MAX6639FAEE+ Maxim Integrated Products, MAX6639FAEE+ Datasheet - Page 14

• Manufacturer Part Number: MAX6639FAEE+
• Description: IC 2CH TEMP MONITOR 16-QSOP
• Manufacturer: Maxim Integrated Products

Specifications of MAX6639FAEE+

• Function: Fan Control, Temp Monitor
• Topology: ADC, PWM Generator, Tach Counter
• Sensor Type: External & Internal
• Sensing Temperature: 0°C ~ 150°C, External Sensor
• Output Type: I²C™/SMBus™
• Output Alarm: Yes
• Output Fan: Yes
• Voltage - Supply: 3 V ~ 3.6 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 16-QSOP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

2-Channel Temperature Monitor with Dual,
Automatic, PWM Fan-Speed Controller
The following registers control the modes of operation
of the MAX6639:
• D7: PWM Mode. D7 = 1 sets the fan into manual
• D[6:4]: Fan Duty-Cycle Rate-of-Change. D[6:4]
Table 5. Fan Duty-Cycle Rate-of-Change
Table 6. Fan RPM Speed
Table 7. RPM-to-Tachometer Count Relationship Examples
* Tachometer count value = ((internal clock frequency) x 60) / actual RPM) (selected number of pulses per revolution / actual fan pulses)
14
MAXIMUM RPM VALUE
REGISTER 10h
OR 14h D[6:4]
REGISTER 10h OR 14h
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.
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 5
______________________________________________________________________________________
000
001
010
011
100
101
110
111
16,000
16,000
2000
4000
4000
4000
Fan 1 and 2 Configuration 1 (10h and 14h)
00
01
10
11
NOMINAL RATE
OF CHANGE (s)
0.0625
0.125
0.25
0.5
0
1
2
4
FAN MAXIMUM RPM VALUE
ACTUAL RPM
1000
1000
3000
3000
8000
8000
A C T U A L R A T E O F CH A N G E AT SPEC IF I C PW M FREQUENCIES
100Hz (s)
16,000
2000
4000
8000
0.06
0.13
0.25
0.5
0
1
2
4
SELECTED NUMBER
OF PULSES PER
50Hz (s)
REVOLUTION
0.06
0.12
0.26
0.5
0
1
2
4
2
2
2
2
4
4
• D[3:2]: Temperature Channel(s) for Fan Control.
• D[1:0]: RPM Range. Scales the tachometer counter
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.
Selects the temperature channel(s) that control the
PWM output when the MAX6639 is in automatic RPM
control mode (PWM mode bit is zero). If two chan-
nels are selected, the fan goes to the higher of the
two possible speeds. If neither channel is selected,
then the fan is in manual RPM mode and the speed
is forced to the value written to the target tach count
register 22h or 23h.
by setting the maximum (full-scale) value of the RPM
range to 2000, 4000, 8000, or 16,000. (Table 3
shows the internal clock frequency as a function of
the range.)
33.3Hz (s)
0.06
0.12
0.24
0.51
0.99
1.98
3.96
0
ACTUAL FAN PULSES
PER REVOLUTION
2
2
2
4
4
2
20Hz (s)
0.05
0.15
0.25
0.5
0
1
2
4
TACHOMETER COUNT
NOMINAL TIME FROM
33% TO 100% (s)
VALUE*
3Ch
3Ch
160
320
78h
28h
14h
78h
10
20
40
80
0
5