EVAL-ADT7467EBZ ON Semiconductor, EVAL-ADT7467EBZ Datasheet - Page 44

• Manufacturer Part Number: EVAL-ADT7467EBZ
• Description: BOARD EVALUATION FOR ADT7467
• Manufacturer: ON Semiconductor
• Series: dBCool®r

Specifications of EVAL-ADT7467EBZ

• Sensor Type: Temperature
• Sensing Range: -40°C ~ 120°C
• Interface: SMBus (2-Wire/I²C)
• Sensitivity: ±1.5°C
• Voltage - Supply: 3 V ~ 5.5 V
• Embedded: No
• Utilized Ic / Part: ADT7467
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

ADT7467
Programming the PWM
The PWM
minimum PWM duty cycle for each output to be configured
from 0% to 100%. This allows the minimum PWM duty cycle to
be set in steps of 0.39%.
The value to be programmed into the PWM
Example 1: For a minimum PWM duty cycle of 50%,
Example 2: For a minimum PWM duty cycle of 33%,
PWM
Register 0x64, PWM1 minimum duty cycle = 0x80 (50% default)
Register 0x65 PWM2 minimum duty cycle = 0x80 (50% default)
Register 0x66, PWM3 minimum duty cycle = 0x80 (50% default)
Fan Speed and PWM Duty Cycle
The PWM duty cycle does not directly correlate to fan speed in
RPM. Running a fan at 33% PWM duty cycle does not equate to
running the fan at 33% speed. Driving a fan at 33% PWM duty
cycle runs the fan at closer to 50% of its full speed, because fan
speed as a percentage of RPM generally relates to the square
root of the PWM duty cycle. Given a PWM square wave as the
drive signal, fan speed in RPM approximates to
STEP 5: PWM
PWM
system runs at during the automatic fan speed control loop.
For maximum system acoustic benefit, PWM
low as possible but capable of keeping the processor below its
maximum temperature limit, even in a worst-case scenario. If
the THERM temperature limit is exceeded, the fans are still
boosted to 100% for fail-safe cooling.
There is a PWM
value of this register is 0xFF and, therefore, has no effect unless
it is programmed.
Value (decimal) = PWM
Value (decimal) = 50%/0.39% = 128 (decimal)
Value = 128 (decimal) or 0x80 (hexadecimal)
Value (decimal) = 33%/0.39% = 85 (decimal)
Value = 85 (decimal)l or 0x54 (hexadecimal)
%
MIN
MAX
fan
Registers
is the maximum duty cycle that each fan in the
MIN
speed
registers are 8-bit registers that allow the
MAX
MAX
=
limit for each fan channel. The default
FOR PWM (FAN) OUTPUTS
PWM
MIN
duty
MIN
Registers
/0.39%
cycle
×
10
MIN
MAX
register is given by
should be as
Rev. 3 | Page 44 of 77 | www.onsemi.com
Programming the PWM
The PWM
maximum PWM duty cycle for each output to be configured
from 0% to 100%. This allows the maximum PWM duty cycle
to be set in steps of 0.39%.
The value to be programmed into the PWM
Example 1: For a maximum PWM duty cycle of 50%,
Example 2: For a minimum PWM duty cycle of 75%,
PWM
Register 0x38, PWM1 maximum duty cycle = 0xFF
(100% default)
Register 0x39, PWM2 maximum duty cycle = 0xFF
(100% default)
Register 0x3A, PWM3 maximum duty cycle = 0xFF
(100% default)
See the Fan Speed and PWM Duty Cycle section.
Figure 60. PWM
Value (decimal) = PWM
Value (decimal) = 50%/0.39% = 128 (decimal)
Value = 128 (decimal) or 0x80 (hexadecimal)
Value (decimal) = 75%/0.39% = 192 (decimal)
Value = 192 (decimal) or 0xC0 (hexadecimal)
MAX
PWM
PWM
Registers
MAX
100%
MAX
MIN
0%
MAX
registers are 8-bit registers that allow the
Determines Maximum PWM Duty Cycle Below the THERM
T
MIN
Temperature Limit
MAX
MAX
Registers
/0.39%
TEMPERATURE
MAX
register is given by