MAX6639F datasheet(7/18 Pages) MAXIM

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of Change drop-down list, audibility of fan-speed

changes can be traded for response time. There are

eight possible options: 0s, 0.0625s, 0.125s, 0.25s,

0.5s, 1s, 2s, or 4s.

The Control drop-down list sets the temperature chan-

nels that control the fan in RPM mode. There are four

options under the control drop-down list: None,

Channel1, Channel2, or Both. Selecting None allows

for manual control of the fan’s RPM. Selecting Channel1,

Channel2, or Both, allows the fan’s RPM to be con-

trolled by the temperature of the selected channel(s).

The RPM Range drop-down list scales the tachometer

counter by setting the maximum (full-scale) value of the

RPM range. There are four possible selections: 2000

RPM, 4000 RPM, 8000 RPM, or 16000 RPM. Select the

closest value that is greater than the fan’s full-speed RPM.

Read the configuration 1 register by pressing the Read

button. Change the configuration by selecting the

desired options and pressing the Write button.

Fan 1 and Fan 2 Configuration 2A

The fan 1 Configuration 2A (0x11) and fan 2

Configuration 2A (0x15) group boxes apply to the

automatic RPM mode (Figure 4). The Configuration 2A

(0x15) group box is not shown, but can be accessed

by navigating to the Fan 2 tab sheet from Figure 4.

These group boxes contain four items: RPM step-size

A, Temp step-size, Positive PWM Polarity, and Min.

speed.

The RPM step-size A drop-down list selects the number

of tachometer counts that the target value decreases for

each temperature-step increase above the fan-start

temperature. The value can be set between 1 and 16.

The Temp step-size drop-down list selects the temper-

ature adjustment for fan control. For each temperature-

step increase, the target tachometer count decreases

by the value of RPM step-size A. The temperature step-

size value can be set to 1 C, 2 C, 4 C, or 8 C.

The Positive PWM Polarity checkbox sets the PWM

output polarity. Checking the Positive PWM Polarity

MAX6639 Evaluation Kit

_______________________________________________________________________________________

Figure 3. MAX6639 EV Kit Software Main Window (Mask Tab)

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