NCT7491MNTXG ON Semiconductor

NCT7491 Remote Thermal Monitor and Fan Controller with PECI 3.0 Interface and SMBus Compatible Master www.onsemi.com The NCT7491 is a twowire 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 QFN24 QSOP24 MN SUFFIX RQ SUFFIX monitor the speed of 4 fans. There are 4 analog inputs, used for CASE 485L CASE 492B measuring 12 V, 5 V, 2.5 V and Vccp channels. The NCT7491 supply voltage and PECI V voltage are also monitored. Each of the TT measured temperature, voltage and fan speed values are compared MARKING DIAGRAMS with programmable limits and if any channel is outside the programmed limit an interrupt is generated via the ALERT output pin. NCT 7491 A THERM output is also available for failsafe thermal control. Up to ALYW 3 GPIO pins are available for digital control or signalling. Communication with the NCT7491 is accomplished via the (Top View) 2 SMBus/I C interface which is compatible with industry standard protocols. The SMBus address is set by 2 address selection pins. A = Assembly Location L = Wafer Lot The NCT7491 is available in a 24lead QFN or QSOP package and Y = Year operates over a supply range of 3.0 V to 3.6 V. W = Work Week = PbFree Package Features (Note: Microdot may be in either location) PECI 3.0 Master for CPU Monitoring SMBus Compatible Master Onchip Temperature Sensor NCT7491 A 2 Remote Sensor Channels YYWWG Series Resistance Cancellation on Remote Sensors 3 PWM Fan Control Outputs (Top View) (Bottom View) 4 Tach Monitoring Input NCT7491 = Specific Device Code A = Assembly Location PWM Automatic Fan Speed Control YY = Year 4 Analog Inputs for Voltage Monitoring WW = Work Week G = PbFree Package Vdd Supply Voltage Monitoring PECI V Voltage Monitoring TT Overtemperature Outputs ORDERING INFORMATION Limit Comparison of Monitored Channels See detailed ordering and shipping information in the package dimensions section on page 79 of this data sheet. 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 Semiconductor Components Industries, LLC, 2016 1 Publication Order Number: June, 2016 Rev. 3 NCT7491/DNCT7491 Table of Contents Features ......................................................................................... 1 NCT7491 QSOP Pinout ............................................................................. 3 NCT7491 QFN Pinout .............................................................................. 3 Absolute Maximum Ratings ......................................................................... 4 Specifications ..................................................................................... 4 QSOP & QFN Package Pin Assignments ............................................................... 7 Comparison of NCT7491 and ADT7490 QSOP pinouts .................................................... 8 Functional Comparison between the NCT7491 and the ADT7490 ............................................ 8 Functional Block Diagram ........................................................................... 9 Typical System Connections ........................................................................ 10 SMBus Slave Interface ............................................................................ 11 Analog Temperature Measurement ................................................................... 13 Push Registers ................................................................................... 15 PECI 3.0 Interface ................................................................................ 15 SMBus Compatible Master Port ..................................................................... 19 Automatic Fan Control ............................................................................ 22 Fan Override Settings ............................................................................. 26 Fan Drive ....................................................................................... 26 THERM Assertion ................................................................................ 32 THERM Timer ................................................................................... 33 SMBALERT Functions ............................................................................ 34 Voltage Monitoring ............................................................................... 35 GPIO Functions .................................................................................. 36 VCCP Low Detection ............................................................................. 37 XNOR Tree Test Mode ............................................................................ 37 Register Tables ................................................................................... 38 Ordering Guide .................................................................................. 79 QSOP Package Dimensions ......................................................................... 79 QFN Package Dimensions .......................................................................... 80 www.onsemi.com 2