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TPS1H100-Q1: For protection with serial resistor

Lee, Sam
Expert 6025 points
Part Number: TPS1H100-Q1

Hi team,

-. In TPS1H100-Q1 datasheet, can you explain more details about the following sentense?

7.3.4.10 Protection for MCU I/Os

"Also, for proper protection against loss of GND, TI recommeds 4.7kohm when using 3.3-V MCU I/Os; 10kohm is for 5-V applications.

-. What is the reason why it uses 4.7kohm? If uses higher resistor, what is the expected problem?

Thanks,

Sam Lee

 

Thanks,

Sam Lee

  • 0
    TI__Mastermind 28200 points
    Hello,

    As you can see the block diagram in figure 43, the TPS1H100 I/O pins have ESD diodes. The MCU pins have ESD diodes/body diode as well. In case of disturbance such as ISO pulses, loss of battery or ground, positive or negative volatge spikes may appear on GND and I/O pins. The ESD diodes may be forward biasing or breaking down. The resistors role is to limit the current circulation in both cases and protect the TPS1H100 I/O and the MCU's as well.
    There is no issue to use higher resistor with 3.3V MCU. The 4.7K is recommended with 3.3V for making sure the TPS4H100 I/O pins receive the correct logic level from MCU in any circumstances. For example voltage drop across the MCU I/O, internal pull down resistance change and logic level tolerances across temperature.

    Regards