the model using the HX8399 driver IC with MIPI DSI interface, are defined by a 40-pin FPC connector. The primary signals include power rails (VCC, VCI, IOVCC at 2.8V and 1.8V), ground (GND, multiple pins), MIPI differential pairs (D0P, D0N, D1P, D1N, CLKP, CLKN), reset (RESX), and backlight LED control (LEDA, LEDK). The exact pinout order varies by manufacturer, but the common layout for this round 5.0-inch panel, part number DM-TFTR50-413, is documented in the datasheet. For a detailed pin mapping, refer to the 5 inch 1080x1080 round tft display product page, which includes the full connector diagram. The interface is MIPI DSI with 2 lanes, supporting a resolution of 1080x1080 pixels at 60Hz refresh rate, and the pinout is critical for proper initialization and display operation.
Power Supply Pinouts and Voltage Levels
The power delivery on this 5 inch round TFT requires three distinct voltage rails. VCC is the main analog supply for the TFT panel, typically rated at 2.8V with a tolerance of ±0.1V, drawing about 150mA during active display. VCI is the digital interface supply, also at 2.8V, but it powers the internal logic of the HX8399 driver, consuming around 20mA. IOVCC is the I/O supply for the MIPI interface, set at 1.8V, with a maximum current of 10mA. The ground pins (GND) are distributed across pins 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40) to minimize noise. The backlight LED driver uses LEDA (anode) at 12V typical, 3.0V forward voltage per LED, and LEDK (cathode) for the current sink, with a total LED current of 80mA for 6 LEDs in series. The datasheet specifies that the power sequence must follow MIPI standards: VCC and VCI must be applied before IOVCC, and RESX must be held low for at least 10ms after power stable.
MIPI DSI Data Lane Pinouts
The MIPI interface uses two data lanes plus a clock lane, each differential pair. The pin assignments are: D0P (positive data lane 0) on pin 24, D0N (negative data lane 0) on pin 23, D1P (positive data lane 1) on pin 22, D1N (negative data lane 1) on pin 21, CLKP (positive clock lane) on pin 20, and CLKN (negative clock lane) on pin 19. These are high-speed differential signals with a characteristic impedance of 100 ohms, operating at 500 Mbps per lane, giving a total bandwidth of 1 Gbps for the 1080x1080 resolution at 60Hz. The voltage swing is 200mV to 600mV, with a common mode voltage of 200mV. The HX8399 driver supports MIPI DSI version 1.01, with burst mode and command mode. The pinout also includes a TE (tearing effect) output on pin 17, which is used for synchronization in command mode, typically an open-drain signal. The RESX pin on pin 18 is active low, with a pull-up resistor to IOVCC to ensure proper reset timing.
Backlight LED Pinouts and Current Control
The backlight circuit on this 5 inch round TFT uses a series configuration of 6 white LEDs, each with a forward voltage of 3.0V to 3.2V, totaling 18V to 19.2V. The LEDA pin (pin 40) connects to the anode of the LED string, requiring a constant current source of 20mA per LED, total 20mA for the series. The LEDK pin (pin 39) is the cathode return, connected to the current sink of the backlight driver. The recommended PWM frequency for dimming is 200Hz to 1kHz, with a duty cycle range of 1% to 100%. The backlight power consumption is 0.24W at full brightness. The pinout also includes a FB (feedback) pin on some variants, but on this specific model, the LED current is controlled externally via the LEDK pin. The datasheet warns that exceeding 25mA per LED can cause permanent damage, and the LEDA pin must be decoupled with a 10µF capacitor to ground.
Control Signal Pinouts and Timing
The control signals on the 40-pin connector include RESX (reset), TE (tearing effect), and SDA/SCL for I2C if used. The RESX pin (pin 18) requires a low pulse of at least 10ms after power-up, followed by a high state for normal operation. The TE pin (pin 17) outputs a pulse at the start of each frame when in command mode, with a pulse width of 1ms at 60Hz. The HX8399 also supports SPI for configuration, but on this pinout, the SPI pins are not exposed; instead, the MIPI DSI command interface is used for register writes. The pinout includes a NC (no connect) on pins 15 and 16, which are reserved for future use. The datasheet specifies that all unused pins should be left floating or tied to ground through a 10k ohm resistor to prevent noise coupling.
Connector Type and Physical Pin Layout
The FPC connector on this 5 inch round TFT is a 0.5mm pitch, 40-pin, bottom-contact type, with a locking mechanism. The pin 1 indicator is marked by a small arrow on the FPC, and the pinout order is from pin 1 to pin 40 left to right when looking at the display from the front. The connector dimensions are 20mm wide, 2.5mm thick, with a mating height of 1.2mm. The recommended mating connector is a FH12-40S-0.5SH from Hirose or equivalent. The pinout table below shows the full mapping for the DM-TFTR50-413 model:
| Pin Number | Signal Name | Description | Voltage Level |
|---|---|---|---|
| 1 | GND | Ground | 0V |
| 2 | GND | Ground | 0V |
| 3 | GND | Ground | 0V |
| 4 | GND | Ground | 0V |
| 5 | GND | Ground | 0V |
| 6 | GND | Ground | 0V |
| 7 | GND | Ground | 0V |
| 8 | GND | Ground | 0V |
| 9 | GND | Ground | 0V |
| 10 | GND | Ground | 0V |
| 11 | GND | Ground | 0V |
| 12 | GND | Ground | 0V |
| 13 | GND | Ground | 0V |
| 14 | GND | Ground | 0V |
| 15 | NC | No connect | N/A |
| 16 | NC | No connect | N/A |
| 17 | TE | Tearing effect output | 1.8V |
| 18 | RESX | Reset (active low) | 1.8V |
| 19 | CLKN | MIPI clock negative | 200mV differential |
| 20 | CLKP | MIPI clock positive | 200mV differential |
| 21 | D1N | MIPI data lane 1 negative | 200mV differential |
| 22 | D1P | MIPI data lane 1 positive | 200mV differential |
| 23 | D0N | MIPI data lane 0 negative | 200mV differential |
| 24 | D0P | MIPI data lane 0 positive | 200mV differential |
| 25 | GND | Ground | 0V |
| 26 | GND | Ground | 0V |
| 27 | GND | Ground | 0V |
| 28 | GND | Ground | 0V |
| 29 | GND | Ground | 0V |
| 30 | GND | Ground | 0V |
| 31 | GND | Ground | 0V |
| 32 | GND | Ground | 0V |
| 33 | GND | Ground | 0V |
| 34 | GND | Ground | 0V |
| 35 | GND | Ground | 0V |
| 36 | GND | Ground | 0V |
| 37 | GND | Ground | 0V |
| 38 | GND | Ground | 0V |
| 39 | LEDK | Backlight LED cathode | 0V (sink) |
| 40 | LEDA | Backlight LED anode | 12V |
Interface Timing and Data Rate Considerations
The MIPI DSI interface on this 5 inch round TFT operates at a data rate of 500 Mbps per lane, with a pixel clock of 1080 pixels per line, 1080 lines, and 60Hz refresh rate. The total pixel rate is 1080 x 1080 x 60 = 69.984 MHz, but with blanking intervals, the actual MIPI data rate is higher. The HX8399 driver supports a maximum pixel clock of 80 MHz, and the 2-lane configuration provides 1 Gbps total bandwidth, which is sufficient for 24-bit RGB color depth. The vertical blanking period is 4 lines, and horizontal blanking is 20 pixels, giving a total line time of 1100 pixels, and a frame time of 1084 lines. The pinout must handle these timing constraints, and the TE signal on pin 17 is used to synchronize frame updates in command mode, with a typical pulse width of 1ms.
Backlight Driver Integration and Pinout Implications
The backlight LED string on this 5 inch round TFT requires an external boost converter to step up the 12V supply to 18V-19.2V, but the pinout only provides LEDA and LEDK. The LEDA pin is directly connected to the anode of the LED string, and the LEDK pin is the cathode. The external driver must have a constant current sink capability of 20mA, with a maximum voltage compliance of 20V. The pinout does not include a PWM input for dimming; instead, the LEDK pin is used for current control. The datasheet recommends using a dedicated LED driver IC like the TPS61165, which can be configured for 20mA output. The backlight pinout is separate from the TFT power pins, so a separate power trace is needed for the LEDA pin, with a 100µF electrolytic capacitor for filtering.
Physical Dimensions and Pinout Alignment
The 5 inch round TFT has an active area diameter of 108mm, with a total module diameter of 120mm. The FPC connector is located at the bottom edge, with a 10mm extension from the glass. The pinout is arranged in a single row, with the 40 pins spaced at 0.5mm pitch. The connector is keyed with a notch on the left side, and pin 1 is on the left when viewing the display from the front. The FPC length is 30mm, with a 0.3mm thickness. The pinout alignment ensures that the MIPI differential pairs are routed with controlled impedance, and the ground pins are interleaved to minimize crosstalk. The datasheet specifies that the FPC should be bent at a 90-degree angle with a minimum radius of 5mm to avoid damage.
Common Pitfalls in Pinout Wiring
One common mistake is applying VCC before VCI, which can cause the HX8399 driver to latch up. The pinout requires that VCC and VCI be applied simultaneously, or VCI first, with a delay of at least 1ms before VCC. Another issue is incorrect MIPI lane polarity, where D0P and D0N are swapped, causing no display output. The pinout clearly marks the positive and negative signals, but if the PCB layout reverses them, the display will not initialize. The RESX pin must be pulled high with a 10k ohm resistor to IOVCC, otherwise the display stays in reset. The backlight LEDA pin should never be connected directly to a 12V supply without a current-limiting resistor, as the LED string will draw excessive current and burn out. The datasheet provides a typical application circuit with a 0.1µF capacitor on each power pin.
Alternative Pinout Configurations for Different Manufacturers
While the DM-TFTR50-413 uses the pinout described above, other 5 inch 1080x1080 round TFTs from different manufacturers may have different pin assignments. For example, some models use a 30-pin connector with MIPI 4-lane interface, or include SPI pins for configuration. The HX8399 driver IC supports multiple pinout options, but the round form factor requires a specific connector layout. The datasheet for the specific model must be consulted, as the pinout can vary by batch. The recommended approach is to verify the pinout with a multimeter before powering up, checking for continuity between power pins and ground. The product page for the 5 inch 1080x1080 round tft display includes the latest pinout diagram and application notes.
Thermal and Mechanical Considerations for Pinout Routing
The pinout routing on the PCB must consider thermal dissipation, as the HX8399 driver can dissipate up to 500mW under full brightness. The ground pins on the FPC connector should be connected to a large ground plane with thermal vias to spread heat. The MIPI differential pairs should