Global Mixed-mode Technology Inc.
Three Remote Temperature Sensors and One PWM
Mode Fan Controllers with SMBus Serial Interface
Measures Three Remote Temperatures
Adjustable Offset for Each Sensor via SMBus
Accuracy: ±1°C (+ 60°C to + 100°C)
±3°C (- 10°C to + 120°C)
+4.5V to +5.5V Supply Range
Programmable Hardware Thermal Shutdown
for Sensor 2 and Programmable Software
Thermal Shutdown for Sensor 1,3.
SMBus 2-Wire Serial Interface with Writting
Alert Signal for Diode Fault, Fan Fail, and Fan
Out of Control
Supports SMBus Alert Response
PWM Mode Speed Control
Closed Loop Speed Control and programmable
8 Bits Open Loop PWM Duty cycle Control for
Wide Speed Control Range for FAN, Accuracy
within 2%, when SET_CNT1 > 50
Internal Current- limit and Over-temperature
Protection for the Fan
SSOP-16 & TQFN4X4-24 Package
Desktop and Notebook
Central Office Computers
Smart Battery Packs
SMBusTM is a trademark of Intel Corp.
The G7951 contains 3 precise digital thermometers,
one fan controllers, hardware and software thermal
The thermometers report the temperature of 3 remote
sensors. The remote sensors are diode-connected
transistors typically a low-cost, easily mounted
2N3904 NPN type or the diode built-in in CPU. Re-
mote accuracy is ±1°C for multiple transistor manu-
facturer. The G7951 also support offset adjust function
via SMBus to fix the error due to different CPU diode
or parasitic resistors.
The 2-wire serial interface accepts standard System
Management Bus (SMBusTM) Write Byte, Read Byte,
Send Byte, and Receive Byte commands. G7951
SMBus address is 7ah for write and 7bh for read. And
supports writting protection function by command 20h
to prevent error behavior of µP.
G7951 contains one PWM mode fan controllers. FAN
controller performs closed-loop and open-loop control.
G7951 determines the current fan speed based on the
FG inputs and an externally supplied 32.768kHz clock.
G7951 also provide ALERT for fan fail and out of control
The G7951 provides hardware and software thermal shut-
down. The hardware thermal shutdown is for the sensor 2.
The trigger point is set external resistors. The trigger points
of software thermal shutdown are set via SMBus. If ther-
mal shutdown event occurs, THERM pin outputs low.
Note: Recommend connecting the Thermal Pad to
the Ground for excellent power dissipation.
Oct 18, 2010