MAX6640ATE 查看數據表（PDF） - Maxim Integrated

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MAX6640ATE

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

Maxim Integrated 

2-Channel Temperature Monitor with Dual

Automatic PWM Fan-Speed Controller

TACH

0xFFh

TMIN-5 TMIN

TB

TEMPERATURE

TACHMAX

TACHA+1

TACHMIN

TACHB+1

Figure 4. Tachometer Target Calculation

TMIN. If bit 0 is equal to zero, the fan will be completely

off below TMIN. When the temperature is falling, it must

drop 5°C below TMIN before the fan turns off. If bit 0 is

set to 1, the fan does not turn off below TMIN, but

instead stays at the maximum tachometer count in reg-

ister 22h or 23h.

When the measured temperature is higher than TMIN,

the MAX6640 calculates the target tachometer count

value based on two linear equations. The target

tachometer count decreases by the tach step size

value stored in bits 7 through 4 of registers 11h and

15h each time the measured temperature increases by

the temperature step size value stored in bits 2 and 3 of

registers 11h and 15h. As the measured temperature

continues to increase, a second tachometer step size

goes into effect. Bits 3 through 0 of register 12h and

16h select the number temperature/PWM steps after

which the new step size takes effect. The new step size

is selected by bits 7 to 4 of registers 12h and 16h.

Register Descriptions

Channel 1 and Channel 2 Temperature Registers

(00h and 01h)

These registers contain the results of temperature mea-

surements. The MSB has a weight of +128°C and the

LSB +1°C. Temperature data for remote diode 1 is in

the channel 1 temperature register. Temperature data

for remote diode 2 or the local sensor (selectable by bit

4 in the global configuration register) is in the channel 2

temperature register. Three additional temperature bits

provide resolution down to 0.125°C and are in the

channel 1 extended temperature (05h) and channel 2

extended temperature (06h) registers. The channel 1

RPM

RPMMAX

TACHB+1

TACHA+1

RPMMIN

0

TMIN-5

TMIN

TEMPERATURE

TB

Figure 5. RPM Target Calculation

and channel 2 temperature registers do not update until

at least 250ms after the access of the associated

extended temperature registers. All values below 0°C

return 00h.

Status Register (02h)

A 1 indicates that an ALERT, THERM, OT, or fan fault has

occurred. Reading this register clears bits 7, 6, 1, and 0.

Reading the register also clears the ALERT and

FANFAIL outputs, but not the THERM and OT outputs. If

the fault is still present on the next temperature measure-

ment cycle, any cleared bits and outputs are set again. A

successful alert response clears the values on the out-

puts but does not clear the status register bits. The

ALERT bits assert when the measured temperature is

higher than the respective thresholds. The THERM and

OT outputs behave like comparators with 5°C hysteresis.

Mask Register (03h)

This register masks the ALERT, OT, THERM, and

FANFAIL outputs. A 1 prevents the corresponding fail-

ures from being asserted on these outputs. The mask

bits do not affect the status register.

Global Configuration Register (04h)

The global configuration register controls the shutdown

mode, power-on reset, SMBus timeout, and tempera-

ture channel 2 source select:

• D7: Run/Standby. Normal operation is run (0).

Setting this bit to 1 suspends conversions and puts

the MAX6640 into low-power sleep mode.

• D6: Software POR. Writing a 1 resets all registers to

their default values.

10 ______________________________________________________________________________________

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