MAX6639 Evaluation Kit

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Change the count by entering the value into the

Tachometer count edit box and pressing the Write

button.

Fan 1 and Fan 2 Pulses per Revolution

and Min Tach Count

The fan 1 Pulses per Revolution and Min Tach Count

(0x24) and fan 2 Pulses per Revolution and Min Tach

Count (0x25) group boxes set the number of tachome-

ter pulses per revolution of the fan and the minimum

allowable tachometer count (maximum speed) for the

fan (Figure 5). The Pulses per Revolution and Min

Tach Count (0x25) group box is not shown, but can be

accessed by navigating to the Fan 2 tab sheet from

Figure 5.

The Tach. Pulses per Rev. drop-down list setting has

four options: 1, 2, 3, or 4.

The Min tachometer count edit box can be set to any

value between 0 and 63. Read the pulses per revolu-

tion and minimum tachometer count by pressing the

Read button. Change the pulses per revolution by

selecting the desired number from the drop-down list.

Change the minimum tachometer count by entering the

value into the edit box. Press the Write button to apply

the changes.

Fan 1 and Fan 2 Duty Cycle

The Duty Cycle tab sheet (Figure 6) contains the PWM

duty cycle value. When operating in RPM mode, this

value is controlled by the MAX6639. In PWM mode, this

is the desired (target) PWM duty-cycle value. The value

can be set between 0 and 120. Any number above 120

is changed to 120.

Read the duty-cycle value by pressing the Read but-

ton. Change the duty cycle by entering the value into

the edit box and pressing the Write button.

Alert

The message ALERT appears in the alert box when an

interrupt condition occurs, unless the configuration reg-

ister is set to mask the alert. The cause of the interrupt

is shown in the Status (0x02) group box. To clear the

interrupt, first eliminate the condition that caused it and

then press the Read Alert button.

Figure 6. MAX6639 EV Kit Software Main Window (Fan Controls | Fan 1 | Duty Cycle Tab)