SDAA172 March   2026 AM13E23019

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2Schematic Design
    1. 2.1  Package and Device Selection
    2. 2.2  Digital Peripherals
      1. 2.2.1 GPIO
      2. 2.2.2 XBARs
      3. 2.2.3 EPI
      4. 2.2.4 MCAN
      5. 2.2.5 UNICOMM
        1. 2.2.5.1 UART
        2. 2.2.5.2 I2C
        3. 2.2.5.3 SPI
    3. 2.3  Control Peripherals
      1. 2.3.1 eQEP and eCAP
      2. 2.3.2 Timers
    4. 2.4  Analog Peripherals
      1. 2.4.1 Choosing Analog Pins
      2. 2.4.2 Analog Voltage Reference
      3. 2.4.3 ADC Inputs
    5. 2.5  Multiplexed Peripherals
    6. 2.6  Power
      1. 2.6.1 Discrete Power Solution
      2. 2.6.2 Power Decoupling and Filtering
      3. 2.6.3 Analog Voltage Reference
      4. 2.6.4 VSS/VSSA
      5. 2.6.5 Power Consumption
    7. 2.7  Reset
      1. 2.7.1 nRST Pin
      2. 2.7.2 BSL Invoke Pin
      3. 2.7.3 WAKE from LPM Pins
      4. 2.7.4 WAKE From STOP/STANDBY Modes
      5. 2.7.5 WAKE from SHUTDOWN Mode
      6. 2.7.6 AM13E230x Hardware Platform Examples
    8. 2.8  Clocking
      1. 2.8.1 Internal Oscillators
      2. 2.8.2 External Crystal Oscillator (XTAL)
      3. 2.8.3 Digital Clock Input
      4. 2.8.4 Output Clock Generation
    9. 2.9  Debugging and Emulation
      1. 2.9.1 Debug Interfaces
        1. 2.9.1.1 JTAG and SW-DP
        2. 2.9.1.2 Trace
      2. 2.9.2 Debug Probes
    10. 2.10 Boot Interfaces
      1. 2.10.1 UART Bootloader
      2. 2.10.2 I2C Bootloader
      3. 2.10.3 MCAN Bootloader
    11. 2.11 Unused Pins
  6. 3PCB Layout Design
    1. 3.1 Layout Design Overview
      1. 3.1.1 Recommended Layout Practices
      2. 3.1.2 Board Dimensions
      3. 3.1.3 Layer Stackup
        1. 3.1.3.1 4-Layer Stackup
        2. 3.1.3.2 6-Layer Stackup
    2. 3.2 Vias
    3. 3.3 Recommended Board Layout
    4. 3.4 Placing Components
    5. 3.5 Ground Planes
    6. 3.6 Signal Routing Traces
    7. 3.7 Thermal Considerations
  7. 4EOS, EMI/EMC, ESD Considerations
    1. 4.1 Electrical Overstress
    2. 4.2 EMI and EMC
    3. 4.3 Electrostatic Discharge
  8. 5Summary and Checklist
  9. 6References
  10. 7Revision History

4.2 EMI and EMC

Electromagnetic Compatibility (EMC) describes the ability of electronic components to function properly amidst interferences and disturbances from other systems. The most important to consider is Electromagnetic Interference (EMI) – radio frequency energy emitted by the MCU device and other nearby devices. This type of disturbance can propagate throughout a system and impact devices through conduction and radiation.

Reducing EMI effects to the system itself should be top priority when it comes to minimizing EMC risk, but it is also important to ensure that EMI emitted from the system in both radiation and conduction does not exceed the maximum allowed per local regulation standards. It is good practice to minimize radiated and conducted EMI to levels far below the limits for certification in order to avoid any project delays due to this easily mitigated component of design. Similarly, the PCB system should be designed with adequate shielding to function properly even while being in contact with radiated and conducted EMI energy from other systems around it.

The majority of system components, including the PCB, connectors, and cables serve as a source of EMI. PCB systems that make use of high frequencies and fast-switching currents & voltages require special care as all of the signal traces act as antennas which radiate electromagnetic energy well.

The five main sources of radiation that designers should look to minimize are:

  1. Digital signals propagating on PCB traces
  2. Current return loop areas
  3. Inadequate power supply filtering or decoupling
  4. Transmission line effects
  5. Lack of power and ground planes

Power supplies are another major contributor to EMI, especially if they are switching or are being switched using PWM signal outputs from the MCU device. It is important to follow the recommended layout for each power supply found in the product’s data sheet.

To reduce unwanted EMI generated by the PCB system and its components, the following guidelines should be met throughout the schematic and PCB layout design process:

  • Use decoupling capacitors on all power inputs to IC devices. Follow the recommended capacitor values as outlined in each IC data sheet. Be aware that every capacitor has a self-resonant frequency.
  • Provide adequate filter capacitors on power supply sources. These capacitors should have low equivalent series inductance (ESL).
  • Create ground planes in available spaces on the PCB routing layers. Connect these ground polygons to the main inner ground plane with vias. Creating a quarter-inch via grid across the PCB is ideal.
  • Keep the current loops as small as possible. Add as many required decoupling capacitors as possible. Always apply current return rules to reduce loop areas.
  • Keep high-speed signals away from other signals and especially away from input and output ports or connectors.
  • Apply current return rules to connect the grounds together while isolating the ground plane for the analog portion. If the project does not use ADC and there are no analog circuits, do not isolate grounds.
  • Avoid connecting the ground splits with a ferrite bead. At high frequencies, a ferrite bead has high impedance and creates a large ground potential difference between the planes or PC board stack-up, add as many power and ground planes as possible. Keep the power and ground planes next to each other to ensure low-impedance stack-up or large natural capacitance stack-up.
  • Add an EMI pi filter on all the signals exiting the box or entering the box.
  • If the system fails EMI tests, find the source by tracing the failed frequencies to their source. For example, assume the design fails at 300 MHz but there is nothing on the board running at that frequency. The source is likely to be a third harmonic of a 100 MHz signal.
  • Determine if the failed frequencies are common mode or differential mode. Remove all the cables connected to the box. If the radiation changes, it is common mode. If not, then it is differential mode. Then, go to the source and use termination or decoupling techniques to reduce the radiation. If it is common mode, add pi filters to the inputs and outputs. Adding a common choke onto the cable is an effective solution but an expensive method for EMI reduction.