ADT7460ARQZ-RL7 ONSEMI [ON Semiconductor], ADT7460ARQZ-RL7 Datasheet - Page 28

• Manufacturer Part Number: ADT7460ARQZ-RL7
• Description: dBCOOL Remote Thermal Monitor and Fan Controller
• Manufacturer: ONSEMI [ON Semiconductor]

PWM Drive Frequency
application. Registers 0x5F to 0x61 configure the PWM
frequency for PWM1 to PWM3, respectively.
Fan Speed Control
modes. The first is automatic fan speed control mode. In this
mode, fan speed is automatically varied with temperature
and without CPU intervention, once initial parameters are
set up. The advantage of this is that, in the case of the system
hanging, the system is protected from overheating. The
automatic fan speed control incorporates a feature called
dynamic T
effort required to program the automatic fan speed control
loop. For more information on how to program the
automatic fan speed control loop and dynamic T
calibration, see AN613/D, the Programming the Automatic
Fan Speed Control Loop Application Note.
control, which is described next.
Manual Fan Speed Control
to be manually adjusted. This can be useful if you want to
change fan speed in software or if you want to adjust PWM
duty cycle output for test purposes. Bits <7:5> of Registers
0x5C, 0x5E (PWM configuration) control the behavior of
each PWM output.
manually updated by writing to Registers 0x30, 0x32
(PWMx current duty cycle registers).
Table 34. PWM1 to PWM3 Configuration
(Reg. 0x5C to 0x5E) Bits
Table 35. PWM1 to PWM3 Frequency Registers
(Reg. 0x5F to 0x61)
Table 36. PWM1 to PWM3 Configuration
(Reg. 0x5C to 0x5E) Bits
<4>
<2:0>
<7:5>
The PWM drive frequency can be adjusted for the
The ADT7460 can control fan speed by two different
The second fan speed control method is manual fan speed
The ADT7460 allows the duty cycle of any PWM output
Once under manual control, each PWM output can be
Bit
Bit
Bit
Mnemonic
MIN
Mnemonic
Mnemonic
BHVR 111
INV
FREQ
calibration. This feature reduces the design
0 = logic high for 100% PWM duty cycle
1 = logic low for 100% PWM duty cycle
000 = 11.0 Hz
001 = 14.7 Hz
010 = 22.1 Hz
011 = 29.4 Hz
100 = 35.3 Hz (default)
101 = 44.1 Hz
110 = 58.8 Hz
111 = 88.2 Hz
Manual mode
Description
Description
Description
http://onsemi.com
MIN
ADT7460
28
Programming the PWM Current Duty Cycle Registers
which allow the PWM duty cycle for each output to be set
anywhere from 0% (0x00) to 100% (0xFF) in steps of 0.39%
(256 steps).
is given by:
Example 1: For a PWM duty cycle of 50%,
Example 2: For a PWM duty cycle of 33%,
can keep track of the current duty cycle on each PWM
output, even when the fans are running in automatic fan
speed control mode or in acoustic enhancement mode.
Operating from 3.3 V Standby
from a 3.3 V STBY supply. In computers that support S3 and
S5 states, the core voltage of the processor is lowered in
these states. If using the dynamic TMIN mode, lowering the
core voltage of the processor would change the CPU
temperature and change the dynamics of the system under
dynamic TMIN control. Likewise, when monitoring
THERM, the THERM timer should be disabled during these
states.
Table 37. PWM Duty Cycle Registers
Figure 52. Control PWM Duty Cycle Manually with a
The PWM current duty cycle registers are 8−bit registers,
The value to be programmed into the PWMMIN register
By reading the PWMx current duty cycle registers, users
The ADT7460 has been specifically designed to operate
Register
Value (decimal) = PWM
Value (decimal) = 50/0.39 = 128d
Value = 128d or 0x80.
Value (decimal) = 33/0.39 = 85d
Value = 85d or 0x54.
0x30
0x31
0x32
Resolution of 0.39%
PWM1 duty cycle
PWM2 duty cycle
PWM3 duty cycle
Description
MIN
VARY PWM DUTY
CYCLE WITH 8-BIT
RESOLUTION
/0.39
0xFF (100%)
0xFF (100%)
0xFF (100%)
Default