NCT7491RQR2G Datasheet, PDF (1/80 Pages) ON Semiconductor – Remote Thermal Monitor and Fan Controller with PECI 3.0 Interface and SMBus Compatible Master

NCT7491
Remote Thermal Monitor
and Fan Controller with
PECI 3.0 Interface and
SMBus Compatible Master
The NCT7491 is a two−wire serially programmable hardware
monitor. It can monitor 2 remote temperature zones and its own
ambient temperature. A PECI 3.0 single wire interface allows the
NCT7491 to monitor CPU temperatures. The NCT7491 also
implements an SMBus compatible master, allowing it to read
automatically from thermal sensors on the SMBus. The NCT7491 can
automatically control the speed of 3 fans using PWM control, and
monitor the speed of 4 fans. There are 4 analog inputs, used for
measuring 12 V, 5 V, 2.5 V and Vccp channels. The NCT7491 supply
voltage and PECI V_TT voltage are also monitored. Each of the
measured temperature, voltage and fan speed values are compared
with programmable limits and if any channel is outside the
programmed limit an interrupt is generated via the ALERT output pin.
A THERM output is also available for fail−safe thermal control. Up to
3 GPIO pins are available for digital control or signalling.
Communication with the NCT7491 is accomplished via the
SMBus/I²C interface which is compatible with industry standard
protocols. The SMBus address is set by 2 address selection pins.
The NCT7491 is available in a 24−lead QFN or QSOP package and
operates over a supply range of 3.0 V to 3.6 V.
Features
• PECI 3.0 Master for CPU Monitoring
• SMBus Compatible Master
• On−chip Temperature Sensor
• 2 Remote Sensor Channels
• Series Resistance Cancellation on Remote Sensors
• 3 PWM Fan Control Outputs
• 4 Tach Monitoring Input
• PWM Automatic Fan Speed Control
• 4 Analog Inputs for Voltage Monitoring
• Vdd Supply Voltage Monitoring
• PECI V_TT Voltage Monitoring
• Overtemperature Outputs
• Limit Comparison of Monitored Channels
• SMBus Address Selection Allows up to 3 Devices
• Meets SMBus 2.0 Electrical Specifications (fully SMBus 1.1
compliant)
• These Devices are Pb−Free, Halogen Free/BFR Free and are RoHS
Compliant
http://onsemi.com
QFN24
MN SUFFIX
CASE 485L
QSOP24
RQ SUFFIX
CASE 492B
MARKING DIAGRAMS
XXXXX
XXXXX
ALYWG
G
XXXXX = Specific Device Code
A
= Assembly Location
L
= Wafer Lot
Y
= Year
W
= Work Week
G
= Pb−Free Package
(*Note: Microdot may be in either location)
xxxxxxxxx
AWLYWW
xxx = Specific Device Code
A
= Assembly Location
WL = Wafer Lot
Y
= Year
WW = Work Week
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ORDERING INFORMATION
See detailed ordering and shipping information in the package
dimensions section on page 79 of this data sheet.
© Semiconductor Components Industries, LLC, 2013
1
October, 2013 − Rev. 1
Publication Order Number:
NCT7491/D