SPRABN2A March   2019  – December 2019 AM3352 , AM3354 , AM3356 , AM3357 , AM3358 , AM3358-EP , AM3359

 

  1.   AM335x Schematic Checklist
    1.     Trademarks
    2. 1 Introduction
    3. 2 Recommendations Specific to AM335x
      1. 2.1  Unused Signals
      2. 2.2  SYSBOOT Configuration and Required Termination
      3. 2.3  System Issues
        1. 2.3.1 Pinmux
        2. 2.3.2 Pullups
        3. 2.3.3 General Debug
        4. 2.3.4 Warm Reset
        5. 2.3.5 Peripheral Clocking
      4. 2.4  Low-Power Considerations
      5. 2.5  Clocking
      6. 2.6  General DDR Guidelines
        1. 2.6.1 DDR2
        2. 2.6.2 DDR3
      7. 2.7  MultiMedia Card/ (MMC)
      8. 2.8  Inter-Integrated Circuit (I2C)
      9. 2.9  LCD
      10. 2.10 Power
      11. 2.11 Touchscreen
        1. 2.11.1 If ADC/Touchscreen is not Used
      12. 2.12 USB
        1. 2.12.1 If USB0 or USB1 is not Used
      13. 2.13 External Interrupt (EXTINTn)
      14. 2.14 Ethernet
    4. 3 References
  2.   Revision History

2.6.2 DDR3

  • For point-to-point DDR3 topologies (single x16 DDR3 IC), VTT termination is not needed. Designs using two x8 DDR3 IC’s may wish to consider using a termination regulator such as the TPS51200 for the address/control signals.
  • If using VTT termination:
    • Do not use VTT termination for DDR_RESET. It should be connected directly from the AM335x to DDR.
    • If VTT regulator is disabled during low power modes (by programming EN=0 using the TPS51200), DDR_CKE should not be connected to termination resistors. The active discharge capability of the regulator can cause a brief dip on this signal, which can be problematic. This would likely be true of any VTT regulator with active discharge capability.
    • Termination for clock signals is VDDS_DDR (along with an AC coupling capacitor), whereas, all other signals need to use VTT for the termination voltage. For more details, see the device-specific data sheet.
  • If not using VTT termination, VREF should be obtained using a resistor divider (10Kohm 1%) with capacitive decoupling to ground, and should be used as a reference for both CA and DQ pins on the memory, as well as the VREF signal on AM335x. Be sure to use high precision (1%) resistors as specified in the data sheet. When not using VTT, be especially sure to follow the routing guidelines in the device-specific data sheet.