ADT7468 Analog Devices, Inc., ADT7468 Datasheet - Page 53

• Manufacturer Part Number: ADT7468
• Description: Dbcool Remote Thermal Controller And Voltage Monitor
• Manufacturer: Analog Devices, Inc.

STEP 10: HIGH AND LOW LIMITS FOR
TEMPERATURE CHANNELS
The low limit defines the temperature at which the T
starts to be increased, if temperature falls below this value. This
has the net effect of reducing the fan speed, allowing the system
to get hotter. An interrupt can be generated when the tempera-
ture drops below the low limit.
The high limit defines the temperature at which the T
starts to be reduced, if temperature increases above this value.
This has the net effect of increasing fan speed to cool down the
system. An interrupt can be generated when the temperature
rises above the high limit.
Programming High and Low Limits
There are six limit registers; a high limit and low limit are
associated with each temperature channel. These 8-bit registers
allow the high and low limit temperatures to be programmed
with 1°C resolution.
Temperature Limit Registers
Reg. 0x4E, Remote 1 temperature low limit = 0x01
Reg. 0x4F, Remote 1 temperature high limit = 0x7F
Reg. 0x50, Local temperature low limit = 0x01
Reg. 0x51, Local temperature high limit = 0x7F
Reg. 0x52, Remote 2 temperature low limit = 0x01
Reg. 0x53, Remote 2 temperature high limit = 0x7F
AMBIENT TEMP
REMOTE 2 =
REMOTE 1 =
VRM TEMP
CPU TEMP
LOCAL =
THERMAL CALIBRATION
THERMAL CALIBRATION
THERMAL CALIBRATION
T
T
T
Figure 70. Operating Point Value Dynamically Adjusts Automatic Fan Control Settings
MIN
MIN
MIN
T
T
T
RANGE
RANGE
RANGE
100%
100%
100%
0%
0%
0%
MIN
MIN
value
value
MUX
Rev. A | Page 53 of 84
OPERATING
POINT
PWM
PWM
PWM
MIN
MIN
MIN
How Dynamic T
The basic premise is as follows:
1.
2.
3.
However, the loop operation is not as simple as described in
these steps. A number of conditions govern the situations in
which T
Short Cycle and Long Cycle
The ADT7468 implements two loops: a short cycle and a long
cycle. The short cycle takes place every n monitoring cycles.
The long cycle takes place every 2n monitoring cycles. The
value of n is programmable for each temperature channel. The
bits are located at the following register locations:
Remote 1 = CYR1 = Bits <2:0> of calibration control Register 2
(Address = 0x37).
ENHANCEMENT)
ENHANCEMENT)
ENHANCEMENT)
TACHOMETER 1
MEASUREMENT
TACHOMETER 2
MEASUREMENT
TACHOMETER 3
MEASUREMENT
Set the target temperature for the temperature zone, which
could be, for example, the Remote 1 thermal diode. This
value is programmed to the Remote 1 operating
temperature register.
As the temperature in that zone (Remote 1 temperature)
rises toward and exceeds the operating point temperature,
T
As the temperature drops below the operating point
temperature, T
reduced.
(ACOUSTIC
(ACOUSTIC
(ACOUSTIC
CONTROL
CONTROL
CONTROL
MIN
RAMP
RAMP
RAMP
AND 4
MIN
is reduced and the fan speed increases.
can increase or decrease.
MIN
GENERATOR
GENERATOR
GENERATOR
MIN
CONFIG
CONFIG
CONFIG
Control Works
PWM
PWM
PWM
PWM
PWM
PWM
is increased and the fan speed is
PWM1
TACH1
PWM2
TACH2
PWM3
TACH3
FRONT CHASSIS
REAR CHASSIS
CPU FAN SINK
ADT7468