ADT7476ARQZ ON Semiconductor, ADT7476ARQZ Datasheet - Page 43

• 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

temperature at which the fan reaches full speed) by setting
T
THERM Limit Registers
Register 0x6A, Remote 1 THERM Limit = 0x64 (100°C default)
Register 0x6B, Local THERM Limit = 0x64 (100°C default)
Register 0x6C, Remote 2 THERM Limit = 0x64 (100°C default)
THERM Hysteresis
via the hysteresis settings (Register 0x6D and Register
0x6E). For example, setting hysteresis on the Remote 1
channel also sets the hysteresis on Remote 1 THERM.
THERM
THERM hysteresis on a particular channel is configured
to that limit (for example, 70°C).
AMBIENT TEMP
REMOTE 2 =
REMOTE 1 =
VRM TEMP
CPU TEMP
LOCAL =
100%
0%
THERMAL CALIBRATION
THERMAL CALIBRATION
THERMAL CALIBRATION
T
T
T
T
MIN
MIN
MIN
MIN
Figure 64. How T
T
RANGE
T
T
T
RANGE
RANGE
RANGE
T
100%
100%
100%
THERM
0%
0%
0%
THERM
MUX
http://onsemi.com
Relates to Automatic Fan Control
43
PWM
PWM
PWM
MIN
MIN
MIN
Hysteresis Registers
Register 0x6D, Remote 1, Local Temperature Hysteresis
Register 0x6E, Remote 2 Temperature Hysteresis
values are programmable from 1°C to 15°C. It is not
recommended to program hysteresis values to 0°C, because
this disables hysteresis. In effect, this causes the fans to cycle
(during a THERM event) between normal speed and 100%
speed, or, while operating close to T
speed and off, creating unsettling acoustic noise.
Because each hysteresis setting is four bits, hysteresis
CONFIG
CONFIG
CONFIG
[7:4], Remote 1 temperature hysteresis (4°C default).
[3:0], Local temperature hysteresis (4°C default).
[7:4], Remote 2 temperature hysteresis (4°C default).
TACHOMETER 1
MEASUREMENT
TACHOMETER 2
MEASUREMENT
TACHOMETER 3
MEASUREMENT
PWM
PWM
PWM
GENERATOR
GENERATOR
GENERATOR
AND 4
PWM
PWM
PWM
ENHANCEMENT)
ENHANCEMENT)
ENHANCEMENT)
(ACOUSTIC
(ACOUSTIC
(ACOUSTIC
CONTROL
CONTROL
CONTROL
RAMP
RAMP
RAMP
MIN
PWM1
TACH1
PWM2
TACH2
PWM3
TACH3
, between normal
FRONT CHASSIS
REAR CHASSIS
CPU FAN SINK