ADT7473 Analog Devices, Inc., ADT7473 Datasheet - Page 53

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

Enabling the THERM Trip Point as the Oper
Bits [4:2] of Dynamic
enable/disable THERM monitoring to program the operating
point.
Dynamic T
Bit [4] PHTR2 = 1, copies the Remote 2 current temperature to
the Remote 2 operating point register, if THERM is asserted.
The operating point contains the tempera
is asserted. This allows the system to run as quietly as p
with
PHT
oper
Bit [3] P
loca
asse
THE
poss
PHTL = 0, ignores any THERM assertions. The local
temperature operating point register reflects its prog
valu
Bit [
the R
The
is as
with
PHT
oper
Enabling Dynamic T
Bits
enab
chan
rted. The operating point co
l temperature operating poin
e.
serted. This allows the system
2] PHTR1 = 1, copies the Rem
[7:5] of the Dynamic T
out affecting system perfor
ible without affecting system p
operating point contains th
out affecting system performa
ating point register reflects its p
ating point register reflects its p
le/disable dynamic T
nels.
R2 = 0, ignores any THERM assertions. The Remote 2
RM is asserted. This allows the system to run as quietly as
R1 = 0, ignores any THERM assertions. The Remote 1
emote 1 operating point regis
HTL = 1, copies the loca
MIN
Control Register 1 (0x36)
T
MIN
MIN
MIN
Control Mode
Control Register 1 (0x36)
MIN
contr
C
mance.
e temperature at which THERM
ntains the temperature at which
ontrol Register 1 (0x36)
l current temperature to the
t register if THERM
ol on the temperature
to run as quietly as possible
nce.
ote 1 current temperature to
ter if THERM
erformance.
rogrammed value.
rogrammed value.
ture at which THERM
ating Point
is asserted.
rammed
is
ossible
Rev. A | Page 53 of 76
Dynamic
Bit [7] R2T = 1, enables dynamic T
temperature channel. The chosen T
adjusted based on the current temperature, operating point, and
high and low limits for this zone.
R2T = 0, disables dynamic T
is not adjusted and the channel behaves as described in the
Automatic Fan Control Overview section.
Bit [6] LT = 1, enables dynamic T
temperature channel. The chosen T
adjusted based on the current temperature, operating point, and
high and low limits for this zone.
LT = 0, disables dynamic T
not adjusted and the channel behaves as described in the
Automatic Fan Control Overview section.
Bit [5] R1T = 1, enables dynamic T
temperature channel. The chosen T
adjusted based on the current temperature, operating point, and
high and low limits for this zone.
R1T = 0, disables dynamic T
is not adjusted, and the channel behaves as described in the
Automatic Fan Control Overview section.
ENHANCING SYSTEM ACOUSTICS
Automatic fan speed control mode reacts instantaneously to
changes in temperature; that is, the PWM duty cycle responds
immediately to temperature change. Any impulses in
temperature can cause an impulse in fan noise. For psycho-
acoustic reasons, the ADT7473 can prevent the PWM output
from reacting instantaneously to temperature changes.
Enhanced acoustic mode controls the maximum change in
PWM duty cycle at a given time. The objective is to prevent the
fan from cycling up and down, annoying the user.
Acoustic Enhancement Mode Overview
Figure 71 gives a top-level overview of the automatic fan control
circuitry on the ADT7473 and shows where acoustic enhance-
ment fits in. Acoustic enhancement is intended as a postdesign
tweak made by a system or mechanical engineer evaluating best
settings for the system. Having determined the optimal settings
for the thermal solution, the engineer can adjust the system
acoustics. The goal is to implement a system that is acoustically
pleasing without causing user annoyance due to fan cycling. It is
important to realize that although a system might pass an
acoustic noise requirement specification (for example, 36 dB), if
the fan is annoying, it fails the consumer test.
TMIN
Control Register 1 (0x36)
MIN
MIN
MIN
control. The T
control. The T
control. The T
MIN
MIN
MIN
MIN
MIN
MIN
control on the local
control on the Remote 2
control on the Remote 1
value is dynamically
value is dynamically
value is dynamically
MIN
MIN
MIN
value chosen is
value chosen
value chosen
ADT7473