MAX6640(2004) Просмотр технического описания (PDF) - Maxim Integrated

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MAX6640
(Rev.:2004)

2-Channel Temperature Monitor with Dual Automatic PWM Fan-Speed Controller

Maxim Integrated 

2-Channel Temperature Monitor with Dual

Automatic PWM Fan-Speed Controller

Table 3. Register Map (continued)

REGISTER

READ/

WRITE

NO.

ADDRESS

POR

STATE

FUNCTION

D7

D6

W

26h

0011 Fan 1 target

1100 duty cycle

MSB

—

R

27h

0000 Fan 2 current

0000 duty cycle

MSB

—

W

27h

0011 Fan 2 target

1100 duty cycle

MSB

—

Channel 1

R/W

28h

0100

000

minimum

fan-start

MSB

—

temperature

Channel 2

R/W

29h

0100

0000

minimum

fan-start

MSB

—

temperature

R

3Dh

0101 Read device

1000

ID

0

1

R

3Eh

0100

Read

1101

manufacturer

ID

0

1

R

3Fh

0000 Read device

0000 revision

0

0

• D5: SMBus Timeout Disable. Writing a zero

enables SMBus timeout for prevention of bus lockup.

When the timeout function is enabled, the SMBus

interface is reset if SDA or SCL remains low for more

than 74ms (typ).

• D4: Temperature Channel 2 Source. Selects either

local or remote 2 as the source for temperature

channel 2 register data. Writing a zero to this bit

selects remote 2 for temperature channel 2.

Extended Temperature Registers (05h and 06h)

These registers contain the extended temperature data

from channels 1 and 2. Bits D[7:5] contain the 3 LSBs

of the temperature data. The bit values are 0.5°C,

0.25°C, and 0.125°C. When bit 0 is set to 1, a diode

fault has been detected.

Channel 1 and Channel 2 ALERT, OT, and THERM

Limits (08h Through 0Dh)

These registers contain the temperatures above which

the ALERT, THERM, and OT status bits set and outputs

assert (for the temperature channels that are not

masked). The data format is the same as that of the

D5

D4

D3

D2

D1

D0

—

—

—

—

—

LSB

—

—

—

—

—

LSB

—

—

—

—

—

LSB

—

—

—

—

—

LSB

—

—

—

—

—

LSB

0

1

1

0

0

0

0

0

1

1

0

1

0

0

0

0

0

0

channel 1 and channel 2 temperature registers: the

LSB weight is +1°C and the MSB is +128°C.

Fan 1 and 2 Configuration 1 (10h and 14h)

The following registers control the modes of operation

of the MAX6640:

• D7: PWM Mode. D7 = 1 sets the fan into manual

PWM duty-cycle control mode. Write the target duty

cycle in the fan duty-cycle register. D7 = 0 puts the

fan into RPM control mode. To set RPM manually, set

both fan-control temperature channels (bits D2 and

D3) to zero and write the desired tachometer count

into the TACH count register.

• D[6:4]: Fan Duty-Cycle Rate-of-Change. D[6:4]

sets the time between increments of the duty cycle.

Each increment is 1/120 of the duty cycle. By adjust-

ing the rate of change, audibility of fan-speed

changes can be traded for response time. Table 4

shows the effect of D[6:4] and, for reference, the

time required for the fan speed to change from 33%

to 100% duty cycle as a function of the rate-of-

change bits.

______________________________________________________________________________________ 13

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