ADT7463 Analog Devices, ADT7463 Datasheet - Page 14

• Manufacturer Part Number: ADT7463
• Description: Dbcool Thermal Management Controller And Voltage Monitor
• Manufacturer: Analog Devices

AN-613
ENHANCE ACOUSTICS REG 1 (REG. 0x62)
Bit 7 (MIN3) = 0, PWM3 is OFF (0% PWM duty cycle)
when Temp is below T
Bit 7 (MIN3) = 1, PWM3 runs at PWM3 minimum duty
cycle below T
Bit 6 (MIN2) = 0, PWM2 is OFF (0% PWM duty cycle)
when Temp is below T
Bit 6 (MIN2) = 1, PWM2 runs at PWM2 minimum duty
cycle below T
Bit 5 (MIN1) = 0, PWM1 is OFF (0% PWM duty cycle)
when Temp is below T
Bit 5 (MIN1) = 1, PWM1 runs at PWM1 minimum duty
cycle below T
DYNAMIC T
In addition to the automatic fan speed control mode de-
scribed in the previous section, the ADT7460/ADT7463
have a mode that extends the basic automatic fan speed
control loop. Dynamic T
ADT7460/ADT7463 to intelligently adapt the system’s
cooling solution for best system performance or lowest
possible system acoustics, depending on user or design
requirements.
AIM OF THIS SECTION
This section has two primary goals:
1. To show how dynamic T
2. To illustrate how the dynamic T
DESIGNING FOR WORST-CASE CONDITIONS
When designing a system, you always design for worst-
case conditions. In PC design, the worst-case conditions
include, but are not limited to:
1. Worst-Case Altitude. A computer can be operated at
2. Worst-Case Fan. Due to manufacturing tolerances,
need for designing for worst-case conditions.
significantly reduces system design and validation
time.
different altitudes. The altitude affects the relative air
density, which will alter the effectiveness of the fan
cooling solution. For example, comparing 40°C air
temperature at 10,000 ft to 20°C air temperature at
sea level, relative air density is increased by 40%. This
means that the fan can spin 40% slower, and make less
noise, at sea level than at 10,000 ft while keeping the
system at the same temperature at both locations.
fan speeds in RPM are normally quoted with a toler-
ance of ±20%. The designer needs to assume that the
fan RPM can be 20% below tolerance. This translates
to reduced system airflow and elevated system tem-
perature. Note that fans 20% out of tolerance will
negatively impact system acoustics since they run
faster and generate more noise.
MIN
MIN
MIN
MIN
CONTROL MODE
– T
– T
– T
HYST
HYST
HYST
MIN
MIN
MIN
.
.
.
– T
– T
– T
HYST
HYST
HYST
MIN
MIN
.
.
.
control alleviates the
control allows the
MIN
control function
–14–
3. Worst-Case Chassis Airflow. The same motherboard
4. Worst-Case Processor Power Consumption. This is a
5. Worst-Case Peripheral Power Consumptions. The
6. Worst-Case Assembly. Every system manufactured is
GOOD VENTING = GOOD AIR EXCHANGE
GOOD CPU AIRFLOW
INTERFACE
INTEGRATED
MATERIAL
can be used in a number of different chassis configu-
rations. The design of the chassis and physical
location of fans and components determine the sys-
tem thermal characteristics. Moreover, for a given
chassis, the addition of add-in cards, cables, or other
system configuration options can alter the system
airflow and reduce the effectiveness of the system
cooling solution. The cooling solution can also be
inadvertently altered by the end user, e.g., placing a
computer against a wall can block the air ducts and
reduce system airflow.
data sheet maximum that does not necessarily reflect
the true processor power consumption. Designing for
worst-case CPU power consumption results in that
the processor getting overcooled (generating excess
system noise).
tendency is to design to data sheet maximums for
these components (again overcooling the system).
unique because of manufacturing variations. Heat
sinks may be loose fitting or slightly misaligned. Too
much or too little thermal grease may be used, or varia-
tions in application pressure for thermal interface
material can affect the efficiency of the thermal solution.
How can this be accounted for in every system? Again,
the system is designed for the worst case.
THERMAL
SPREADER
VENTS
I/O CARDS
VENTS
FAN
HEAT
HEAT
SINK
SUBSTRATE
THERMAL INTERFACE MATERIAL
Figure 18. Chassis Airflow Issues
Figure 19. Thermal Model
SUPPLY
POWER
DRIVE
BAYS
FAN
CPU
EPOXY
PROCESSOR
VENTS
POOR VENTING = POOR AIR EXCHANGE
I/O CARDS
POOR CPU
AIRFLOW
JTIM
SA
TIMS
CTIM
TIMC
T
T
T
T
T
TIM
TIM
A
S
T
C
J
CS
SUPPLY
POWER
DRIVE
BAYS
FAN
CA
CPU
REV. 0
JA