ADT7473 Analog Devices, Inc., ADT7473 Datasheet - Page 55

• Manufacturer Part Number: ADT7473
• Description: Dbcool Remote Thermal Monitor And Fan Controller
• Manufacturer: Analog Devices, Inc.

The ramp rates in the enhanced acoustics mode are selectab
from the values 1, 2, 3, 5, 8, 12, 24, and 48. The ramp
discrete time slots. For example
time slots
PWM duty cycle needs to be increased. If the PWM duty cycle
value needs to be decrea
Figure 73 shows how the enhanced acoustics mode algorithm
operates.
The
d
PWM
th
either 1, 2, 3, 5, 8, 12, 24, or 48 time slots, depending on the
settings of the enhance acoustics registers. If the new PWM
duty cycle value is less than the previous PWM value, the
previous PWM duty cycle is decremented by 1, 2, 3, 5, 8, 12, 24,
or 48 time slots. Each time the PWM duty cycle is incremented
or decremented, its value is stored as the previous PWM duty
cycle for the next comparison. A ramp rate of 1 corresponds to
one time slot, which is 1/255 of the PWM period. In enhanced
acoustics mode, incrementing or decrementing by 1 changes the
PWM output by 1/255 × 100%.
PWM_OUT
33% DUTY
uty cycle based on the temperature measured. If the new
en the previous PWM duty cycle value is incremented by
CYCLE
enhanced acou
duty cycle value is greater than the previous PWM value,
Figure 72. 33% PWM Duty Cycle Represented in Time Slots
are added to the PWM high duty cycle each ti
TIME SLOTS
Figure 73. Enhanced Acoustics Algorithm
TEMPERATURE
BY RAMP RATE
85
DUTY CYCLE
stics mode algorithm calculates a new PWM
CALCULATE
IS NEW PWM
PWM VALUE
INCREMENT
NEW PWM
PREVIOUS
PREVIOUS
VALUE >
VALUE?
READ
sed, it is decreased by eight time slots.
= 255 TIME SLOTS
YES
(ONE PERIOD)
PWM OUTPUT
, if
NO
TIME SLOTS
the ramp rate is 8, then eight
170
BY RAMP RATE
DECREMENT
PWM VALUE
PRE
VIOUS
rates are
me the
le
Rev. A | Page 55 of 76
STEP 12: RAMP RATE FOR ACOUSTIC
ENHANCEMENT
The
thro
has
logg
solu
Enhance Acoustics Register 1 (0x62)
Bits [2:0] ACOU, select the ramp rate for PWM1.
Enhance Acoustics Register 2 (0x63)
Bits
Bits [6:4] ACOU2, select the ramp rate for PWM2.
Another way to view the ramp rates is to measure the time it takes
for the PWM output to ramp up from 0% to 100% duty cycle for an
instantaneous change in temperature. This can be tested by putting
the ADT7473 into manual mode and changing the PWM output
from 0% to 100% PWM duty cycle. The PWM output takes 35
seconds to reach 100% when a ramp rate of 1 time slot is selected.
been finished. Th
tion.
ugh system char
ed, if possible, t
[2:0] ACOU3, s
optimal ramp
000 = 1 time sl
001 = 2 time slots = 17.6 s
010 = 3 time slots = 11.8 s
011 = 5 time s
100 = 8 time slots = 4.4 s
101 = 12 time
110 = 24 time
111 = 48 time
000 = 1 time slot = 35 s
001 = 2 time slots = 17.6 s
010 = 3 time s
011 = 5 time slots = 7 s
100 = 8 time s
101 = 12 time
110 = 24 time
111 = 48 time slots = 0.8 sec
000 = 1 time slot = 35 sec
001 = 2 time slots = 17.6 sec
010 = 3 time slots = 11.8 sec
011 = 5 time slots = 7 sec
100 = 8 time slots = 4.4 sec
101 = 12 time slots = 3 sec
110 = 24 time slots = 1.6 sec
111 = 48 time slots = 0.8 sec
rate for acoustic enhancement can be found
lots = 7 sec
lots = 11.8 sec
lots = 4.4 sec
slots = 3 sec
slots = 1.6 sec
slots = 0.8 sec
slots = 3 sec
slots = 1.6 sec
ot = 35 sec
o determine the best setting for a given
elect the ramp rate for PWM3.
acterization after the thermal optimization
e effect of each ramp rate should be
ec
ec
ec
ec
ec
ec
ADT7473