ADT7473 Analog Devices, Inc., ADT7473 Datasheet - Page 48

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

ADT7473
Dynamic T
Dynamic T
fan control loop by adjusting the T
performance and measured temperature. This is important
because instead of designing for the worst case, the system
thermals can be defined as operating zones. The ADT7473 can
self-adjust its fan control loop to
zone temperature or a system target temperature. For example,
it can be specified that the ambient temperature in a system
should be maintained at 50°C. If the temperature is below 50°C
the fans might not need to run, or might run very slowly. If the
temperature is higher than 50°C, the fans need to throttle up.
The challenge presented by any thermal design is finding the
right settings to suit the system’s fan cont
involve designing for the worst case, followed by weeks of
system thermal characterization, and finally fan acoustic
optimization (for psycho-acoustic reasons). Getting the most
benefit from the auto
izing the system to find the best T
control loop, and the best PWM
speed setting. Using the ADT7473’s dynamic T
mode, however, shortens the characterization time and
alleviates tweaking the control loop settings because the de
can self-adjust during system operation.
Dynamic T
operating zone temperatures required for the system.
Associated with this control mode are three operating po
registers, one for each temperature channel. This allows th
system thermal solution to be broken down into distinct
thermal zones. For example, CPU oper
70°C, VRM operating temperatu
operating temperature is 50°C. The ADT7473
alte s the control solution to maintain each zone temperature as
close
Ope
Register 0x33, Remote 1 Operating Point = 0xA4
(100°C default)
Regi
(100°C default)
Regi
(100
r
ster 0x34, Local Temperature Operating Point = 0xA4
ster 0x35, Remote 2 Operating Point = 0xA4
°C default)
rating Point Registers
ly as possible to its target operating point.
MIN
MIN
MIN
control mode builds up
control mode is operated by specifying th
Control Overview
matic fan control mode involves character-
MIN
re is 80°C, and ambient
maintain either an operating
MIN
MIN
value for the quietest fan
and T
value based on system
on the basic automatic
ating temperature is
rol solution. This can
RANGE
dynamically
MIN
settings for the
control
e
int
e
vice
Rev. A | Page 48 of 76
,
Figure 63 shows an overview of
operation of the dynamic T
Table 15 provides a brief description of each parameter.
Table 15. T
Parameter
T
T
T
Oper
Point
T
T
Dynamic T
Because the dynamic T
the automatic fan control mode, program the automatic fan
control mode parameters first, as described in Step 1: Hardware
Configuration to Step 8: T
proceed with dynamic T
LOW
HIGH
MIN
THERM
RANGE
atin
T
LOW
g
MIN
MIN
T
MIN
Control Loop Parameters
Control Programming
Description
If the tem erature dr
er
SMB
If the tem
erro
SMBA
The temp
under automatic fan speed contro
The ta
tempe
maintain system temperature at about the
operating point by adjusting the T
of the control loop.
If the temperature exceeds this critical limit, the
fans can be run at 100% for maximum cooling.
Programs the PWM duty cycle vs. temperatu
control slope.
Figure 63. Dynamic T
OPERATING
ror flag is set in a st
POINT
r flag is set in a st
ALER
LER
rg
ra
MIN
et temper
MIN
ture zone
T interrupt can be generated.
T interrupt
p
peratur
erature a
HYST
control mode is a basic extension of
MIN
T
control mode programming.
HIGH
for Temperature Channels, then
control loop.
the parameters that affect the
T
e ex
THERM
. Th
MIN
atu
t w
Control Lo p
can be gene
ops below th
atus regist
ceeds the
atus registe
re for a partic
e ADT7473 a
hich the fan turns on
T
RANGE
o
T
TEMPERATURE
er an
HIGH
r an
rat
e T
tte
l.
MIN
u
ed.
limit, an
lar
d an
d an
LO
mpts to
parameter
W
limit, an
re