MON35W42 datasheet(21/60 Pages) SMSC

21 / 60 page

Fan speed control

The MON35W42 provides four sets of controls for fan PWM speed control. The duty cycle of the PWM

can be programmed by a 8-bit registers which are defined in the Bank0 CR5A, CR5B, CR5E, and

CR5F. The default duty cycle is set to 100%, the default 8-bit registers is set to FFh. The duty cycle can

be calculated as follows.

100

255

Value

bit

Programmed

(%)

cycle

Duty

(

The PWM clock frequency also can be program and defined in the Bank0.CR5C and Bank4.CR5C.

The application circuit is shown in figure 14.

FIGURE 14

Temperature Measurement Machine

The temperature data format is 8-bit two’s-complement for sensor 1 and 9-bit two’s-complement for

sensors 2/3. The 8-bit temperature data can be obtained by reading the CR[27h]. The 9-bit temperature

data can be obtained by reading the 8 MSBs from the Bank1/2 CR[50h] and the LSB from the Bank1/2

CR[51h] bit 7. The format of the temperature data is show in Table 1.

Table 2

8-Bit Digital Output

9-Bit Digital Output

Temperature

8-Bit Binary

8-Bit Hex

9-Bit Binary

9-Bit Hex

+125°C

0111,1101

7Dh

0,1111,1010

0FAh

+25°C

0001,1001

19h

0,0011,0010

032h

+1°C

0000,0001

01h

0,0000,0010

002h

+0.5°C

0,0000,0001

001h

+0°C

0000,0000

00h

0,0000,0000

000h

-0.5°C

1,1111,1111

1FFh

-1°C

1111,1111

FFh

1,1111,1110

1FFh

-25°C

1110,0111

E7h

1,1100,1110

1CEh

-55°C

1100,1001

C9h

1,1001,0010

192h

+12V

FAN

NMOS

PNP Transistor

PWM Clock Input

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