ADT7476AARQZ ON Semiconductor, ADT7476AARQZ Datasheet - Page 40
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ADT7476AARQZ
Manufacturer Part Number
ADT7476AARQZ
Description
IC REMOTE THERM CTRLR 5V 24QSOP
Manufacturer
ON Semiconductor
Series
dBCool®r
Datasheet
1.ADT7476AARQZ.pdf
(67 pages)
Specifications of ADT7476AARQZ
Function
Fan Control, Temp Monitor
Topology
ADC, Comparator, Fan Speed Counter, Multiplexer, Register Bank
Sensor Type
External & Internal
Sensing Temperature
-40°C ~ 125°C, External Sensor
Output Type
SMBus™
Output Alarm
No
Output Fan
Yes
Voltage - Supply
3 V ~ 3.6 V
Operating Temperature
-40°C ~ 125°C
Mounting Type
Surface Mount
Package / Case
24-QSOP
Temperature Threshold
+ 150 C
Full Temp Accuracy
+/- 0.5 C
Digital Output - Bus Interface
SMBus
Digital Output - Number Of Bits
8 bit
Supply Voltage (max)
3.6 V
Supply Voltage (min)
3 V
Description/function
Remote Thermal Controller
Maximum Operating Temperature
+ 125 C
Minimum Operating Temperature
- 40 C
Supply Current
1.5 mA
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
Available stocks
Company
Part Number
Manufacturer
Quantity
Price
Programming the PWM Maximum Duty Cycle
Registers
registers that allow the maximum PWM duty cycle for each
output to be configured anywhere from 0% to 100%. This
allows the maximum PWM duty cycle to be set in steps of
0.39%.
duty cycle register is given by:
Example 1: For a maximum PWM duty cycle of 50%,
Example 2: For a minimum PWM duty cycle of 75%,
PWM Maximum Duty Cycle Registers
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)
Step 6—T
fan control occurs once the programmed T
has been exceeded. T
PWM
linearly. Otherwise stated, it is the line drawn between the
T
intersection points.
The T
MIN
Figure 57. T
The PWM maximum duty cycle registers are 8-bit
The value to be programmed into the PWM maximum
T
RANGE
Value (decimal) = PWM
Value (decimal) – 50/0.39 = 128 (decimal)
Value = 128 (decimal) or 80 (hex)
Value (decimal) = 75/0.39 = 85 (decimal)
Value = 192 (decimal) or C0 (hex)
1. Determine the maximum operating temperature for
2. Determine experimentally the fan speed (PWM
/PWM
MIN
RANGE
that channel (for example, 70°C).
duty cycle value) that does not exceed the
temperature at the worst-case operating points. For
example, 70°C is reached when the fans are
running at 50% PWM duty cycle.
PWM
RANGE
100%
and 100% PWM where the fan speed changes
is the range of temperature over which automatic
MIN
MIN
0%
is determined by the following procedure:
RANGE
and the (T
for Temperature Channels
T
RANGE
MIN
Parameter Affects Cooling Slope
is the temperature range between
MAX
MIN
/0.39
T
+ T
RANGE
TEMPERATURE
RANGE
MIN
)/PWM100%
temperature
http://onsemi.com
40
changes.
gets smaller, the fans reach 100% speed with a smaller
temperature change.
Figure 58. Adjusting PWM
Figure 60. Changing PWM Max Does Not Change the
As PWM
As T
3. Determine the slope of the required control loop to
4. Using the ADT7476A evaluation software, you
Figure 59. Increasing T
meet these requirements.
can graphically program and visualize this
functionality.
RANGE
100%
100%
100%
PWM
MAX
10%
50%
33%
10%
T
0%
0%
0%
MIN–HYST
MIN
T
MIN–HYST
is changed, the slope changes. As T
is changed, the automatic fan control slope
T
T
MIN
MIN
Fan Control Slope
AFC Slope
AFC Slope
MIN
T
30°C
RANGE
30°C
40°C
RANGE
Changes the Automatic
45°C
54°C
Changes the
RANGE