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TMS320F28062: Connect C2000 with 5V device via SPI

Young Hu
Expert 4185 points
Part Number: TMS320F28062


Hi Champs,

My customer is designing traction control board using F28062. In their system, there is a SPI slave device(5V powered) connected to C2000(master). The MOSI line is 3.3V, and can be accepted by SPI slave. The want to know whether current-limiting resistor can be used to be the level shifter circuit as follows.

If disabling C2000 GPIO's internal pull-up resistor, and if current-limiting resistor can share 1.5V, and also internal clamp diode can be used, looks this solution is feasible. Would you kindly help to check whether this method can be implemented to this simple 5V to 3.3V level shifter? If so, what's the proper resistor value?

Thanks.

Regards,

Young

  • 0
    Guru 30330 points
    Young,
    This configuration is not something that we support. The internal ESD Diode is not intended for continuous operation, nor have we validated such a condition. In addition, the user will need to ensure that the 5V supply is never powered before the 3.3V for the F28062. I would recommend using a simple level shifter IC. TI offers many and they eliminate any of the potential issues that using a discrete solution may cause.

    Thanks,
    Mark
  • 0 in reply to Mark Labbato
    TI__Expert 4185 points
    Mark,
    Thanks for your explanation.
    I will talk to customer.
    Thanks.

    Young
  • 0 in reply to Mark Labbato
    TI__Expert 4185 points

    Hi Mark,

    Customer improved the level shifter circuit as follows. External Schottky diode is added to clamp input signal to 3.3V, and also resistor divider is to share the voltage.

    Do you think this workable? 

    Thanks.

    Regards,

    Young