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AMC6821: Can it operate w/o a CPU?

John Garrett
Expert 4220 points
Part Number: AMC6821

I have a customer who needs a good fan controller that operates as a standalone unit - hence requires no I2C to start / no CPU to control its functionality.  Please clarify if the AMC6821 can be used in a system w/o a CPU.  The datasheet says:

“The device does not perform any monitoring functions until the START bit of Configuration Register 1 is set ('1').”

However, my understanding is that the AMC6821 can be used without a CPU.  Per the product folder:  "Auto Temperature-Fan mode is an intelligent, closed-loop control that optimizes fan speed according to user-defined parameters. This mode allows the AMC6821 to run as a stand-alone device without CPU intervention; the fan can continue to be controlled (based on temperature measurements) even if the CPU or system locks up. Software-RPM mode is a second closed-loop control. In this mode, the AMC6821 adjusts the PWM output to maintain a consistent fan speed at a user-specified target value; that is, the device functions as a fan speed regulator. Software-RPM mode can also be used to allow the AMC6821 to operate as a stand-alone device."

Hope the part can be used without a CPU.  If it can, I have some follow-up questions:

·       What mode should we operate in?

How do we set the thermal limit for the over-temperature fail?

·       How do we set the target temperature for the auto mode?

Thanks, John Garrett TI-AFA

  • 0
    TI__Expert 7845 points
    I will look into this and get back to you.

    -Kelvin
  • 0
    TI__Expert 7845 points

    John,

    Based on what I have read you do need to set the START bit after POR using a controller/cpu to enable the device operation.  

    "After programming, the AMC6821 runs stand-alone, even without the intervention of the micro-controller."

    This implies you need to configure the device first.

    Please refer to pg. 25 of the datasheet for the descriptions of the three modes:

    • software DCY control
    • software RPM control
    • auto temperature fan control

    Upon POR, the default is auto mode.  

    Please refer to pg.27 for the description of how to set the target temperature in auto mode (e.g. setting the Local TEMP-FAN Control Register, Remote TEMP-FAN Control Register, and the DCY-RAMP Register. ).

    -Kelvin