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LMG1205: LMG1205 Inputs and External Pulldown Resistors

Stefan Weller
Prodigy 65 points
Part Number: LMG1205

Tool/software:

Hello, I have a question about the LMG1205.


In the datasheet, section 7.3.1 Input and Output states:

"If the input signal for either of the two channels, HI or LI, is not used, the control pin must be tied to either VDD or VSS. These inputs must not be left floating."

However, in the Electrical Characteristics it also mentions that there is an internal pulldown resistor.

My question: Even when using HI and LI, is it still recommended to add  external pulldown resistor each pin? If no external pulldown is present, what kind of malfunction or failure mode could occur – or would there be none at all?

Kind regards

Stefan Weller

  • 0
    TI__Prodigy 600 points

    Hi Stefan, 

    If you are using HI or LI, then it isn't recommended to add an external pulldown resistor because there is already a strong internal pull down. The datasheet recommendation to not leave the input pins floating is good practice to reduce noise introduced to the system. There should be no issues if you just use the internal pull down resistor.  

    Thanks,

    Annabelle

  • 0 in reply to Annabelle Alemand
    Prodigy 65 points

    Hi Annabelle,

    Thank you very much for the quick response – I really appreciate that.

    Just one more thing to add: I’m using a TI microcontroller, and during boot-up, the GPIO pins for LI and HI could be floating (high-Z). Would you still consider the internal pulldown to be sufficient in that case?

    Best regards
    Stefan

  • +1 in reply to Stefan Weller
    TI__Prodigy 600 points

    Hi Stefan,

    Yes, I would consider the internal pulldown to be sufficient. The boot up time should be very short, so any noise introduced by the floating MCU pins should not be an issue and can be handled by the internal pulldown.

    Thanks,

    Annabelle