Precision 24-Bit ADC Signal Chain Layout Ground Plane Splitting for Medical Transducers

Architectural Challenge

High-throughput automotive networks require migrating from Classical CAN (1 Mbps max) to CAN-FD (up to 5-8 Mbps in data phase). Achieving bit-timing margins without frame errors requires precise register configuration.

1. Nominal vs Data Phase Timing Segments

• Nominal Bit Rate (Arbitration): Typically 500 kbps across network nodes.
• Data Bit Rate (Payload): 2 Mbps or 5 Mbps with Transceiver Delay Compensation (TDC).

#include "stm32g4xx_hal.h"

void MX_FDCAN1_Init(FDCAN_HandleTypeDef *hfdcan) {
    hfdcan->Instance = FDCAN1;
    hfdcan->Init.FrameFormat = FDCAN_FRAME_FD_BRS;
    hfdcan->Init.Mode = FDCAN_MODE_NORMAL;
    hfdcan->Init.AutoRetransmission = ENABLE;
    hfdcan->Init.TransmitPause = ENABLE;
    
    // Nominal Bit Timing (500 kbps, 80% sample point at 80 MHz clock)
    hfdcan->Init.NominalPrescaler = 1;
    hfdcan->Init.NominalSyncJumpWidth = 16;
    hfdcan->Init.NominalTimeSeg1 = 127;
    hfdcan->Init.NominalTimeSeg2 = 32;
    
    // Data Bit Timing (2 Mbps, 75% sample point)
    hfdcan->Init.DataPrescaler = 1;
    hfdcan->Init.DataSyncJumpWidth = 4;
    hfdcan->Init.DataTimeSeg1 = 29;
    hfdcan->Init.DataTimeSeg2 = 10;
    
    HAL_FDCAN_Init(hfdcan);
}

2. Physical Layer Integrity & Termination

1. Split Termination: Use two 60Ω resistors with a 4.7nF capacitor to ground for common-mode filtering.
2. Common Mode Choke: Place a CAN-FD rated choke (e.g. TDK ACT1210R) within 15mm of the connector.
3. ESD Protection: Dual bidirectional TVS diode array (PESD2CANFD) rated for 30kV contact discharge.

3. Firmware Queue & Task Priority Architecture

• Isolate the FDCAN RX interrupt to a dedicated high-priority FreeRTOS task using direct-to-task notifications.
• Ensure ring buffers are sized to prevent overrun during burst message traffic.