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AMC6821: Fan Control Questions

SSF
Intellectual 2025 points
Part Number: AMC6821

Hi Team,

We have a customer looking to use AMC6821 in their design to control the fan and has a couple of questions. They are trying to use this chip in as much of a standalone application as possible. They are using a 16-bit MCU with an I2C interface to the AMC6821 to load the various register settings (they have checked the various electrical specs and it looks like it should work). They will try to run the chip in “Auto Temperature Fan Mode” with [FDRC1:FDRC0] = [11] for the “maximum fast-speed calculated control mode.”

In this mode, is it required that they add a remote temperature sensor or could they leave the IN+ and IN- pins N/C?

PWM-Out: can this be attached directly to the PWM input on most 4 wire fans (with a pull-up resistor to account for the open-drain)? They hope to use this fan.

Thanks for the assistance,
SSF

  • 0
    TI__Expert 6715 points

    Hi SSF,

    Sorry for the delayed response.  I was recently assigned to this thread.  I will look into this.

    -Kelvin

  • 0
    TI__Expert 6715 points

    SSF,

    The device has the ability to detect open-circuit condition, a short-circuit to ground, or a short-circuit (IN+) to (IN–) condition. I would recommend shorting the IN+ and IN- pins together to avoid floating. Reading the fault sensor returns a value of -128°C (0x80), which means that the "maximum fast-speed calculated control mode" will choose the local for speed calculation.

    From section 13, page 7 of the fan datasheet, it's not clear if the fan driver circuit is integrated within the fan. If it is indeed integrated then the fan PWM wire (yellow wire) can be connected directly to the AMC6821 device pwm pin without additional components (pull up resistor and mosfet driver). If the driver circuit is not integrated, then the customer will have to add those external components to drive the fan.

    -Kelvin

  • 0 in reply to Kelvin Le THS
    TI__Intellectual 2025 points

    Hi Kelvin,

    Thanks for the response here. Customer is double checking with their fan manufacturer regarding your comment above.

    Regards,
    SSF