EVAL-ADT7475EB ON Semiconductor, EVAL-ADT7475EB Datasheet - Page 32

• Manufacturer Part Number: EVAL-ADT7475EB
• Description: BOARD EVALUATION FOR ADT7475
• Manufacturer: ON Semiconductor
• Series: dBCool®r
• Type: Temperature Sensorr

Specifications of EVAL-ADT7475EB

• Contents: Evaluation Board
• For Use With/related Products: ADT7475
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

Mux Configuration Example
system using the ADT7475 to control three fans. The CPU
fan sink is controlled by PWM1, the front chassis fan is
controlled by PWM2, and the rear chassis fan is controlled
by PWM3. The mux is configured for the following fan
control behavior:
•
•
Step 3: T
automatic fan control. The speed at which the fan runs at
T
chosen are temperature channel specific, for example, 25°C
for ambient channel, 30°C for VRM temperature, and 40°C
for processor temperature.
Offset 64, that can be programmed in 1°C increments. There
is a T
measurement channel: Remote 1, local, and Remote 2
temperatures. Once the T
on and runs at the minimum PWM duty cycle. The fan turns
off once the temperature has dropped below T
MIN
This is an example of how to configure the mux in a
T
T
PWM1 (CPU fan sink) is controlled by the fastest speed
calculated by the local (VRM temperature) and
Remote 2 (processor) Temperatures. In this case, the
CPU fan sink is also used to cool the VRM.
PWM2 (front chassis fan) is controlled by the Remote 1
Temperature (ambient).
MIN
MIN
is programmed later in the process. The T
MIN
is the temperature at which the fans turn on under
is an 8−bit value, either twos complement or
MIN
AMBIENT TEMP
REMOTE 2 =
REMOTE 1 =
register associated with each temperature
Settings for Thermal Calibration Channels
VRM TEMP
CPU TEMP
LOCAL =
THERMAL CALIBRATION
THERMAL CALIBRATION
THERMAL CALIBRATION
MIN
T
T
T
MIN
MIN
MIN
value is exceeded, the fan turns
T
T
T
RANGE
RANGE
RANGE
Figure 47. Mux Configuration Example
100%
100%
100%
0%
0%
0%
MIN
MIN
− T
http://onsemi.com
values
MUX
HYST
.
32
PWM
PWM
PWM
MIN
MIN
MIN
•
Example Mux Settings
Bits [7:5] (BHVR), PWM1 Configuration Register (0x5C).
Bits [7:5] (BHVR), PWM2 Configuration Register (0x5D).
Bits [7:5] (BHVR), PWM3 Configuration Register (0x5E).
TACH rising edges are counted. See the Fan Startup
Timeout Section for more details. In some cases, primarily
for psycho−acoustic reasons, it is desirable that the fan never
switch off below T
Register 1 (0x62), when set, keep the fans running at the
PWM minimum duty cycle, if the temperature should fall
below T
T
Register 0x67, Remote 1 Temperature T
Register 0x68, Local Temperature T
Register 0x69, Remote 2 Temperature T
MIN
These settings configure the mux, as shown in Figure 47.
To overcome fan inertia, the fan is spun up until two valid
CONFIG
CONFIG
CONFIG
PWM3 (rear chassis fan) is controlled by the Remote 1
Temperature (ambient).
TACHOMETER 1
MEASUREMENT
TACHOMETER 2
MEASUREMENT
TACHOMETER 3
MEASUREMENT
101 = Fastest speed calculated by local and Remote 2
000 = Remote 1 temperature controls PWM2
000 = Remote 1 temperature controls PWM3
PWM
PWM
PWM
GENERATOR
GENERATOR
GENERATOR
Registers
AND 4
PWM
PWM
PWM
MIN
temperature controls PWM1
.
MIN
ENHANCEMENT)
ENHANCEMENT)
ENHANCEMENT)
(ACOUSTIC
(ACOUSTIC
(ACOUSTIC
CONTROL
CONTROL
CONTROL
. Bits [7:5] of Enhanced Acoustics
RAMP
RAMP
RAMP
MIN
PWM1
TACH1
PWM2
TACH2
PWM3
TACH3
MIN
MIN
= 0x5A (90°C)
FRONT CHASSIS
REAR CHASSIS
CPU FAN SINK
= 0x5A (90°C)
= 0x5A (90°C)