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MSP430FR5969-SP: MSP430FR5969-SP 3.3V interface to 1.8V

Zeev Leshem
Prodigy 70 points
Part Number: MSP430FR5969-SP

Hello,

The question is about MSP430 mode of work while being powered with 3.3V VDD against 1.8V I/O GPIOs (input and output) from external devices

We need to know the Vit+, Vit- for 3.3V – I’m afraid that 1.8V as an input might be marginal for the MSP430 to be understood as '1'

 

Regarding MSP430 output side:

When driving output toward 1.8V it could be done with 3-state buffer and external pull-up to 1.8V.

I didn’t see 3-state output option for I/O – Is there a way to activate it?

Thanks,

Zeev.

  • 0
    Guru 18835 points

    The usual way to tristate an output is to make it an input.

  • 0
    TI__Mastermind 26046 points

    Hi Zeev,

    At VCC = 3.3V, we cannot directly state what the Min and Max VIT+ and VIT- voltages will be since that VCC is not listed in the table. The only VCC level that will be acceptable is VCC = 2.2V as the 1.8V will exceed the threshold without issue.

    A good workaround is the TXS0104 bidirectional level shifter. You can set the OE pin high to allow GPIOs to talk from the MSP430 to the 1.8V external device. Or you can set the OE pin low to put the outputs in 3-state mode.

  • 0 in reply to Aaron Barrera
    Prodigy 70 points

    Hi Aaron,

    Thanks for the answer.

    I'm aware of using the option of using external level shifter.

    However, TXS0104 isn't space grade and I don't think TI have such product available.

    We are trying to minimize external devices and have only the MSP430 to enhance system reliability 

  • 0 in reply to Zeev Leshem
    TI__Mastermind 26046 points

    Hi Zeev,

    Thanks for your patience. 

    Texas Instruments does not have space-grade level shifters. 

    The only solution that can be implemented is that VCC must be greater than 1.99V in order to allow the GPIOs to communicate at 1.8V, as long as host MCU VDD = 1.8V. Therefore the 2.2V specification is used in the datasheet, but this requires external 2.2V LDO. This is the only way we know for 1.8V I/O to work. 

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