Analog Devices dBCool ADT7473 Manual page 56

ADT7473
Figure 74 shows remote temper
c ycle for enhanced acoustics m
which corresponds to the fastest ra
temperat e read g is available ur in
it takes approximately 0.76 seconds to go from 33% duty cycle to
100% duty cyc le (f ull speed). Ev
increa ses ve rapidl ry y, the fan ra
140
( ° C)
R
TEMP
120
100
80
60
PWM CYCLE (
40
20
0
0
TIME (s)
Fig ure 74. nhanced Acoustic E
Figur e 75 s hows ow changing t h
affects the contro l loop. The o
slower . Be cause th e ramp ra te is redu d, it ta
fan t o achiev ull e f running speed.
appr oxima tely 4 .4 seconds for the fan to
120
°C)
R (
TEMP
100
80
60
40
20
0
0
TIME (s)
Fig ure 75 nhanced Acoust . E
ature plotted against PWM duty
ode. The ramp rate is set to 48,
mp rate. Assume that a new
every 115 m s. W ith th ese settings
en tho h the te ug mp eratur e
mps up o full sp t eed gradually.
120
100
80
60
%)
40
20
0
0.76
s Mo de with Ra mp Rate = 4 8
he ramp rate f m 48 t ro o 8
verall response of the fan is
ce kes lo nger for the
In this case, takes it
reach full speed .
140
120
100
80
PWM DUTY CYCLE (%)
60
40
20
0
4.4
ics M ode wi th Ra mp Rate 8 =
Figure 76 shows the PWM output response for a ramp rate of 2.
In this instance, the fan took about 17.6 seconds to reach full
running speed.
,
140
R (°C)
TE MP
120
10 0
80
60
40
20
0
0
Figur e 76
Fi gur e 77 sh ows
wi th the slow t ramp es
ot r contro arameters remain he same. W he l p
ra p rate se m lec
sp d. ee
12 0
R
TEMP
10 0
80
60
40
20
0
0
Figure 77. Enhanced Acoustics Mode with Ramp Rate = 1
As Figure 74 to Figure 77 show, the rate at which the fan reacts
to mperatu change te re
th e enha nce d aco
faster the fan reaches the newly calculated fan speed.
Rev. A | Page 56 of 76
P WM DUTY CYCLE
TIME (s)
. Enhanced Acousti cs M ode with Ram
how t he c ontro l lo op reacts to temperature
rat e. The ram p rate is s
t
ted, it takes 35 se nds for the co
(°C)
PWM DUTY CYCLE
TIME (s)
is dependent on the ra
ustic s regist ers . The higher t
120
100
80
60
(%)
40
20
0
17.6
p Ra te = 2
et to 1 , wh e all il
ith th e slo est w
fan t o reach full
140
120
100
80
60
(%)
40
20
0
35
mp ra te se cted in le
he ram p r ate, t he