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TCA9535: If we not use the extra GPIO then?

Yash Dave
Prodigy 95 points

Part Number: TCA9535

TCA9535RTWR.png

We are using the TCA9535RTWR IC in our product. I have attached the image for your reference.

As shown in the figure, ports P15, P16, and P17 are tied to GND with 100k pull-down resistors.

Can we remove the pull-down resistors on these pins and leave them as NC (Not Connected)?

Please advise.

  • +1
    TI__Guru 60808 points

    Hi Yash,

    You can leave them NC by removing PD 100k resistors, but I would suggest that you set P15/P16/P17 as OUTPUT's to prevent excess ICC current consumption from a floating CMOS input. 

    Any reason you have not considered TCA9555RTWR as this device implements internal 100k PU resistors on all IO pins. 

    Regards,

    Tyler

  • 0
    Prodigy 95 points

    We had previously selected the TCA9555RTWR, but after comparing it with the TCA9535RTWR, the main difference was the cost. Therefore, we decided to select the TCA9535RTWR IC.

    As per your suggestion, we can remove the pull-down resistors. However, we will ensure that P15, P16, and P17 are configured as outputs to prevent unnecessary current consumption. Is that correct?

    Also, regarding the 100k pull-up resistor shown in the image — should we mount a pull-up resistor on each port?

    Can we remove the Pull up resistor? please suggest this.

  • +1 in reply to Yash Dave
    TI__Guru 54611 points

    Hi Yash,

    We are still looking into this and will provide a response shortly.

    Regards,

    Jack

  • +1 in reply to Yash Dave
    TI__Guru 60808 points

    Hi Yash,

    Yash Dave said:
    As per your suggestion, we can remove the pull-down resistors. However, we will ensure that P15, P16, and P17 are configured as outputs to prevent unnecessary current consumption. Is that correct?

    Yes. This is to prevent excess current consumption through ICC, as well as prevent an unwanted interrupt from triggering. 

    Yash Dave said:
    Also, regarding the 100k pull-up resistor shown in the image — should we mount a pull-up resistor on each port?

    I do not know the intricacies of your system. If you can guarantee that each of the inputs will be driven by a GPIO either to VCC or GND and there is no tri-state or float state, then you can remove the pull-up resistors. 

    IF you expect the pin to float at any point, this could cause undesired interrupt triggers and increased ICC current consumption. 

    Regards,

    Tyler

  • 0 in reply to Jack Guan
    Prodigy 95 points

    Ok , and thanks for the support.

  • 0 in reply to Yash Dave
    TI__Guru 60808 points

    Hi Yash,

    You're welcome. IF any further questions, please feel free to re-open this thread or submit a new question. Thanks. 

    Regards,

    Tyler