f75377 Feature Integration Technology Inc., f75377 Datasheet - Page 12

• Manufacturer Part Number: f75377
• Description: Monitor With Automatic Speed Control
• Manufacturer: Feature Integration Technology Inc.

F75377
6. Function Description
F75377 is a system hardware monitoring and automatic fan speed controlling IC specific designed for
graphic cards and PC etc. The F75377 can monitor several critical hardware parameters of the system,
including temperatures and fan speeds which are very important for the system to work stably and
properly.
The chip can monitor up to 3 fan tachometer inputs and 9 temperature inputs (6 remotes from external
sensor devices by I2C/SST interface, 2 remotes from external sensor D1+/D2+ and 1 local sensor). The
remote temperature sensor can be performed by transistor 2N3906 and CPU/GPU thermal diode. The
F75377 also supports beta-compensation algorithm (BJT Model) for new generational 45nm CPU.
In fan control machine, the F75377 can provide automatic fan speed control so that the system can
operate at the minimum acoustic noise. This chip supports not only PWM duty mode (PWMOUT) for fan
speed control. The F75377 supports Heceta-like function; the fan speed control can follow one or more
different temperature inputs. Besides 3 sets temperature inputs, also can read temperature from other
devices by I2C, SST and PECI interfaces. The I2C Master supports general temperature sensor device
protocol, AMD TSI protocol and next generational Intel chipset MCTP SMBus protocol. Others, internal
oscillator was built in this chip. Also the users can set up the upper and lower limits (alarm thresholds) of
all monitored parameters and the F75377 can also issue warning messages for system protection when
there is something wrong with monitored items.
6.1 Access Interface
The F75377 can be connected to a compatible 2-wire serial system management bus as a slave device
under the control of the master device, using two device terminals SCL and SDA. The F75377 supports
I2C protocol of, “Write Byte”, “Read Byte”, both with or without Packet Error checking (PEC) which is
calculated using CRC-8. For detail information about PEC, please check I2C specification. F75377 also
supports Alert Response Address (ARA) protocol.
The operation of the protocol is described with details in the following sections.
(a)
I2C write to internal address register followed by the data byte
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March.
, 2008
V0.12P