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PWM_OUT

TACH

INT

FAN_FAULT

Full-Speed

Continuing

TACHFailure

StatusRegisterReadtoClearInterrupt

FourthTACHFailure

FifthTACH

Failure

ThirdTACHFailure

FAN-FAULT PIN

FAN-FAULT

10kW

AMC6821

FanFailure

(belowminimumspeed

afterfifthspin-up)

PinisEnabled

AUL -ENbit=1)

AN-F

AMC6821

SBAS386C – MAY 2006 – REVISED JULY 2007

The SMBALERT pin continues to generate interrupts after the assertion of the FAN-FAULT pin because the tach

measurement continues even after a fan failure. Should the fan recover from the failure condition, the

FAN-FAULT pin signal is negated and the fan returns to normal operating speed. Figure 20 shows the operation

of a FANS interrupt.

INT is a Fan-Slow (FANS) Interrupt Through the SMBALERT Pin

Figure 20. Operation of the FAN-FAULT Pin with a Spin-Up Time = 2 Seconds

The FAN-FAULT pin is an open-drain output pin, as shown in Figure 21. When the FAN-FAULT-EN bit of

Configuration Register 1 is cleared ('0'), this pin is disabled and is always in a high-impedance status. When

FAN-FAULT-EN = 1, the pin is enabled and the status indicates a fan-failure. The pin asserts low when a fan

failure occurs. FAN-FAULT is negated when the fan returns to normal speed.

Figure 21. FAN-FAULT Pin

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