ADT7475ARQZ ON Semiconductor, ADT7475ARQZ Datasheet - Page 38

• Manufacturer Part Number: ADT7475ARQZ
• Description: IC REMOTE THERMAL CTRLR 16-QSOP
• Manufacturer: ON Semiconductor
• Series: dBCool®r

Specifications of ADT7475ARQZ

• 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: 16-QSOP
• Full Temp Accuracy: +/- 0.5 C
• Digital Output - Bus Interface: Serial (3-Wire, 4-Wire)
• Maximum Operating Temperature: + 125 C
• Minimum Operating Temperature: - 40 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Step 8: T
the temperature measured has dropped back below T
before the fan turns off. The premise for temperature
hysteresis (T
chatter, or cycle on and off regularly, whenever the
temperature is hovering at about the T
needed for the system to cool down or heat up as the fan turns
on and off. Values of hysteresis are programmable in the
range 1°C to 15°C. Larger values of T
from chattering on and off. The T
at 4°C.
hysteresis for fan on/off, but the same setting is used for the
T
The T
The T
HYST
HYST
HYST
HYST
is the amount of extra cooling a fan provides after
AMBIENT TEMP
REMOTE 2 =
REMOTE 1 =
HYST
VRM TEMP
CPU TEMP
value chosen determines the amount of time
setting applies not only to the temperature
for Temperature Channels
LOCAL =
100%
0%
) is that, without it, the fan would merely
THERMAL CALIBRATION
THERMAL CALIBRATION
THERMAL CALIBRATION
T
T
T
T
MIN
MIN
MIN
MIN
Figure 59. How T
HYST
T
RANGE
HYST
MIN
T
T
T
RANGE
RANGE
RANGE
default value is set
T
setting.
100%
100%
100%
prevent the fans
THERM
0%
0%
0%
THERM
MUX
http://onsemi.com
MIN
Relates to Automatic Fan Control
38
T
Temperature Channels. Therefore, programming Register
0x6D and Register 0x6E sets the hysteresis for both fan
on/off and the THERM function.
below T
Enhanced Acoustics Register 1 (0x62) allow the fans to be
turned off or to be kept spinning below T
always on, the T
temperature drops below T
THERM Hysteresis
Register 0x6E also applies to hysteresis on the appropriate
THERM channel.
PWM
PWM
PWM
MIN
MIN
MIN
THERM
In some applications, it is required that fans not turn off
Any hysteresis programmed via Register 0x6D and
CONFIG
CONFIG
CONFIG
MEASUREMENT
MEASUREMENT
MEASUREMENT
TACHOMETER 1
TACHOMETER 2
TACHOMETER 3
PWM
PWM
PWM
GENERATOR
GENERATOR
GENERATOR
MIN
hysteresis value, described in Step 6: T
AND 4
PWM
PWM
PWM
but remain running at PWM
HYST
value has no effect on the fan when the
ENHANCEMENT)
ENHANCEMENT)
ENHANCEMENT)
(ACOUSTIC
(ACOUSTIC
(ACOUSTIC
CONTROL
CONTROL
CONTROL
RAMP
RAMP
RAMP
MIN
.
PWM1
TACH1
PWM2
TACH2
PWM3
TACH3
MIN
MIN
FRONT CHASSIS
REAR CHASSIS
. If the fans are
CPU FAN SINK
. Bits [7:5] of
RANGE
for