What is the pinout of HDMI to 4 lane MIPI DSI adapter?

The pinout of an HDMI to 4 lane MIPI DSI adapter is not standardized across all manufacturers, but based on common designs from brands like Toshiba, Texas Instruments, and dedicated display module suppliers, a typical pinout maps HDMI signals to a 30-pin or 40-pin flexible flat cable (FFC) connector. For a 4-lane MIPI DSI output, the adapter board converts HDMI’s TMDS (Transition Minimized Differential Signaling) data and clock lines into MIPI D-PHY signals. A standard configuration includes: 4 differential data lanes (D0+, D0-, D1+, D1-, D2+, D2-, D3+, D3-), 1 differential clock lane (CLK+, CLK-), power supply pins (3.3V, 1.8V, and GND), control signals like TE (Tearing Effect), RESET, backlight enable (BL_EN), PWM (Pulse Width Modulation) for brightness, I2C lines (SCL, SDA) for display configuration, and sometimes GPIOs for interrupt or touch. The HDMI input side typically uses a Type A connector with 19 pins, where pin 1 is TMDS Data2+, pin 2 is TMDS Data2 Shield, pin 3 is TMDS Data2-, pin 4 is TMDS Data1+, pin 5 is TMDS Data1 Shield, pin 6 is TMDS Data1-, pin 7 is TMDS Data0+, pin 8 is TMDS Data0 Shield, pin 9 is TMDS Data0-, pin 10 is TMDS Clock+, pin 11 is TMDS Clock Shield, pin 12 is TMDS Clock-, pin 13 is CEC (Consumer Electronics Control), pin 14 is Reserved (NC), pin 15 is SCL (DDC Clock), pin 16 is SDA (DDC Data), pin 17 is DDC/CEC Ground, pin 18 is +5V Power, and pin 19 is Hot Plug Detect. The adapter board’s bridge chip, often a TC358870XBG from Toshiba or an LT8912B from Lontium, handles the protocol conversion, re-timing, and voltage level shifting. The MIPI DSI output side uses a 0.5mm pitch FFC connector, with pin assignments varying by vendor. For example, a common 30-pin layout for a 4-lane MIPI DSI output is: pin 1 GND, pin 2 D0+, pin 3 D0-, pin 4 GND, pin 5 D1+, pin 6 D1-, pin 7 GND, pin 8 CLK+, pin 9 CLK-, pin 10 GND, pin 11 D2+, pin 12 D2-, pin 13 GND, pin 14 D3+, pin 15 D3-, pin 16 GND, pin 17 RESET, pin 18 TE, pin 19 BL_EN, pin 20 PWM, pin 21 VCC (3.3V), pin 22 VCC (1.8V), pin 23 SCL, pin 24 SDA, pin 25 GND, pin 26 GND, pin 27 NC, pin 28 NC, pin 29 VCC (3.3V), pin 30 GND. Some adapters use a 40-pin connector to include additional GPIOs or touch interface signals. Always verify the specific datasheet of your hdmi to 4 lane mipi dsi adapter because pin order can be reversed or swapped between manufacturers.

Signal mapping and electrical characteristics

To understand the pinout fully, you need to grasp how HDMI signals are remapped. HDMI uses four TMDS differential pairs: three for data (channels 0, 1, 2) and one for clock. Each TMDS pair operates at a voltage swing of 3.3V with a differential impedance of 100 ohms. The MIPI D-PHY, on the other hand, uses a low-voltage differential signaling (LVDS) style with a common mode voltage of 200mV and a differential swing of 200mV to 400mV, operating at 1.2V or 1.8V logic levels. The adapter’s bridge chip converts the 3.3V TMDS signals into 1.2V MIPI signals, re-clocks them, and splits the data into up to 4 lanes. The MIPI DSI clock lane runs at a frequency that is typically half the pixel clock, but for 4-lane mode, the clock frequency can be as low as one-quarter of the pixel clock to reduce EMI. For example, a 1080p display at 60Hz with a pixel clock of 148.5MHz would require a MIPI clock frequency of 74.25MHz in 4-lane mode. The pinout must support this high-speed differential routing with controlled impedance traces on the PCB. The adapter board usually includes a 25MHz or 27MHz crystal oscillator for the bridge chip’s PLL (Phase-Locked Loop), which generates the MIPI clock. Power supply pins on the MIPI side are critical: 3.3V for the display panel’s logic, 1.8V for the bridge chip’s I/O, and sometimes 1.2V for the MIPI PHY. The GND pins are interspersed between differential pairs to maintain signal integrity, a practice called “ground stitching.” The TE pin (Tearing Effect) is used by the display to signal the adapter that it is ready for a new frame, preventing tearing in video playback. The RESET pin is active-low and must be held low for at least 10ms after power-up, then released high. The BL_EN pin controls the backlight driver, typically active-high, and the PWM pin accepts a 1kHz to 30kHz signal for brightness dimming. The I2C pins (SCL, SDA) are used to read the display’s EDID or configure the bridge chip’s registers. Some adapters also include an interrupt pin (INT) for touch panels or a GPIO for display ID detection.

Common connector types and pin count variations

The MIPI DSI output connector on HDMI adapters is almost always a 0.5mm pitch FFC/FPC (Flexible Flat Cable) connector, with pin counts ranging from 30 to 50 pins. The most common are 30-pin and 40-pin, but 50-pin connectors exist for displays with touch or additional features. In a 30-pin configuration, the pinout typically follows the sequence: differential pairs are grouped together, with each pair having a ground pin on both sides. For example, lane 0 (D0+, D0-) is surrounded by GND pins to reduce crosstalk. The clock lane (CLK+, CLK-) is placed in the middle of the data lanes to minimize skew. In a 40-pin connector, you often see additional pins for touch interface (I2C or SPI), backlight power (VLED+ and VLED-), and extra GPIOs. Some adapters use a 31-pin connector, which is a 30-pin with an extra key pin for alignment. The HDMI input side uses a standard Type A female connector, but some adapters include a micro-HDMI (Type D) or mini-HDMI (Type C) for space-constrained applications. The adapter board’s PCB is usually 4-layer or 6-layer to maintain controlled impedance for the differential pairs. The trace width for MIPI signals is typically 0.1mm to 0.15mm, with a spacing of 0.15mm to 0.2mm, and the impedance target is 100 ohms differential, 50 ohms single-ended. The bridge chip’s datasheet will specify the exact pin mapping from HDMI to MIPI, including the polarity of each differential pair. For instance, the Toshiba TC358870XBG maps HDMI TMDS channels to MIPI lanes as follows: TMDS Data0 to MIPI Lane 0, TMDS Data1 to MIPI Lane 1, TMDS Data2 to MIPI Lane 2, and TMDS Clock to MIPI Clock. The fourth MIPI lane (Lane 3) is derived from the TMDS Data2 channel when the HDMI source is in 3D mode or uses a higher pixel clock. Some adapters also support 2-lane mode, where only two data lanes are active, which reduces the pin count but limits resolution to 720p or lower.

Power sequencing and voltage requirements

The pinout includes multiple power pins that must be sequenced correctly to avoid damaging the display or the adapter. The typical power-up sequence is: apply 3.3V first, then 1.8V, then 1.2V (if used), and finally the MIPI signals. The power-down sequence is the reverse. The adapter board often includes a power management IC (PMIC) or LDOs (Low Dropout Regulators) to generate these voltages from the HDMI 5V input. The HDMI 5V pin (pin 18) provides up to 50mA, which is enough for the bridge chip but not for the display backlight. The backlight power is usually supplied by an external source or a separate boost converter on the adapter. The pinout for backlight typically includes VLED+ (12V or 24V) and VLED- (GND), but some adapters use a single BL_EN pin to control an external backlight driver. The I2C pins (SCL, SDA) are open-drain and require pull-up resistors to 3.3V, typically 4.7k ohms. The PWM pin can be driven by a 3.3V or 5V logic signal, but the frequency and duty cycle must match the display’s backlight driver specifications. The TE pin is an output from the display, sending a pulse when the display is ready for the next frame. The pulse width is typically 1ms to 10ms, and the polarity is active-high or active-low depending on the display. The RESET pin must be held low for at least 10ms after power-up, and the datasheet of the display will specify the exact timing. Some adapters include a built-in delay circuit to handle this automatically.

Data lane mapping and protocol details

The MIPI DSI protocol uses a packet-based structure where each lane carries data in bursts. The bridge chip converts HDMI’s TMDS stream into MIPI DSI packets, including video data, blanking packets, and sync packets. The pinout must support the D-PHY’s high-speed (HS) and low-power (LP) modes. In HS mode, the differential voltage swing is 200mV to 400mV, and the data rate can be up to 1.5Gbps per lane for a total of 6Gbps in 4-lane mode. In LP mode, the voltage swing is 1.2V, and the data rate is 10Mbps, used for control signals like LP-11, LP-01, LP-00, and LP-10. The pinout includes the clock lane, which is always in HS mode during data transmission, and the data lanes can switch between HS and LP modes. The bridge chip handles the state machine transitions. The I2C interface on the MIPI side is used to read the display’s configuration registers, such as the panel ID, resolution, and timing parameters. The adapter’s firmware may also use the I2C bus to update the bridge chip’s firmware or adjust the output timing. The pinout for I2C includes SCL (clock) and SDA (data), both with pull-up resistors. Some adapters also include a dedicated I2C address for the display, typically 0x3C or 0x3D. The GPIO pins on the MIPI connector can be used for display detection, touch interrupt, or backlight control. For example, a GPIO might be configured as an input to detect a display’s presence by reading a pull-up or pull-down resistor on the display’s PCB.

Physical layout and signal integrity considerations

The pinout is not just a list of pins; it’s a critical factor in signal integrity. The adapter board’s PCB layout must ensure that each MIPI differential pair has equal length traces to minimize skew. The typical skew tolerance for MIPI is 0.2ps per meter, but for a short PCB trace, the tolerance is 0.1mm to 0.2mm. The ground pins in the pinout provide a return path for the differential signals, reducing loop area and EMI. The FFC connector’s pinout often has a staggered arrangement where signal pins are separated by ground pins to reduce crosstalk. For example, a 30-pin connector might have the pattern: GND, D0+, D0-, GND, D1+, D1-, GND, CLK+, CLK-, GND, D2+, D2-, GND, D3+, D3-, GND, and then control signals. The power pins are usually grouped together at the end of the connector to avoid coupling noise into the high-speed signals. The FFC cable itself must be rated for high-speed signals, with a characteristic impedance of 100 ohms differential. The cable length should be kept under 10cm to avoid signal degradation. The adapter board’s HDMI input also requires careful routing. The TMDS pairs must have equal length traces, typically within 0.5mm of each other, and the impedance should be 100 ohms differential. The HDMI connector’s shield pins (pin 2, 5, 8, 11, 17) must be connected to the PCB ground plane with low impedance. The adapter board’s bridge chip is usually a BGA (Ball Grid Array) package with 0.5mm or 0.65mm pitch, requiring multiple PCB layers for routing. The pinout from the bridge chip to the FFC connector is often a direct mapping, but some adapters include ESD protection diodes on the MIPI lines, which add capacitance and must be accounted for in the impedance calculation.

Compatibility and troubleshooting based on pinout

If you’re using an HDMI to 4-lane MIPI DSI adapter, the pinout determines which displays are compatible. Many displays use a standard 30-pin or 40-pin pinout, but there are variations. For example, some displays swap the order of the data lanes or use a different voltage for the backlight enable. The adapter’s pinout must match the display’s pinout exactly, or you’ll need a custom FFC cable or a pinout converter board. The most common mismatch is the position of the TE pin or the RESET pin. Some displays use a 2-lane MIPI interface, which requires only two data lanes, and the other two lanes are left unconnected. The adapter can be configured via I2C to disable the unused lanes. The bridge chip’s registers can be read or written using a USB-to-I2C adapter, allowing you to change the lane mapping, clock polarity, or data polarity. The pinout for the I2C interface is usually pins 23 and 24 on a 30-pin connector, but some adapters use different pins. The power supply voltage is another common issue: some displays require 3.3V for the logic, but others require 1.8V. The adapter’s pinout should include both 3.3V and 1.8V pins, but if your display needs 1.2V, you’ll need an external regulator. The backlight voltage is often 12V or 24V, and the adapter may not provide this voltage directly. In that case, you need to connect an external backlight driver to the BL_EN and PWM pins. The PWM frequency must match the display’s backlight driver, typically 1kHz to 30kHz. If the display flickers, the PWM frequency is too low or the duty cycle is too high. The TE pin is essential for tear-free video, but if your display doesn’t support TE, you can leave it unconnected. The RESET pin must be driven high after power-up, but some adapters have a pull-up resistor that does this automatically. If the display doesn’t power on, check the voltage on the RESET pin with a multimeter. It should be 3.3V or 1.8V, depending on the display’s logic level. The I2C bus can be used to read the display’s EDID, which contains the resolution and timing information. If the display is not detected, the I2C lines might be swapped or the pull-up resistors are missing. The pinout of the adapter’s I2C interface is usually 3.3V, but some displays use 1.8V I2C, requiring a level shifter.