ADT7473_11 ONSEMI [ON Semiconductor], ADT7473_11 Datasheet - Page 52

• Manufacturer Part Number: ADT7473_11
• Description: dbCOOL Remote Thermal Monitor and Fan Control
• Manufacturer: ONSEMI [ON Semiconductor]

temperature 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
still 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
much longer ramp times by slowing the ramp rates. Each
ramp rate can be slowed by a factor of 4.
PWM1 Configuration Register (0x5C)
Bit [3] SLOW, 1 slows the ramp rate for PWM1 by 4.
PWM2 Configuration Register (0x5D)
Bit [3] SLOW, 1 slows the ramp rate for PWM2 by 4.
Figure 81. How Fan Reacts to Temperature Variation
Figure 81 shows the behavior of the PWM output as
The ADT7473/ADT7473−1 can be programmed for
90
80
70
60
50
40
30
20
10
0
in Enhanced Acoustics Mode
TIME (s)
R
TEMP
PWM DUTY CYCLE (%)
(5C)
http://onsemi.com
90
80
70
60
50
40
30
20
10
0
52
PWM3 Configuration Register (0x5E)
Bit [3] SLOW, 1 slows the ramp rate for PWM3 by 4.
SLOW bit is set for each PWM output.
Enhanced Acoustics Register 1 (0x62)
Bits [2:0] ACOU, select the ramp rate for PWM1.
Enhanced Acoustics Register 2 (0x63)
Bits [2:0] ACOU3, select the ramp rate for PWM3.
Bits [6:4] ACOU2, select the ramp rate for PWM2.
The following sections list the ramp−up times when the
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