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  • TI Thinks Resolved

TCA9539: Rds on when I/O pin has pull low

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Replies: 2

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Part Number: TCA9539

Hi Sir,

If the TCA9539 I/O pin has 10K ohm pull low resistor as below, how is the Rds on for the TCA9539?

Thanks

  • Hi Anne,

    I-V curves can be found in section 6.9 of the datasheet. They display the I-V characteristics of the I/O pins at different temperature and supply levels. The device will be able to sink plenty enough current to pull the WP line low with a 1k pull-up to 3.3v.
    What is your concern in adding the 10k-Ohm pulldown? Are you concerned that the device will not meat the threshold required for FRU?

    Regards,
    Eric

  • We can assume that Rdson is << than 10k ohms. Then say that IoL will be about 3.3V/1k when driving low. this gives around 3.3mA of IoL (we assume Rdson is much lower than 1k).

    According to the datasheet, VoL will be 0.4V or lower at 3mA. This means Rdson will be 133 ohms or less.

    -Bobby

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