ADT7476ARQZ ON Semiconductor, ADT7476ARQZ Datasheet - Page 44

• Manufacturer Part Number: ADT7476ARQZ
• Description: IC REMOTE THERMAL CTRLR 24QSOP
• Manufacturer: ON Semiconductor
• Series: dBCool®r

Specifications of ADT7476ARQZ

• 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
• 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 hovers around the T
needed for the system to cool down or heat up as the fan is
turning on and off. Values of hysteresis are programmable in
the range 1°C to 15°C. Larger values of T
fans from chattering on and off. The T
set at 4°C.
T
The T
HYST
HYST
is the amount of extra cooling a fan provides after
HYST
AMBIENT TEMP
HYST
REMOTE 2 =
REMOTE 1 =
VRM TEMP
value chosen determines the amount of time
CPU TEMP
LOCAL =
for Temperature Channels
100%
Figure 65. The T
) is that without it, the fan would merely
0%
THERMAL CALIBRATION
THERMAL CALIBRATION
THERMAL CALIBRATION
T
T
T
T
MIN
MIN
MIN
MIN
MIN
HYST
T
setting.
RANGE
HYST
T
T
T
Value Applies to Fan On/Off Hysteresis and THERM Hysteresis
RANGE
RANGE
RANGE
HYST
T
100%
100%
100%
default value is
THERM
0%
0%
0%
prevent the
MUX
http://onsemi.com
MIN
44
PWM
PWM
PWM
MIN
MIN
MIN
hysteresis for fan on/off, but the same setting is used for the
T
Temperature Channels. Therefore, programming Register
0x6D and Register 0x6E sets the hysteresis for both fan
on/off and the THERM function.
below T
Enhance 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 hysteresis on the appropriate
THERM channel.
THERM
The T
In some applications, it is required that fans not turn off
Any hysteresis programmed via Register 0x6D and
CONFIG
CONFIG
CONFIG
TACHOMETER 1
TACHOMETER 2
TACHOMETER 3
MEASUREMENT
MEASUREMENT
MEASUREMENT
PWM
PWM
PWM
GENERATOR
GENERATOR
GENERATOR
MIN
AND 4
HYST
PWM
PWM
PWM
hysteresis value, described in Step 6 − T
but remain running at PWM
setting applies not only to the temperature
HYST
ENHANCEMENT)
ENHANCEMENT)
ENHANCEMENT)
value has no effect on the fan when the
(ACOUSTIC
(ACOUSTIC
(ACOUSTIC
CONTROL
CONTROL
CONTROL
RAMP
RAMP
RAMP
MIN
.
PWM1
TACH1
PWM2
TACH2
PWM3
TACH3
MIN
MIN
FRONT CHASSIS
REAR CHASSIS
CPU FAN SINK
. If the fans are
. Bits [7:5] of
RANGE
for