NCT7491 Series

Remote Thermal Monitor and Fan Controller with PECI 3.0 Interface and SMBus Compatible Master

Catalog

Remote Thermal Monitor and Fan Controller with PECI 3.0 Interface and SMBus Compatible Master

Part	Operating Temperature [Max]	Operating Temperature [Min]	Package / Case	Package / Case [custom]	Voltage - Supply [Max]	Voltage - Supply [Min]	Output Fan	Supplier Device Package	Topology	Function	Accuracy	Output Alarm	Sensor Type	Output Type	Mounting Type
ON Semiconductor NCT7491RQR2G	125 °C	-40 °C	24-SSOP	0.154 " 3.9 mm	3.6 V	3 V		24-QSOP	ADC Comparator Multiplexer Register Bank	Temp Monitoring System (Sensor)	3.5 °C		Internal and External	2-Wire Serial I2C/SMBus	Surface Mount

Catalog

Remote Thermal Monitor and Fan Controller with PECI 3.0 Interface and SMBus Compatible Master

Key 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 VTTVoltage Monitoring

• Over temperature 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 PbFree, Halogen Free/BFR Free and are RoHS Compliant

Description

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 VTTvoltage 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.