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AM2434: Some questions about AM243 schematic

Hang Yang
Intellectual 2751 points
Part Number: AM2434

Hi all,

I have a few questions about the AM243x schematic, could you please help answering them?

  1. USB0_VBUS pin requires the VBUS voltage to be scaled down. My customer has trouble following the exact circuit in the LP, so they are using their own circuit. What's the requirement of the scaled signal? .Is there any scaling ratio my customer has to refer to?
  2. Datasheet mentioned connection requirements of MMC0 pins when MMC0 is not used, is this requirement applicable to MCC1 too? (and I2C0, I2C1 as well)
  3. There is a recommended crystal circuit in the data sheet, however, the LP uses a difference design. The crystal output connected to the device through a buffer. Customer followed the LP design but with CLK buffer removed, the crystal output is connected to the device through a 33Ohm-12pF RC filter, is this OK?
  4. There is a power-up sequence for this device, and MCU_PORz is the last to set high. Is it ok to simplify use RC to delay the MCU_PORz high signal (from 1v8 rail) to achieve this? If it is, what's the threshold of this pin?

Thanks,

Hang.

  • +1
    TI__Genius 10634 points

    Hang,

    1. USB0_VBUS pin requires the VBUS voltage to be scaled down. My customer has trouble following the exact circuit in the LP, so they are using their own circuit. What's the requirement of the scaled signal? .Is there any scaling ratio my customer has to refer to?
      1. The maximum voltage of USB0_VBUS as listed in section 7.4 (Recommended Operating Conditions) of the AM243x Datasheet is 3.465V
      2. The recommended scaling ratio can be found in section 9.2.4, Figure 9-5 in the AM243x Datasheet
    2. Datasheet mentioned connection requirements of MMC0 pins when MMC0 is not used, is this requirement applicable to MCC1 too? (and I2C0, I2C1 as well)
      1. See AM243x Datasheet Table 6-86 for ALV Package Pin Connectivity Requirements, Table 6-87 for ALX Package Pin Connectivity Requirements - they will differ between packages
      2. The connection requirements of MMC0 pins only apply to the ALV package of AM243x MCU.  This requirement is NOT applicable to MMC1 peripheral.  MMC1 pins can be treated as GPIO, and can be left NC if unused
      3. I2C0 peripheral pins on ALV Package have the following requirements (Table 6-86)
      4. I2C0 peripheral pins on ALX Package have the following requirements (Table 6-87)
      5. I2C1 peripheral pins on both ALV and ALX Packages can be treated as GPIO (NC) if unused
    3. There is a recommended crystal circuit in the data sheet, however, the LP uses a difference design. The crystal output connected to the device through a buffer. Customer followed the LP design but with CLK buffer removed, the crystal output is connected to the device through a 33Ohm-12pF RC filter, is this OK?
      1. While this is not what TI recommends, the design is reasonable.  TI cannot guarantee the correct operation of this design, and it is up to the customer to verify correct functionality.
    4. There is a power-up sequence for this device, and MCU_PORz is the last to set high. Is it ok to simplify use RC to delay the MCU_PORz high signal (from 1v8 rail) to achieve this? If it is, what's the threshold of this pin?
      1. This is ok as long as it meets the MCU_PORz Timing Requirements, found in Table 7-5 in the AM243x Datasheet 
      2. The threshold of the MCU_PORz pin is found in the AM243x Datasheet section 7.1 (Absolute Maximum Ratings) - 3.63V 

    Regards,

    Brennan