ADM1030ARQ Просмотр технического описания (PDF) - Analog Devices
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ADM1030ARQ Datasheet PDF : 28 Pages
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ADM1030
140
120
120
100
100
RTEMP
80
80
60
60
PWM DUTY CYCLE
40
40
20
20
0
0
0
12
TIME – s
Figure 13. Filtered Mode with Ramp Rate = 8
Figure 14 shows how changing the ramp rate from 8 to 4 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 22 seconds for
the fan to reach full speed.
120
140
120
110
RTEMP
100
80
80
60
PWM DUTY CYCLE
60
40
40
20
20
0
0
0
22
TIME – s
Figure 14. Filtered Mode with Ramp Rate = 4
Figure 15 shows the PWM output response for a ramp rate of 2.
In this instance the fan took about 54 seconds to reach full
running speed.
140
120
120
100
100
RTEMP
80
80
60
60
PWM DUTY CYCLE
40
40
20
20
Finally, Figure 16 shows how the control loop reacts to tem-
perature with the slowest ramp rate. The ramp rate is set to 1,
while all other control parameters remain the same. With the
slowest ramp rate selected it took 112 seconds for the fan to
reach full speed.
120
140
120
110
RTEMP
100
80
80
60
60
PWM DUTY CYCLE
40
40
20
20
0
0
0
112
TIME – s
Figure 16. Filtered Mode with Ramp Rate = 1
As can be seen from Figures 13 through 16, the rate at which
the fan will react to temperature change is dependent on the
ramp rate selected in the Fan Filter Register. The higher the
ramp rate, the faster the fan will reach the newly calculated
fan speed.
Figure 17 shows the behavior of the PWM output as tempera-
ture varies. As the temperature is rising, the fan speed will ramp
up. Small drops in temperature will not affect the ramp-up func-
tion since the newly calculated fan speed will still be higher than
the previous PWM value. The Filtered Mode allows the PWM
output to be made less sensitive to temperature variations. This
will be dependent on the ramp rate selected and the ADC sample
rate programmed into the Fan Filter Register.
90
90
80
80
PWM DUTY CYCLE
70
70
60
60
50
50
RTEMP
40
40
30
30
20
20
10
10
0
0
TIME – s
Figure 17. How Fan Reacts to Temperature Variation in
Filtered Mode
0
0
0
54
TIME – s
Figure 15. Filtered Mode with Ramp Rate = 2
REV. A
–17–
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