ADT7463 Analog Devices, ADT7463 Datasheet - Page 25

• Manufacturer Part Number: ADT7463
• Description: Dbcool Thermal Management Controller And Voltage Monitor
• Manufacturer: Analog Devices

ENHANCE ACOUSTICS REGISTER 2 (Reg. 0x63)
<2:0> ACOU3 Select the ramp rate for PWM3.
<6:4> ACOU2 Select the ramp rate for PWM2.
Another way to view the ramp rates is the time it takes
for the PWM output to ramp from 0% to 100% duty cycle
for an instantaneous change in temperature. This can be
tested by putting the ADT7460/ADT7463 into manual
mode and changing the PWM output from 0% to 100%
PWM duty cycle. The PWM output takes 35 seconds to
reach 100% with a ramp rate of 1 time slot selected.
Figure 32 shows remote temperature plotted against
PWM duty cycle for enhanced acoustics mode. The
ramp rate is set to 48, which would correspond to the
fastest ramp rate. Assume that a new temperature read-
ing is available every 115 ms. With these settings, it took
approximately 0.76 seconds to go from 33% duty cycle
to 100% duty cycle (full speed). Even though the tem-
perature increased very rapidly, the fan ramps up to full
speed gradually.
REV. 0
140
120
100
80
60
40
20
0
Figure 32. Enhanced Acoustics Mode with
Ramp Rate = 48
0
000 = 1 Time Slot = 35 seconds
001 = 2 Time Slots = 17.6 seconds
010 = 3 Time Slots = 11.8 seconds
011 = 5 Time Slots = 7 seconds
100 = 8 Time Slots = 4.4 seconds
101 = 12 Time Slots = 3 seconds
110 = 24 Time Slots = 1.6 seconds
111 = 48 Time Slots = 0.8 seconds
000 = 1 Time Slot = 35 seconds
001 = 2 Time Slots = 17.6 seconds
010 = 3 Time Slots = 11.8 seconds
011 = 5 Time Slots = 7 seconds
100 = 8 Time Slots = 4.4 seconds
101 = 12 Time Slots = 3 seconds
110 = 24 Time Slots = 1.6 seconds
111 = 48 Time Slots = 0.8 seconds
R
TEMP
( C)
PWM CYCLE (%)
TIME – s
0.76
120
100
80
60
40
20
0
–25–
Figure 33 shows how changing the ramp rate from 48 to
8 affects the control loop. The overall response of the
fan is slower. Since the ramp rate is reduced, it takes
longer for the fan to achieve full running speed. In this
case, it took approximately 4.4 seconds for the fan to
reach full speed.
Figure 34 shows the PWM output response for a ramp
rate of 2. In this instance, the fan took about 17.6 sec-
onds to reach full running speed.
120
100
140
120
100
80
60
40
20
80
60
40
20
0
0
Figure 33. Enhanced Acoustics Mode with
Ramp Rate = 8
Figure 34. Enhanced Acoustics Mode with
Ramp Rate = 2
0
0
R
R
TEMP
TEMP
( C)
TIME – s
TIME – s
PWM DUTY CYCLE (%)
PWM DUTY CYCLE (%)
17.6
4.4
AN-613
140
120
100
80
60
40
20
0
120
100
80
60
40
20
0