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TPS25751: Clarification on handling unused GPIOs in TPS25751S

Conor
Guru 12235 points
Part Number: TPS25751

Tool/software:

Hi,

My customer is currently designing with TPS25751S and has a question regarding the proper treatment of unused GPIO pins.

According to the datasheet (Table 5-2), GPIO0/1/2/3/4/5/6/7/11 should be “tied to ground when unused”. At the same time, the TRM describes that GPIOs can be configured as inputs with optional internal pull-downs through register settings.

To confirm:

  1. For unused GPIOs, is the recommended practice to physically tie the pins to GND on the PCB (as stated in the datasheet), rather than just leaving them unconnected and relying on internal pull-down configuration?

  2. For I2Cc_IRQ, the datasheet states “Do NOT tie to ground when unused”, while I2Ct_IRQ may be tied to GND. Could you confirm if this interpretation is correct and if any additional precautions are required?

  3. Would you also recommend configuring unused GPIOs as input/Hi-Z in firmware, even if they are already tied to GND at the board level?

We would appreciate your guidance to ensure that the unused GPIO pins are treated correctly in hardware and firmware.

Thanks,

Conor

  • 0
    TI__Mastermind 35005 points

    Hello Conor-san,

    Find the answers below:

    1. Tying them physically to ground would be the advised approach. Coming out of reset, the IOs are high-impedance so the internal pull-down isn't activated. While it won't make a huge difference if you left them floating as they high impedance coming out of reset, tying them to ground would guarantee a known state.
    2. Your understanding is correct. As this is an input for an interrupt, it is advised against putting the pin to ground.
    3. All of the IOs are already high impedance out of reset:

    Making them high-impedance would be advisable as it would help ensure no erroneous potentials are seen on the pin. 

    Best Regards,
    Tim