ADT7467 Analog Devices, Inc., ADT7467 Datasheet - Page 56

• Manufacturer Part Number: ADT7467
• Description: Dbcool Remote Thermal Monitor And Fan Controller
• Manufacturer: Analog Devices, Inc.

ADT7467
Figure 80 shows the behavior of the PWM output as tempera-
ture varies. As the temperature increases, the fan speed ramps
up. Small drops in temperature do not affect the ramp-up
function, because the newly calculated fan speed is higher than
the previous PWM value. Enhanced acoustics mode allows the
PWM output to be made less sensitive to temperature
variations. This is dependent on the ramp rate selected and
programmed into the enhanced acoustics registers.
Slower Ramp Rates
The ADT7467 can be programmed for much longer ramp times
by slowing the ramp rates. Each ramp rate can be slowed by a
factor of 4.
PWM1 Configuration Register (Reg. 0x5C)
<3> SLOW, a setting of 1 slows the ramp rate for PWM1 by 4.
PWM2 Configuration Register (Reg. 0x5D)
<3> SLOW, a setting of 1 slows the ramp rate for PWM2 by 4.
PWM3 Configuration Register (Reg. 0x5E)
<3> SLOW, a setting of 1 slows the ramp rate for PWM3 by 4.
The following sections list the ramp-up times when the SLOW
bit is set for each PWM output.
90
80
70
60
50
40
30
20
10
0
Figure 80. Fan Reaction to Temperature Variation
in Enhanced Acoustics Mode
R
TEMP
PWM DUTY CYCLE (%)
(°C)
Rev. A | Page 56 of 80
Enhanced Acoustics Register 1 (Reg. 0x62)
<2:0> ACOU selects the ramp rate for PWM1.
Enhance Acoustics Register 2 (Reg. 0x63)
<2:0> ACOU3 selects the ramp rate for PWM3.
<6:4> ACOU2 selects the ramp rate for PWM2.
000 = 140 sec
001 = 70.4 sec
010 = 47.2 sec
011 = 28 sec
100 = 17.6 sec
101 = 12 sec
110 = 6.4 sec
111 = 3.2 sec
000 = 140 sec
001 = 70.4 sec
010 = 47.2 sec
011 = 28 sec
100 = 17.6 sec
101 = 12 sec
110 = 6.4 sec
111 = 3.2 sec
000 = 140 sec
001 = 70.4 sec
010 = 47.2 sec
011 = 28 sec
100 = 17.6 sec
101 = 12 sec
110 = 6.4 sec
111 = 3.2 sec