MAX6641AUB90+ Maxim Integrated Products, MAX6641AUB90+ Datasheet - Page 10

• Manufacturer Part Number: MAX6641AUB90+
• Description: IC TEMP MONITOR SMBUS 10UMAX
• Manufacturer: Maxim Integrated Products

Specifications of MAX6641AUB90+

• Function: Fan Control, Temp Monitor
• Topology: ADC, PWM Generator, Tach Counter
• Sensor Type: External & Internal
• Sensing Temperature: -40°C ~ 125°C, External Sensor
• Output Type: I²C™/SMBus™
• Output Alarm: Yes
• Output Fan: Yes
• Voltage - Supply: 3 V ~ 5.5 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 10-MSOP, Micro10™, 10-uMAX, 10-uSOP
• Full Temp Accuracy: +/- 4 C
• Digital Output - Bus Interface: Serial (2-Wire)
• Digital Output - Number Of Bits: 8 bit
• Maximum Operating Temperature: + 125 C
• Minimum Operating Temperature: - 40 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Set bit D7 to 1 in the OT mask register to prevent the
OT output from asserting on faults in the remote-diode
temperature channel. Set bit D6 to 1 to prevent the OT
output from asserting on faults in the local-diode tem-
perature channel. The POR state of the OT mask regis-
ter is 00h.
The fan-start duty-cycle register determines the PWM
duty cycle where the fan starts spinning. Bit D3 in the
configuration byte register (MIN DUTY CYCLE) deter-
mines the starting duty cycle. If the MIN DUTY CYCLE
bit is 1, the duty cycle is the value written to the fan-
start duty-cycle register at all temperatures below the
fan-start temperature. If the MIN DUTY CYCLE bit is
zero, the duty cycle is zero below the fan-start tempera-
ture and has this value when the fan-start temperature
is reached. A value of 240 represents 100% duty cycle.
Writing any value greater than 240 causes the fan
speed to be set to 100%. The POR state of the fan-start
duty-cycle register is 60h, 40%.
SMBus-Compatible Temperature Monitor with
Automatic PWM Fan-Speed Controller
Table 2. Configuration Byte Definition (02h)
10
______________________________________________________________________________________
BIT
7
6
5
4
3
2
1
0
FAN PWM INVERT
MIN DUTY CYCLE
SPIN-UP DISABLE
TIMEOUT
NAME
—
—
—
—
Fan-Start Duty Cycle (07h)
OT Mask (06h)
POR STATE
X
X
0
0
0
0
0
0
The fan maximum duty-cycle register sets the maxi-
mum allowable PWMOUT duty cycle between 2/240
(0.83% duty cycle) and 240/240 (100% duty cycle).
Any values greater than 240 are recognized as 100%
maximum duty cycle. The POR state of the fan maxi-
mum duty-cycle register is F0h, 100%. In manual con-
trol mode, this register is ignored.
In automatic fan-control mode, this register contains the
present value of the target PWM duty cycle, as deter-
mined by the measured temperature and the duty-
cycle step size. The actual duty cycle needs a settling
time before it equals the target duty cycle if the duty-
cycle rate of change register is set to a value other than
zero. The actual duty cycle needs the time to settle as
defined by the value of the duty-cycle rate-of-change
register; therefore, the target duty cycle and the actual
duty cycle are often different. In manual fan-control
mode, write the desired value of the PWM duty cycle
directly into this register. The POR state of the fan-tar-
get duty-cycle register is 00h.
Reserved. Set to zero.
Reserved. Set to zero.
Set TIMEOUT to zero to enable SMBus timeout for
prevention of bus lockup. Set to 1 to disable this function.
Set FAN PWM INVERT to zero to force PWMOUT low when
the duty cycle is 100%. Set to 1 to force PWMOUT high
when the duty cycle is 100%.
Set MIN DUTY CYCLE to zero for a 0% duty cycle when
the measured temperature is below the fan-temperature
threshold in automatic mode. When the temperature
equals the fan-temperature threshold, the duty cycle is the
value in the fan-start duty-cycle register, which increases
with increasing temperature.
Set MIN DUTY CYCLE to 1 to force the PWM duty cycle to
the value in the fan-start duty-cycle register when the
measured temperature is below the fan-temperature
threshold. As the temperature increases above the
temperature threshold, the duty cycle increases as
programmed.
Set SPIN-UP DISABLE to 1 to disable spin-up. Set to zero
for normal fan spin-up.
Don’t care.
Don’t care.
Fan Maximum Duty Cycle (08h)
FUNCTION
Fan-Target Duty Cycle (09h)