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AMC6821-Q1: RPM mode and DCY mode response time

Paddy Chao
Prodigy 220 points
Part Number: AMC6821-Q1
Other Parts Discussed in Thread: AMC6821

Hi,

We try to use AMC6821-Q1 to control and adjust fan speed from 1000rpm to 9000rpm every 250ms for thermal thrattling.

Currently we do see a high flutuation in terms of fan speed (sometimes higher and sometimes lower speed) when we use RPM mode.

May I know how soon MCU can get stable reported rpm from tachometer both in RPM and DCY mode? 

  • 0
    TI__Genius 9675 points

    Hi Paddy,

    You will need to use Software RPM mode to have the AMC6821 control the fan RPM. The monitoring and adjustment of the RPM is made once every second, or once ever 250ms, as determined by the TACH-FAST bit. The difference between the values of the TACH-DATA and TACH-Setting registers are measured and checked to see if they are ≤ 0x000A, and the adjustment will finish. (Section 8.2.8.3.2 if the datasheet)

    Can you provide a register dump so I can see how you have the AMC6821 configured? Can you also share a schematic of how the AMC6821 is connected to the fan?

    Thanks,

    Jalen