One of the most complex pages of the Raspberry Pi 4 schematic is the Power Delivery Network. The Pi 4 requires significantly more power than previous generations, transitioning its primary input to USB Type-C. The MaxLinear MXL7704 PMIC
: The schematic routes high-speed data lines to LPDDR4 SDRAM, available in 1GB, 2GB, 4GB, or 8GB configurations.
Unlike older models where the WiFi chip was mounted on an SD card-sized adapter, the Pi 4 has a surface-mount module (usually Cypress or Murata) directly on the PCB. The schematic shows how this connects via SDIO for WiFi and UART/PCM for Bluetooth. Raspberry Pi 4 Model B Full Schematic
: Details the USB-C power input circuitry, which requires a 5V/3A supply. It includes specific voltage regulators for the DDR memory and SoC rails.
While the Pi 4 boots at 3.3V signaling for legacy compatibility, the schematic supports UHS-I mode voltage switching (dropping signaling down to 1.8V) to enable much faster read/write speeds on compatible high-speed MicroSD cards. 6. The 40-Pin GPIO Expansion Header One of the most complex pages of the
The standard HDMI port was replaced with two micro-HDMI ports, enabling dual-display support at resolutions up to 4Kp60.
With the full schematic in hand, you can start designing your own custom projects. Here are some examples: Unlike older models where the WiFi chip was
Note that the GPIO pins connect directly to the SoC silicon with minimal inline resistance. They operate strictly at 3.3V logic levels . Applying 5V directly to any GPIO pin will bypass protection and permanently destroy the BCM2711 SoC. Summary Engineering Specifications Matrix Schematic Implementation Key Components Main Processor ARM Cortex-A72 Quad-Core 28nm Broadcom BCM2711 Power Management Multi-Rail Buck Regulators + LDOs MaxLinear MxL7704 USB 3.0 Controller PCIe x1 Gen 2 Interface Bridge Via Labs VL805 Ethernet PHY Direct RGMII Connection Broadcom BCM54213PE Wireless Module SDIO (Wi-Fi) / UART (BT) Cypress CYW43455 Video Engine Dual micro-HDMI (4K60 support) VideoCore VI Troubleshooting Layout & Design Notes
While this configuration worked correctly with simple, non-e-marked USB-C cables, it caused a failure with . These smart cables contain an e-mark chip that presents an Ra resistor (800-1200Ω) on one CC line. Because the Pi 4 combines both CC lines into a single resistor, the charger detects a non-standard resistance combination and mistakenly identifies the Pi 4 as an audio adapter accessory , thereby refusing to supply power.