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LM96163: Tachometer input - Resistor network

Rutvik Naik
Prodigy 110 points

Part Number: LM96163

Hello TI team,

I am using the LM96163CISDX/NOPB fan controller in my design and would like to clarify the recommended resistor network for the tachometer (TACHO) input.

image.png

 

The datasheet specifies a 1K - 13K - 10K resistor network with a pull-up voltage of either 5V or 12V. Is there a specific reason this network must be implemented as shown, or is there flexibility in selecting these resistor values? 

 

Thank you!

  • +1
    TI__Mastermind 45445 points

    The TACH pin has an Absolute Maximum Rating of 6V. When connecting the output from a 12V fan, you must protect the LM96163 from being exposed to 12V. That is the only purpose for the resistor network. The resistors can be omitted when lower voltage fans are used. The signal that reaches the TACH pin must also meet the VIH and VIL input voltage specifications.

    thanks,

    ren