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Original question:

TMP117: Pull-up value for SDA/SCL

TMP117: pull-up value for ALERT

R.Fukunaga
Expert 2525 points
Part Number: TMP117

Hi all,

I would like to ask about the pull-up resistance value.

Is it okay to set the pull-up resistance of the ALERT pin to 100 kΩ instead of 5 kΩ?

If Vdd=3.3 V, a current of about 33uA will flow through a 100 kΩ resistor.

Since the Input Leakage current is said to be 0.1uA, I think the current will flow through the resistor without any problem and it can be set to Low.

Let me know if you have any problems.

Best Regards,

Ryusuke

  • +1
    TI__Expert 7170 points

    Hi Ryusuke-san,

    Adding a 100k ohm pullup resistor to the alert line will increase the RC constant of the circuit making it 20 times slower vs. using a 5k ohm. It should work ok, but you need to be mindful of the added delay when it comes to sampling the alert line with an MCU and reading the configuration register--i.e. in certain cases you may clear the alert flag before the line drops low. This will ultimately depend on parasitic capacitance on the traces.

    Best regards,

    Simon Rojas